Thermostat issue or air in cooling system?

Jackkep · **Posted:** Tue Jul 10, 2018 10:40 pm

Hey guys. I finally got my crd back on the road. Now I'm having a different issue, it won't get up to temp. After putting in the new radiator I bled out the air through the bleed valve and then again later by closing the bleed valve and leaving the radiator cap off and massaging the hoses. The temp still won't get up to spec.

This is how high it goes: https://photos.app.goo.gl/DFp4GhdkZVBSSPNq8

I'm imagining thermostat issue and I plan on ordering one tomorrow but I'm making sure there's not something I'm missing. I was never actually able to get coolant to come out of the radiator bleed valve, and the upper radiator hose gets tight and hot but does not feel like it's filled with coolant. If I pull it off while it's running a little trickles through like the bypass valve is working but doesn't seem like the thermostat is opening

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

There are several factors that may be at play here...

1) Do not trust your O.E. engine temperature gauge. These gauges have proven to be inaccurate and non-linear in the temperature readings. With the engine warmed up as much as is indicated by the O.E. gauge, take a reading with an infra-red temperature gun with the laser pointed to the top of the thermostat housing. Cross reference the reading you get with the gun with another reading taken with an OBDII reader measuring temperature through the engine's computer, (the reading from the OBDII reader ultimately gets its readings from the O.E. temperature sending unit threaded into the firewall side of the thermostat. The readings should be the same or almost the same. If they are not, you either have a faulty O.E. temperature sending unit or an inaccurate infra-red gun. This is a very good test, as it would be exceedingly rare that both test methods have inaccuracies.

2) The O.E. thermostat is a P.O.S. and a waste of time. Better to throw your money down the toilet and save yourself the grief of installing one. The O.E. thermostat is a throwaway part that you have to change out every 50,000 miles or so. At about $150.00 USD plus your time to install it - every time - you can quickly see how soon this gets old. The other problem is the thermostat valve inside the assembly for the North American market Liberty CRDs is set to open up at 176 degrees Fahrenheit... about 20 degrees cooler than the valves in O.E. assemblies in other markets around the world. The reason for the ridiculously low operating temperature is to allow the engine to meet the Environmental Protection Agency's unreasonable NOx pollution standards. So even with a BRAND NEW O.E. thermostat assembly your engine is not getting up to a proper operating temperature. There are other options available than the O.E. thermostat if you know where to look that will get your engine up above 200 degrees Fahrenheit... where it belongs.

3) Are you pulling the radiator hose off just after starting your engine? Pulling the upper rad hose when fully hot is dangerous and should not be attempted. It does appear by your description that you are low on coolant, and that may also be affecting your engine temperature readings. What is the level like in your coolant overflow tank?

Jackkep · **Posted:** Wed Jul 11, 2018 4:07 am

TURBO-DIESEL-FREAK wrote:

There are several factors that may be at play here...

1) Do not trust your O.E. engine temperature gauge. These gauges have proven to be inaccurate and non-linear in the temperature readings. With the engine warmed up as much as is indicated by the O.E. gauge, take a reading with an infra-red temperature gun with the laser pointed to the top of the thermostat housing. Cross reference the reading you get with the gun with another reading taken with an OBDII reader measuring temperature through the engine's computer, (the reading from the OBDII reader ultimately gets its readings from the O.E. temperature sending unit threaded into the firewall side of the thermostat. The readings should be the same or almost the same. If they are not, you either have a faulty O.E. temperature sending unit or an inaccurate infra-red gun. This is a very good test, as it would be exceedingly rare that both test methods have inaccuracies.

2) The O.E. thermostat is a P.O.S. and a waste of time. Better to throw your money down the toilet and save yourself the grief of installing one. The O.E. thermostat is a throwaway part that you have to change out every 50,000 miles or so. At about $150.00 USD plus your time to install it - every time - you can quickly see how soon this gets old. The other problem is the thermostat valve inside the assembly for the North American market Liberty CRDs is set to open up at 176 degrees Fahrenheit... about 20 degrees cooler than the valves in O.E. assemblies in other markets around the world. The reason for the ridiculously low operating temperature is to allow the engine to meet the Environmental Protection Agency's unreasonable NOx pollution standards. So even with a BRAND NEW O.E. thermostat assembly your engine is not getting up to a proper operating temperature. There are other options available than the O.E. thermostat if you know where to look that will get your engine up above 200 degrees Fahrenheit... where it belongs.

3) Are you pulling the radiator hose off just after starting your engine? Pulling the upper rad hose when fully hot is dangerous and should not be attempted. It does appear by your description that you are low on coolant, and that may also be affecting your engine temperature readings. What is the level like in your coolant overflow tank?

