Cooling system Question

All right Ive spent hours searching and can not find anything about my problem and this is my first post so bear with me. I own a 2000 XJ. She has 98,000 miles on her . When I got her the coolant was looking old (greenish but with a slight rust tinge. So the system looked all original right down to the hoses.I replaced everything, radiator,waterpump, thermostat,hoses,fan clutch,shroud(cracked) Thermo housing ,idle pulley, belt, sensor in housing, Radiator cap. Since then I have two problems that are stmping me.

1) The temp gauge fluctuates from just below 210 mark to a tad over. this is while moving down highway. If I am sitting it stays steady for a longer period of time. People have told me that this is the thermo opening and closing. I thought once the thermo opened it stayed open? Any sugestions?

2) Since replacing everything , my system does not pressurize. I see the coolant in the recovery tank go higher when hot and go lower when the Jeep has sat overnight. And I have heat inside. Both sides of the upperhose are hot. Again I am stumped. I even replaced the radiator cap with two other brands with no sucess. Should I be concerned that it is not pressurizing since everything seems to be working , I have heat, no signs of any overheating, she is ruunning great. Am I hurting anything?:huh: Please help. Ive posted this on other XJ sites so I can get everyones thoughts. Mike

Did you by chance replace everyhting at once or did you do it one at a time? Did you do it yourself?

OT: not to be a jerk or anything but there are no "other" XJ sites.

ok if you want to be specific other Jeep sites that include XJ. What does it matter. Boy try and find some help is real hard .No wonder people complain about forums. Just looking for help thats all if you can not help me do not answer my questions.

The thermostat is constantly adjusting the opening to try and keep a constant temperature in the motor. Kind of a variable valve, mostly closed until the rated temperature is reached, then it has a variable opening. The rating on the thermostat is actually supposed to be indicative of the temperature it first opens. A 180 starts opening at 180, a 192 begins opening at approx. 192. Thermostats aren't really fine instruments and many have individual quirks.
There is a constant bypass of coolant through the heater lines and the heater valve.
A universal gasket for a thermostat will sometimes cover the bypass opening for the heater bypass and cause erratic thermostat function (an OEM gasket is best). The constant small flow by and around the thermostat (through the heater hoses) helps the thermostat feeler to react quicker to temperature changes in the motor.
Air trapped in the system, can also cause problems. The thermostat reacts erratically (the air is often hotter than the coolant and/or interrupts the flow of coolant). It sometimes takes awhile for all the air to work itself out of the system, after a service. It sometimes takes a more radical approach to get enough air out, for the system to function at all.
The system is supposed to pump a half quart or so of coolant (from expansion) into the recovery bottle and then suck it back into the cooling system during a cool down cycle. The system typically builds more than 15 or so PSI of pressure from expansion of the coolant. If it ever gets up around 30 PSI things can pop, like the radiator seals. It sounds like your system is working well.
Very small, hardly noticeable pin hole lelaks at the hoses or whatever can cause problems. When the motor goes into cool down cycle, the pin holes can suck some air. Instead of the coolant from the recovery bottle or a mixture of both. And as mentioned before, air in the coolant system can cause erratic thermostat function.
Canadian_XJ's attemp at humor sounded pretty darned mild to me, try and grow some thickness to your skin guy. My attempts at humor, are often much less subtle than his.
Much of what I know about XJ cooling systems, I picked up from Eagle. You might try a search on his name and read some of his radiator posts. He taught me some things, when I was a snotty kid.
If you find the guys on this board to be rude, the guys over at Pirate are a bunch of really nice guys and have a wealth of knowledge.
I have to apologize for my dyslexia and the poor spelling, my computer isn't really bilingual and my spell checker crashes it.

xj00ny said:

ok if you want to be specific other Jeep sites that include XJ. What does it matter. Boy try and find some help is real hard .No wonder people complain about forums. Just looking for help thats all if you can not help me do not answer my questions.

Click to expand...

Boy do you know now to mke friends!
The temp gauge thing is no problem.
The T-stat will open and close as needed.
As for not pressurize. As long as you have good heat and she not blowing anti all over the gauge reads about right. (IMO) LEAVE IT ALONE. Forgive the caps please.

