Thermostat Q's

hey
i went into the parts store to get a new thermostat and the one tha tthe guy gave me was a 192* t-stat, im sure this will be fine, just wondering if anyone had any huge problems with my t-stat opeining at 3* sooner than theirs...

Also - My engine seems to be running hot and i am more than a little concenred because i am driving to CA from NE on saturday. I just got full gauges about 1 month ago, so i was never able to see this before, but it seems to be only happening now that there is cold weather.... anyway -
My Cherokee runs at around 210* at 2500 RPM and about 230*-235* idle - then something happens and it will drop. I suspect at that point the T-stat is opening, so im guessing that i just have an old t-stat...

I also got my colant ssytem flushed recently, buy a piss poor shop that screwed mucho stuff up, so i could see them having something to do with this...


anyother ideas?

Whats happening is that it will heat up to about 220-230 and the electric fan will kick on and cool it to 210 and shut off. Ive done alot of stuff to my cooling system and it still does this while sitting at idle, just not as aften or as quick. If im going to be sitting for a while, Ill put the air or defrost on so the electric fan cycles, this keeps it right at 210. Ive never been comfortable with an engine running over 210 but these things seem to do it and they like it.

If you have a 90 or older, you have the awful closed system. The shop probably got air trapped in it, and that is the cycling. T-stat is likely not the problem. Find a way to get the air out of it. Also, don't worry about it if you can't get it out. The engine will be ok running at that temp.

I think hes got a 92

Increased temperature at idle usually means - all thing being equal - a problem with your fan clutch. As for getting the air out, run the front of your jeep offf the curbe so there is a significant rise in the back end of the engine. Slowly unscrew the temperature sensor at teh back of the back end of the engine - On teh driver's side by the corner of the valve cover, however, I am unsure if the 92 is there, mine is an 89 XJ. Do not take it out but rather let it bleed the air out until coolant is flowing out.
BSD

192*? Does it fit? What's the part number? I've been looking for something around 185-190*

The 3*s isn't going to make a huge difference or anything. I ran a 180* for a while. Just didn't get as much heat in the winter, which sucked.

You need to do the things others have suggested. My local radiator shop told me if you heat a thermostat to 225F one time you can damage the mechanism inside. Also you mention the engine gets hotter while at idle.

When you changed instrument clusters you did change the engine temp sensor used by the instrument cluster? On my 88 XJ that sensor in the head back by the fire wall. If you have not changed that then do, you may have a problem caused by a wrong sensor. If you did change the sensor at the same time then....

There two things we need to look at, coolant flow, Heat rejection and air flow.

Coolant flow through the radiator is controlled by the thermostat. No coolant moves through the radiator until the thermostat opens.

Heat rejection is the ability of the heat to be released through the radiator. If you have a 92 and it is the stock radiator then you are due for a new radiator. You most likely have stopped up tubes and not enought coolant can release heat. You may also want to examine your lower radiator hose. The factory hose has a spring in it to keep it from sucking shut when water pump pulls coolant out of the radiator.

Air flow, you say it decent at speed but you get hot at idle. The mehcanical fan clutch is worn out, don't attempt to test, go buy a new one at the parts store. If you have a second vehicle then pull of the fan clutch, remove the fan and take the clutch to the parts store so you will get a new one of idential demensions. Some aftermarket clutches are just not the right size.

Also IF you decide to change the radiator then I'd get new upper and lower radiator hoses at the dealer. I'd also get from the dealer a new thermostat since you cooked the one you have, plus a new radiator cap. The heat most likely has damaged the cap also.

The dealer radiator hoses comes with the antichafe and the lower one comes with a fill length spring to prevent suction collapse.

If you change out coolant then use distilled water instead of tap, at 80 cents a gallon you can't go wrong. Flush out the block with distilled and then add 1/2 the volume with full strengh coolant, then top off with distilled. Run and let them mix.

But at a minimum you need a new fan clutch, a new DEALER therostat, and and a new DEALER radiator cap.

