Topic: Something is cracked, just don't know what

[meBrian]

Here's what I've got: 1992, 2.5l, 120k

I've been losing coolant into the oil for some time. I know of one time that the engine overheated but I don't know if it was turned off by the driver in time or whether it just quit.
I have to change the air filter every couple of weeks and do an oil change monthly just to try and keep things as they are. My crankcase makes yogurt and spits it up into my airbox. The oil looks more like chocolate milk when I drain it. Yum, Yum.

So, I pulled the head many months ago and replaced the gasket. It was my first time to dig into an engine.
The old gasket didn't look bad when I replaced it, but I was told that doesn't mean it wasn't the problem. Unfortunately, the problem wan't solved.

I'm thinking that a crack somewhere is the most likely scenario, and not a gasket. My question is whether it is the head or block.
How likely is it that the head would crack before the block? Does anyone know of any history pointing to one part or the other?

I can by a new head for $350, or a new engine for $1,600 + labor (That job is probably too big for me).

I'm not ready to replace the engine, but is replacing the head a worthwhile endeavor?

[FourbangerYJ]

Pull the head and have it magnafluxed. It will find a crack if there is one there. If not then I would imagine it's the block.

[sharpxmen]

it is more likely to be the head than the block, but that is just a probability - did you got the head checked if it's warped when you changed the gasket? - it could be that it needs to be planed and maybe even the block is crooked, that depends on how much it overheated. Also, did you retorque the head after 500 miles or so? Did it show water in oil right away after you changed the cyl head gasket or it took some time to appear again? Do you get any bubbles in the coolant circuit and is it creating pressure in the cooling circuit? did you try running the engine w/o the radiator cap and see if the amount of water in the oil decreases?

answers to these questions can give some clues as in what's going on, for example if you get constant bubbles in the cooling circuit then it could be the following: the head cracked (in the chamber, usually between valves is where the crack would develop, but in your case with the overheating could be in other spots too), the head or block warped or the gasket not sealing or busted.

if you don't get bubbles then it could be the gasket between water circuit and oil return from the rockers under valve cover (that can also be due to warped head and/or block), could be a crack in the head or in the block.

Point is if you get constant bubbles if it is not due to gasket sealing properly due to reasons explained above including improper torquing of the bolts then it is the cylinder head (unless a cylinder is cracked which is unlikely with the engine still running fine as yours seems to).

I'm not ready to replace the engine, but is replacing the head a worthwhile endeavor?

i would take the cyl head off again and get it at least checked to see if the seating surface is flat - my guess, if you cannot see a crack on any of the chambers between the valves (clean the deposits off well, you should be able to see it if it's there), is that you need to get the surface machined so it's all leveled and will seat properly on the block - make sure that you torque it in sequence and re-torque (not sure when the 2.5 is required to be re-torqued, every motor has it's own requirement and torquing sequence and procedure for the cyl head, look in the FSM and follow the exact steps from there). You should also check the block as well, use a long straigh liner and a thickness gauge to see how much is curved - again check the FSM to see what is acceptable before requiring to be machined and in that case (and same for the head) make sure the shop where you do it will tell you how much they had to take off so you can get a proper thickness gasket if necessary.

Or what Fourbanger ^ suggested, and i assume they will also check the head if it's flat if not machine it for you anyway - only thing that i don't know is if the crack is internal or somewhere in a place that is not directly visible if they'll be able to tell

you can also try to use some hairline fracture penetrating spray to identify the crack

[meBrian]

Unfortunately, I didn't get the head checked while I had it off. I was under time constraints (I needed it to be running to drive to work on Monday morning) so my focus was on the gasket.

@sharpxmen
"Also, did you retorque the head after 500 miles or so? "
I did not retorque the head since putting it back on.

@sharpxmen
"Did it show water in oil right away after you changed the cyl head gasket or it took some time to appear again?"
There may have been a reduction is the amount of coolant lost for a short time (a couple of weeks perhaps). I ran some of that block sealant through the system when I put everything back together, too. Don't know what effect that might have had in helping.

@sharpxmen
"Do you get any bubbles in the coolant circuit and is it creating pressure in the cooling circuit?"
I do notice that my temp gauge bounces when the coolant level has dropped. I am assuming the reason is that there are pockets of air which are forming as a result of the lost fluid which is causing problems with circulation of what fluid is still in the system. Is that what you're asking? 

@sharpxmen
"did you try running the engine w/o the radiator cap and see if the amount of water in the oil decreases?"
No, I have not. But I will do that.

Thanks for the quick response. I will test this a bit more and post the results.

[sharpxmen]

@sharpxmen
"Also, did you retorque the head after 500 miles or so? "
I did not retorque the head since putting it back on.

@sharpxmen
"Do you get any bubbles in the coolant circuit and is it creating pressure in the cooling circuit?"
I do notice that my temp gauge bounces when the coolant level has dropped. I am assuming the reason is that there are pockets of air which are forming as a result of the lost fluid which is causing problems with circulation of what fluid is still in the system. Is that what you're asking? 

going on a guess again based on what you mentioned  - since it decreased and then came back to the same level might be b/c you did not re-torque

what i was asking about bubbles - if you have a crack in one of the chambers or between the chamber and the coolant circuit that piston will pump exhaust gasses in your coolant circuit like an air compressor. If you have a big gash in your gasket it will throw water out your exhaust in which case would be dramatic, won't run properly like yours does.

EDIT: you can also try to re-torque now and see what the result is - if it decreases it could point to the cyl head being crooked, but could also be a hairline crack depending where it is.

[andrew383]

are you seeing alot of white smoke from the exhaust at all times?