Opions will vary, but here are some of the thoughts:

1. "Why fix what aint broke?"
If your engine isnt showing any signs of a head gasket leak, why bother with head studs?
Some will advocate installing head studs, as a preventative measure, when replacing the timing belt along with inspecting/replacing the rocker arms.
(you're already in that far, so why not do it?)

2. "The engineers designed the engine perfectly, spared no expense, and therefore hardware upgrades are not necessary."

Ok, so we all know thats not true.
However, if you operate this engine like a responsible adult, and never do anything crazy like go out on a remote offroad adventure, or tow a boat/camper on a family vacation, then you probably wont ever have a head gasket problem and never need head studs.

My opinion is that if you DO develop a head gasket leak, or have to pull the head for any reason, then you should install the head studs. You're already in that far, so just do it.

Also, I've seen plenty of Powerstroke, Duramax, and Cummins engines develop head gasket problems and then have studs installed. So its not just a Liberty CRD thing.
Were all those engines modded?
Some, yes.
But most were stock.
And all of them were used for actual WORK.
Not just as grocery getter.

_________________
U.S. Army Retired

THE FOLLOWING 3 FACTS SHOULD BE CAREFULLY CONSIDERED BEFORE CONTEMPLATING A COMMON AND SHORT-SIGHTED “FIX” FOR FAILED THERMOSTAT ASSEMBLIES IN V.M. MOTORI R425 AND R428 ENGINES, WHICH IS THE INSTALLATION OF ANOTHER THERMOSTAT VALVE IN THE UPPER RADIATOR HOSE. WHILE IT IS APPEALING THAT THIS SHORT-CUT IS SO INEXPENSIVE, YOU WILL LIKELY CAUSE A GREAT DEAL OF DAMAGE TO YOUR ENGINE OVER A PERIOD OF TIME BY MAKING CHANGES TO HOW THE COOLING SYSTEM OPERATES IN WAYS NEVER INTENDED BY THE DESIGNERS OF THESE ENGINES.

1) The thermostat you stick in the upper radiator hose is designed to regulate engine temperatures on a smaller, lighter engine designed to make a lot less power and do less work. The heat created in the Renault engine is far less than the heat created in the 2.5L or 2.8L CRD engines and therefore the Renault has a much smaller cooling system with a significantly smaller thermostat valve designed for it. In situations where you are working your CRD engine very hard, it will likely NOT flow the engine coolant you need to keep the engine temperatures down.

2) The inline thermostat valve is quite a distance away from the coolant outlet at the cylinder head. There is a question of accuracy with which the inline valve can control engine temperatures as there is some cooling of the engine coolant after it leaves the cylinder head and before it can reach the valve. Therefore, if the valve is designed to open up at 195 degrees Fahrenheit, the engine is going to be hotter than that opening temperature. This inaccuracy creates another risk of overheat situations occurring.

3) The greatest problem that occurs with this specific situation, (addition of a second thermostat valve controlling coolant flow through the radiator circuit on a V.M. Motori R425 and R428 engine), is that it creates a situation where there are times during operation of the engine that you have NO coolant flow through the engine. Over a long period of time, this can lead to the cylinder head warping and cylinder head gasket failure. Read further for a detailed explanation of this…

ALL LIQUID COOLED INTERNAL COMBUSTION ENGINES HAVE BYPASS CIRCUITS IN THEIR COOLING SYSTEM. These circuits were deemed necessary many years ago because it was determined that coolant must always be circulating around inside the engine to keep hot spots from forming, typically around the exhaust ports in the cylinder head.

http://www.stant.com/index.php/english/ ... ermostats/

A very simple 1-circuit liquid cooling system without a thermostat valve accomplishes this, because there is no valve to stop coolant flow. The problem with this simple system is that it over-cools the engine; the results of which are poor fuel economy and build-up of contaminants in the engine oil, and a shorter engine life. Thermostat valves were developed to properly regulate engine temperature, but then the engines started to have all kinds of cylinder head gasket failures and warped cylinder heads.

