if your tank got really big then part of the problem is your reservour cap its failed mine did that and my tank cracked (stupid puke tank). try giving it a good flush too that could be a problem. I had similar isues on a full size truck i had so i took out the radiator and filled it with a deluted mixture of naval jelly and water (DONT LEAVE IT SIT TOO LONG IT WILL EAT YOUR RADIATOR IF SAT TOO LONG) and let it sit about 5 min and swoushed it around then drained in bucket, reinstaled and filled and problem was gone. you wouldnt believe the crap that cam out when i did this!!! good luck

 

it has a new cap it has pretty much new everything. tha radiator is brand new so it should not have ne thing in it.

 

Is this the original radiator? If so alot of times so much crap has built up in it, it does not provide sufficient flow, it could possibly use a rodding and cleaning, fairly cheap considering what you have already done.Also burp like was mention above.

 

it is brand new not the original.

 

You say the cap expands. Where is all that pressure coming from? If I had to guess I would say you might have head gasket problems, especially if has been hot.

 

if i leave the cap off it doesnot overheat as fast and the oil looks clean and ive done a leak down test and compresion check so i dont know what it is but its making me mad.

 

TrekkerJmm, what kind of flex fan are you using? I like that idea.

 

If it overheats faster without the cap, then my guess is head gasket. All you are doing is venting the gasses through the fill when the cap is off. I know it is a pain in the a$$, but fix that gasket and yo will be OK. Summer is coming and your overheating problem will only get worse.

 

i hope not. but im gana try everything else first

 

Other than needing a 3 core radiator with a cap, the rest of your OEM cooling system is good. After replacing all the parts you said you have, It should be running fine. Look for oil in the coolant and coolant in the oil. Pull the plugs and do a compression check in all cylinders. If you have coolant or oil where it doesn't belong or low compression, I'd say you have a bad head gasket.

 

no coolent in the oil or oil in the coolent i did a compression test and it was good.

 

what all do i haft to do to switch it over to a radiator with a cap?

 

I have a 97 XJ and I too had some similar problems with overheating. I had replaced almost everything. new rad. new hoses. new trans filter and oil. new water pump. new electric fan. radiator flush. new thermostat with new housing. I was stumped. I got the Jeep running better and not as hot but it was not where it needed to be. I live in deep south texas and I needed to fix this problem as it is 95-105 everyday in the summer. I finally decided to replace the fan clutch and that did the trick. I picked one up from the local auto parts store for $35, swaped it with the original and no more overheating problem.

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97 XJ
ALL STOCK plus Roof Rack, Olympic 4x4 front bumper