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4.0L blowing water, can't find source

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?
 
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Every year this time this same issue comes up. It is common for most vehicles to spit out water and steam after you drive it, park it in the evening and then start it up the next morning. It will not smell like antifreeze or oil, but rather be what it really is, mainly a crude version of distilled water formed when the engine starts and the warmer exhaust gas goes through a cool exhaust system causing the natural humidity to condense.
 
Every year this time this same issue comes up. It is common for most vehicles to spit out water and steam after you drive it, park it in the evening and then start it up the next morning. It will not smell like antifreeze or oil, but rather be what it really is, mainly a crude version of distilled water formed when the engine starts and the warmer exhaust gas goes through a cool exhaust system causing the natural humidity to condense.

I WANT to believe... But none of the other vehicles are doing this. Seriously, when it starts up in the morning, I can't see to the end of my driveway because the vapour's so thick. Got heaps of other trucks here and none do anything like this.
Threw some copper rad/head sealant in. Figure at this point, if it ruins something, I"ll be forced to just get the new motor :)
 
Mine spits out about a 15" circle of condensation every time I start it up for about 5 min. Did it before and after I put the new head on. Just means your cat is working.
 
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.

most of your story makes me think it's condensation, except this one comment.
is it actually blowing it out, or slowly building pressure and over flowing?
if it is sealed when it's cold and leaking when it's warm, it's an expantion or warping issue.
if there is alot of airflow, there is a substantial leak.
it makes me think of a problem i had on a 4 cylinder Ford Ranger. when it was cold there was no leak, but as it heated up the head gasket would develop an external leak. it turned out one of the head bolts had stretched and "cracked" between 2 threads so when it heated up it would warp and the cylinder pressure and/or water pressure would overcome the torque on the head and it would lift a corner of the head and piss fluid out. but only under actual driving conditions, took forever to troubleshoot where the coolant was going because it wasnt leaving a stain on the engine where it flowed.

i think your issue is the head gasket, AND condensation. have you ever put a rag over the tailpipe when it was smoking to collect a sample to smell or taste?
even a small trace of coolant will have a distinct taste...

hope this helps.
 
most of your story makes me think it's condensation, except this one comment.
is it actually blowing it out, or slowly building pressure and over flowing?
if it is sealed when it's cold and leaking when it's warm, it's an expantion or warping issue.
if there is alot of airflow, there is a substantial leak.
it makes me think of a problem i had on a 4 cylinder Ford Ranger. when it was cold there was no leak, but as it heated up the head gasket would develop an external leak. it turned out one of the head bolts had stretched and "cracked" between 2 threads so when it heated up it would warp and the cylinder pressure and/or water pressure would overcome the torque on the head and it would lift a corner of the head and piss fluid out. but only under actual driving conditions, took forever to troubleshoot where the coolant was going because it wasnt leaving a stain on the engine where it flowed.

i think your issue is the head gasket, AND condensation. have you ever put a rag over the tailpipe when it was smoking to collect a sample to smell or taste?
even a small trace of coolant will have a distinct taste...

hope this helps.

I'm thinking the same thing, when the headgasket went in my Renix is was unmistakable, the copper sealing ring and adjacent composite gasket blew a chunk. There was actually debris in the cylinder on top of the piston (number 6). When my Chev 5.7 blew a head gasket it was less dramatic. The copper sealing rind had maybe 1/16"-1/8" gap and a tiny snake trail through the composite material to the piston. It would act much like you describe, cold it would spew steam, hot it would almost disappear. In the beginning I assume dit was just condensation, the humidity at the time was way high and it was cold out. I also mushroomed a valve from hydro lock, coolant buildup in that cylinder. The odd part was my compression was still good and a leak down test was inconclusive. I think my issue with the leakdown test was, I never removed the thermostat. I'd very occasionally get a few bubbles to the top of my radiator while applying air pressure to that cylinder (at TDC for that cylinder). I finally figured it out by blue tinted (white lite grey) deposits on that plug (a very light tint the same color as my coolant, blue at the time) and a very slight tint in the droplets (caught on a white paper towel) coming out of my exhaust end just after a cold start. I never did get a positive with a exhaust in the coolant test.

If I had it to do over again, I have an endoscope now. Pressure up the cooling system on a cold motor to around 20 PSI and look in that cylinder for any signs of moisture (coolant). Hard to see in there, on cylinder 6, without and endoscope, though a welders mirror and a good flashlight might do in a pinch.

