Need help troubleshooting overheating 258 in XJ

It's easy to get the air out just leave the cap off and let it run a little. The air will come out pretty quick. Can you see air at the top of the radiator? I think the coolant would have to be pretty low to see the temp go up like that? Honestly 140,000 isn't high milage for a 4.0 thats still just wearing in. I've seen cherokees run well past 250,000. They were DD's with highway miles though. You've got me baffled only things I would know to check would have been, Head gasket, have rad rodded out, check thermos, flush block, check fans, and rad cap. I had the same problem with my jeep but I had a 302 in it. It was fine while a idle but when I drove down the road it got hot 50-60mph. I finally figured out it was the fan. I had to install another fan and used a electric thermos to cut it on.
 
I would pull the t-stat out completely it is summer no need for heat now until you can get it figured out. Next i would do a compression test to make sure head gasket wasn't blown. I have seen slight head gaskets leaks that have no other syptoms except overheating. If compression test is inconclusisive or however you spell that. Put dye in your coolant and pressurize the system to see if coolant is leaking anywhere. If none of that works pull your radiator and take it to a radiator shop for a thorough cleaning and pressure test but you would have already tried that above. And if you can't figure it out after that, you better take it to one hell of a shop b/c you have exhuasted almost every possible possibility.
 
You can't take a therostat out and it work right. The thermostat keeps the coolant in the radiator long enough to cool , it opens and radiator coolant goes into engine, and engine coolant goes into radiator. If you take it out the coolant doesn't have time to cool. You can get by with it on the highway but in town stop and go it'll over heat for sure.

I talked with rob today by phone and I am pretty sure from all he told me it is a head gasket or a cracked head. Symptoms:

Resevoir always empty
Canstantly adding coolant
Heats up more at higher revs
Clutch fan checked when hot is hard to turn(so should be working right)
Forget the guages, it gets hot enough to puke out
No H2O in the oil( not always a sympton of a blown head gasket)
HE can't see into the radiator to see if water is circulating, but has a relativly new pump and thermstat


I told him to get a coolant system presure test and watch the guage to see if it leaks down. This would indicate a headgasket blown, or a cracked head. BEst to check cold since a crack closes up some when hot.
I also told him to fill rad up and resevoir to cold level. run it till at operating temp and cut off, as it cools, watch the resevoir. add(measured) water to the resevoir to keep it from sucking dry, this will give an idea as to how much coolant is escaping from somewhere.

IF I were a betting man I would say one of three things. Water pump, head gasket, or cracked head. That is if the thermostat is working properly
 
upnover said:
You can't take a therostat out and it work right.
Click to expand...

Wrong once hot water hits thermostat it stays open until it reaches cool temps. My hot rod is only driven in summer, so I've never had a Tstat in it (No need for winter heat, no roof!)
ou can however debate the merits of a thermostat as a flow restricter/ pressure builder, but those effects are minimal.



upnover said:
I told him to get a coolant system presure test and watch the guage to see if it leaks down. This would indicate a headgasket blown, or a cracked head. BEst to check cold since a crack closes up some when hot.
I also told him to fill rad up and resevoir to cold level. run it till at operating temp and cut off, as it cools, watch the resevoir. add(measured) water to the resevoir to keep it from sucking dry, this will give an idea as to how much coolant is escaping from somewhere. [/Quote}

Also can try a " leak down" compression test this is the most accurate way I know to check compression.

One final check for head gasket/cracked head.
To prevent the flame wars, I will provide the disclaimer that this is only like 95% effective. :flipoff2:
Since a cracked head or blown gasket will let minimal amounts of water in the CC there is a less efficient burn in the affected cylinder. One way to check is using a test light, connect the clip to the NEGATIVE (-) battery terminal, and then poke each plug wire one at a time at the dist. cap. This will cause it to "short out" the spark and prevent that cylinder from getting fire. If that cylinder is fully operational you can audibly hear the motor stumble as it loses a cylinder. If there is no stumble or hesitation on one (or worse 2 side-by-side cylinders) then that is a key that that cylinder is not functioning properly and is most likely a head/hg victim.

