Overheating Problems 00 XJ

Alright so I have a 2000 xj and i've had an ongoing overheating problem for about a year now, its day to day but now that summer is here, its becoming a serious problem. The engine sits at 210 for most of the ride, and then at any given moment into my commute, BAM! it jumps to 260 and boils out of the reservoir. Recently i did a bit of an overhaul with no progress. I put in a 180 thermostat, a new radiator and cap, and tested the electric fan which works. The upper hose is hot to the touch which means the water pump is working and this is verified by poking it and feeling fluid in it, plus i started the motor with the thermo housing off for a sec and the coolant blew everywhere=works lol. So that leaves the head gasket? which ive put $55 dollar blue devil in as sort of a tester-fixer. All this has been done and yet it still overheats. Very depressing, any help would be great.

BTW ive also put in a new temperature coolant sensor

My buddy has an 89 that had overheating problems and he went through all the same tests but he finally cured it by replacing the radiator. alot of times the fins on the radiator get bent over or plugged with bugs and mud which basically stops airflow through the radiator. A lot of times just the fans pushing air over the motor is enough but when the engine is understress or under a heavy load it needs alot more air.

ok so i just reread your post and i feel like and idiot. well all i can figure is your head gasket. have you pressurised you cooling system. If the pressure gauge shows the pressure dropping and you have no leaks then it has got to be the head gasket. Do you lose coolant? Does the Jeep blow out white smoke out the exhaust? Are you getting combustion in your coolant? You said it blew a bunch of coolant out your thermostat housing that sound like combustion in the coolant. Do you have a slight miss?

By the way I haven't figured out how to post anything. Can some one help me

It's a single layer radiator, i'm thnkin it may just not be enough, but why wud they sell it if it didnt work. No smoke, just put a new dynomax exhaust on btw. Havnt had it pressure tested but from what I can see theres no leaks other than when it overheats, and overflows the reservoir, i thnink im gunna attempt a head gasket replacement, and if that doesnt work, ill just get a friggen performance radiator for 500 off quadratec. The stuff only blew out because i had the whole housing off when i was replacing the thermo, and wanted to blow out all the preexisting fluid

you may have cracked cylinder head.

that sudden rse is coolant temp could be combustion gasses leaking into the coolant.

if you pull the head off, send it out for magnafluxing.

Both cracked heads and blown gaskets can "open up" suddenly, usually when the engine is at full temperature.
Its like a expansion joint, and it closes up as the engine cools.

The 2000 4.0l is known for cracked cylinder heads. You can find it by installing coolant dye and using a uv light to look in the oil fill hole.

kidcahtah said:

Alright so I have a 2000 xj and i've had an ongoing overheating problem for about a year now, its day to day but now that summer is here, its becoming a serious problem. The engine sits at 210 for most of the ride, and then at any given moment into my commute, BAM! it jumps to 260 and boils out of the reservoir. Recently i did a bit of an overhaul with no progress. I put in a 180 thermostat, a new radiator and cap, and tested the electric fan which works. The upper hose is hot to the touch which means the water pump is working and this is verified by poking it and feeling fluid in it, plus i started the motor with the thermo housing off for a sec and the coolant blew everywhere=works lol. So that leaves the head gasket? which ive put $55 dollar blue devil in as sort of a tester-fixer. All this has been done and yet it still overheats. Very depressing, any help would be great.

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I just had some of the same over heating issues you had. My upper rad hose was hot too...but check the lower. If the lower is cool, the water pump isn't pulling anything out. I wouldn't rule out the water pump and would look at that before the head gasket. I will have a pic in my thread shortly.