I've used unsweetened Cool-Aid powder to find tiny fluid leaks. I wonder if it would hurt anything to squirt a gram into a cylinder? The color of Cool Aid powder gets really bright when it's wetted.

A motor in high humidity pumps alot of water through the cylinders. It can be as high as an ounce of water for every three cubic yards of air moved through the motor. It adds up quick.
 
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Okay, so no matter where I put the #6 piston, about 20psi air into the spark hole always comes out the rad. I'm told that this must mean a bad head gasket or some imperfection in the deck, but the deck looked good, the old HG looked good, and I can't see any evidence of any leak in the new HG either. It's bone dry on both sides.

At this point, all I can come up with is that there must be a crack below the deck, but above the compression/oil rings, so the coolant can get into the cylinder and exhaust into the coolant, but no coolant into the oil or vice versa. Does this make sense?

I'm losing my ****ing mind on this one as I've already spent almost a grand trying to pass emissions, and I'm still no closer to an answer. I figure the cat was destroyed by coolant, and coolant is continuing to leak into the exhaust. Installing a new cat right now seems like a waste of money if I'm still leaking coolant, and if I'm right about the cracked block, I need a new block as well. By the time I'm finished this, I could've bought 2 Jeeps in better condition :) All to pass emissions testing that will be phased out in 13 months, for a vehicle who's use is 95% wheelin' *facepalm*.

Who thinks I should just bite the proverbial bullet, and spend $300 on another long block, and another $150 on a good cat? I'd hate to take this last step and have it STILL not solve the problem (ie: find out every 4.0L will leak some air into the rad at Xpsi and that my emissions problem was a vacuum leak in my intake)...

*edit* Who wants to go check their intake vacuum at idle for me (on a 97+ 4.0L that's running well)? I've got 16in cold, and 17in hot. I thought it was supposed to be 19in, but I can't find a leak.
 
There is some UV dye that you can put in the radiator and use a black light to see it to check for leaks.
 
WHich of the head bolts has to be sealed to keep coolant apart from combustion pressure? I remember something about this but not enough to say whether it's #6 or #1.

I've found that a fiber optic attachment for a mini-mag lite sold as a gun bore inspection tool is a really great way to put light onto something down a hole.
Turn all the lights in the garage off, stick the fiber light down the hole and now you can see quite well.

(I use this to look for head cracks on my 0331 heads thru the oil add hole)
 
There is some UV dye that you can put in the radiator and use a black light to see it to check for leaks.

You think that'll show up in the combustion chamber? I've never seen the stuff, but always seemed like it should exist.

WHich of the head bolts has to be sealed to keep coolant apart from combustion pressure? I remember something about this but not enough to say whether it's #6 or #1.

I've found that a fiber optic attachment for a mini-mag lite sold as a gun bore inspection tool is a really great way to put light onto something down a hole.
Turn all the lights in the garage off, stick the fiber light down the hole and now you can see quite well.

(I use this to look for head cracks on my 0331 heads thru the oil add hole)

It's the #11 bolt (drivers side closest to radiator) but the bolt just goes through a water jacket. It won't leak into the combustion chamber unless your HG is bad and you forgot to install the bolt with thread sealant.
 
I couldn't recall about that bolt. So that's not it.



The UV dye kits are pretty inexpensive but the part that's substandard in the kits is the flashlight blacklight part. I played around with one for awhile and found that the UV flashlight just wasn't strong enough to show anything - even when shining it on dye on my finger just out of the bottle in dim light (garage lights off).

Leakdown tester at 100psi might help find the problem quickly (leave the rad cap off).
THis is how lightplanes are tested for compression.
 
Okay, so no matter where I put the #6 piston, about 20psi air into the spark hole always comes out the rad. I'm told that this must mean a bad head gasket or some imperfection in the deck, but the deck looked good, the old HG looked good, and I can't see any evidence of any leak in the new HG either. It's bone dry on both sides. .

forget what "looked good" before..
when you say the 20PSI comes out the rad... how fast does it do this? does it slowly leak down? or does it actually blow thru and blow out?
if it's blowing right thru, your head isnt sealed. a small crack in the cylinder will not blow thru unless it is a hole or mechanical damage of some kind. at which point cylinder pressure would overcome the water pressure while the engine is running and your cooling system would be blowing off pressure even when it was cold.
you've narrowed the trouble spot down to the #6 cylinder. pull the head and stop pulling your hair out. it's more likely that the head or the gasket is the problem, not so much the block.
 
forget what "looked good" before..
when you say the 20PSI comes out the rad... how fast does it do this? does it slowly leak down? or does it actually blow thru and blow out?
if it's blowing right thru, your head isnt sealed. a small crack in the cylinder will not blow thru unless it is a hole or mechanical damage of some kind. at which point cylinder pressure would overcome the water pressure while the engine is running and your cooling system would be blowing off pressure even when it was cold.
you've narrowed the trouble spot down to the #6 cylinder. pull the head and stop pulling your hair out. it's more likely that the head or the gasket is the problem, not so much the block.

