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Overheating / Cracked Head?

seanof30306@yahoo.

NAXJA Forum User
Location
Tulsa, Ok
OK, so on a cooler day, my temp gauge sits just to the left of 210. Anything over 90, and it sits just to the right of 210. That's a recent development. I bought my XJ new in '96, and it's always operated just to the left of 210, even on really hot days.

Back in 2004 (70,000 miles) the guys at Goodyear didn't put the radiator cap all the way back on when they serviced it, it blew all the coolant out, overheated, and cracked the head. Replaced it with a '95 head, replaced the radiator, and it was all good. The only time it ever got over 210 was in the Summer of 2011. We had over a dozen days in a row where it got to 115 or more, and the old XJ ran fine, but it was at around 220, or so.

Last summer it blew the top radiator hose off and overheated. I was afraid I'd cracked a head (again). it skipped and ran terribly.

Pulled the plugs and found the #2 plug was cracked. Replaced it, and it ran fine, except right on startup. It would skip for 10-15 seconds, then run perfectly.

Researched it on the internets and found a lot of intel saying it could be a slight crack in the head. When the Jeep sat overnight with the cooling system still under pressure right after it was shut off, water would leak into the combustion chamber, causing it to skip on startup the next morning until it ran for a moment or two and blew all the water out of the cylinder and the plug dried off.

Stuck a camera down in it after letting it sit overnight and sure enough, there was coolant down there in the good old #2 hole.

There was no coolant in the oil, and the compression on #2 was right in line with the rest of the cylinders, so we decided to give Barr's Stop Leak a try before pulling the head. I followed the directions, and the skip on start-up went away. It ran perfectly all the rest of last Summer and Fall and this Winter and Spring. I also replaced the water pump and the radiator (again). Also hoses, thermostat and cap.

About a month ago, the skipping on start-up returned. It's literally gone after the first time I hit the gas after backing out of the driveway, but it's definitely back. Not sure whether to do another Barr's Stop leak, or bite the bullet and pull the head.

It was 95 degrees the other day, and the temp was where it's been all summer ... just north of 210. It sat at idle for about 5 minutes and it went up to just under the red zone, but didn't go any higher. I drove it for 5 minutes, or so, and it went back to just over 210. I repeated this a couple of times, and it was the same. Idle for 5 minutes it goes up to just under the red zone on the gauge. Start driving it again and the temp quickly comes down.

I've burped the system a couple of times by driving the front wheels up on ramps and leaving the cap off overnight. Someone said I should do it with the Jeep running, so I did that today.

I drove it up on the ramps, and left it running with the cap off. Couldn't see any coolant in the radiator till it got to 195 and the thermostat opened after running for about 5 minutes. Then this:

https://www.facebook.com/sean.phillips.5836711/videos/1784345424912900/?hc_location=ufi

The electric fan hadn't come on yet. It definitely looked to me like there were air bubbles coming out of there. It quit after a few minutes.




The second video was taken after 10 minutes' running, and you can see the coolant reservoir is empty.

https://www.facebook.com/sean.phillips.5836711/videos/1784346571579452/?hc_location=ufi

So, it kept running. I couldn't see the coolant in the radiator. Every couple of minutes, it would surge for a couple of seconds, pushing out coolant and what looked like more air bubbles.




The third video is after 15 minutes' running. The surges continued to happen ever 2-3 minutes. You can see one of the surges at the beginning of the video. The temp is about 220:

https://www.facebook.com/sean.phillips.5836711/videos/1784351644912278/?hc_location=ufi






The fourth video is after 20 minutes. Temp appears to be stable at around 220-225. It hasn't burped any air bubbles in awhile. I'm going to quit while I'm ahead.


https://www.facebook.com/sean.phillips.5836711/videos/1784360611578048/?hc_location=ufi

So, I'm going to restart it while it's warmed up and top the radiator off with coolant. Not sure what to do with reservoir, though. If I put coolant in it, since it's empty, won't that just reintroduce more air bubbles?




EDIT: Took just under a gallon of 50/50 mix coolant. Didn't seem like it burped that much out. I'll be going to work in an hour ... we'll see.
 
Last edited:
UPDATE:

Well, that appears to have fixed it.

It was 94 degrees when I left for work at 5:15pm. I was running a little late, so I drove 80 mph on the highway. It never got over 210.

I got right out of work and drove home on the highway at 60. 95 degrees outside, A/C on high, never got over 195.

I drove all around town on surface streets in very light traffic. Always under 210.

I sat and idled for 30 minutes. Still 95 degrees. It went up to 211-212, but never went any higher.

I think I'm good.
 
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