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Coolent problems

thewrath

NAXJA Forum User
Location
Nashville, TN
i have a 2000 XJ with 101K mi. Ive had on and off overheating problems for the past 18 months, especially when idleing in traffic in the summer. So far the dealership has blamed the problem on and replaced the: radiator, water pump, t-stat, t-stat housing, and radiator cap. And the systems has been flushed a few times as well.

It has been running fine untill a few days ago when it got a little hotter than normal, but not into the red. I figured it was finally time to give that watter wetter a try. So i went out and bought a bottle. When i poured it in, i noticed that the overflow resivoir was filled up past the full level, and that the radiator wasnt full. I ended up pouring in 1/2 gallon of distilled water before the radiator was full. I drove it around for a day and checked the levels again. The radiator needed anohther quart or so of water and the overflow bottle was fuller than last time.

Anyone have any ideas as to what is going on. Only thing i can think of is that the coolent expands and goes into the resivoir, but then when it cools off, it doesnt make it back into the radiator for some reason. Another concusion that I have painfully come to is that the head gasket is on its way out, allowing gasses from the combustion chamber into the coolent. Any ideas on why the overflow bottle keeps filling up and the radiator keeps losing fluid?
 
Pressure cap, as the system heats up the coolant expands into the coolant bottle then as it cools down it is supposed to get sucked back in, if the pressure cap is bad and not holding pressure the coolant never gets pulled back into the radiator. Replace the cap with a new one. If it still does it have the system pressure checked. It should hold pressure for about an hour or more with no problems. If not then you have a leak somewhere but with a leak like that you should see coolant...

The only other sympton you describe is that it heats up in traffic, thats an almost positive sympton of a bad mechanical fan clutch....
 
is there a possibility that the hose running to the overflow bottle could be slightly cloged, and that the sucktion caused by the coolent cooling down isnt strong enought to suck coolent by the blockage, but it is strong enought to push past it when the engine heats up?

should i just go get a new pressure cap and try it out?

and do i have a mechanical fan clutch? the mechanical fan runs constently, and the secondary electric fan kicks on at like 215F or so.
 
The cap is the best bet to start, use a dealer OEM one, it is possible that you have some kind of crud in the bottom of the overflow tank that allows coolant in and then falls back and blocks the hose, boy could you drive someone nuts with a single marble :D, easy enough to remove the bottle, dump the coolant into a bottle and clean out the gunk that gets in there after a few years then refill with new 50/50 mix of distilled water and coolant. When I do my cooling system maintenance I always remove the bottle and clean it out with fantastic/409 or whatever is handy.

Yes, all XJ's have two fans, one mechanical and one electric. The mechanical fan has a fluid operated clutch and they do go bad. There is a method for troubleshooting them that involves drilling a hole thru the fan shroud and sticking a thermometer in there to measure temp changes. Never tried it but the procedure is in the factory service manual.
 
hey rich can u pm me the procedure on how to remove the bottle and stuff? my radiator has been leaking on and off, but i cant find the hole or leak....today the jeep was leaking water from the r/h side bout 1/3 of the way back....i dont know if it's the a/c compressor drainline or whatnot....any idears?
 
finally got around to pulling off that coolent bottle. no marble found. but with some clean water in it, blowing in the line that goes to the pressure cap doesnt produce any bubbles coming from the bottom. Apparently there is a crack somewhere inside the bottle. THis allowing coolent to flow into the bottle from the pressure cap, but when the coolent cools off, the vacum created doesnt suck coolent back into the radiator, it sucks air. Thus explaining my mysterious ever increasing level.

Guess i need a new plastic bottle. If you all agree let me know, and ill go get one on monday.
 
ladywolf said:
hey rich can u pm me the procedure on how to remove the bottle and stuff? my radiator has been leaking on and off, but i cant find the hole or leak....today the jeep was leaking water from the r/h side bout 1/3 of the way back....i dont know if it's the a/c compressor drainline or whatnot....any idears?
Kris - you got your answer already? I just realized you have a '99 and can get you an FSM if it's still available. Without going outside to look (it's cold out there!) there are only a couple bolts holding the bottle in after you pull the rubber line from the radiator.
jul06002.jpg


The condensation is almost for sure because you were running the Defrost - that makes the a/c run to dry the air and it will drain down just in front of the firewall on the pax side.

Rich - apparently not all XJs have the electric fan, although all have the mechanical one. At least with the earlier ones they usually had to have a/c or a towing package to get the electric fan added. The good news is that the new-style fan sucks more air but will drop right in the same place as the older ones.
 
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Wondering if replacing the bottle did the trick. Did my weekly inspection of things today and notice my overflow bottle went from halfway b/w "add" and "full" where it's been since I purchased it in Jan. Today it was about a quarter of the way up between the "full" mark and the top of the bottle. Drove it to work tonight thinking maybe things will settle down a bit, with no problems. Ran perfect. Drove it tonight and checked it again and now it's about halfway between full and the top. Wondering if it's the pressure cap or the bottle (hoping cap). Any idea how much one of those caps runs? I've also heard the dealer is the best place to get one. Any input is appreciated.

Forgot it's a 99 4.0L
 
It is supposed to vary like that, when it's hot there should be more coolant in the overflow bottle, when it is cold there should be less. If the cap is bad and releasing at say 10lbs you might get more coolant in the bottle, would not hurt to replace the cap.
 
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