It leaks through, but not explosively. It's definitely a very small leak. The compression test shows 160psi, so it can't be anything big. It's not going to be a gaping hole in the HG. Leaktdown ... If I give it 20psi, it'll leakdown to 0psi in about 10-20 seconds.

Pulled the head again and can't find any evidence of any crack. Keep in mind, this is the second head on this block, and both had exactly the same issue, but the issue didn't affect the second head for 4 years (at least not noticeably) until I pulled the exhaust.
The previous head went to the machinist for re-manufacture, and he couldn't find any problem with it other than a sticky intake valve on #1. Perhaps he missed something, but I'm guessing the problem is going to be in the block.

Ordered a new cat. I figure it's possible there's something horribly weird going on with the cat, causing a tonne of condensation to build up, and the coolant leak in #6 is just unrelated. I figure, with the downpipe removed, let the engine cool overnight, and start it up with some paper towel around the header, there's no water coming out, and no vapour. It's only when I connect the cat to the system that I get vapour production again.

Going to install the new cat and see what happens. If it gives me a massive power boost and my MPG comes back up to around 22-24mpg, I'll go try to pass emissions and forget about the engine until I stumble onto a suitable replacement.
 
... It's only when I connect the cat to the system that I get vapour production again.

Two things you have said are
1. You get the cloud of condensation in the morning
2. You get it only if the cat is connected.

Which brings me back to an earlier comment -- are you sure what you are seeing is not just water vapor that has collected in the exhaust system (primarily cat and muffler) from the previous night's run?

Do you drive far enough the previous night so that the exhaust system is really toasty-hot before the Jeep is shut down for the night? If not, you are blowing out not only what is being generated in the morning, but the previous night's water as well.

Just a thought.

Oh yes -- at one point you seemed to indicate the vapor is water -- it didn't smell like it had any coolant. Did you ever do the rag test and taste the result?

I hope this helps.
 
Two things you have said are
1. You get the cloud of condensation in the morning
2. You get it only if the cat is connected.

Which brings me back to an earlier comment -- are you sure what you are seeing is not just water vapor that has collected in the exhaust system (primarily cat and muffler) from the previous night's run?

Do you drive far enough the previous night so that the exhaust system is really toasty-hot before the Jeep is shut down for the night? If not, you are blowing out not only what is being generated in the morning, but the previous night's water as well.

Just a thought.

Oh yes -- at one point you seemed to indicate the vapor is water -- it didn't smell like it had any coolant. Did you ever do the rag test and taste the result?

I hope this helps.

This is the thing. There are three issues:

1. Was this vapour always being produced, and I just never noticed it because I normally never let my Jeep warm up before driving away?
2. If this is a new issue, how did tearing apart the exhaust cause it? Did I somehow damage the Cat, and the Cat is now just producing more vapour, or did I somehow crack the block/head while reefing on the exhaust? Maybe an exhaust restriction introduced during the exhaust work, led to the development of a crack?
3. Either way, I've got the issue with #6. I KNOW there's a leak from #6 to coolant because I can blow air through it, and when I disconnect fuel or spark from #6 while running, I start blowing vapour.

No matter what, there is an issue with #6. I don't know what caused it, but I know that if it's not making combustion, it's making water vapour, and tonnes of it. It seems too coincidental that I ALSO blow vapour during cold startup, and that i've never noticed either issue until just now.
I suppose it's possible I've been blowing coolant this whole time, but the cat was either plugged and not vapourizing the coolant as much, or the cat was working, and vapourizing the coolant/water fast enough that it didn't have time to fog up my entire driveway.

I sorta think this last bit is probably right. I think I've been blowing coolant for years, both before and after installing the new head, but my cat was masking the symptoms until I broke the cat. Sound reasonable?
 
My 97 4.0 drips all the time. I dont see It as an Issue.
 
I'm betting on a deck imperfection, warped head or block, or ****ed head gasket... or it is just blowing condensation.

Mine doesn't do it that much but eh, I have no idea what else it could be especially if it doesn't smell sweet.
 
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