I'm going to buck the trend of a dealer T-stat. I bought one per the advice here and it was a POS made in Mexico by the lowest bidder. Sure it said MOPAR on the box, but it did not work properly.
Replaced it with whatever Stant calls there premium made in the USA model and it has been fine ever since!
(nothing against Mexico or Mexicans, but a POS is a POS, and I like made in the USA when I can get/afford it)

martin said:

You need to do the things others have suggested. My local radiator shop told me if you heat a thermostat to 225F one time you can damage the mechanism inside. Also you mention the engine gets hotter while at idle.

When you changed instrument clusters you did change the engine temp sensor used by the instrument cluster? On my 88 XJ that sensor in the head back by the fire wall. If you have not changed that then do, you may have a problem caused by a wrong sensor. If you did change the sensor at the same time then....

There two things we need to look at, coolant flow, Heat rejection and air flow.

Coolant flow through the radiator is controlled by the thermostat. No coolant moves through the radiator until the thermostat opens.

Heat rejection is the ability of the heat to be released through the radiator. If you have a 92 and it is the stock radiator then you are due for a new radiator. You most likely have stopped up tubes and not enought coolant can release heat. You may also want to examine your lower radiator hose. The factory hose has a spring in it to keep it from sucking shut when water pump pulls coolant out of the radiator.

Air flow, you say it decent at speed but you get hot at idle. The mehcanical fan clutch is worn out, don't attempt to test, go buy a new one at the parts store. If you have a second vehicle then pull of the fan clutch, remove the fan and take the clutch to the parts store so you will get a new one of idential demensions. Some aftermarket clutches are just not the right size.

Also IF you decide to change the radiator then I'd get new upper and lower radiator hoses at the dealer. I'd also get from the dealer a new thermostat since you cooked the one you have, plus a new radiator cap. The heat most likely has damaged the cap also.

The dealer radiator hoses comes with the antichafe and the lower one comes with a fill length spring to prevent suction collapse.

If you change out coolant then use distilled water instead of tap, at 80 cents a gallon you can't go wrong. Flush out the block with distilled and then add 1/2 the volume with full strengh coolant, then top off with distilled. Run and let them mix.

But at a minimum you need a new fan clutch, a new DEALER therostat, and and a new DEALER radiator cap.

Click to expand...

thanks for all the help, but this is happening at highway speed as well, not just at stnad still. By idle i meant the RPM was about 300-500... also at about 3000, the heat sarts rising... A little- then will drop back to 210...

any other ideas? im gonna run to the Jeep "Ram you in the ass AND take your money" dealer and get the t-stat and cap...

Yeah - I like Made in USA too - Stant has always been pretty good to me.

Gimme yer email addy, and I'll pass along a writeup of the cooling mods I've done to my XJ's. Factory op temp is supposed to be about 210-215*, but I've lowered mine into the 180's without any trouble and without any negative smog impact (which is important to the California Air Police.)

FYI - THREE RENIX XJ's - 1987, 1988, 1989. All still have the closed system, and all work well.

5-90

Distilled water, is that just bottled water, or is it labelled distilled? I've always just grabbed the hose and used tap water.

Yech - use either distilled or reverse osmosis-filtered water.

The problem with tap water is that it carries not only the minerals and stuff that comes out of the ground with it, but also any scale and crud it picked up from the plumbing along the way.

Get RO or distilled water, and store it in clean plastic cannisters of some sort with a tight-fitting lid. And, since you've been using tap water, give yourself a swift kick in the backside, then flush everything out and refill with distilled/RO. Make sure you do a good job on the flush!

5-90

This also goes for batteries - they should get nothing but pure water.

I'm going to agree with BSD--check the fan clutch. The 2000 FSM says to test it this way:
(1) Drill a 3.12-mm (1/8-in) diameter hole in the top center of the fan shroud.
(2) Obtain a dial thermometer with an 8 inch stem (or equivalent). It should have a range of -18°-to- 105°C (0°-to-220° F). Insert thermometer through the hole in the shroud. Be sure that there is adequate clearance from the fan blades.
(3) Block the air flow through the radiator. Secure a sheet of plastic in front of the radiator (or air conditioner condenser). Use tape at the top to secure the plastic and be sure that the air flow is blocked.
(4) Be sure that the air conditioner (if equipped) is turned off.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR FAN. DO
NOT WEAR LOOSE CLOTHING.
(5) Start the engine and operate at 2400 rpm. Within ten minutes the air temperature (indicated on the dial thermometer) should be up to 93° C (200° F). Fan drive engagement should have started to occur at between 82° to 91° C (180° to 195° F). Engagement is distinguishable by a definite increase in fan flow noise (roaring).
(6) When the air temperature reaches 93° C (200° F), remove the plastic sheet. Fan drive disengagement should have started to occur at between 57° to 79° C (135° to 175° F). A definite decrease of fan flow noise (roaring) should be noticed. If not, replace the defective viscous fan drive unit.
Of course, I'd skip numbers one and two and just follow the rest. HTH

scott in NH said:

