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  1. #1
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    Exhaust in my coolant, but good compression?

    My 2002 9-5 Aero wagon has been losing (somehow) about 8 to 12 ounces of coolant every 100 miles, or 2 hours of driving. I noticed a hissing sound when removing the coolant reservoir cap and what smelled like exhaust. I also see bubbles coming into the reservoir from the small, upper hose while the engine is running. There was also the smell and steam of coolant coming from the exhaust manifold/turbo area. A friend and I tried to see the exact place of the source, but just couldn't see it. Also, the engine is running VERY strong, but has a bit of a hard time starting sometimes. I believe the onset of the two issues are about the same, but not sure. Turbo boost is good. No visible smoke, steam, or water coming out of the exhaust pipe. Get the "fill engine coolant" message after a while (expected) and get the P0116 code if I don't keep the reservoir kinda full.

    Assuming the vapors were due to a blown head gasket, but being in denial, I checked the exhaust manifold nuts/studs for tightness. Several were not quite tight enough, and one was broken. It still is. Still hoping NOT to have to do the head gasket (at least I've already done one), I started looking and asking around for other paths in which exhaust/coolant could find their way into each other's realms. I thought I remembered there being coolant connections in the turbo, so got my hopes up that there could be crossover there, but someone in one of the forums said the coolant paths in the turbo wouldn't have any access to the exhaust path unless the turbo had a bad crack. The turbo is working quite well.

    I re-torqued the head bolts. Only one seemed to be less tight than the others. This seemed to help a bit, but now, two weeks later, were back to the same amount of coolant loss. No drips apparent either. The coolant smell is practically gone, but that's probably because I've completely diluted the antifreeze by only adding water. Don't see the "coolant vapor" rising from the exhaust manifold/turbo area any more, either.

    I checked compression, and with the engine hot got 160-170-160-177psi for cylinders 1-4, respectively. Spark plugs looked good (clean, dry and light toasty tan/brown). These numbers seem normal to me, and I'd hate to go through a head gasket job only to end up with the same problem - especially since the car runs so well.

    Any ideas? How else could the exhaust and coolant mix if not the head gasket? Just want to exhaust other pathways before replacing the head gasket. Thanks in advance for your thoughts!

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  2. #2
    Marty Jackson
    Saab Addict Finding41's Avatar
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    I'd check the coolant by-pas valve. Mine was leaking on my 03 and I couldn't find a puddle or any wet spots.... I noticed a white colour directly below it though. The coolant was evaporating off the exhaust...
    I think any exhaust gas getting into the coolant would need a pretty catastrophic gasket failure.
    1-Here is a picture of the block with the gasket on.
    2 Block no gasket.
    3 head.
    Attached Images Attached Images    

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    finding41
    Marty Jackson
    www.northchannelcharters.com

  3. #3
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    Thanks, Finding41. Great reply! You've given me hope. I'll check the bypass valve tomorrow and reply (I'm out of town until late tonight). I'm not sure how its failure would result in that smell in the reservoir, but it sounds like we agree that the compression test indicates a sound head gasket.

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  4. #4
    mdb99@bellsouth.net
    Oh! I Get It Now Mike Brennan's Avatar
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    I believe you can have a defective head gasket which lets out combustion into the cooling system but still works to keep coolant out of the oil. It would seem your coolant loss is the water in the coolant boiling out as steam. Just don't think the CBV is the issue here.

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    Last edited by Mike Brennan; 06 April 2014 at 17:30.

  5. #5
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    Mike Brennan, you reminded me that I forgot to mention that there is no sign of water/froth in the oil. Thanks for touching on that. Everyone's been saying that if the head gasket has failed, the compression would be drastically lower in at least one cylinder. But I wonder if a smallish leak (between the cylinder and coolant passage) could represent itself as a compression reduction within the variation of the other cylinders, yet enough to replace coolant (drawing it in du4ing the intake stroke?) with exhaust (during combustion) or compressed fuel (air/gas mixture on the compression stroke). Or just forcing the coolant out somewhere else I haven't pinpointed. Still planning on checking the CBV as a matter of course. It's probably due anyway. 140k miles and hasn't been changed. I had one fail on my '01 9-5 Aero sedan.

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  6. #6
    mdb99@bellsouth.net
    Oh! I Get It Now Mike Brennan's Avatar
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    Well, you have exhaust in your expansion tank so I can't think of what else it might be. Try to PM Burnside. He knows everything.

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  7. #7
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    Thanks, Mike Brennan. Will do. I will update this post with progress.

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  8. #8
    Marty Jackson
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    Guys how much pressure can the cooling system take?
    I mean... If it's pressurising the cooling system it's got to blow off some where.
    Wouldn't it blow off through the cap on the expansion tank?
    I think something has to give in the way of blowing off. I think the weak link in the cooling system is the bypass valve. (Maybe that is what kills the bypass valves.)
    I hope it's not the head gasket. If it turns out that it is it's not to hard to replace.

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    finding41
    Marty Jackson
    www.northchannelcharters.com

  9. #9
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    Thanks, finding41. I've done the headgasket on my '01 Aero. You're right. It's not too bad. Life is always most demanding when time is short. When I filled the reservoir (not what I normally do), coolant DID blow out of the cap. I should replace it, since there's some brownish crud around the neck off the reservoir, and I DID just recently have to replace the radiator, due to its tank separating from the aluminum. This happened right after gunning it for the first time in a while. Made me wonder if there was too much pressure in the cooling system. Bad cap combined with vapor leak into the coolant? The cap DID seem to work when I overfilled the reservoir.

    Anyway, I'll check the coolant bypass valve tomorrow. Just don't understand the exhaust/fuel smell in the reservoir. Especially with good compression.

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    Last edited by Saabster Tale; 08 April 2014 at 00:17.

  10. #10
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    I changed the typo, "overcooked" to "overfilled".

    More importantly, I let the engine warm up and let it idle for about 25 minutes. The occasional bubbling into the reservoir was present, but I could find NO drips anywhere. I had a clear view of the Coolant Bypass Valve, and it was dry (maybe the leak is too slow to see regardless of where it is). If it loses 12 ounces in an hour, that's an ounce every 10 minutes. That's 2.8 ml/minute, or about one drop/second. I think I'd see even one drop every 4 seconds without much difficulty, unless it's oozing onto something very hot. Still wondering if a leak that slow would really show up in a compression check.

    I checked all the coolant connections I could think of, and even had a friend double check and rethink new places to look. There was a tiny puddle of water just inside the end of the exhaust pipe, but I'd expect that to be normal. Nothing visibly leaking from the front of the head, the radiator ports or drain plug, the water pump, the turbo connections, or the other ends of the radiator hoses. Nothing on the ground. Still get that exhaust/fuel smell from the neck of the reservoir upon opening.

    Unless other ideas surface, I'll just keep using the car as is, with a gallon of backup water for maintaining the proper coolant level in the reservoir, and just keep checking things as they get worse. What makes this extra fun, is that I just learned I'm moving to Hawai'i for 1 to 3 years, and this is the car I'd like to have shipped there (we get one car shipped for free). I won't be equipped there for doing the kind of diy stuff that I do here. Definitely need to resolve this before it ships anywhere. Thanks for all the great input so far! Still hoping to hear from burnsside42.

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    Last edited by Saabster Tale; 08 April 2014 at 00:49.

 

 

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