Some automotive engineer many years ago figured out that a second cooling system circuit can be added to the engine; one which has the same coolant pathways in the engine block and cylinder head(s), but one that loops back on itself and “bypasses” the radiator…. Hence the name “bypass circuit”.

Old engines typically had a low power-to-displacement ratio, and it was O.K. to have an open bypass circuit. This was because these engines did not create enough heat, (due to their low power output), to overwhelm the cooling system even when the engine was worked hard and some coolant bled off through the open bypass circuit rather than going through the radiator circuit.

On the other hand, modern engines like the R428 have a much higher power-to-displacement ratio, and can create tremendous heat that must be shed off to prevent overheat situations from occurring. These engines must have more efficient cooling systems, and therefore typically have a valve controlled bypass circuit. Valve controlled bypass circuits increase cooling system efficiency because the bypass circuit is shut off when there is heavy demand placed on the engine… ALL the coolant is forced through the radiator circuit where it can have maximum heat shedding ability.

Typically, a cooling system that has a valve controlled bypass uses a thermostat valve where the wax motor, (AKA a heat motor or wax pellet, as some might refer to it), has a radiator circuit valve on one end, and a spring-loaded bypass valve on the other end. The operation of this valve is very simple; when one valve on one end is stroking open, the other is stroking closed by default. With this design, it is not possible to shut down coolant flow throughout the engine because one or the other circuit is open…. coolant is – under all circumstances – continually flowing around the engine to keep engine temperatures EVEN. The Jeep Cherokee CRD has this design thermostat valve in its thermostat assembly.

Furthermore, it is well known that thermostat valves are designed to fail OPEN; and by this I mean that the valve controlling coolant flow to the radiator will fail open. This is deliberately designed for the rather obvious reason that if the valve controlling flow to the radiator were to fail closed, then the driver would experience a serious overheat situation and a possible boil-over of the cooling system, with possible serious damage occurring to the engine.

The above information is not in dispute, and anyone can take a little time and easily research this for themselves.

Consider then what would happen if a thermostat valve with a spring loaded bypass valve were to fail; the main valve controlling coolant flow to the radiator would fail open, and the BYPASS VALVE WOULD FAIL CLOSED BY DEFAULT. In effect, your entire cooling system bypass circuit would be shut down, but you would still have necessary coolant flow throughout your engine because the radiator circuit is now open all of the time.

If your O.E. type thermostat assembly is starting to fail or has completely failed – as indicated by your engine running cooler and cooler with the resultant loss of fuel efficiency and long-term reliability problems – and you then decide to be cheap and install an inline thermostat in whatever form they may come in, ANY TIME that inline thermostat valve is closed, (like during warm-up of your engine or often during operation in very cold climates), you will have virtually NO coolant flow throughout the engine. Hot spots will start to form in your cylinder head or heads; right around the exhaust ports as this is always the hottest part of the engine. Your cylinder head or heads will warp over time and you will have a head gasket failure.


ADDENDUM

It is no surprise to me and other CRD owners who think like me that the damages that can occur to CRD engines as a result of installing an inline thermostat of any type are precisely the SAME damages that are complained about most often by people online in this forum and in other forums.

The CRD engine is a consumer grade diesel engine with its aluminum head/iron block architecture and timing belt design. Aside from the higher service costs of changing out the timing belt every 100,000 miles or so, designing an engine this way practically guarantees a limited service life verses a similar diesel engine that has iron head/iron block architecture with gear driven cams. All aluminum head/iron block engines are subject to more frequent head gasket failures and head warpage because of the fact that aluminum has almost 2 times the thermal expansion factor of iron. This is especially true of consumer grade diesel engines due to their high compression ratios and use of turbochargers. If this is common knowledge, why in hell would anyone mess with the design and function of the CRD engine cooling system and risk creating hot spots in the cylinder head, right around the exhaust ports?

For those new Liberty CRD owners who are only now finding out the problems associated with our little tractors, there is a high propensity of the following problems… head gasket failures, cylinder heads warping and/or cracking, engines eating exhaust valves and ceramic glow plugs cracking with pieces falling into the engine. These are all problems that are far more prevalent when you have a cooling system that does not have a functioning bypass circuit with a second independent thermostat valve controlling flow to the radiator.

Consumer grade diesel engines are precisely designed with limited service life because the automobile manufacturer wants to make more money off of you through servicing the vehicle with high cost O.E. proprietary throwaway parts, and then for you to scrap the vehicle after approximately 6 years with the end result of going back to the dealership and purchase another one. Their rather arrogant and self-serving attitude assumes you can afford this.

It is up to the vehicle owner to realize this strategy is being employed against them and to take appropriate counter-measures to make the vehicle last longer. This means – especially for diesel engines – proper driving techniques and service practices; either by himself or by someone he or she trusts. Any deviation from proper service techniques and practices, proper driving habits and other factors will result in problems down the road far more often with a consumer grade engine than a commercial grade engine. Thoughtless upgrade modifications like the installation of an inline thermostat in the upper radiator hose is not in keeping with proper service practices.

REGARDING THE ARP HEAD STUD ISSUE:

Automotive Racing Products, (ARP), DOES NOT recommend the use of their products in the CRD engine as they have not done the research themselves to see what works and what does not for this specific application. The reason you see "kits" available through parts shops like Sasquatch Parts and I.D. Parts is that those kits are put together by ARP as specified by those shops; no warranty is implied or offered. The only criteria used to make up these kits is by identifying exactly what size, length and type of thread ARP studs would be required. No testing had been performed to the long-term effects of using ARP studs by ARP technicians and engineers themselves.

Don't believe me? Here is ARP's Order Desk and Technical Support number... 1-800-826-3045; their main sales/marketing number is 1-805-339-2200.

FOR THE RECORD, I AM NOT BASHING THE QUALITY OF ARP PRODUCTS, THEIR TECHNICAL SUPPORT OR THE COMPANY ITSELF; INDEED, THEY MAKE OUTSTANDING PRODUCTS. THE PROBLEM IS THAT THE APPLICATION IS INCORRECT AND THE RESULTS ARE LONG -TERM PROBLEMS FOR YOUR NON-COMPETITION ENGINE THAT HAS ALUMINUM HEAD/IRON BLOCK ARCHITECTURE. PLEASE READ ON FOR A FURTHER EXPLANATION...

The PRIMARY target market for ARP is performance/motorsport competition; not every day or even commercial use. We are talking racing engines here; where modifications are performed on engines to make them produce 2, 3, and even 4 times the original amount of power the engine was designed to produce; using 2, 3, and even 4 times the amount of fuel and air that a stock engine would. This creates tremendous pressures on competition engines, and incredibly strong fasteners are required to keep those engines from flying apart. Therefore, holding the engine together during racing or other motorsports competition becomes the first, second and third priority; in other words, the ONLY priority. The incredibly strong ARP fasteners, by the very fact that they are so incredibly strong, completely dismiss other necessary requirements for accommodating aluminum head/iron block architecture.

What do I mean by this, you might say? Well, there are indeed other factors at play when you are talking about cylinder heads and proper integrity with the engine blocks they are bolted to. Thermal expansion/contraction and pressure changes occur during normal engine operation; control over these must be maintained while maintaining cylinder head gasket integrity over the long term on normal and commercial engines. People want their grocery-getter and boat hauling engines to last a long time. Cylinder head gaskets fail and cylinder heads warp or crack due to a number of factors, most of which are listed below…

1) Temperature differentials in the metal that is warping or cracking. The more radical the temperature differentials, the greater the chance of the metal warping or cracking.

2) The closer the temperature differentials are to each other, the greater the chance of the metal warping or cracking.

