rayra
Expedition Leader
A. That the smoke appears after you let off the accelerator seems to indicate either oil or water is being drawn into a cylinder (or more than one) during the intake stroke and when there is less or negligible backpressure. Whatever is being drawn in is happening at negative manifold pressure.
B. What does that exhaust smell and taste like? Is it sweet? Does it smell / taste like burning sugar / glycol? It's white-ish, would sure seem to be coolant. But hard to really tell in your vids. I've seen bad oil ingestion problems that generate similar smokescreens. So the smell/taste is important.
A & B combined, could very well be - especially on an older high-mileage engine - worn (baked hard, cracked) valve stem seals or valve guides. The lower pressure on #4 with little change on a wet/oil test would also correlate with a valve problem. So would the smoke bloom at throttle let-off.
Not meaning to send you on a goose chase in another direction, but these are similar symptoms and should be considered and ruled out.
C. none of the plugs pictured were getting much if any coolant on them, before your rebuild. They would be much cleaner on the electrode / in-cylinder ends, much like a steam-cleaning. You might consider reinstalling those plugs and see which ones get cleaned by whatever is going on now.
D. The bubbles in the funnel mean very little. Even once the engine is 'burped' as you put it, it would generate bubbles on its own with no leaks, just as coolant boils near the combustion chamber. Put the pressure cap on and seconding the advice to borrow a coolant system pressure testing tool and see if you really have a coolant system breach. If there was a much larger air flow coming out, it would be determinative of a head or head gasket problem.
E. your numbered compressions, I don't usually see them numbered like that across a page and it actually helps in diagnosis to arrange the values the same way the pistons are arranged. As most often a head gasket failure occurs in adjacent chambers, typically 3-5 and 4-6.
That you have (surprisingly, in an old motor) very consistent compression readings across all but 1 cylinder and little change in the wet test of that cylinder would seem to indicate either a head gasket leak affecting only one cylinder or a valve / valve guide / valve seal problem or a possible head crack.
At this point and especially if that smoke cloud is sickly sweet and not just burnt smelling, I would perform a coolant system pressure test and I would consider introducing some stop leak into the system. Delco's large pellets or BAR's similar ground walnut shell product works well and it has completely stopped a head casting fracture problem on my motor. I've also successfully used Almuna-seal and Bronze-seal powdered metal products in emergencies.
It would solve two of the three possible problems / scenarios.
It's up to you whether to consider the stop leak a long term solution. It's a factory solution in the case of my CASTECH heads. It would certainly help determine that it's a head fault, re coolant getting into one or more cylinders. I would consider it as part of the diagnostic process, low / no labor one at that. And an interim solution to the problem itself. Frankly I'd put it in, do some low-engine-load local driving in it, run a few errands, re-test and maybe replace the oil if necessary and then drive it 'for real'. And make sure you have 'AAA Plus'.
eta
You've made major progress so far, even if it might not feel like it with the setbacks. Don't get discouraged. You haven't wasted your time. At a minimum you're learning new things. And at the very least you've done an otherwise good intake / fuel injection rebuild. Just need to nail down how you (seem to be) are getting coolant in the combustion (chambers)
One othe rthing I noticed in your pics, a lot of debris around the bolt holes in the heads when the intake was pulled? was that metal? some sort of thread sealant? Was their an variance in bolt lengths in the intake to head bolts and did they all go back in the same holes? There's a small possibility of over penetration of a bolt causing a crack resulting in a leak. It's possible to OVERtighten stuff too.
B. What does that exhaust smell and taste like? Is it sweet? Does it smell / taste like burning sugar / glycol? It's white-ish, would sure seem to be coolant. But hard to really tell in your vids. I've seen bad oil ingestion problems that generate similar smokescreens. So the smell/taste is important.
A & B combined, could very well be - especially on an older high-mileage engine - worn (baked hard, cracked) valve stem seals or valve guides. The lower pressure on #4 with little change on a wet/oil test would also correlate with a valve problem. So would the smoke bloom at throttle let-off.
Not meaning to send you on a goose chase in another direction, but these are similar symptoms and should be considered and ruled out.
C. none of the plugs pictured were getting much if any coolant on them, before your rebuild. They would be much cleaner on the electrode / in-cylinder ends, much like a steam-cleaning. You might consider reinstalling those plugs and see which ones get cleaned by whatever is going on now.
D. The bubbles in the funnel mean very little. Even once the engine is 'burped' as you put it, it would generate bubbles on its own with no leaks, just as coolant boils near the combustion chamber. Put the pressure cap on and seconding the advice to borrow a coolant system pressure testing tool and see if you really have a coolant system breach. If there was a much larger air flow coming out, it would be determinative of a head or head gasket problem.
E. your numbered compressions, I don't usually see them numbered like that across a page and it actually helps in diagnosis to arrange the values the same way the pistons are arranged. As most often a head gasket failure occurs in adjacent chambers, typically 3-5 and 4-6.
That you have (surprisingly, in an old motor) very consistent compression readings across all but 1 cylinder and little change in the wet test of that cylinder would seem to indicate either a head gasket leak affecting only one cylinder or a valve / valve guide / valve seal problem or a possible head crack.
At this point and especially if that smoke cloud is sickly sweet and not just burnt smelling, I would perform a coolant system pressure test and I would consider introducing some stop leak into the system. Delco's large pellets or BAR's similar ground walnut shell product works well and it has completely stopped a head casting fracture problem on my motor. I've also successfully used Almuna-seal and Bronze-seal powdered metal products in emergencies.
It would solve two of the three possible problems / scenarios.
It's up to you whether to consider the stop leak a long term solution. It's a factory solution in the case of my CASTECH heads. It would certainly help determine that it's a head fault, re coolant getting into one or more cylinders. I would consider it as part of the diagnostic process, low / no labor one at that. And an interim solution to the problem itself. Frankly I'd put it in, do some low-engine-load local driving in it, run a few errands, re-test and maybe replace the oil if necessary and then drive it 'for real'. And make sure you have 'AAA Plus'.
eta
You've made major progress so far, even if it might not feel like it with the setbacks. Don't get discouraged. You haven't wasted your time. At a minimum you're learning new things. And at the very least you've done an otherwise good intake / fuel injection rebuild. Just need to nail down how you (seem to be) are getting coolant in the combustion (chambers)
One othe rthing I noticed in your pics, a lot of debris around the bolt holes in the heads when the intake was pulled? was that metal? some sort of thread sealant? Was their an variance in bolt lengths in the intake to head bolts and did they all go back in the same holes? There's a small possibility of over penetration of a bolt causing a crack resulting in a leak. It's possible to OVERtighten stuff too.
Last edited:
