Blown head gasket? Help me confirm and really make my day! -
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post #1 of 12 Old 04-25-2013, 08:35 PM Thread Starter
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Blown head gasket? Help me confirm and really make my day!

Yeah, so my first post here (woohoo!!!), sadly I don't think it'll be a cheerful one. Sorry about the sarcasm, this comes on the back of having to replace the engine on wife's Acura after an oil pump failure.

I have a 97 GC, 4.0l, Automatic, 160k miles. I've had the car for 12 years, it's been great to me. No issues, no problems and no rust although it's been driven in Chicagoland. Always started up first time and frankly, I was pleased with the gas mileage - 16.7 mpg mix.

Until Monday night. Driving on the highway at 65 mph, car stalls suddenly with a check engine light. No coughing, no bucking. Just a sudden stall. Pull on the side of the road, key trick, code 11 - Crankshaft sensor. Not a big deal, we know these are finicky on Jeeps. Tried to start car, engine turns but does not try to fire. Called tow to get back home. When we arrived back, car fired right up and was driven off the tow truck into the garage. Stalled the moment it got parked!

Next morning I give it another shot, car fires right up, runs for 10 mins. No stall, no issues. Turn off and back on a couple of times, fires right up. Check Engine code clears up!!!! which means it only threw the code the 1st time it happened.

Still, given that the CPS is a known issue, I go buy another one and put it in. Only took me 1.5 hours with its ridiculous location. Car fires right back up and I take off for work. About 15 mins into the ride, there are a few small misfires, nothing big. NO attempt to stall. A few mins later, the gas needle starts to do small jumps. Aftermarket CPS are hit or miss; I clearly missed I thought.

Still car drove fine overall. Drove back home at night and noticed that for the first time in all the years I own it, the oil pressure starts to climb when I accelerate. Always used to be at 35 regardless, now it went up to 45 and even 50 under acceleration! Hmmm.

No time to work on it Tuesday night. Drove it to work this morning, exactly same behavior. Drove back home, same thing. Picked up another CPS to put in and while I was at it, I thought I'd do my annual pre-summer spark plug change and do the oil too while I was at it.

So, I get this all done. No problem, much faster on CPS this time. Fire the car up. Fires up first time. A min later starts a lot of -small- misfires, can hardly keep idle, tries to stall but doesn't. Oil pressure going up again when I step on gas. I rev it up a bit for a min, let it come down again. Same thing, running really bad, rpm needle keeps jumping.

Turn engine off and I hear a sound of liquid coming down and like a tank was emptying (gurgling sound). I look under car, coolant is coming down from the front of engine, right in front of the radiator fan. Decent amount but not huge. I feel the water, it's *cold*. Cracked hose, I thought.

Grab my light, can't see or feel a wet hose. Water pump? I walk out the garage a min, notice a BIG puddle under my exhaust! Looks like water with a hint of oil perhaps?

SOB! Go make a coffee, it'll be a long night. Back 5 mins later. I put paper towels under exhaust so I can easier see what's coming out. Start the car, runs just as rough, vey rough. Rev it up a bit, grab my light to find leak.... Wait, there's no coolant leaking!!! rev engine more, still no leaks! After 10 mins, I turn the engine off.

Still no visible water leaks. But as soon as the engine is off, I can hear liquid dripping under engine. I jump under, definitely something dripping into oil pan? I look at the water tank, way under Minimum. It was full just 2 days ago. Radiator is still full. Looking at towels under exhaust, big water puddle with a whole bunch of black spots - oil or carbon deposits?

No, I can't see foaming in the radiator. Pulled oil stick out, since I just changed oil it looks clear. Can't swear on consistency.

And there's my story ladies and gents. What do the esteemed members of the forum think? water pump or head gasket? Me thinks if the water pump gave up, I wouldn't be hearing dripping into the engine, no? what about all the initial water visibly leaking from up front?? I am quite puzzled.

Apologize about the verbose post. I always hate incomplete information although I may have overdone it this time

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post #2 of 12 Old 04-25-2013, 10:54 PM
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Did you lay under the jeep to look right under the water pump to see if it was really wet?
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post #3 of 12 Old 04-25-2013, 11:43 PM
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When a head or head gasket fails you will usually have one or more of the following happen.

1. If leaking coolant into a cylinder you will normally have a thick cloud of white smoke (fog actually) coming from the tail pipe.
2. You will have oil leak to a cooling passage, causing a nasty chocolate milkshake appearance in your radiator.
3. You will have a coolant passage leaking into an oil return passage causing the chocolate milkshake appearance in your oil, visible on the dipstick.
4. You will have cylinder pressure leaking into the cooling system causing the coolant to leave the cooling system rapidly and in a fairly large volume.
5. You will have oil and/or coolant leaking externally at the seam between the head and block.

