I was over at a buddies house today looking at his 88 XJ 4.0 AW4 4x4 that he wants to sell to me. The engine ran great as did the transmission, couldn't find any leaks. As I'm telling him that I wanted to buy the XJ, it was idling next to us the coolant tank cap blew off. The bottle and cap looks new but he said that this has happened before. What would cause this to happen? I had a 90 XJ with the closed system and I never had this happen. Any ideas?

 

Too much coolant and not enough expansion space??

 

shouldn't the relief valve in the cap allow for the extra expansion?

 

Change it over to the later open system and cut the cooling problems in half.

 

gotta solve the system pressure problem first. no reason that cap should blow off like that.

 

It seemed like the cap slipped up a couple threads. But the owner said that he put in a new bottle, I wonder if the vent plug is seated and won't allow presure to be released.

 

where'd he get the new bottle? the ones from auto zone and Oreilly's are junk

 

not sure, but i bet that he got it from orielly's. i'm hoping to sell my grand cherokee tomorrow so that i can go get this one. i will probably get a new bottle/cap on my way to pick it up and swap them right there.

 

If the bottle is new (and not a balloon already) and he still has the old one, try using the old cap, it may save you a few bucks if it works.

 

when i was able to get the cap completely off after it cooled down a bit, it seemed like there was a bunch of give in the sides. if you held it on the sides and squeezed it would flex. that why I'm thinking just get a new cap and bottle on the way over to pick it up. it belongs to a friend of mine so he isn't going to do anything with it until he hears from me.
unfortunately i couldn't tell if the thing got super hot because it only had an idiot light on the dash, no gauge.

 

the idiot light has about 40 to 60 degrees give to it +/-, so if it didn't come on it's okay. but it does sound like the tank got ballooned.

 

if everything goes well tomorrow im going to swing through napa in the afternoon and get a new cap/bottle and swap them. one of them is screwed up and considering im only paying 400 for the xj, i don't mind tossing 60 bucks at replacing the bottle.

 

fair price for 60 bucks. Bought my son a 93 mustang conv. for 300 last year and a 40 dollar fuel pump was all that was wrong.

 

It has been sitting for about a year or so. It had a death wobble at 45 and my buddy through 800 at it to get it some what drivable then parked it. I didn't get it going fast enough to feel the DW but it looks like the draglink is the only thing that looked worn out.