the varied price of thermostat replacements

foxhunter · **Posted:** Mon Jan 30, 2017 2:40 am

they seem to run from reasonable to stupid. prozone 35.00 shipped with 2 year warranty and trustbuilt for the same price, up to 434.00, a misprint I think. and then you have crown which everyone say's stay away from.

jws84_02 · **Posted:** Mon Jan 30, 2017 8:36 am

Stay away from any of the "cheap" ones. Those ones you mentioned I'm guessing are crown clones. Oem should be around $115.

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

Get the real thing right away. A servicable thermostat housing, home made or the HDS model 001 , and get your engine running at a real diesel temperature and change your thermostat for 10$ in 15minutes.

I now have the HDS in 2 CRD and don't regret it ! I run 203F in my Jeep this winter and it's some really nice heat :SOMBRERO:

will probably go down to 190F this summer !

Ceearedeedriver · **Joined:** Fri May 06, 2016 8:44 pm **Posts:** 177

I note from your original post that you're price sensitive. If you have the skills and equipment or access to someone who can do it for you then modding you're OE housing is a no brainer. Failing that, the #2 choice would be simply sticking in a new OE housing.

foxhunter · **Posted:** Tue Jan 31, 2017 9:33 am

i'm waiting on a dead thermostat as we speak, just have to figure out how to get it apart. I know it's a 2 piece unit and there is a lip of some sort. I have heard chisel and dramel both can be used. to many years of spending 10.00 or less to replace a thermostat. maybe there was no other way to design this thing but I doubt that.

after a gde tune, lift pump, new silicone hoses, new glow plugs, 4 new tires and new cps all in the last 90 days, I guess I might be flinching at prices now, just a little.

not my first rodeo. 1947 cj2a with a mod or 2. buick 225 v6, dana front and rear 4:10 ratio

Ceearedeedriver · **Joined:** Fri May 06, 2016 8:44 pm **Posts:** 177

foxhunter wrote:

i'm waiting on a dead thermostat as we speak, just have to figure out how to get it apart. I know it's a 2 piece unit and there is a lip of some sort. I have heard chisel and dramel both can be used.

I've done 4 of them. I cut through the lip with a junior hacksaw and once about through just snap it off. The rough edge can then easily be filed down with a hand file. It takes about 15 minutes once you know what you're doing.

ATXKJ · **Posted:** Wed Feb 01, 2017 6:45 pm

if you have a dead unit to play with

http://www.jeepkj.com/forum/f228/diy-serviceable-thermostat-59804/

foxhunter · **Posted:** Wed Feb 01, 2017 7:08 pm

thanks but beyond my mechanical ability.

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

either way you choose to go having a servicable unit is the way to go !

very nice CJ2 by the way :wink:

foxhunter · **Posted:** Wed Feb 08, 2017 10:17 pm

[quote="Ceearedeedriver"][
I have the dead unit, after looking at it i'm guessing you are referring to cutting at the back of the crimp????? how did you put it back together? I've seen jb weld mentioned>
thx

Ceearedeedriver · **Joined:** Fri May 06, 2016 8:44 pm **Posts:** 177

foxhunter wrote:

I have the dead unit, after looking at it i'm guessing you are referring to cutting at the back of the crimp????? how did you put it back together? I've seen jb weld mentioned>
thx

Yeah, there's a line around the housing where the crimp is formed. Make your cut around (just above) this line. I did Sarge's mod linked to a few posts back. This involves turning a couple of flanges and welding them onto the housing. These are then used to fasten the two halves back together.

I know others have used JB Weld to join the two halves back together when they've just been gutting the internals to use with an inline. Personally I'm neither fond of JB Weld or the inline option.

foxhunter · **Posted:** Thu Feb 09, 2017 9:02 pm

getting mixed messages about the inline t-stat, some say gut and use the inline others say it will crack the head. it would be interesting to know how many inlines are out there and whether the housing was gutted or not and what percentage of those had a cracked head.
one post kind of explained how the t-stat works with the bypass closing when the main opens. I have this one apart but i'm not sure which outlet is the bypass and which does something else.

here is what I have so far. note the hole in the t-stat with a check ball in it, didn't expect that.

there was an oring inside the crimp, makes sense.

everthing fits back together just fine.

