xjpettit99

Ok I have a 99 XJ with 169,xxx mi it has the 0630 head. When the issue first started it was July in 90* heat. At first it was running a little warm then on a ride my electric fan when out and that was the first time it over heated. After that it would run hot then once it got to 210 the temp needle would suddenly go to the roof. After that I would let it cool down topped off the coolant and it would be fine for a little while then do it again. I did notice it was using coolant about .5 gal in a day. Didn't notice any leaks, smoking, or anything out of the ordinary so replaced thermostat still overheated. Checked the oil and it was clean so I changed it the be sure and still looked new ( only had been 300 mi since last oil change). My thought was head or head gasket so I currently have my motor stripped down and piston are in good shape all cylinders are Same color. Head has been completely stripped down and cleaned up and can't find anything out of the ordinary checked for cracks the usual suspect places and everything is clean and nothing is noticeable. So I'm trying to determine if I upgrade the cooling system it that will fix the issue( mine is tired and under maintained) or if there it something that I'm over looking. Any and all suggestions are greatly appreciated.

Ant.

Since you have it all apart I think it is better to take the head to the machine shop and have it check for cracks and make sure its tru and do a valve job.. Then put it back on, Hate to hear ya had to break it down again...

Just a thought..

Ant...

belvedere

What does the head gasket look like (does it show signs of leaking)? Did you pressure test the cooling system before you tore it down? I would certainly have the head checked out at a machine shop.


Edit: Beat me to it, Ant!

Ant.

HEHE!!!

xjpettit99

Ok just picked my head up from the machine shop. The guy said it was off 8/1000ths off, he showed me a spot on cylinder 3 where he said it looks like the head lifted. The valves were pretty bad 3 of the exhaust valves were out of round and not sealing. The good news it was fixable and there were no cracks that could be found. So in going to put it back together and replace the entire cooling system in order to make sure that there are not any leaks or blockages.

bdub11

what all do you plan on replacing when you are talking about the entire system? I am thinking of doing this as well, but not sure if I need to include the heater core as part of that project (which of course will also mean the AC equipment since I will be under the dash)...