BOTH of these facts speak very loudly to the reasons why you preheat an engine before putting a load on it. This is trucking 101; every trucker or commercial operator who has to pay to maintain their vehicle preheats the engine before putting a load on it. Truckers always have their truck engine block heaters plugged in and turned on in the winter, or they have invested in a Webasto coolant heater to pre-heat their engines before starting them. Once started, they go and perform a pre-trip inspection before driving off. By the time the pre-trip inspection is finished and the paperwork is done, the engine should be about 1/2 way to full hot. Then the driver eases away gently and works the engine lightly until it is fully warmed up.

Ideally, pre-heating an engine should be done by an external heater, be it a powerful electric engine block heater or a diesel fuelled engine coolant heater before you even start the engine; you end up with elevated temperatures that are EVEN throughout the engine and that are much closer to the operating temperature when it is working. However, even idling the engine to warm it up is better than some of the dumb-ass things I have witnessed. I have seen videos of guys starting their engines in very bad conditions. Those cold-start contests I have seen are really, really dumb. The same can be said of people starting their engines and putting their foot into it, (often hard), before the engine is even slightly warm. I would not be surprised to see engines treated in the manners described above to have a severely shortened life.

3) The number of times the engine goes through a heat cycle from cold to fully warmed up. The more heat cycles an engine experiences in its lifetime, the more times there are temperature differentials in areas that can warp, like the cylinder head around the exhaust ports.

The number 1 area of the engine that is going to warp is the exhaust port area of the cylinder head, which is BY FAR the area that experiences the greatest temperature differentials. The warping that can occur here can be bad enough that the exhaust valves are no longer aligned properly on the seats, and end up striking one side of the seat more than the other. This can weaken the valve and eventually cause it to break. Forget about the whole narrative about the valves in the CRD engine being of poor quality; severe head warpage is the real cause of premature exhaust valve failure.

4) The final issue that contributes to a cylinder head gasket failure, cylinder head warping and cracking is the use by manufacturers of aluminum head/iron block architecture. I personally do not like aluminum head/iron block architecture for precisely the reasons I am about to describe; it is a significant exacerbating factor to cylinder head gasket integrity and head warping/cracking. Give me iron head/iron block architecture any day over what we have here for the CRD engine.

The thermodynamic properties of aluminum and of iron are quite different, and this contributes greatly to head gasket problems and cylinder head warpage. Aluminum has about twice the thermal expansion factor of iron. Take exact same sized cubes of aluminum and iron, measure them at room temperature and again at 300 degrees Fahrenheit; you will find that the aluminum has increased in size twice as much as the iron has, (that is to say, the amount of the expansion of the aluminum is about twice the amount of expansion of the iron). This creates interesting challenges to engineers wanting to have an aluminum cylinder head properly bolted to an iron engine block that will have permanent, leak-free combustion chambers.

The thermodynamic differences between aluminum and iron are the whole reason why torque-to-yield bolts were created. TTY bolts allow the aluminum cylinder head to properly expand more than the iron block underneath it during operation of the engine, all while maintaining sufficient clamping force to seal those combustion chambers. These bolts stretch a little to accommodate that expansion, and will then shrink down after the engine has cooled off. TTY bolts also act as a sacrificial part when the cylinder head starts to warp; they will stretch beyond their limits and allow the head to warp.

When this happens, you will find upon tear-down of the engine that many of these bolts are barely on, and this has led some people to believe that the TTY bolts are junk. Nothing could be further from the truth… It is much preferred to destroy the bolts and have the cylinder head warp than it is to use a head stud that is so strong that it does not allow the head to properly expand during normal operation or stretch beyond its limits to allow the head to warp if that is what is going to happen. If you were to use such incredibly strong studs, the cylinder head will likely end up cracking and becoming useless junk, (or, incredibly expensive to repair).