I did drop the t-stat in a pot of water on the stove, all I saw was the center shaft slowly move out about 3/4 of an inch.

flash7210 · **Posted:** Thu Feb 09, 2017 9:35 pm

The bottom part of the thermostat is the bypass.

I did the inline thermostat and had a cracked head.
Some have had the same experience as me.
Others are still using the inline and have not had any cosequences.

IMO, if you are unable to make a modified thermostat housing then either buy the HDS model or a factory replacement.

Ceearedeedriver · **Joined:** Fri May 06, 2016 8:44 pm **Posts:** 177

foxhunter wrote:

getting mixed messages about the inline t-stat, some say gut and use the inline others say it will crack the head. it would be interesting to know how many inlines are out there and whether the housing was gutted or not and what percentage of those had a cracked head.

The mixed messages is because everyone has an opinion and no one knows the real answer. Yeah, a proper study would be nice but that is never going to happen. The data we currently have is too little and too distorted to be statistically relevant.

What we do know is that either inline option, with or without the OE gutted, both significantly change the system behaviour and how the coolant flows through it. How the flow is divided between radiator and bypass is the main difference. Without proper analysis and testing these have got to be the higher risk options but the level of risk is totally unknown. We also know that cooling system failure or poor design poses a high risk for overheating and head failure. Are you prepared to take on this unknown level of risk?

foxhunter wrote:

I did drop the t-stat in a pot of water on the stove, all I saw was the center shaft slowly move out about 3/4 of an inch.

That shaft you see moving pushes against the upper housing. You need to have it installed in the upper housing to see the valve open. If you place the whole upper half, as you show in your second pic, in water you will see it opening.

Given your stated mechanical ability and price sensitivity it would appear that a replacement OE stat is your only real option.

WWDiesel · **Posted:** Fri Feb 10, 2017 11:07 am

flash7210 wrote:

IMO, if you are unable to make a modified thermostat housing then either buy the HDS model or a factory replacement.

A very profound and realistic statement of which I think most would agree! :!:

An inline thermostat due to the way this cooling system flows and operates is not really a viable option along with a known history of possibly causing a cracked head or blown head gasket....

As Ceearedeedriver stated, a study would be nice, but I do not think it is necessary since some things have already been established to wit!

The bypass function of the OEM designed thermostat is a very important component of the coolant flow through the head during the warmup period of operation and cannot be duplicated simply by adding an inline thermostat valve in the top radiator hose!!!

An important design fact to understand: With this particular bypass design, the thermostat as it heats up and moves from fully closed (bypass fully open), to an open position of some amount to maintain coolant temperature at the desired setpoint (bypass partially or fully closed) maintains a proportional flow through the head at all times regardless of it's position. As the top part of the thermostat valve opens, the bottom part bypass valve closes off in direct proportion until it is fully closed and the majority of the flow is directed to the radiator with some small amount going to the heater core via the viscous heater.

Problems with an inline thermostat as I see it:

This synopsis may not be all-inclusive, but I believe it covers the majority of the important points to consider before installing an inline thermostat....which I simply would not do on this vehicle due to it's cooling system design! :roll:

Ceearedeedriver · **Joined:** Fri May 06, 2016 8:44 pm **Posts:** 177

Good synopsis of the inline situation WWDiesel. Liberal use of words like "may", "could" and "suspect" relay the level of uncertainty in the absence of proper analysis and measurements which, I think is fair to say, implies an unknown level of risk.

I believe the most common configuration for the inline thermostat is to leave the failed OE housing intact. One other point to note about this configuration is that the unknown level of failure of the OE stat will likely change with age. When you initially install the inline the OE thermostat may be stuck partially open (bypass partially closed) and after some months/years may end up stuck fully open (bypass fully closed) all the time. This change may take you from a situation where the inline works fine to one where it is at high risk of overheating because there is insufficient flow during warmup. This could explain why there are a number of owners here that have run inline thermostats without issue for many thousands of miles.

WWDiesel · **Posted:** Fri Feb 10, 2017 12:18 pm

Ceearedeedriver wrote:

Good synopsis of the inline situation WWDiesel. Liberal use of words like "may", "could" and "suspect" relay the level of uncertainty in the absence of proper analysis and measurements which, I think is fair to say, implies an unknown level of risk.

