Recently purchased a 2000 Jeep Cherokee with 128K. Fairly slow leaking coolant (1 inch/day from reservoir). See no revealing exhaust, no sign of milky oil stick, no leaking outside engine. So I had block lock dye tested and head pressure tested - no cracks. Head re-surfaced. Head gasket in bad shape and replaced.

I've had the Jeep back now for three days and already the reservoir down to just below fill line, and this after hardly driving the rig. I saw steam coming out after removing the oil cap. My mechanic says he owes me so is going back in in two days.

I'm sumped as to what could be wrong. With the gasket replaced and no crack in engine block or head, then what could possible be the answer?

 

To add to the above question, I should say also that the previous owner may have been chasing this same problem in that the jeep has a new water pump and radiator, so that rules out those two components, and all hoses and the reservoir itself are good, and I've had a coolant chem. test done: negative.

 

"Fairly slow leaking coolant (1 inch/day from reservoir)."

Thats a bunch, unless the is a big puddle underneath where you park it's probably due to a cracked cylinder head. What is the oil pressure like?

ETA: New water pump & radiator due to an overheat?

 

No puddles found doing the time since leak discovered not long after buying the Jeep. Not only no puddles but no spots found. Oil pressure has held since purchase; no evidence here of a problem.

The new water pump and radiator came with the purchase, so were replaced by previous owner. Can only guess that the previous owner had an overheat, though can't know for sure. The machine shop said the head was far off balance so needed to be re-surfaced quite a bit.

Seems like I've covered all the bases yet no diagnosis of where the leak originates. Perhaps the block and head tests were faulty and a crack didn't show.

I've been told that from a machine shop that he's heard of a time when the block was replaced with a 4.2 rather than a 4.0, and if so the head needed to be replaced with a 4.2 fit as well, and if not, then this could be the source of the leak. So he recommends checking the serial number of the block.

I also wonder about the intake manifold having a crack, but this seems unlikely.

 

If there are no external signs of a leak, it has to be internal... somewhere. How long before you purchased did the PO replace the water pump and radiator? Is it possible that you're seeing air being purged from an improperly replaced cooling system and that's what is causing the level to drop?

 

2000 model Jeep with 0331 head and consuming coolant = red flag warning on cracked head.

It was already warped so somebody got it real hot--probably more than once.

 

Bought from a Dealer so no way to know when the PO replaced the pump and rad.

Leakage has been ongoing - noticed not long after purchase. So it doesn't seem like air pockets could be the problem; they'd already be worked out.

How likely is it that a head crack exists even though it wasn't identified/located with machine shop pressure test?

 

"How likely is it that a head crack exists even though it wasn't identified/located with machine shop pressure test?"

Almost a certainty. See my earlier post please.