C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Head gasket?

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Old Apr 8, 2025 | 07:53 PM
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Default Head gasket?-UPDATE-happened again!!

1996 with 80k miles. So here’s the scenario. Took it out for a spirited drive, everything running great. Parked for a short walk, got back in and almost immediately noticed a bad miss, pulled out onto the highway and saw a lot of smoke coming out the back. Drove a couple miles and the low coolant and check engine light came on, by now I’m starting to worry so I found a good place to park. Nothing leaking from the engine bay, completely dry. Checked the oil and it was HIGH and looking a little milky! Let it cool down completely and checked the coolant and it was LOW and kinda oily. I thought it best not to drive any further and had it towed home. At this point I was able to drive it off the wrecker and into the garage, running smooth and no odd noises, just some smoke out the right exhaust. So, do I have a head gasket job to look forward too, and if so any tips are welcomed.

Last edited by gtFOOTw; Apr 26, 2026 at 10:52 AM. Reason: Update
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Old Apr 8, 2025 | 08:34 PM
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Yes, sir. You do have a head gasket job on order. Could be worse if a chunk of cylinder head cracked/broke.
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Old Apr 8, 2025 | 10:06 PM
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Originally Posted by marshallnoise
Yes, sir. You do have a head gasket job on order. Could be worse if a chunk of cylinder head cracked/broke.
The more I think about this I believe that’s the situation. Last fall after the annual oil change I had a Blackstone oil analyst done and it had high levels of potassium and sodium which indicate coolant contamination. I hardly drove it over the winter and was just gonna keep an eye on coolant level, now this.
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Old Apr 8, 2025 | 11:29 PM
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I would not start the engine until the cylinder head came off and the issue resolved.
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Old Apr 9, 2025 | 11:54 AM
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Originally Posted by pltmgr
I would not start the engine until the cylinder head came off and the issue resolved.
Or at least pulling the plugs and checking for water in the cylinders. It could be a teeny amount. But much more than a spoonful would indicate a big problem.
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Old Apr 10, 2025 | 12:16 PM
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Ordered new gaskets and bolts, about to begin disassembly. I’ll update with my findings and progress. I have the FSM and watched a number of videos so I feel pretty comfortable with the task. Btw, called a local “classic car” shop and they quoted me 15 hours and $3k! Nope that wasn’t happening.
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Old Apr 10, 2025 | 12:18 PM
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Originally Posted by gtFOOTw
Ordered new gaskets and bolts, about to begin disassembly. I’ll update with my findings and progress. I have the FSM and watched a number of videos so I feel pretty comfortable with the task. Btw, called a local “classic car” shop and they quoted me 15 hours and $3k! Nope that wasn’t happening.
Yeah, screw that! Its not that hard. The worst part to me is getting the Torx bolts out. There are 17 bolts in each head so just count them before prying the head off. You got this!
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Old Apr 10, 2025 | 03:36 PM
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I will do it for $2.5K

I will eventually have to travel this same road... best of luck to ya.
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Old Apr 11, 2025 | 04:09 PM
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I got confirmation that it’s a head gasket by the looks of this milkshake ****. But now a problem, can’t get this air pump line nut to come loose. Could feel the open end wrench start deform it so stopped and got a flair nut wrench. It’s still wanting to deform before budging. I soaked it with PB blaster for a day but no luck. Not sure how to proceed?

Milkshake
Milkshake
Stubborn nut
Stubborn nut
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Old Apr 11, 2025 | 04:29 PM
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Originally Posted by gtFOOTw
I got confirmation that it’s a head gasket by the looks of this milkshake ****. But now a problem, can’t get this air pump line nut to come loose. Could feel the open end wrench start deform it so stopped and got a flair nut wrench. It’s still wanting to deform before budging. I soaked it with PB blaster for a day but no luck. Not sure how to proceed?

Milkshake
Milkshake
Stubborn nut
Stubborn nut
Yessir! That's a smoking gun.

I would get a torch and heat the ever loving crap out of that nut. Then hit it with WD or your lubricant of choice. Do not breathe the fumes (duh). Wash, rinse repeat. Also try tightening the nut first a teeny bit, then work it back and forth like you are chasing a thread with a tap. You'll get it.
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Old Apr 11, 2025 | 04:58 PM
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Originally Posted by marshallnoise
Yessir! That's a smoking gun.

I would get a torch and heat the ever loving crap out of that nut. Then hit it with WD or your lubricant of choice. Do not breathe the fumes (duh). Wash, rinse repeat. Also try tightening the nut first a teeny bit, then work it back and forth like you are chasing a thread with a tap. You'll get it.
What he said
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Old Apr 11, 2025 | 05:09 PM
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Take acetone and mix it 50/50 with automatic trans fluid. Put it in an oil squirt can and shoot it on seized parts and give it time to soak. It works better than anything else Ive used. You will probably need it on the exhaust manifold flange nuts underneath too. When you get to those, use 6 point sockets only.

Order exhaust manifold flange stud kit while you’re at it
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Old Apr 11, 2025 | 08:52 PM
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I finally got it out, but I don’t think it’s reusable. Does this pos need to be reinstalled? Tearing it off and putting a plug in that hole sure would be nice

Nut is trashed, threads look stripped
Nut is trashed, threads look stripped
And the there was a hidden bracket attached to the back of the head! I had enough, it got the sawzall.
And the there was a hidden bracket attached to the back of the head! I had enough, it got the sawzall.
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Old Apr 12, 2025 | 02:19 PM
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It's the air injection. If you don't have smog check in your area then just plug it.
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Old Apr 13, 2025 | 12:17 PM
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Default Update

Small victory this morning! Block sensors, dipstick and exhaust manifolds removed without a hitch. Now just intake then the heads, ez pz right? On previous issue full emissions required where I live so ordered new air injection pipe from ZIP.
No problem
No problem
EZ
EZ
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Old Apr 13, 2025 | 12:41 PM
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It’s always nice when exhaust bolts cooperate. 👍
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Old Apr 13, 2025 | 03:23 PM
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Gasket left
Gasket left
Block left
Block left
Head left
Head left
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Old Apr 13, 2025 | 03:28 PM
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Heads are off! I don’t see any obvious failures but I don’t know what to look for. Any experienced eyes see a problem?
Gasket right
Gasket right
Block right
Block right
Head right
Head right
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Old Apr 13, 2025 | 04:14 PM
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Some additional information, when I pulled the knock sensors the coolant looked very pure, so I don’t think much oil got in it.
But you could see from the “milkshake” in earlier pictures there’s definitely coolant in the oil. Another odd thing, the intake manifold bolts were very loose, some seemed finger tight, is this normal?
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Old Apr 13, 2025 | 04:23 PM
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Take some pictures of the intake gaskets, especially the ends that go around the water jackets. You might have been losing coolant into the crankcase via bad intake gasket
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