Overcooling....engine's too cold

[87manche]

to check the t-stat start the motor, then go and put your hand on the upper radiator hose.

It should not warm gradually. If it does the stat is not closing. When it opens the hose should get very warm, very suddenly, that's when the stat is opening.

 

[Crawler]

Good advice on the fan-clutch. Sounds a lot like the results I got when trying one that had been drilled and bolted so as not to slip. You might also want to try turning your heater completely OFF, as well... ;^]

Seriously, those high performance t-stats open a tad too much when they open and can definitely give you a lower reading or "swing". They're great in the desert, but OEM would have been better in your coastal environment and I'll bet would go a long way towards solving your problem. It's also remotely possible your guage is only inaccurate at the lower end. Mine was off at only the higher end, showing the auxilliary fan coming on at 225*-230*. Drove me nuts until I laser-thermometer checked the system.

DO keep us posted... ;^]

 

[dutchjeep]

Good advice on the fan-clutch. Sounds a lot like the results I got when trying one that had been drilled and bolted so as not to slip. You might also want to try turning your heater completely OFF, as well... ;^]

Seriously, those high performance t-stats open a tad too much when they open and can definitely give you a lower reading or "swing". They're great in the desert, but OEM would have been better in your coastal environment and I'll bet would go a long way towards solving your problem. It's also remotely possible your guage is only inaccurate at the lower end. Mine was off at only the higher end, showing the auxilliary fan coming on at 225*-230*. Drove me nuts until I laser-thermometer checked the system.

DO keep us posted... ;^]

Yep, I also thought that maybe the gauge may be accurate only in a range, but not calibrated correctly.

I did have and OEM stat in there before, and I thought it had stuck open (I had the same problems and it all looked so much like a t-stat stuck open). So then I thought I'd be an idiot to try and save a few bucks on a cheap t-stat so figured if I was going to replace it I might as well throw in a high-performance stat. I thought they were supposed to be more accurate and keep the temp closer to 195.

Will check the clutch, will feel the upper hose to see what that t-stat is actually doing, and will try to verify the measured temps somehow.

Will definitely report back.

 

[J-Roc]

High jack, ok here is my piss poor photo chop...

That yellow line is the average temperature that my 96' runs at... is that TOO cold? If I put my heater on it will drop almost damn close to the first 1/4 marking, just slightly above...

Now whats confusing the hell out of me is...I'm not running a fan shroud so temps should technically be warmer...I have water wetter in the rad but it shouldn't make that big of a difference should it? My Tstat is a brand new 195

 

[Blaine B.]

In the coldest of days in the winter mine will just sit a hair below 210. Once it is warmed up, of course.

Stays the same in warm weather too.

 

[dutchjeep]

High jack, ok here is my piss poor photo chop...

That yellow line is the average temperature that my 96' runs at... is that TOO cold? If I put my heater on it will drop almost damn close to the first 1/4 marking, just slightly above...

Now whats confusing the hell out of me is...I'm not running a fan shroud so temps should technically be warmer...I have water wetter in the rad but it shouldn't make that big of a difference should it? My Tstat is a brand new 195

Mine is even a little colder (on the gauge) and I am not running a shroud either. My wife's got the XJ out this week so haven't been able to check those other things yet.

 

[Blaine B.]

Make sure your coolant resivoir return hose is tied out of the way of the mechanical fan blades.........running without a fan shroud makes these easy to contact eachother

 

[dutchjeep]

Make sure your coolant resivoir return hose is tied out of the way of the mechanical fan blades.........running without a fan shroud makes these easy to contact eachother

Coincidently, I started thinking along these lines when I was working on the P/S pump bracket two weeks ago. To ease my concience I added a tie rip to that hose to make sure it would be less likely to end up in the grinder. Looks a lot safer this way!

Will be replacing the radiator this summer and figured I might as well throw in a new shroud while I am at it:roll:.

 

[Blaine B.]

Yea, that's what I did too when I didn't have a shroud for a few weeks......just a ziptie on the hose to the upper radiator cover on both sides of the mechanical fan kept it out of the way.