It is all about what is less expensive to replace and repair; relatively inexpensive TTY bolts and milling the cylinder head mating surface flat; or replacing a whole cylinder head that has cracked. It doesn’t take a lot to find out that it is the latter that is much more expensive, not the former. Using ARP head studs will greatly increase the chances of the cylinder head eventually cracking, all while doing nothing to prevent a cylinder head gasket failure or the head warping at all.

I can practically guarantee that the O.E. torque-to-yield bolts are not the problem, as suggested to by several LOSTJEEPS.com members.

You may criticize this write-up by explaining that ARP head studs are used all the time in aluminum head/iron block racing engines, and you would be correct. The operative words here are “racing engines”. The common theme of all competition engines are that they do not last very long before they either need to be rebuilt are they catastrophically fail. As such, they simply do not go through nearly enough heat cycles for head warping to become an issue before there is major servicing performed or a rebuild done or there is a major failure.

Racing engines are started, allowed to fully warm up before heading to the track, and are then driven very, very hard so at no point during the race the engine is anything other than blistering hot. When the race is over and if the engine has not catastrophically failed, the engines are allowed to run relatively gently to allow them to cool off slowly, and then they are shut off and the oil changed for the next race. Repeat perhaps as many as 5 or 6 more times, and then it gets torn down for major servicing and/or a rebuild. It is very unlikely that a head warp or head gasket failure will occur during this period of time unless there is a cooling system failure/overheat event or there was a mistake made in building the engine.

Some interesting points, thanks for the detailed response!

Late response; it's been a rather hectic couple of weeks around here. Anyway:



Speaking as someone who has owned four Renault 5s (two NA-spec 1.4-litre longitudinally-engined models (1977 & 1980) and two transverse-engined Supercinq models (1986 and 1988)), I cannot understand why anyone would pick an inline thermostat from a vehicle with 50% of the engine capacity of a CRD KJ.

Apart from all of the other reasons why this is a bad idea, from a purely coolant flow standpoint, it's impossible to see how this could properly scale to a CRD. Just because it fits doesn't mean it should be installed.



^^^ This. Anyone thinking of doing it... Just don't.



We talked about this, and that's not going to happen. There's nothing stopping anyone from digging up an old thread on the subject and replying to it, or starting their own topic about it. Best thing to do is to just let them know why it's a bad idea and go from there.

_________________
2005 KJ CRD Limited 4x4:
245/75R16 BFG TA KO2s
OME / Clevis 2.5" Lift
JBA Lifted A-Arms
IRO WJ Short Rear UCA/WWDiesel mount
Skid Row Skidplates
HDS Model 001 Thermostat (190°F)
Suncoast TC
Full Weeks Kit
Bosch 5V glow plugs
Hayden 2986 fan clutch / GM 11-blade fan
Samco / Sasquatch Intake Hoses
Carter in-tank pump
Provent 200
V6 Airbox

We talked about this, and that's not going to happen. There's nothing stopping anyone from digging up an old thread on the subject and replying to it, or starting their own topic about it. Best thing to do is to just let them know why it's a bad idea and go from there.[/quote]


I agree... I really do not think it is a good idea to shut down the discussions of the Inline Thermostat upgrade. Let them postulate on the "magic bullet" they found and then give them the reasons why it is a bad idea. You will get some of them thinking twice about it, but others are simply wedded to the idea that the cheaper the fix, the better... no amount of logic can convince them otherwise. Check out this latest thread from the Jeep Liberty CRD Facebook page...

https://www.facebook.com/groups/liberty ... 0888104638

Yes we discussed the request to lock the thread and both were of the opinion there was nothing wrong posted.
No adbuse, illegal links, etc...

Nothing wrong with posting to an old thread if you have questions or need advice.
As long as the discussions remain civil and done with respect, they are healthy and may actually help some poor soul from making a very expensive mistake.

But as some of us have wofully learned, you can lead a horse to water, but you can't always make them drink! And this is sadly true with the in-hose thermostat issue.
Lord knows several of us have beat this poor old horse to death over the past five years or so and tried to educate posters, yet it still seems to keep resurfacing and just does not want to die.
Unfortunately, some owners are bound and determined to be their own worst enemy.