Without seeing it I would guess that what you are seeing at the tailpipe is just normal condensation from the exhaust which will have carbon flakes in it. If you were blowing a fog of coolant out the tailpipe you'd have a hard time not seeing it or smelling burnt coolant.

As for the dripping sound in the oil pan after you turn the engine off, I would guess you are hearing normal engine oil drainback from the top of the engine to the pan.

Your description of where the coolant was dripping confuses me a little. I consider the radiator to be in front of the fan, and the water pump to be behind it. Were you seeing coolant coming from the radiator or water pump? Both of those are common problems.

The gurgling sound you heard was the radiator trying to pull coolant from the coolant resevoir. If the level is low it will make a pronounced gurgling sound.

Personally, from your descriptions I would guess you have a leaking water pump or radiator, or even the hose going to the coolant resevoir. You're going to have to refill the cooling system to make sure where the coolant is coming from.

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post #4 of 12 Old 04-25-2013, 11:45 PM
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Coolant in front of engine. Possibles:
1. Radiator leak. ( common. Most of us have replaced at least one by now.)
2. Water pump, or the obvious...a bad hose.
3. Radiator overflow line ( rubber tube) has a leak.

Gurgling: Cooling system regurgitating into coolant bottle near passenger side firewall, hopefully....

Coolant coming out of exhaust. Are you sure it's not being blown back by the fan and then running along the outside of the pipe? ( a stretch, I know..but I'm trying to remain optimistic here...) If it's coming from inside the pipe....well....this isnt good, my friend. ( duh)

I'd first opt to locate and repair the front coolant leak.
Then I'd drain the oil and take a look at it. If there are any milky streaks you might have a cracked head ( yeah, they do that too) or a blown head gasket. But I dont think that's your issue...after re-reading your post.

I'd also pull a spark plug to see if there is any rust or water droplets on it. ( this is how I diagnosed a leaky head gasket on my outboard in time to fix it before it blew it up) ( water doesnt compress)

The oil pressure will normally increase as RPMs increase...but it doesnt "jump", nor does it move much. It'll cost you 5 qts of oil to find out. Good luck !

2007 5.7 Hemi, Ltd. QD II -
1997 ZJ, 4,0 select trac, Up country, track lok.
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post #5 of 12 Old 04-26-2013, 04:39 AM
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One way to diagnose a blown head gasket

Walk up to the vehicle when you've been away from it for an hour or two, so your nose has good sensitivity to fuel/exhaust.

Open the radiator cap, stick your nose as close to in the radiator as possible.

If you smell fuel or exhaust, that's a blown head gasket.

BTW- some black condensate from the exhaust is normal, especially during humid spring weather. But only on a cold engine. If you've driven +10 miles and it's still pumping water out the tailpipe, that's probably a head gasket. Put your hand down and catch some of this water, does it smell sweet like antifreeze?
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post #6 of 12 Old 04-27-2013, 05:40 PM Thread Starter
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Hey guys, I am sorry for the late reply. It's been a little crazy.

To answer the questions:
- coolant leak was coming from front of engine. If you're standing in front of Jeep, you have radiator, fan, engine block. That was not the radiator leaking. I've run the car a few times since, that is still the only time that I saw coolant leaking!
- checked on the exhaust again. No white smoke (phew??), but the condensation puddle is huge in just 5 mins of running engine. Lots of carbon flakes as expected, no oil visible now. But it still pumps up a LOT of water throu exhaust, mostly when gas is applied. Hot, cold engine, has made no difference.
- definitely coming out from inside exhaust.
- coolant in radiator looks & smells normal.
- same thing for engine oil but keep in mind it was just changed when this happened. So unless a lot of coolant ended up in it, itd take a while to look fouled.
- pulled the brand new sparks, no water droplets, no rust.

I am missing a lot of coolant and amount missing is not consistent with what I saw leaking out. Have felt around all radiator hoses, can't find a bad one. I do think the water pump somehow has failed so I'll be replacing that tomorrow. Still doesn't account for all those symptoms and there was only one leak.

I am still concerned because the engine is running just so horribly bad, I know what the CPS does but that's too extreme to be just CPS. Also miffed about Oil Pressure; in all these years it has been extremely consistent and has never increased pressure when accelerating. Yes, I am aware that a lot of ZJ owners experience this and it's generally regarded as normal but when it's never been an issue...