 

[dutchjeep]

Ok, just reporting back. In a nutshell:

1) replaced waterpump (was leaking) + t-stat (for no particular reason other than that it is convenient to do when the w-pump is replaced).
2) after that engine temps too low (160 highway, 170 city with 60-65 ambient outside temps), symptoms resemble t-stat malfunction.
3) replace t-stat with Mr Gasket high-performance t-stat (original replacement was standard stant); I always use 195 degrees t-stats.
4) temps again low (same as before)-> concluded: it's not t-stat (just replaced).
5) post , re-burp, change temp-sensor, check fan-clutch, think deep....
6) ran out of fantastic scenario's and back to t-stat, must be t-stat (although statistically mysterious)
7) Today replace t-stat with dealer OEM t-stat......voila, temps are great nice around the 200, just where they should be!!

I'm clueless how I could have had two malfunctioning t-stats in a row but its seems that way after all. I did test that MrGasket in a pot of water on the stove and it seems to work reasonable, but for some reason it performed poorly in the Heep. Anyway, this is just to give you guys a heads up on progress. If you have any thoughts on the t-stat mystery let me know!

Tim

 

[Blaine B.]

I wonder why that is.

I mean, water temp is water temp, right? If there are 2 correctly functioning thermostats, nothing should be different....right?

Still confusing. See what Mr. Gasket has to say about this.

 

[dutchjeep]

Didn't have an accurate thermometer in the pot, just noticed that the water was almost at boiling when it opened. Seemed reasonable. Will do some oven-testing when I get a change.

I've thought also about maybe something wrong with installing it. Maybe not placed correctly in the engine block or somehow the water manages to bypass the t-stat os's(impossible, right?). As I said I've contemplated some fantastic scenarios just because I believe(d) too firmly in the concepts of statistics (my believes have been thoroughly shaken:laugh3. However, when I took the t-stat housing off today, everything seemed to sit fine; little hole in the 12'o clock position and nice an tight in the engine block. I'm just clueless....but happy that the Jeep is warm-blooded again.

Tim

 

[Blaine B.]

Sounds like the thermostat was opening at the round-about correct temperature....as water boils at 212'F.

So it shouldn't have caused your engine to run cool!

Wow....this is strange.

 

[dutchjeep]

It is really strange. I agree. It's been mind-boggling for me too. Will report back if I happen to run across any acceptable explanation for this.

 

[techno1154]

I had the same problen a few years ago. I tried the high priced thermostats then the low priced thermostats. They all had widely fluctuatung but mostly low temperature. The OEM from the stealership put things on the mark.

 

[Blaine B.]

My Stant superstat thermostat never fluctuated.....but I believe it is "bad" as my Jeep will get up to 235-240 degrees when on the highway!

Always stays at 210 around town. But lately on the highway it's getting hot.....

 

[XJPhoenix]

My Stant superstat thermostat never fluctuated.....but I believe it is "bad" as my Jeep will get up to 235-240 degrees when on the highway!

Always stays at 210 around town. But lately on the highway it's getting hot.....

This might indicate another problem other than the thermostat...

Lower hose collapsing under high-rpm suction... Partially blocked radiator... Other folks will have better info than I.

 

[Blaine B.]

Yeah, I'm going to make sure it's something before I tear into it.

I don't exactly FEEL like loosening the 10 or so bolts on the power steering pump to loosen the belt and then replace the thermostat to find out it didn't make a difference....lol! What a retarded tensioner, I tell ya.....heh!

My new lower radiator hose doesn't have a spring....

But I never had this problem before. And I've had that hose on since October....

Besides that, the origional hose on the Jeep didn't have the lower spring either. I've had the Jeep since September of 05 and never had the lower hose collapse. AND the older hose was more spongy/flexible from age, as I do believe it was the origional.

So I'm probably putting "collapsing hose" at the end of the list as a cause to this issue.

 

[MidlandXJ]

i have changed my water pump, t stat, flushed the system and my temp, just barely goes past the 40 mark,