Nw that I have totally put the cart befor the horse, have you checked oil and ATF to make sure ther is enough of both, abnd that neither is in dire need of a change? How about air portiong toward the radiator? any trim or "lower spoilers" been damaged alterd or removed lately?
Click to expand...
 
ShyHiK5 said:
Wrong once hot water hits thermostat it stays open until it reaches cool temps. My hot rod is only driven in summer, so I've never had a Tstat in it (No need for winter heat, no roof!)
ou can however debate the merits of a thermostat as a flow restricter/ pressure builder, but those effects are minimal.
Click to expand...

This has not been my experience. As I said, stop and go traffic will surely get the temps up. Unless maybe you have a super cooling rad and a good fan system.

The last three used cars I bought had no t stat and ran hot. I put one in and wah-lah no more cooling problems in town.
 
Yes, but the reason is that thet thermostat adds pressure as pressure increase boiling temp increases, blah, blah, blah

If you stand in front of a car you can the thermo "pop" it will not pop back and forth..
Just once it reaches operating temp...
 
I would disagree.. the t-stat doesn't add pressure. that's a function of the cap... It does restrict flow, just like the restrictor plates that are sold instead of t-stats for the circle track crowd..

I would agree that once the t-stat opens it won't fully close again, unless you had some mega-incredible cooling system with dry ice around it.. :D
 
It may be pressure but you do something totally differant with your car. It's a street rod. I wouldn't run my rig with the thermostat off your just asking for trouble. The thermostat opens up and allows water to move at a faster rate once open but there is still some restriction. If you tell me thats not true then something is very wrong. If the engine and fans are factory I'd make sure it had a thermostat.
 
I sorta skimmed through the post so forgive me if I repeat something that has been mentioned. First of all what year is it? early (pre-91) had a closed cooling system , plastic resevior and no cap on the actual radiator. People claim this system doesn't work well, it does, it's just a bastard to get the air out of. There should be a temp switch on the side of the radiator, with the key on jump the connection at the switch see if the electric fan activates. Make sure that fan is coming on when its hot, if not ..bad switch. Make sure the fan clutch is working, it's pretty loud when it's engaged and this is a very common problem with XJs. Don't know if you have a winch or anything in front of the raditor, this too is a common overheating problem. If the radiator is more than a couple of years old and not an OEM part, this too will cause a problem...the radiator is sorta puny to cool that long ass motor. Another problem that is not easy to cure, the cooling jackets in the block and head will get partialy blocked over time, I never really bought into this theroy until I rebuilt my motor and it ran cool as cucumber. Hopefully this isn't the case for you (unless someone knows of a mechanic in a bottle that will free up the blockage) The only other thing I know of is the obvious blown head gasket,does the system build pressure when accelerating hard or reving the motor? That's about the only way to really tell if one is blown and they are pron to blow with several good overheatings. Hope this isn't the case for you, but good luck.
 
oh, its a 95. no winch in front. Bone stock 2WD (bring on the slammin, I'm ready).

Back to the topic, its got pressure, but don't know if its retained in the cooling system. Right now its at the shop getting pressure tested (I hope) and checking the fan clutch and timing. I've noticed its been running rough and high rpms at idle, so maybe its timing. Anyway, I hope its not a cracked head or blown gasket. The radiator is no factory and was replaced with a new one a few years ago, maybe 3 at the most. So, hopefully its not that, but it could be. Could also be blockage in the block. If all turns out OK today, I'll have it all flushed to see if anything comes out and if it runs any better.

Rob
 
stop and go traffic, I'm ok cause it doesn't overheat at idle, only when its subjected to long periods of 1700+rpms wether it be at 30mph or 70mph, it still overheats the same. Right now I'm thinking clogged radiator or bad clutch fan.

I added the water into the puke bottle (cold), marked it, and ran it. It puked into it and didn't overflow. When it cooled down, it sucked it back in at the same mark (within an 1/8" or so +/-). It did this all yesterday afternoon and this morning. I don't think I'm loosing coolant anywhere, so hopefully its not a cracked head or blown gasket.

Its getting tested right now.


rob
 
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