(nothing against Mexico or Mexicans, but a POS is a POS, and I like made in the USA when I can get/afford it)

Click to expand...

It could still be made by a Mexican even if it's made in the USA, so don't count on "made in USA" necessarily being of higher quality. Again, nothing against Mexicans.
XJ_ranger's problem does seem like either a bad thermostat or a clogged radiator. A bad pressure cap/cracked overflow bottle are other possibilities. To check if the t'stat is at fault, start the engine from cold and keep it revving at a fast idle. Put your hand on the upper radiator hose and gently squeeze it intermittently. As long as the t'stat is closed, the hose will feel cool and soft. When the t'stat opens, the hose will suddenly harden and hotten. When that happens, check the reading on the temp. gauge. If it's below 210*, the t'stat is good. If it's 210* or higher, replace it. If the hose is still cool & soft by the time the electric fan kicks in at 220*, you DEFINITELY need to replace the t'stat.

First off I do not work for Chrysler or own stock in the company but part of my real life job involves procurment of military spare parts. First off I'd say to manufacture most themostats, regardless of the manufacturer will cost approximately the same. So why do pay more for some over others. It is inpections, testing, and warranty.

At my job I can not believe what screaming companies make when the requirement is to 100 percent inspect some feature, and record the results. The real bite is that inspections are right up front, nothing hidden.

It a little known fact but by US Law Dealer parts "have to" work. Aftermarket parts "should" work but there is no real legal requirment. Chrylser adds additional inspections to make sure the parts to work, that adds to the cost but reduces the chance of getting a bad part.

Unlike my Buick dealer, my Jeep dealer prices lots of items competitively with the big box stores. I got a set of dealer spark plug wires for my 88 XJ, cost $31.00, and they fit & worked. I have seen wires costing twice as much at the parts stores which I still feel suspect about.

I agree Stant a good company but countless posts on here about burping the air out of the engine is complicated by a themostat without the bleed hole in it. The Stant thermostat does not had the bleed hole, the dealer one does. Also the dealer thermostat comes with a very nice gasket, you still have to buy a gasket when you buy an aftermarket themostat so you need to add both of those prices together to compare to dealer prices.

The thermostat is a component that can toast your engine if it sticks shut. I will spend the $8-$10 for a dealer themostat, it will work and if it does not it has a 12 month/12,000 mile warranty. I really don't car where the component comes from as long as Chrysler is standing behind the warranty.

Also with radiator caps on my XJ, I'l go with a dealer cap. I have the pressure bottle still on my 88 XJ so it is the only place I can buy the cap without the bottle.

I have learned the hard way, if the engine gets hot then change the themostat AND the radiator cap. Both are damaged by high temps. You can change both for less than a $20 bill with dealer parts.

Now that there been more added to this thread I agree Ranger needs a cooling system renewal - radiator, hoses, fan clutch, themostat, radiator cap and might as well through in new heater hoses. Just imagine if he did not install gauges he'd still be drivng around with this "problem".

ok,
Replaced the T-stat and Cap, filled with Distilled Water and radiator fluid, bled system and all is good. Drove all the way from NE to CA at 210*... Till the front driveshaft blew up... garbage...

anyway - thanks for all the help, wanted to make this thread complete, so if others find it, they know how it worked out....

I did have a new water pump put in, and know that i need to do the hoses soon, but dont have the cash right now. The radiator is fine, had it flushed AGAIN and they said that it would be good for a while - looked inside with some camera or somehin' Want to upgrade when i get a new one anyway... dont have the cash... Just droped 535.25 ar Rubicon Express for a new driveshaft and upper control arms...