blistovmhz
NAXJA Forum User
- Location
- Vancouver, BC
Several threads on this already on several forums, still haven't found the answer, but continue to learn so reposting with what I know.
98XJ, 4.0L with 280k. Head replaced (reman) about 40k ago. Replaced due to intermittent rough idle which turned out to be a sticky valve. I also had an issue with coolant disappearing, but as I had a small leak in the rad, I figured that accounted for it.
Two weeks ago I took off my downpipe to knock out a dent and weld up a hole. Took a bit of a beating to get the cat(back) separated from the downpipe, and more beating to get it all back together. After re-assembly, Jeepy started blowing a tonne of water vapour on startup. Would cloud up the entire driveway for about 15 minutes, then clean right up and blow perfectly clean. Once it's warm and blowing clean, if I disconnect the #6 injector lead, or #6 spark, it'll start blowing vapour again in about 60-90 seconds, and will do so until I plug everything back in. This doesn't happen with any other cylinder.
Put 40psi air into the #6 at TDC (cold) and removed the rad cap, and nothing happens. Warm it up so the thermostat opens up and do it again, and I blow water out the rad. Clearly there's a leak somewhere, but I can't find it.
If I remove the downpipe and let the exhaust out the header, there is no vapour at all, ever. Only happens if the exhaust hits the cat.
Replaced head gasket and have the exact same problem. Old HG was clean and looked to be in perfect condition.
So, is there anywhere in the head that might've cracked? I figure if I'm at TDC and still blowing coolant, the leaks gotta be north of the block deck right? Maybe I'm looking for a water leak when the problem is something in the Cat instead?
Visual inspection of the head itself didn't give anything up.
Vapour really doesn't smell like coolant at all, but doesn't smell like exhaust. Smells like clean water steam.
Any idea's?
Some idea's that I've used to rule stuff out:
* If there's a crack in the head, it won't be in the intake or exhaust port, as my pressure test wouldn't have blown air into the coolant.
* If there is a crack in the block, it would have to be very near the block deck, as I pressure tested at TDC, and there's no oil in coolant nor coolant in oil.
* Again, assuming there's a crack somewhere, as the engine warms up, it's sealing the crack, but the crack opens up again as the cylinder cools down (like when I remove spark or fuel from the #6).
Would some of that awful cylinder/HG sealant stuff maybe actually work for me in this case? I figure I'm already at the point where I'm going to throw out a mostly good working engine. How much damage will that sealant do?
98XJ, 4.0L with 280k. Head replaced (reman) about 40k ago. Replaced due to intermittent rough idle which turned out to be a sticky valve. I also had an issue with coolant disappearing, but as I had a small leak in the rad, I figured that accounted for it.
Two weeks ago I took off my downpipe to knock out a dent and weld up a hole. Took a bit of a beating to get the cat(back) separated from the downpipe, and more beating to get it all back together. After re-assembly, Jeepy started blowing a tonne of water vapour on startup. Would cloud up the entire driveway for about 15 minutes, then clean right up and blow perfectly clean. Once it's warm and blowing clean, if I disconnect the #6 injector lead, or #6 spark, it'll start blowing vapour again in about 60-90 seconds, and will do so until I plug everything back in. This doesn't happen with any other cylinder.
Put 40psi air into the #6 at TDC (cold) and removed the rad cap, and nothing happens. Warm it up so the thermostat opens up and do it again, and I blow water out the rad. Clearly there's a leak somewhere, but I can't find it.
If I remove the downpipe and let the exhaust out the header, there is no vapour at all, ever. Only happens if the exhaust hits the cat.
Replaced head gasket and have the exact same problem. Old HG was clean and looked to be in perfect condition.
So, is there anywhere in the head that might've cracked? I figure if I'm at TDC and still blowing coolant, the leaks gotta be north of the block deck right? Maybe I'm looking for a water leak when the problem is something in the Cat instead?
Visual inspection of the head itself didn't give anything up.
Vapour really doesn't smell like coolant at all, but doesn't smell like exhaust. Smells like clean water steam.
Any idea's?
Some idea's that I've used to rule stuff out:
* If there's a crack in the head, it won't be in the intake or exhaust port, as my pressure test wouldn't have blown air into the coolant.
* If there is a crack in the block, it would have to be very near the block deck, as I pressure tested at TDC, and there's no oil in coolant nor coolant in oil.
* Again, assuming there's a crack somewhere, as the engine warms up, it's sealing the crack, but the crack opens up again as the cylinder cools down (like when I remove spark or fuel from the #6).
Would some of that awful cylinder/HG sealant stuff maybe actually work for me in this case? I figure I'm already at the point where I'm going to throw out a mostly good working engine. How much damage will that sealant do?
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