Head gasket shot?

[east302]

Truck is my son’s 1998 K1500, 350 with 240k on it. He got home yesterday saying it was smoking out the exhaust but didn’t overheat (per the dash gauge).

I started it yesterday within a few minutes of him getting home, saw no smoke but coolant was low. It took 1/2 gallon to top it off. The coolant in the reservoir was bubbling while running and continued for a minute or two after shutdown.

I let it cool down for a few hours and went to start it, intending to open the cap, warm it up and see if it was bubbling in the radiator neck. It was seized, wouldn’t turn over at all with the crank pulley and a breaker bar (belt off).

Pulled the starter and tried again. Wouldn’t turn with the belt off. Pulled plug #7 and got it to turn. It then started and now smokes like a chimney. There looks to be fluid dripping out of the driver exhaust flange.

The front and back of the intake manifold seams are wet. The sides against the valve covers are dry. This wasn’t leaking a week ago and I replaced the gaskets with the metal backed Felpro a year or so ago.

The rear left corner at the block/head seam is wet with coolant as well but it could be dripping down from the intake. Can a head gasket leak be external?

Not sure where to go with this, honestly - could a head gasket leak cause the intake to start leaking so suddenly? Any suggestions on how to confirm if it is a head gasket? I’m now hesitant to run it to operating temperature to see if it’s bubbling in the radiator but it may be a moot point by now.

Oily looking fluid leaking from exhaust flange bolt:

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Cold start, 70 degrees outside and it’s smoking pretty good:

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Oil looks ok to me:

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[RichLo]

A compression check would tell you a lot.

 

[SAATR]

He's dead, Jim.

Time to start the autopsy. Driver's side head or gasket. Might be an easy fix, no guarantees without teardown and inspection.

 

[east302]

He's dead, Jim.

Time to start the autopsy. Driver's side head or gasket. Might be an easy fix, no guarantees without teardown and inspection.

Thanks guys.

So best case, just a head gasket. Going down the line, next could be warped head, cracked block and complete rebuild? The head(s) I could deal with but my garage isn’t big enough for an engine swap.

Having no sentimental attachment to this, trying to gauge the finances of it all and whether to cut my losses now.

Junior can take the bus to school, lol.

 

[RichLo]

Oil looks fine, Let us know the results of a compression test. Could be something besides the worst case scenario....

 

[Supercharged111]

Are we ruling out intake gaskets?

 

[east302]

Are we ruling out intake gaskets?

They’re definitely leaking, it’s just that it went from no leak last week to front and back walls being wet now. On my other two 98s, the leaks on those were more gradual and never this bad or had the steam coming out the exhaust or the bubbling in the coolant reservoir.

That’s what’s throwing me off, that and that it seized, but I don’t know what I don’t know. You know?

@RichLo how many revolutions for a compression test? Just be consistent on all cylinders? Never done one, will grab a kit tomorrow.

 

[PlayingWithTBI]

Since he's not onsite right now, I'll chime in.

Remove all spark plugs. Install compression tester in one hole, open throttle all the way, and crank until the gauge stops climbing. Write it down and move on to the next hole, rinse and repeat

Edit: A leak down test will help if your compression test doesn't show much difference between the cylinders.

 

[east302]

Roger that, thanks

 

[SAATR]

Not to disparage anybody's advice @east302 , but any testing you do from this point is purely academic. You named these symptoms:

1. Smoking (steaming) out of exhaust
2. Bubbling in coolant reservoir while running and after shutdown
3. Apparent hydrolock relieved by removing cylinder 7 spark plug.
4. Coolant at front and rear of intake manifold.
5. Coolant dripping from driver side exhaust flange.
6. Potential external coolant leak on the left rear (driver side rear?) head.

A bad or failed intake gasket could explain all but 2. The kicker is that both the coolant seal and the intake runner seal on one of the corner cylinders would have to both fail, together or separately, to allow coolant into the intake runner. For this to happen on a rubber/metal gasket in less than a year is improbable, at best.

The only explanation that incorporates all symptoms, including #2, is that the leak is in the combustion chamber itself, which is the only way you get compression/combustion in the cooling system and coolant in the exhaust. That means blown head gasket, cracked head, cracked cylinder. The most reliable way to confirm that is through disassembly. A compression test may point to the culprit, but a fair number of cracks and fire ring ruptures only show up on a hot engine, and test fine when cold. This one did just that:

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Notice the shiny spot in the fire ring area at the lower right quadrant. The leak only showed up when hot, nothing cold.