Two Qiuckie Questions

AngryDog · Jan 21, 2005

1). What temp should I be getting from my 1989 XJ? I changed my thermostat and refilled the rad. I burped the system well. I am pertty fairly sure there is no air in the system. I am running about 165 degrees and it doen't seem to want to go any higher, even setting in the grage idling.

2.) I have to replace the missing bumpstops on the rear frame above the axles. I went to the parts store to get them and it seems there are two options. 53mm and 74 mm or about 3 1/2 or 5+. Is the smaller stock with no lift and the lager for a lift or do I have to make a choice?

shawn_c · Jan 21, 2005

AngryDog said:
1). What temp should I be getting from my 1989 XJ? I changed my thermostat and refilled the rad. I burped the system well. I am pertty fairly sure there is no air in the system. I am running about 165 degrees and it doen't seem to want to go any higher, even setting in the grage idling.

2.) I have to replace the missing bumpstops on the rear frame above the axles. I went to the parts store to get them and it seems there are two options. 53mm and 74 mm or about 3 1/2 or 5+. Is the smaller stock with no lift and the lager for a lift or do I have to make a choice?

#1. I dont think there is anything wrong with it running colder like that. Mine seems to hover around 175 or 180......

2. Sorry I dont know. If your stock I dont think I would worry to much about the bump stops, unless your running a taller tire and gettin your tire into the body?

Digger87xj · Jan 22, 2005

1. it should be running about 200 on the guage... I suspect the sending unit has gone bad. it sits in the rear of the head on the manifold side. They run about 25 bucks for a new one.

2. the larger of the two is most likely for towing or the up country edition. If yours is lifted, get the larger one.

JEEPZZ · Jan 22, 2005

My 87 Renix XJ never get much past 170 and I've had it since 91.
My 97 XJ runs at 200-210 which is normal for OBDII vehicles. 2 different systems that are worlds apart.
I say your good to go.

Pete M · Jan 22, 2005

I'm confused, I was under the impression the older 4.0s were designed to run at 210*?

Did the engine do this before the new stat went in? The shop manual says low temps would either be caused by a faulty stat, faulty sending unit, or faulty guage.
Jeep on!
--Pete

Eagle · Jan 22, 2005

The XJ (aall years) is designerd to run at 195 degrees, which is what the factory thermostst is. The gauge usually reads about 210 in the older ones because it's getting data from a sender in the rear corner of the head, which is a localized hot spot. Running at an real 165 degrees can be harmful, because that temp may not be hot enough to get the ECU out of open loop (warm-up) mode and into closed loop operating mode. The result would be lousy fuel mileage, plus the possibility of ruining the catalytic converter by constantly feeding it too much unburned hydrocarbons.

WobblesXJ · Jan 22, 2005

I'm sure the ecu bumps out of "warm up" before 160º. I can feel when mine goes out of "warm up" as well as smell the difference.

I was under the impression the thermostat was a 190º. You can watch my needle run up to the 190º mark then the thermo opens and it jumps back down to almost the 1/4 mark on the temp gauge then back up and does that repeatedly. Never getting to the middle. If yours is doing this then I don't think you should have any problem. If it's not getting to the point to open the thermo then I'd suspect the sender.

Pete M · Jan 22, 2005

I looked it up and my 89 shop manual says that the t-stat begins to open at 195* (open .003") and is fully open at 218*. Sounds like that would be the normal operating range. I bet that's the reason my gauge says 210 on it (along with 100 and 260) and nothing else. How on earth can you guys tell what temp your engine is using that gauge? Do the later years have more numbers on them?
Jeep on!
--Pete

Eagle · Jan 22, 2005

WobblesXJ said:
I'm sure the ecu bumps out of "warm up" before 160º. I can feel when mine goes out of "warm up" as well as smell the difference.

I was under the impression the thermostat was a 190º. You can watch my needle run up to the 190º mark then the thermo opens and it jumps back down to almost the 1/4 mark on the temp gauge then back up and does that repeatedly. Never getting to the middle. If yours is doing this then I don't think you should have any problem. If it's not getting to the point to open the thermo then I'd suspect the sender.

There is no 190º mark. There's a 210º mark. The temp gauge is not calibrated linearly, so without hooking one up to a pot of water with a known value thermostat for calibration there is no way to know what temperature is represented by the unnumbered hash marks, or at any point between the marks.

The point at which the ECU goes from open loop to closed loop is right around 160º to 165º, which is why running a 165º thermostat is not a good idea. It's too close to the line when any minor discrepancy means it won't change modes.

AngryDog · Jan 22, 2005

OK so it's borderline bad. I am strickly going by my temp guage. Is there a way to tell if the guage or sender might be bad. Could be why I am getting poor gas mileage. Should I go with a higher than 195 sat? I think you can get a 210.

pabloconrad · Jan 23, 2005

Just a sidebar, running and engine cooler than the specs can add to more internal engine wear as well. The cooler temps don't allow your piston rings to expand properly and you end up burning more oil.

Two Qiuckie Questions

AngryDog

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shawn_c

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Digger87xj

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JEEPZZ

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Pete M

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Eagle

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WobblesXJ

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Pete M

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Eagle

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AngryDog

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pabloconrad

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