8Mud said:

The thermostat is constantly adjusting the opening to try and keep a constant temperature in the motor. Kind of a variable valve, mostly closed until the rated temperature is reached, then it has a variable opening. The rating on the thermostat is actually supposed to be indicative of the temperature it first opens. A 180 starts opening at 180, a 192 begins opening at approx. 192. Thermostats aren't really fine instruments and many have individual quirks.
There is a constant bypass of coolant through the heater lines and the heater valve.
A universal gasket for a thermostat will sometimes cover the bypass opening for the heater bypass and cause erratic thermostat function (an OEM gasket is best). The constant small flow by and around the thermostat (through the heater hoses) helps the thermostat feeler to react quicker to temperature changes in the motor.
Air trapped in the system, can also cause problems. The thermostat reacts erratically (the air is often hotter than the coolant and/or interrupts the flow of coolant). It sometimes takes awhile for all the air to work itself out of the system, after a service. It sometimes takes a more radical approach to get enough air out, for the system to function at all.
The system is supposed to pump a half quart or so of coolant (from expansion) into the recovery bottle and then suck it back into the cooling system during a cool down cycle. The system typically builds more than 15 or so PSI of pressure from expansion of the coolant. If it ever gets up around 30 PSI things can pop, like the radiator seals. It sounds like your system is working well...

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X2

sounds normal to me. as the coolant gets hot filling the overflow. as it cools it retracts pulling from the coolant overflow.

I put a couple of marks with a permanent marker on the side of the recovery bottle in the wifes 96. One at the hot level and one at the cold level. I can tell at a glance if something isn't right.

Thanks for all the replies. If it sounds like it is normal then fine. If it takes a while for the air to escape then , should I help it get along better by putting the jeep on a incline with the cap off and run it for a while? If my reply to Canadian XJ sounded harsh, It was not ment to be, Was just making a point that Ive seen other people on sites ask what other people think are silly questions and get picked on . As you can see it was my first post. At least let someone get a few under them before going on . I personally do not do that to someone who is looking for a possible answer to their problem. I appreciate the info from 8MUD . PS I live in NY how much more thick skinned can you get. Mike

Hello Mike,

I followed the burping procedure given at:
http://www.jeepsunlimited.com/forums/showthread.php?t=656646

And also did a good backflush of system by removing the thermostat housing and forcing water first into the cylinger head, then reversing flow and forcing water into the hose line. Then put thermostat housing back on (w/o t-stat) and using Prestone Super Flush (or equivalent). Then doing clear water flush again. Then installing t-stat and new gasket for t-stat housing. That procedure along with burping and parts replacement similar to what you did -- cured my overheating problems in '89 XJ. Now runs around 195 all the time (of course it's 0 F at the moment outside in eastern Oregon...). I think the burping procedure is far and away one of the most important things to do on your Jeep. Also, to make sure you have a lower radiator hose that has a spring inside to prevent collapsing. You can get an OEM hose with spring at: www.moparstore.com or make your own using heavy duty compression spring from mcmaster.com and a Gates or other non-OEM hose (that's what I did). Good luck and welcome to the forum! If you're like me, you'll find that many people here know a lot about Cherokees and are very friendly and helpful. Rick

GOOD INFO. Thanks!

xj00ny said:

All right Ive spent hours searching and can not find anything about my problem and this is my first post so bear with me. I own a 2000 XJ. She has 98,000 miles on her . When I got her the coolant was looking old (greenish but with a slight rust tinge. So the system looked all original right down to the hoses.I replaced everything, radiator,waterpump, thermostat,hoses,fan clutch,shroud(cracked) Thermo housing ,idle pulley, belt, sensor in housing, Radiator cap. Since then I have two problems that are stmping me.

1) The temp gauge fluctuates from just below 210 mark to a tad over. this is while moving down highway. If I am sitting it stays steady for a longer period of time. People have told me that this is the thermo opening and closing. I thought once the thermo opened it stayed open? Any sugestions?

2) Since replacing everything , my system does not pressurize. I see the coolant in the recovery tank go higher when hot and go lower when the Jeep has sat overnight. And I have heat inside. Both sides of the upperhose are hot. Again I am stumped. I even replaced the radiator cap with two other brands with no sucess. Should I be concerned that it is not pressurizing since everything seems to be working , I have heat, no signs of any overheating, she is ruunning great. Am I hurting anything?:huh: Please help. Ive posted this on other XJ sites so I can get everyones thoughts. Mike

Click to expand...

What about your radiator cap? is it holding pressure(coolant will boil at lower temp.....with out pressure.) I now that ya said that it was replace but if it not building pressure either there is no temp(t-stat stuck open) or the pressure is leaving the radiator before its pressure! or it could also be leaking on the ground but you would have noticed it by now.....right?

Flash.

Flash.