I believe the most common configuration for the inline thermostat is to leave the failed OE housing intact. One other point to note about this configuration is that the unknown level of failure of the OE stat will likely change with age. When you initially install the inline the OE thermostat may be stuck partially open (bypass partially closed) and after some months/years may end up stuck fully open (bypass fully closed) all the time. This change may take you from a situation where the inline works fine to one where it is at high risk of overheating because there is insufficient flow during warmup. This could explain why there are a number of owners here that have run inline thermostats without issue for many thousands of miles.

A very good additional point indeed that I had not considered, Thanks for pointing it out!
And I totally agree, and that was my intended objective point, that installing a inline thermostat is very simply not a good idea or worth the risks based on what we now know or do not know for sure.... :roll:

flash7210 · **Posted:** Fri Feb 10, 2017 2:37 pm

WWDiesel wrote:

2. OEM thermostat housing gutted & valve removed. -- Until inline thermostat starts to open to allows flow to the radiator, all flow is directed through the bypass circuit and heater core circuit. But without a bypass valve in the circuit to control the flow, the flow through the bypass circuit is continuous regardless of the position of the inline thermostat valve. The coolant flow in this case will always take the path of least resistance,
and I fully suspect the bypass from the thermostat housing to the water pump suction would always be the path of least resistance....
So in this case, the inline thermostat may never see the true temperature of the coolant since so much of the flow is traveling the bypass circuit, but the head will certainly be exposed to it...

On this point I disagree.
Mainly because the outlet to the radiator is larger making it the path of least resistance.
But also because many older engines operated just fine without a valve to block the bypass.
Yes, I know, just because grandpa did it this way doesn't mean its the best way.

None the less...
Because I know cylinder head temp might be a concern, I added a temperature sensor to the head.
Its a cheap sensor, just stuck to the surface of the head between cylinders 3 and 4. But it has provided me some good data about cylinder head temperatures under a variety of operating conditions. And I chose that location for the sensor because it is farthest away from the thermostat outlet.
For example:
1. While cruising at about 65mph, 1900rpm, head temperature is on average 20 deg F cooler than coolant temperature. This has been consistent under a variety of conditions, both summer and winter.
2. After cruising at 65 and then coming to a stop, just idling, head temp will rise to within 1-5 deg F of coolant temp. Again, this has been very consistent, both summer and winter.

What those two things tell me is that at higher rpm there is greater coolant flow and that the coolant is doing its job pulling heat away from the aluminum head.
Then, while idling at a low rpm, there is less coolant flow and the head temp will become near equal to coolant temp. (let it idle long enough and the temperatures will equalize)

So I guess I am the test subject for this type of thermostat setup (gutted + inline) and if anything goes awry I will definitely report it.
Until then we can just agree to disagree

This pic was taken on a cool spring morning after a 20min drive to work and idling in the parking lot:

joe_ · **Posted:** Fri Feb 10, 2017 6:00 pm

flash7210 wrote:

Because I know cylinder head temp might be a concern, I added a temperature sensor to the head.
Its a cheap sensor, just stuck to the surface of the head between cylinders 3 and 4. But it has provided me some good data about cylinder head temperatures under a variety of operating conditions. And I chose that location for the sensor because it is farthest away from the thermostat outlet.

I've noticed in the parts catalog PDFs it shows a temperature sending unit where we have that threaded plug on the intake side of the head between cylinders 3 and 4, and no sending unit on the thermostat housing. I've thought of adding one there to see the temperature difference. Thanks for the info!

WWDiesel · **Posted:** Fri Feb 10, 2017 10:44 pm

flash7210 wrote:

Mainly because the outlet to the radiator is larger making it the path of least resistance.

With all due respect, I am not sure this statement is quantifiable without some sort of measurement devices to determine actual flow rates through the two different coolant routes.
Even though the radiator outlet and hose is larger, I believe the radiator itself would act as a higher restriction to flow rates with all its small flues (sort of like a bunch of small orifices) versus the bypass hose that goes back to the water pump suction which has little or no restrictions. That is why the two hoses are so much different in size! But my opinions are certainly subjective without data to back either probability up...but at this point all probabilities are purely subjective without hard data to back them up...

At this point, I still would not recommend anyone to install an inline thermostat based on what I know now, but that is my opinion...
If you want to install one, do it, but be willing to suffer the consequences if bad things happen.... :2cents:

the varied price of thermostat replacements

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