Shame cause I love this Jeep. It's never given me any problems and has been rock solid. No rust, no damage.
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post #7 of 12 Old 04-28-2013, 11:08 AM
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Is it possible he has only a minor leak of coolant and most of it's getting vaporized?
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post #8 of 12 Old 04-28-2013, 10:03 PM
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Well, I still think you're chasing three or four different problems that have either happened at the same time or have been noticed at the same time.

On the oil pressure problem I hadn't seen before that you had just had the oil changed and the problem showed up after that. Considering where the oil pressure sending unit mounts on your engine it is possibly that it was damaged during the filter change. The only sure fire way of knowing what is going on with your oil pressure is to hook up a mechanical gauge and see what it shows. Still, I think you have a damaged sender.

On the coolant leak I still would think the water pump is a good bet. You said you were going to replace it today. Did you look the old one over, did it show signs of coolant leakage at the weep hole area?

On the running rough problem it may be an installation problem with the crank position sensor. I know a lot of guys here say Mopar or nothing on it, but at the shop we also had good luck with the aftermarket ones. Two things you have to look out for on the installation. One is the thickness of the sensor spacer. The Mopar sensor spacer is 0.033" thick. Most of the aftermarket sensors have spacers running .050 to 0.070 thick. That places the sensor too far away from the drive plate and can cause poor running. The other thing that's tougher to do is to hold the sensor in position so it is just touching the drive plate as the mounting bolt is tightened. The long slot on aftermarket sensors can allow the sensor to move as it is tightened if you don't keep a light pressure on it.

As for a bad head or head gasket, from your observations I still would shy away from that until I checked or fixed the other problems. Your description of symptoms just doesn't indicate that to me. As for the moisture coming from the tailpipe, depending on weather conditions I've seen vehicles (including my own) that at times will seem to have an excessive amount of moisture in the exhaust, other times hardly any. Bear in mind also that running the engine for 5 or 10 minutes at a time doesn't get the exhaust warm enough to get rid of all the moisture, but it does get it warm enough to add more as the exhaust cools.

Let us know what you find.

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post #9 of 12 Old 04-28-2013, 10:07 PM
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Originally Posted by Moparmissus View Post
Is it possible he has only a minor leak of coolant and most of it's getting vaporized?
Not from his descriptions. Sounds like a pretty serious coolant leak, and he says he see's no sign of coolant vaporization, which would be steam coming from the exhaust if an internal leak, or under the hood if an external leak.

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post #10 of 12 Old 04-28-2013, 10:52 PM
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I concur with almost everything posted thus far...except for the possibility of a tiny radiator leak. 'Seen it happen too many times. Mine did the same thing. It was a biotch to locate until it got bad.

If you havent replaced your radiator cap yet, go ahead and do so. I've seen them leak slightly. Another possibility is a freeze plug. Most of us have replaced the side ones at least by now ( while we're replacing the factory exhaust manifold which cracked)

There are also a couple on the rear of the block.....or at least one small one as I recall. You wont see that one leak until it gets bad, most likely, due to it's location.

I've also seen cracked coolant bottles.

As for your fuel gauge jumping around, I'd start with cleaning all engine ground points. Fender well, near oil dipstick, coil, and of course, at the battery.
There was a recall of some of the fuel tank sending units on the 97 models. Might want to check that.

Another tidbit: If your batttery is the least bit low, go ahead and replace it. ( after checking the alternator output)
Jeeps HATE bad batteries and "unclean" 12v power to the PCM.

2007 5.7 Hemi, Ltd. QD II -
1997 ZJ, 4,0 select trac, Up country, track lok.
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post #11 of 12 Old 04-29-2013, 08:32 AM
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It's not a Jeep... but a few months ago while servicing my daughters Toyota 4runner, I noticed that her coolant level was down. I was having to refill it once a week. There was no visible leaks or puddles. Oil was ok. Then one day the truck starting running rough as in it was misfiring. While under the hood trying to find the problem..... the while smoke started pouring out the exhaust...HEAD GASKET. looks like it was slowly on the way out. Luckily it never overheated so repair was basic. So.. my guess if you are having unexplained fluid loss... beware. Oh and preceding the breakdown, there was more than usual condensation from the tailpipe.

1994 JGC Laredo
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post #12 of 12 Old 04-29-2013, 04:53 PM
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Changing the head gasket on a 4.0 is simple enough. If you are leaning towards it being bad, go ahead and change it. The hardest part is cleaning everything.

My cylinder head overhaul:
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My transmission overhaul:
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blown head gasket. 4.0 , cps , crankshaft sensor , water pump failure

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