Late '85 HT 4100 white smoke from exhaust. Are there specific gasket tests?
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HT4100 4.1, 4.5, 4.9 Discussion, Late '85 HT 4100 white smoke from exhaust. Are there specific gasket tests? in Cadillac Engine Technical Discussion; Hi everyone, I've been out in the garage slowly bringing the '85 Seville back to life. It's been driven only ...
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    highonchai's Avatar
    highonchai is offline Cadillac Owners Fanatic
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    Late '85 HT 4100 white smoke from exhaust. Are there specific gasket tests?

    Hi everyone, I've been out in the garage slowly bringing the '85 Seville back to life. It's been driven only once a year for the past 3 years, and currently has 135k on the odo. I drove it across town last June and it's been sitting since then. I started it up two weeks ago, and after a short time at cold idle white smoke started to billow from the exhaust, so we know it's a coolant issue, and most of what i've read points to an intake gasket leak.
    Now there's a lot of shifty info to sift through about head gaskets, intake gaskets, a cracked block or head. Is there a simple way to check for an intake gasket leak? To my knowledge the car has never overheated, so I'm not going to jump to any conclusions about the head gaskets, block or cyl-heads just yet. Is it a good idea to just go ahead with an intake gasket replacement since it's cheap and reasonably easy to tackle?
    She's an '85 Commemorative Edition, built at the end of the '85 model run, so I'm going to assume it has the updated intake gasket/ hardware setup.
    I'll plan on doing an oil change before, after, and soon after a gasket change to help flush out any coolant. Is there anything else i should be concerned about or looking for when I tear down the intake? Any serious issues that traces of coolant sitting in the combustion chamber or valve train might cause?
    This car sees less than 200 miles a year (which is a crying shame that I'm finding a remedy for), are there extra precautions I should take concerning the engine while it's in storage?

    Thanks for any help!
    Please do me a huge favor and refrain from the "The 4100 sucks, scrap it!" type comments, id appreciate it.

    As always, y'all make the Cadillac of automotive forums! Thanks again,
    -Alex

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    drewsdeville is offline Cadillac Owners Master
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    Re: Late '85 HT 4100 white smoke from exhaust. Are there specific gasket tests?

    You can assume an intake gasket leak by eliminating everything else. Any other symptoms? Any bubbling coolant in the radiator or reservoir? Does the coolant smell like exhaust? Any coolant in the oil? If so, how much?

    Any other symptoms at all?

    Frankly, if I was pulling the intake on a 30 year old engine, I'd want to replace the head gaskets whether they were currently leaking or not. Remember, on this engine, the valve covers and rockers need to be removed to get the intake off. That said, you'll be 95% of the way to the head gaskets. All you'd need to do is remove the head bolts and pull the heads off. You may need to repair some head bolt threads in the block, but it's not as scary as it sounds...

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    highonchai's Avatar
    highonchai is offline Cadillac Owners Fanatic
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    Re: Late '85 HT 4100 white smoke from exhaust. Are there specific gasket tests?

    Thanks for the reply drewsdeville,
    Haven't seen a false boil or bubbling in the reservoir, nor does the coolant smell like exhaust. I haven't checked the radiator cap though. The oil looks and smells like oil (not milky), although the car doesn't see much run-time, so it seems there's little opportunity to pick up much coolant. Unfortunately, this also allows little opportunity to notice other symptoms other than the white plume out of the rear. I'll pull the codes this evening to see if anything gels.

    That's a good tip - it makes perfect sense to replace all top-end gaskets while it's torn down, I was just having nightmarish thoughts about pulling the heads, so thanks for the moral support! (But the engine is only 27, I feel old enough, I'm not about to start rounding up and telling folks I'm 30

    I'll post any other findings tonight.
    Thank you again drewsdeville!

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    highonchai's Avatar
    highonchai is offline Cadillac Owners Fanatic
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    Re: Late '85 HT 4100 white smoke from exhaust. Are there specific gasket tests?

    Well, I started her up again this evening and instead of billowing gobs of white exhaust, it hummed just like it used to with a steady, dissipating puff-puff of fog. I'm beginning to wonder if a good amount of moisture had gathered in the tank over the fall/winter and just needed to burn out, or maybe the coolant additive is doing its job? Certainly no oil or coolant contamination or bubbling. I certainly don't believe I'm out of the weeds on this, but I'll grab a bottle of dri-gas and add a bit of fresh fuel; see if it clears up even more.
    The only code it threw was E30, ISC RPM Out Of Range.
    I'll keep you updated. Thanks again for the advice!

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    brougham is offline Cadillac Owners Master
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    Re: Late '85 HT 4100 white smoke from exhaust. Are there specific gasket tests?

    It's probably just condensation. That's the most common cause of white smoke. If it doesn't smell like burning coolant and the level isn't dropping don't worry about it.

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    carnut is offline Cadillac Owners Master
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    Re: Late '85 HT 4100 white smoke from exhaust. Are there specific gasket tests?

    As an ex Cadillac service advisor when these cars were about 3 years old, the best way I found to verify an intake gasket leak was to remove the oil fill cap or PCV valve. If the underside of the cap or PCV had a milky residue, 99% of the time, the intake gasket was corroded away at the front coolant crossover passage. Smoke and coolant steam are two different things! Steam dissipates quickly, smoke lingers and does not evaporate. Catching the leak early prevents the camshaft and lifters from being damaged. As you know coolant needs to be drained and replaced every 2 years regardless of mileage. Pulling heads on a 4100 is easy but realigning the piston barrels or liners for deck height requires special measuring tools to get right. This engine has 8 individual barrels holding the pistons, all of them have shims at the top and bottom to set proper deck height. The head clamps the barrels down, not the conventional top deck on a cast iron block.
    highonchai and highonchai like this.

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