Missing T-stat?

I know I need to go look, but maybe you guys can help me figure this out..

My girlfriend's 98 XJ takes FOREVER to get up to operating temp (it can take more than an hour of driving), yet my 00' XJ heats up to operating temp in 10-20 minutes just idling in the driveway. I think the t-stat may be stuck open or missing.. The dude she bought it from was missing a couple teeth and drilled a hole in the exhaust :roflmao:"cuz it soundz coo":roflmao: so it wouldn't surprise me if he removed it because of cooling problems...

Opinions? :confused1

Dont complain about previous owners... you literally bought their refuse... you signed on. If hes an idiot, and you bought a car he worked on, what does that make you? =)

But yes, its common practice to remove thermostats... they get left out sometimes.... If what you say is true, lets hope this is your only P.O. problem.

Double post...

I know that I have to deal with the PO's ghetto-rig fixes, "upgrades", etc. I just discovered that her corners are cut-n-folded earlier tonight, at least he did that right! I also had to replace his 'cold air intake' which was a filter on the end of the intake.. The stock box performs better, lol. I also patched the whole in the exhaust, replaced the clutch, and I'm sure I'll discover more crap wrong with it down the road. It's a good thing this XJ was only $1300!

What is the coolant temp on your dash gauge? Cab heat is simply a product of that coolant temperature. So let that be your guide.

But with any "new-to-you" vehicle, basic maintenance including a complete coolant flush and a new quality thermostat (Jeep or Stant SuperStat 195 degree) is money well spent.

As well as a wholesale replacement of all other fluids. They're the lifeblood of your vehicle....

When my factory t-stat failed, the Jeep temp gauge registered halfway between 100 and 210.(40 degree weather here) Cabin heat wasn't very strong. When I removed it, it looked normal and was in the closed position. Swapping it, fixed the problem.

Ronbo said:

When my factory t-stat failed, the Jeep temp gauge registered halfway between 100 and 210.(40 degree weather here) Cabin heat wasn't very strong. When I removed it, it looked normal and was in the closed position. Swapping it, fixed the problem.

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That's basically the same, she really has to push to get it to go above that mark. The heater takes forever to start working, and when it does it's pretty sub-par. So far it has new oil and I have the fluid to do the Diffs. The coolant was flushed and replaced pretty soon before she bought it, he had records.

Pull the thermostat housing and either replace the tstat, or put one in if it's not there. Bring it up to temp at idle and keep a close eye on the gauge. If it acts normal and stays at normal temp, go for a short drive, but not too far from home in case something goes wrong in a hurry. If it was removed to "cure" a problem, you may find out pretty quickly.

Running cold like that for that long isn't good at all for everything else. You're still running in open loop and not getting into closed loop when the engine warms up. This means you're running rich (bad mpg's and hard on the engine in general really).

Sidenote on open loop: Mine will switch to open loop with water temps as low as 60*. I think it's based on the O2sensor heater or something, because my junk is in open loop within a minute and a half from a cold (~30*) start. But yeah, it will run richer than normal, and that isn't a bonus.

Since we are on the topic of T-stats I have a question. I have read somewhere that you want to position the bleed hole at the 12 o clock position. Also drill a small hole in the 3 o clock position. Can anyone verify if this is true?

I am using only the factory stats now with the "jiggle valve". I had 2 Stant superstats fail on me by opening too early, one with a hole drilled at 12 o'clock and one not.

The tstat is one of the easiest jobs on the XJ. Its just two bolts and the tstat + gasket will run you less than $20. Do not use the included gasket unless you want your housing to leak. Buy a fel-pro one and don't even worry about using any additional sealant. You want a tstat in there so do it sooner than later since winter is almost in full force.

I've got the superstat myself because I fear it sticking closed again, but I totally understand cruiser54's thinking on OEM parts only. As simple as some things may appear, I trust the original factory parts more than aftermarket for some things. A lot of engineering went into those parts.

hubs97xj said:

Sidenote on open loop: Mine will switch to open loop with water temps as low as 60*. I think it's based on the O2sensor heater or something, because my junk is in open loop within a minute and a half from a cold (~30*) start. But yeah, it will run richer than normal, and that isn't a bonus.

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Yep .... ... heated 02 sensors are used to get into "closed loop" ASAP. From a cold start ... about 60* happens to be the coolant temp it occurs.

A lower running temp will cause a slightly richer fuel mix ... as the PCM selects one of the fuel mappings based on all the sensor inputs ... but the running temp should need to be regularly, at or below about 160* to really notice a difference.

160* is about the "warmed" temp the PCM is looking for .... its in the FSM. If I recall correctly ... some of the post 2000 models list 170*.

Dirt Yota said:

Since we are on the topic of T-stats I have a question. I have read somewhere that you want to position the bleed hole at the 12 o clock position. Also drill a small hole in the 3 o clock position. Can anyone verify if this is true?

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The general idea of the jiggle pin is to help with air pockets in the head before the thermostat opens - at whatever temp setting its rated for .... so 12:00 is generally the best spot.

Drilling an additional hole any where below 12:00 ... just turns a 195* t'stat ... or whatever temp rating ... into a slightly lower operating temp thermostat/prolongs warmup minutely/provides a minimal degree of additional coolant flow ..... Can be usefull - depending on driving circumstances.

space_monkey said:

I trust the original factory parts more than aftermarket for some things. A lot of engineering went into those parts.

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... as long as what they are selling is still being made by a thermostat manufacturer - to the original specs ... if there were any .... And not just mopar repackaging, whatevers available on todays market.

Carves: Don't forget the MotoRad thermostat you recommended to me that O'reilly's carries here in the states.

cruiser54 said:

Carves: Don't forget the MotoRad thermostat you recommended to me that O'reilly's carries here in the states.

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Yeah wouldnt be any harm in putting them on the shopping list option ... been happily using em for a long while in lots of different vehicles ...

Only ever had one , maybe two, that were iffy from new. Down here we get the premium versions tho ... not the economy versions.

I noticed stant do a premium and an economy version of the same stats as well .... Id be avoiding "economy" versions i think ... brand regardless.

I've had 2 of the stant premiums fail. I'd like to get a look at the MotoRad stat.

My favorite are stats purchased directly from Jeep. Their OEM stats are excellent quality and have the jiggle valve.

Never a fail with those in 38 years......

I think I like the term "jiggle valve". Who came up wth that?

You just get up Tom?

Maybe it's just me, but I use regular stant tstats...never had a failure either. Only issue i've ever had was somebody, somewhere, put the wrong thermostat in the wrong box. Meaning, the part number on the box was correct for the Jeep, but the tstat in it was wrong. Didn't realize it till I put it in and started having overheating problems...in the middle of January when it was 20 degrees outside.

Once I got the correct tstat, and held the two side by side, you could just barely see the difference in the two. The wrong one was just a tick smaller than the correct one. No clue what it was for, or when it was supposed to open. All I know is it opened later than needed for the Jeep as I would get up to 225 on the initial warm up from a cold start before the tstat opened up.

UNCC_99XJ said:

Only issue i've ever had was somebody, somewhere, put the wrong thermostat in the wrong box. Meaning, the part number on the box was correct for the Jeep, but the tstat in it was wrong.

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I blame the parts guy who sold it to you:roflmao: