I read this thread and I think I found my answer but I am gonna throw my question out here anyway.

I just flushed my cooling system with a cleaner, replaced the thermostat housing, t-stat, and temp sensor. I bought a 195 degree t-stat from Auto Zone with the fail safe.

After putting it all back together, adding coolant and burping it, my temp runs hotter now than it did when the radiator was full of muddy looking coolant.

What gives here? At idle it gets up to around 225-230 degrees. Maybe at tad higher at one point. It was staying at around 210.

 

Forgot to mention I changed the hoses too. Not sure why it is running hotter now than before.

 

Did u replace the rad? Cleaner could have crudded/clogged the old one good. Did u "burp" the cooling system? If it's actually hit 230, I would check the t-stat 'cause it could be "locked" open......might as well not have a t-stat then.

 

I did not replace the radiator. But after flushing the system I pulled everything back apart and hosed it out as directed on the bottle of cleaner.

I had the two radiator hoses off so I stuck the hose in the upper radiator opening and flushed it out where it came out the lower end. I did not see any crud or goo coming out. The water was pretty clear when I started flushing.

What happens if I pull the t-stat out? Any chance of damage to the motor?

I think I burped the system correctly. I filled up the radiator and reservoir, left the radiator cap off and cranked it up. I watched the system letting air out as it ran and also the level dropped as well so I added coolant as needed until all the bubbling quit and the radiator was topped off. Did I do it right?

 

Did you turn the heat on? a lot of people forget this.

 

On '97 up turning the heater on shouldn't be necessary as coolant flows thru the heater core as soon as the engine starts (no heater control valve on '97 up). A properly functioning t-stat needs to be installed. How old is the rad? Rads have very small passages that can easily get plugged. Flushing water thru simply tells u it's not 100% plugged......but is it maybe 50% plugged? Who knows, only a radiator shop can tell.

 

The cherokee I was working on is a 96. It has the heater control valve. I think I ran the heat when I was burping it. I can't remember for sure. Seems like I would have because I ran it when I used a flushing cleaner.

I just drove it down the road and back about a total of 10 miles and after getting warmed up it stayed at 210 right in the middle all the way there and back. Strange thing is as soon as I pulled in the driveway and put it in park I let it idle a few minutes just to see what would happen and it did go up to about 220 I am guessing but it held there and did not go any higher so I think it is okay.

Not sure what is going on. I will keep an eye on it.

By the way, I put a brand new t-stat in when I was changing the fluid so it should be fine. I did think of one thing though. Is it possible to put the t-stat in wrong? I did not look to see how the other was in when I took it out. So I took my best guess and put the spring looking part inside the engine block. There was a saddle looking piece on the front and I think it was horizontal when I put it in.

I know that sounds stupid and if everyone rags me for asking if you can put the t-stat in wrong I can take it!

 

Sounds like u put the t-stat in correctly, spring side in the head (not block). I'm not a big fan of so called "fail safe" t-stats......they're a gimmick, IMHO. Never seen a regular t-stat fail in the open position.....it's when they fail in the closed position that causes problems, so what guarantees a "fail safe" t-stat will open. A motor needs to warm up quickly to correct operating temp 160F+. If the "fail safe" t-stat locks open (fails), warm up takes longer and u probably won't discover somethings wrong 'till next winter (no/weak heater).

 

I felt like I had it right. I was just reading up on how the whole cooling system works as I had no clue. Now I understand what the purpose of the t-stat is and how the whole system works.

If what I read is true, I guess the engine operates more efficiently at higher temps so if mine does not get much above the 210 mark I guess it is alright. It seems to stay at 210 when you are driving and getting air flow to the radiator.

 

Do u have access to a infrared point-n-shoot temp gun? Point it at the t-stat cover to verify the dash gauge (they're known inaccurate). If it should overheat, check the t-stat to see if it "locked" open.

 

I can see if I can get my hands on one. The t-stat is brand new. I don't think it is locked open.

Wouldn't it run cooler if it was locked open anyway? It would be the same as not having a t-stat basically because coolant would be flowing through the engine and the radiator with it open.

If I understood what I read correctly, when you first crank up the cold engine, the t-stat stays closed letting no coolant to the engine so it will heat up quicker. Then once heated the t-stat opens so coolant can flow to the engine, thus cooling it down.

I don't know, maybe I am not understanding something.

 

If locked open, it will run cooler/cold in cool/cold ambient temp and that really when it needs to warm up quickly. When the t-stat is closed, coolant re-circulates thru the block/head, When the t-stat opens, coolant flows from the block/head, thru the rad (to be cooled) and back to the block/head.

A t-stat opens/closes very slowly and "hovers" between full closed/full open, depending on various conditions.

 

I will see if I can get my hands on an infra red temp gun. I reckon Auto Zone may sell them? If they are not real expensive I may just buy one. I can always use it.

When you are sitting at idle for several minutes does your temp gauge move above the 210 mark? And I mean more than just a hair.

I drove my 2000 up the road to get it heated up then came back and let it sit in the drive idling for about 5 minutes. The temp stayed at 210 for the most part. It might have moved just a hairline above but not like the 96xj.

I may be worrying for nothing. It's not like the temp on the 96' is getting anywhere near the red zone on the temp gauge but I am curious as to why it runs a little warmer at idle than my 2000xj.

 

Virtually any water cooled engine will run a little warmer while idling.....that's when the least amount of air is flowing thru the rad and removing heat. At speed, rad fan(s) aren't needed as plenty of air flows thru the rad. Slow/no vehicle speed, high ambient temp etc. is when any vehicles cooling system must be in top notch shape (all components).

We've got the best of both worlds in our XJ, bright red warning lights that get your immediate attention AND a digital ScanGauge to see any gradual changes. It'll be several more months before we see regular 200F readings. We have momentarily seen temp creep to 230....stopped 30 min in bumper-2-bumper heavy traffic, 100+ degree ambient, on hot black asphalt pavement, a/c chillin'. Once moving, temp will drop to under 200 (180 t-stat).

The infrared temp gun is handy as a pocket on a shirt and they can be had for about $25.

 

just dont run a thermostate it will run between 150-180 all the time witch is cold for a jeep the only down side to bypassing your thermostate is you loss you heater