Fresh Rebuild Coolant in Exhaust/Exhaust in Coolant - Cracked Head?

[e30austin]

you should post some pictures of your cylinder head. top side with emphasis on the cam line, and the mating surface.

[zaq123]

tried this thing (link) into your expansion tank lid? if, no try it. -25 inHg of vacuum will find your crack or wherever the coolant ig going.

https://www.harborfreight.com/coolin...kit-64985.html

2 min test vacuum test with this endoscope into your spark plug holes

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[TobyB]

All I can add-

Get it hot and try pressurizing #6 at TDC compression. (basically, do a hot leakdown test)

My not- very- clever vote would be a crack somewhere which
only opens up when hot.

Is the head corroded?

I once put together an M10 that had corrosion in a water jacket that breached into a head bolt hole,
and only did it hot. Eventually, it left a trail on top of the head where coolant escaped from under the washer.

If you can't find anything else, yes, I'd try a different head. Especially if the gasket seal this time looks good as well.

Pictures always help, too, as sometimes a picture sees in ways eyes don't...

t

[digger]

i think the first reply still stands.

[thisismedriving]

Are you sure theres not something really dumb we're missing here.

Nope, that's why I'm asking the community.

isn't there water in the throttle body on some cars?

Yep.

that cant get sucked into the intake manifold somehow if that fails?

Nope.

I mean if you've got a 2nd head there, you'd think your luck cant be bad twice.

That logic only works if a bad head caused the problem in the first place.

id go down that route, maybe with a different shop...?

Yeah, that's the provisional plan, unless someone else has other ideas I can try in the meantime.

[e30davie]

Are you sure theres not something really dumb we're missing here. ive done a top end rebuild on an m20 and i cant think of anything too useful....isn't there water in the throttle body on some cars? that cant get sucked into the intake manifold somehow if that fails?

I mean if you've got a 2nd head there, you'd think your luck cant be bad twice. id go down that route, maybe with a different shop...?

[thisismedriving]

The head could still be cracked somewhere. They would need to pressure test it while at operating temp to know for sure. There is a dye they can use to pinpoint leaks. Perhaps find another shop that specializes in cylinder heads and have them test it? They might have better equipment or more insight on aluminum heads. You could also try another head in the meantime if you can find one locally.

I'm suspecting exactly what you've suggested re: dye and testing at operating temperature. I just don't want to throw a bunch of money at this head which (in my mind, at least) is probably bad just to confirm my suspicion when I could put that money towards prepping a known good head.

I have another head (off the good running 2.5 that came out of my car before I swapped in the stroker), so I'm thinking that even if I have the machine work done and it doesn't solve my issue, I'll at least have one head (or maybe two) that I know is good. It's kind of a lot of work to swap again without knowing for sure, though, which is why I was hoping I could find a smoking gun in the meantime.

[reelizmpro]

The head could still be cracked somewhere. They would need to pressure test it while at operating temp to know for sure. There is a dye they can use to pinpoint leaks. Perhaps find another shop that specializes in cylinder heads and have them test it? They might have better equipment or more insight on aluminum heads. You could also try another head in the meantime if you can find one locally.

[thisismedriving]

are you actually losing coolant?

Yes, obviously it's going out the tailpipe...

if you are it is going somewhere.

No shit.

there's a fail somewhere

NO SHIT?

it results in the head coming off in every circumstance.

No shit. The head HAS BEEN OFF and checked for cracks and flatness by a machine shop. That's why it's so frustrating that the same failure happened again after putting everything all back together.

you started with a known good flat block and head, they may no longer be that way at present.

The head was checked for flatness both before AND after failure. The engine was not overheated at any point since I assembled it, especially before the first failure, so there's no reason anything should have warped in the meantime.

with luck it's just a head gasket. probably poor from factory.

Thanks for your insight. If a manufacturing defect were the root cause, this wouldn't have happened twice in a row with two different brands of gasket.


Thanks and no (okay some) offense, but I think I'd prefer for you to step back and let someone else weigh in if you're not going to read anything I've written. You haven't actually given any pertinent advice and we're not really getting anywhere.

[82eye]

Yes, as stated. The head was milled and confirmed flat by two machine shops, though. There are no obvious cracks in the block or coolant in the oil, which you would expect if the block itself failed.

are you actually losing coolant? if you are it is going somewhere. if it's bad enough to be making white smoke it's significant. there's a fail somewhere, and it results in the head coming off in every circumstance.
you started with a known good flat block and head, they may no longer be that way at present.

with luck it's just a head gasket. probably poor from factory. it may not have overheated to the point of warping a head.

[thisismedriving]

if it's not cracked something is either warped or not mating properly. it could be either the head or block. block itself could also be cracked but that again is generally easy to find.

Yes, as stated. The head was milled and confirmed flat by two machine shops, though. There are no obvious cracks in the block or coolant in the oil, which you would expect if the block itself failed.

[82eye]

Yes, I had removed the head, taken it to a machine shop, had it pressure tested, and they found nothing. Looking for ideas for how else I can diagnose this.

Is it possible a pressure test at room temp wouldn't conclusively find a crack that reveals itself at operating temp?

pressure test should find it no matter. if it's not cracked something is either warped or not mating properly. it could be either the head or block. block itself could also be cracked but that again is generally easy to find.

[thisismedriving]

not sure what is left aside from a pressure test and remove the head for inspection. had heads on cars crack both to the inside and outside. only found internal cracks after removal. outside ones are obvious.

Yes, I had removed the head, taken it to a machine shop, had it pressure tested, and they found nothing. Looking for ideas for how else I can diagnose this.

Is it possible a pressure test at room temp wouldn't conclusively find a crack that reveals itself at operating temp?

[82eye]

not sure what is left aside from a pressure test and remove the head for inspection. had heads on cars crack both to the inside and outside. only found internal cracks after removal. outside ones are obvious.

[thisismedriving]

can you check the spark plugs to see if one or more look different?

The first time this happened, I pulled the plugs and 6 was obviously fouled and wet with (blue) coolant. The piston crown and combustion chamber were notably cleaner than the other cylinders, too (steam cleaned). Cylinder 3 seemed to have similar symptoms, but less pronounced.

It's obvious to me which cylinder(s) is/are affected. The question to me is why. If it's definitely a cracked head, then the next step is obvious. If it's not, then I need to figure out where to look next.