I do own a fairly nice infrared heat gun so I will use that to register temperature. What are the readings that I should be seeing? I do have an OBD tool order to read the temperature sensor readings. Regardless of all this how do I indicate whether or not the thermostats actually opening allowing coolant to flow through the engine? I have no problem dealing with a faulty temperature reading as long as my engine is cooling correctly. Yes there is coolant in the reservoir. After I installed the new radiator I made sure that it was filled.

papaindigo · **Posted:** Wed Jul 11, 2018 7:09 am

Sigh. Proper coolant fill procedure assuming system has been drained AND radiator drain valve is closed - 1) use only HOAT coolant (ca. 50/50 mix with demineralized water); 2) open radiator cap (cap on top of coolant bottle) and bleed valve on passenger side top of radiator (twist to 4 o’clock position and pull up to remove); 3) fill by slowly pouring coolant mix into coolant bottle on firewall until coolant comes out of radiator bleed valve; 4) “burp” upper radiator hose several times to help remove air; 5) top off from coolant tank as needed; 6) close bleed valve (with valve at 4 o’clock position push down gently and twist closed); 7) continue filling until coolant is ca. 1” above the coolant tank mid-line;

after several hot to cold drive cycles check coolant tank level which ideally will now be at mid-line, top up if need be.

The OEM tstat is not a POS but it’s not a wonderful design either. Issues - 1) it’s sealed so you cannot replace the tstat without replacing the entire housing; 2) the tstat is a bit on the cool side for ideal diesel operation; 3) its life span can be on the short side (as little as 35K miles); and 4) a good/bad feature is that when it fails it fails open or by opening too soon. Your temp gauge position indicates yours if failing by opening too soon (same as mine did years ago) which causes the engine to run cool at a 10-20% drop if mpg. Solutions - 1) OEM replacment ca. $150 or HDS replacement (ca. $500 IIRC). HDS solution is ideal (better operating temp and replacable tstat) if pricey. In line tstat is NOT a viable option other than short term as it causes coolant circulation issues that may cause head problems. Yes there are DIY mods to the OEM that allow tstat replacement if you have access to machine shop equipment.

The OEM temp gauge is not linear but is accurate if you understand needle position. See the first image at http://www.greendieselengineering.com/j ... st/19.page As noted you are running cold.

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

papaindigo wrote:

Sigh. Proper coolant fill procedure assuming system has been drained AND radiator drain valve is closed - 1) use only HOAT coolant (ca. 50/50 mix with demineralized water); 2) open radiator cap (cap on top of coolant bottle) and bleed valve on passenger side top of radiator (twist to 4 o’clock position and pull up to remove); 3) fill by slowly pouring coolant mix into coolant bottle on firewall until coolant comes out of radiator bleed valve; 4) “burp” upper radiator hose several times to help remove air; 5) top off from coolant tank as needed; 6) close bleed valve (with valve at 4 o’clock position push down gently and twist closed); 7) continue filling until coolant is ca. 1” above the coolant tank mid-line;

after several hot to cold drive cycles check coolant tank level which ideally will now be at mid-line, top up if need be.

The OEM tstat is not a POS but it’s not a wonderful design either. Issues - 1) it’s sealed so you cannot replace the tstat without replacing the entire housing; 2) the tstat is a bit on the cool side for ideal diesel operation; 3) its life span can be on the short side (as little as 35K miles); and 4) a good/bad feature is that when it fails it fails open or by opening too soon. Your temp gauge position indicates yours if failing by opening too soon (same as mine did years ago) which causes the engine to run cool at a 10-20% drop if mpg. Solutions - 1) OEM replacment ca. $150 or HDS replacement (ca. $500 IIRC). HDS solution is ideal (better operating temp and replacable tstat) if pricey. In line tstat is NOT a viable option other than short term as it causes coolant circulation issues that may cause head problems. Yes there are DIY mods to the OEM that allow tstat replacement if you have access to machine shop equipment.

The OEM temp gauge is not linear but is accurate if you understand needle position. See the first image at http://www.greendieselengineering.com/j ... st/19.page As noted you are running cold.

Papaindigo:

I would add to your proper coolant fill procedure that it is easier to accomplish a complete fill of coolant if your CRD is on ramps... essentially, with the nose of the vehicle pointed upwards about 15 - 20 degrees. This assures that the bleed valve is at the highest point in the cooling system... if there are any bubbles in the cooling system that is where they likely will go.

Regarding the O.E. thermostat assembly... you and I will disagree on this. I call it a POS because of the reasons you have written. A throwaway part is deliberately designed NOT to last so the service department of your friendly local stealership can hose you on the expensive POS replacement, and the labor to replace it.... often. Your contention that it is "a bit on the cool side" is a matter of opinion... down in Florida it makes less of a difference than it does where people have to endure -40 degree climate.... I can guarantee you that a 203 degree Fahrenheit opening temperature verses the O.E. 176 degree Fahrenheit opening temperature is a WORLD of difference.

Regarding the O.E. temperature gauge... if it is not linear... it is not accurate. IMHO, the O.E. gauge was deliberately made without numbers on it so savvy diesel owners would not clue into how low the engine operating temperature was.

flash7210 · **Posted:** Wed Jul 11, 2018 9:04 am

Jackkep wrote:

I was never actually able to get coolant to come out of the radiator bleed valve, and the upper radiator hose gets tight and hot but does not feel like it's filled with coolant. If I pull it off while it's running a little trickles through like the bypass valve is working but doesn't seem like the thermostat is opening

I'm having a hard time understanding this part.

When I fill my empty radiator, I completely remove the plug from the top of the radiator and fill the coolant tank back on the firewall.
I fill it until water comes out of the top of the radiator and then quickly put the plug back in.

Because the coolant tank is at a higher level than the radiator, if the coolant tank is full, water will always come out of the bleed valve when open. Engine running or not.

So, either the bleed valve opening is plugged, or the coolant tank isn't full.
With the bleed valve plug completely removed, you can look into it and see the water level inside the radiator.

Regarding the thermostat...

Yes, the thermostat sucks.
Yes, the temp gauge sucks.
(sorry Papa, if a gauge doesn't have any actual REAL numbers on it, it sucks!)

The factory thermostat, if working properly, should open at about 176F. A little bit early for some tastes but it is what it is.
The factory thermostat typically fails by either being suck open, or opening too soon.
So, if your engine coolant temps never get above 176, then yes, you need a new thermostat.

Now, this running too cool problem usually isn't discovered until winter time.
In a Florida summer, creeping through slow moving, hot afternoon, Orlando traffic on Colonial or Semoran (or pretty much anywhere), with the AC on, your coolant temps should have no problem getting well above 180F. Even with a stuck open thermostat.
Been there, done that.

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

"The factory thermostat, if working properly, should open at about 176F. A little bit early for some tastes but it is what it is."

It is not a matter of some peoples' tastes, flash7210. It is too cold a thermostat opening temperature... period. ESPECIALLY for a diesel engine that relies on enough heat of compression - aided and abetted by the operating temperature of the engine - to properly combust the fuel oil that is being misted into the cylinders. Diesel engines do not run well at all when they are cold primarily because the fuel is not being combusted properly.

What worked well in the 1960s and 1970s - where engines commonly had 160 and 170 degree thermostat valves in them - does not work well here. Modern engines are designed to produce much more power per cubic inch of displacement in an effort to be as efficient as possible... to squeeze as much mechanical energy out of every gallon of fuel burned. To take maximum advantage of these more advanced designs and higher tuning specifications you have to run the engine as hot as safely possible.

Clearly, by the fact that North American spec Liberty CRDs are being run about 20 degrees cooler than every other market in the world should tell you something is wrong and how counter-productive the EPA's NOx pollution standards are.

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

I don't disagree that the thermostat opens too early for winter situations and that is why I use a winter front but in summer the way I run this vehicle the T-stat functions fine. I typically am on the expressway running 75-80 mph. The gauge is near straight up 12 noon. I have checked it with an IR gun and it tests 195 - 200F.

Jackkep wrote:

I'm imagining thermostat issue and I plan on ordering one tomorrow but I'm making sure there's not something I'm missing. I was never actually able to get coolant to come out of the radiator bleed valve, and the upper radiator hose gets tight and hot but does not feel like it's filled with coolant. If I pull it off while it's running a little trickles through like the bypass valve is working but doesn't seem like the thermostat is opening

My concern is why you don't have fluid coming out the bleed valve and when you remove the upper hose why fluid doesn't just pour out. It should be filled 100%. Thermostat issue or not, this hose should be filled if radiator is full.

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

joelukex4 wrote:

I don't disagree that the thermostat opens too early for winter situations and that is why I use a winter front but in summer the way I run this vehicle the T-stat functions fine. I typically am on the expressway running 75-80 mph. The gauge is near straight up 12 noon. I have checked it with an IR gun and it tests 195 - 200F.

Jackkep wrote:

I'm imagining thermostat issue and I plan on ordering one tomorrow but I'm making sure there's not something I'm missing. I was never actually able to get coolant to come out of the radiator bleed valve, and the upper radiator hose gets tight and hot but does not feel like it's filled with coolant. If I pull it off while it's running a little trickles through like the bypass valve is working but doesn't seem like the thermostat is opening

My concern is why you don't have fluid coming out the bleed valve and when you remove the upper hose why fluid doesn't just pour out. It should be filled 100%. Thermostat issue or not, this hose should be filled if radiator is full.

With the gauge just before straight up you are anywhere between 170 and 210...... if you get over 210 the gauge just climb up way higher than the actual temp.

Seem like they didn't want you to see the fluctuation around the thermostat temp. so you feel at the normal temp range but as soon as it get just a little too hot it exaggerate the real temp.....
So basically a temp gauge for the dumb !!!

I have a obd2 reader onboard as well as a Autometer temp gauge for the record

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

I am a bit late to this conversation, but FWIW here's my recent experience.

I had been seeing cold temps on the factory gauge, and had assumed that a new thermostat was in my immediate future. Then I noticed the temps climbing up a long hill; nothing awful but higher than they should have been. No signs of coolant loss or contamination, so I assumed it was the fan clutch which was still the original. I replaced the fan clutch. Solved the high temps going up long hills, and surprisingly also solved the running at cold temps too!!!

I can only assume that the old fan clutch was stuck in a middle position, half engaged all the time. It spun too much when the engine was cold and not enough when the engine was hot.

In any case a new fan clutch solved both an over and under heating issue.

WWDiesel · **Posted:** Sat Jul 28, 2018 9:43 pm

Steve777 wrote:

I am a bit late to this conversation, but FWIW here's my recent experience.

I had been seeing cold temps on the factory gauge, and had assumed that a new thermostat was in my immediate future. Then I noticed the temps climbing up a long hill; nothing awful but higher than they should have been. No signs of coolant loss or contamination, so I assumed it was the fan clutch which was still the original. I replaced the fan clutch. Solved the high temps going up long hills, and surprisingly also solved the running at cold temps too!!!

I can only assume that the old fan clutch was stuck in a middle position, half engaged all the time. It spun too much when the engine was cold and not enough when the engine was hot.

In any case a new fan clutch solved both an over and under heating issue.

Now that is really interesting....... :shock:

GordnadoCRD · **Posted:** Sun Jul 29, 2018 2:10 am

If your thermostat was working properly, the stuck fan clutch, or even a solid fan, shouldn't be able to cool below the thermostat opening point.

My guess is the heating brought the clutch problem to your attention, but your thermostat is still on it's way out the door.

vwroad87 · **Posted:** Sun Jul 29, 2018 12:53 pm

Interesting thread. I had a cold motor when I bought my jeep. The heater would never really be warm. I replaced the O.E. thermostat with a Hot Diesel billet version. Really nice piece of kit and the jeep runs in the middle of the gauge no matter the conditions. Also if I want to change the temp range of the thermostat it's a very simple job. I opted for a 193F thermostat.

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

vwroad87 wrote:

Interesting thread. I had a cold motor when I bought my jeep. The heater would never really be warm. I replaced the O.E. thermostat with a Hot Diesel billet version. Really nice piece of kit and the jeep runs in the middle of the gauge no matter the conditions. Also if I want to change the temp range of the thermostat it's a very simple job. I opted for a 193F thermostat.

We're also running an HDS Model 001 thermostat for exactly the same reasons, and I'll echo the comments re: build quality (which is exceptional). The cooling system actually turned out to have multiple issues (bad fan clutch, radiator on its way out) which the HDS helped with showing up, but I mean that in a good way - without the thermostat working properly, diagnosing the other problems wouldn't have been as obvious.

One thing related to the above that I'll mention: we ordered ours with the 203°F thermostat. This is fantastic for Winter and Spring, but as we got into Summer I ended up going back to a 193°F unit. We get quite a few 100°F-plus days here, and the 203°F thermostat brought A/C efficiency a little lower in start-stop traffic (even with an 11-blade fan upgrade) than was what I wanted it to be.

There were no issues with overheating, the engine running warm, or anything like that - but I'll leave it on 193°F until probably around Thanksgiving, which will be the cutoff between having good enough weather to replace it in the driveway and wanting faster warm-up times in Winter, at which point the 203°F unit will go back in. It is so nice to now have the option to be able to do that.

snowballs · **Joined:** Sun Aug 13, 2017 4:05 pm **Posts:** 85

Just ordered the HDS thermostat and looking forward to replacing the OEM unit :pepper:

Thermostat issue or air in cooling system?

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