_________________
Supporting Vendor and Moderator of LOST
05 Jeep Liberty CRD Limited
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount
98 Dodge Cummins 24 Valve

I mean, doesn't owning one of these trucks in the first place make you your own worst enemy?

Labor of love for some to have such a unique and rare vehicle.
Owning any unique vehicle comes with challenges, the fun part is trying to eliminate the problem areas before they happen.

_________________
Supporting Vendor and Moderator of LOST
05 Jeep Liberty CRD Limited
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount
98 Dodge Cummins 24 Valve

Hey TURBO-DIESEL-FREAK, I think you used the wrong word! Its not an upgrade to use an inline thermostat! its a downgrade!

_________________
Australian KJ CRD 2006

The problem with those problem areas is that you don’t know they are a problem until they become a problem.

Myself, I’m all outta love.

_________________
U.S. Army Retired

My other car is a Ferrari, trust me this Jeep is not even close to that challenge!

_________________
2005 limited, tinted, OME lift, falken wildpeak 245/75-16, Suncoast, Transgo, Chevy fan+clutch, 195° Kap Stat Mod, Derale tranny cooler, Provent, Stage 2 tune, EGRdelete, Cat delete, Group65 batt, V6 airbox, tow brakes, switchblade key, DIY roof rack, DIY Front bumper,
Future; rear bumper, true tracs, tank fuel pump, webasto heater, 5sp manual

Yeah, they're difficult, but not the worst by a long shot.

For sure, I once replaced the clutch and pressure plate in a Triumph TR7, just the parts were over 1k, cost him almost 2 grand to have the clutch replaced.

Worked on a Fiat X19 one time and replaced the water pump, dang it was a mid engine and very tight hole to work in. Had to disassemble the whole top of the engine to replace the water pump. The water pump was as long as the engine, it was belt driven on the front end and drove the AC compressor belt on the back end. It resided under the intake and exhaust manifold, a very stupid design! Water pump cost over $900 dollars and at the time in the US was almost impossible to find one. Labor cost to replace was more than the water pump.

So yes, there are a lot of vehicles out there you could own and have to work on and buy parts for....

_________________
Supporting Vendor and Moderator of LOST
05 Jeep Liberty CRD Limited
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount
98 Dodge Cummins 24 Valve

YES! Yes indeed the inline thermostat is most definitely a downgrade!

WWDiesel... Your quote...

"But as some of us have wofully learned, you can lead a horse to water, but you can't always make them drink! And this is sadly true with the in-hose thermostat issue.
Lord knows several of us have beat this poor old horse to death over the past five years or so and tried to educate posters, yet it still seems to keep resurfacing and just does not want to die.
Unfortunately, some owners are bound and determined to be their own worst enemy. "



Excellent post! Truer words were never spoken. What you wrote here reminds me of at least some of the words of "The Boxer" by Simon & Garfunkel....

I am just a poor boy
Though my story's seldom told
I have squandered my resistance
For a pocket full of mumbles
Such are promises
All lies and jests
Still a man hears what he wants to hear
And disregards the rest

I love Simon & Garfunkel.
So True!
Thank you for the compliment, coming from you I am quite impressed since you can be very hard and blunt at times.
Even though we don't totally agree on everything, we can agree that stupidity has no place when dealing with these unique vehicles.

One of my favorite quotes: "But I could care less, 'cause I was all alone"

_________________
Supporting Vendor and Moderator of LOST
05 Jeep Liberty CRD Limited
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount
98 Dodge Cummins 24 Valve

WWDiesel; Your quote:

"Thank you for the compliment, coming from you I am quite impressed since you can be very hard and blunt at times.
Even though we don't totally agree on everything, we can agree that stupidity has no place when dealing with these unique vehicles."



Most certainly we agree; you are posting the truth here, WW!

