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| Joined: | 04-07-2022 |
| Location: | Oregon USA |
| Posts: | 111 |
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Greetings All,
My wife's JH recently developed a lot of white smoke from the exhaust. Prior to this the car ran fine with only a trace of greyish smoke on acceleration. It happened immediately after starting a flooded engine. I thought it would clear up do to the flooded engine but the white smoke persists and gets worse as the car is driven. I understand white smoke from the exhaust is caused by coolant entering the cylinders and could be due to a blown head gasket or even cracked cylinder. So I did a few test to see if I could determine the cause.
1. Compression test good with all cylinders 175-180 lbs. Thought this might show any issue with a blown head gasket.
2. Leak Down Test. All cylinders except #3 20% or under. But #3 around 50% leakage and bubbles appearing in the radiator. So this now looks like a blown head gasket.
I was thinking it might also be a blown intake manifold gasket but no air leakage around this manifold.
Thanks,
Brit
I agree with your diagnosis of a blown head gasket. It has blown between a cylinder and the cooling system - all the symptoms you describe point to it. It is not too surprising that the compression test came out normal. The "flooded" engine may have in reality been difficult to start because coolant had leaked into a cylinder overnight. You may have done nothing wrong...
The grayish smoke on acceleration indicates you are a touch rich while accelerating. I don't know if you have the Dellortos or Strombergs. If you have the latter, you should try some thinner oil in the dash pots. If you have the former, you probably need to reduce your accelerator pump shot.
Many things can cause a head gasket failure; A cracked head, improper torque on the head studs, warped head, a liner that is recessed relative to the others (spec is + 0.001" across all the liners), tightening the studs in the wrong order, etc.
Do not drive the car - the coolant is highly corrosive when it becomes steam in the combustion chamber and it will start pitting the head and valves.
Suffice to say when you replace the gasket, you will need to scrutinize everything; cracks, uniformity of the liner heights, calibration of your torque wrench, verify tightening sequence, check head for warpage, blah, blah, blah.
I just had my head reworked as part of my restoration. Aluminum heads cannot be crack checked except by inspection. I had a crack in my head that did not become apparent until after the head was skimmed. Interestingly, it was a crack originating in a cooling passage between cylinders one and two. The car had obviously been driven for a while, as those two cylinders had significant pitting. So the head gasket did not cause the failure, but a crack did. Then the car was parked and not driven for years. I acquired it and have been restoring it for the last 2-1/2 years. Just getting around to reassembling the motor.
So, it may not be the gasket that failed, rather something else that caused the gasket to let go. You won't know until you open the motor and inspect things. The good news is that you need not pull the motor although it would be easier to work on the engine if you do. Your call.
Vance
Last edited on 07-09-2025 06:31 pm by vnavaret