Yes, I am a very uncompromising, hard-assed sort of guy on some things. I am a product of my unique circumstances; both nature and nurture. I can't honestly apologize for this character trait because it is this very same uncompromising attitude that made the Hot Diesel Solutions Model 001 thermostat assembly what it is today.

My conscience will not give me any peace if I manufacture and sell a substandard product. I always strive to make my product the absolute best it can be, and I employ a machine shop that values my sentiments. Where I see that improvements to the Model 001 housings are required, the machine shop will design in those improvements. The latest batch of housings are the best that have ever been made, with simplifications to the machining program that have actually improved strength in the area of the side mounting tab.

OK guys, here is my experience on using the "Renault 5 hack". The OEM stat on my 2.8 CRD KJ was stuck wide open, and the temperature gauge would still be on cold even after driving for 10 miles at 60mph on a motorway! Clearly this would have to be sorted out ASAP.
I am currently out of work, and can only afford to spend tiny amounts of money on maintaining my KJ, so replacing the OEM stat would have been way too expensive...I heard about the Renault 5 Hack on a KJ group on Facebook, and it seemed to be the solution I needed, so I did some research of Renault 5 Thermostats and I ended up buying the cheapest one I could find...An Intermotor 75035, that opens at 86.5'C (187.7'F), and it cost me just £4.24 on ebay. I already had another Stainless steel 50mm hose clamp so I was ready to install it as soon at arrived.
I figured some lube would be handy to help push it into the hose...So I used a smear of Vaseline on in the inside of the hose. There is a round lip at the bottom of the large end of the stat, and you can push it in that far easily, then the lip stops it going any further. So I had to lever the end of the hose out a bit with a flathead screwdriver to get the lip inside the hose...You can then push about half of the stat into the hose but to avoid damaging the three fingers holding the smaller copper end to the larger end, I then used a Vaseline lubricated deep 27mm socket to push it right in, till the end of the copper bit was flush with the end of the hose.
Then I used my 50mm hose clamp to clamp the large end of the stat inside the hose in place, then fitted the hose back onto the OEM housing and tightened up the original hose clamp...The whole operation only took 2-3 minutes, and I could have done it quicker than that but I had to keep going indoors to get more tools out.

Results: After running the engine on tick over for about 3-4 minutes the temperature gauge started to move slowly upwards and after about 5-6 minutes it would reach a fraction under half way, and stay there. Driving down the road warms it up even quicker.
The temperature gauge has not gone over half way (normal operating temperature), even after driving 6-7 miles, so this a very stable mod too.
I should add that a few weeks before doing the Renault 5 hack, I swapped my OEM 5 blade metal fan for a used 11 blade plastic fan off the 3.7 V6, but with the original 2.8 CRD viscous clutch bolted onto it...The plastic fan blows more air than the metal one, it's 500g lighter, and it's quieter too, so it definitely an upgrade. KJ 2.8 CRD exported to Australia got the same fan as stock, presumably because it's better airflow helps with the hot summers there.
The 7 blade plastic fan off the KK would have been my first choice, as it would absorb less power than the 11 blade, giving better fuel economy, but it was too expensive for me, so the 11 blade had to do.
If you live somewhere with a very warm average climate, and you still have the stock steel fan, then it's possible the temp gauge will go over 1/2 with this mod, but I can't confirm that as it's Autumnal weather here at the moment, and starting to get colder as the weeks go by. Summary:
Pros: Works perfectly, extremely quick to install, very simple to install and very cheap to do. (over 3x cheaper than the cheapest aftermarket alternative to the OEM thermostat, and over 100 times cheaper than some alternatives being offered!)
Cons: None (so far).
There are several KJ CRD owners that have been running the Renault 5 hack for over 6 years, and they have clocked up over 100,000 miles with no issues whatsoever, so I for one have no problems recommending this mod.
I put this diagram together to better show the mod to those interested:

Your both wrong! It is most definitely an upgrade!!!