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Help diagnose cracked head vs. cracked block

D

Dave12

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Location
London, Ontario Canada
Well I finally got the heads on my engine pulled. I just got off the phone with the mechanic and this is what he tells me.

-No visible signs of cracking on the heads.

-No signs of washing on the tops of the cylinders, no signs of coolant getting through anywhere from the head.

-Head gaskets look good, no signs of tearing.

-Lots of goop/sludge under both valve covers and all through the valve train (I tasted this goop through the CDR hole on the passenger's side cover and it was sweet tasting).

-Oil analysis was done when I first started loosing coolant and it came back saying there was excessive amounts of gycol in the oil.

The mechanic is going to send the heads out to be magnafluxed. He wants to rule out the heads as the problem. If the heads come back good he figures the block is cracked somewhere. He said he couldn't see any obvious signs of cracking in any of the cylinders.

Does this sound reasonable? Can anyone give me the tell tale signs of what one would see when dealing with a cracked head vs. a cracked block?

Thanks,

Dave
 
Sounds awful familiar...turned out to be a cracked block in my case...

Wait for the magnaflux results.
 
Dave, -as long as the heads are off, you can also have a look around in the lifter/pushrod galleys. I just recently discovered a crack in one of my blocks that was on the rear upper head bolt hole on #7.

It took a careful eye to see it, -but it was clearly cracked into the water jacket (I confirmed this by shooting brake-clean into the head bolt hole and seeing it weep out into the lifter/pushrod galley).

This block I speak of was a '93 599. I realize yours is a later 506, -but if a 599 can suffer from this problem, -a 506 surely can also.

I'm just throwing this out there, because I had never seen or heard of one of these blocks failing where this one 599 did. It's pretty easy to access the lifter/pushrod galleys with the heads off, -and all you really need to do is clean the galleys up with some brake cleaner to get them clean and dry. Then go in there with a propane torch and see if you can spot anything around where the head bolt holes are.

It can't hurt to check.

I'm hoping the mag-test reveals problems with your heads, -that would sure be nice.

-Man, -that sounds bad saying I hope your heads are cracked, -doesn't it??

You ended up with that other motor, -didn't ya?
 
Rich,

I do have another motor. The guy doing the work now is the guy that was selling the motor. When he drained the oil to start working on my motor he said the oil looked good which had him thinking it was maybe just a cracked head or gasket rather than the block. He thought it was best to pull the heads with the motor in the truck and see if that was the problem. If he didn't need to sell me the motor that was fine with him, he had another buyer waiting in the wings but is giving me first dibs on it. This is what I had been trying to get done for weeks with the other guy but he just kept jerking me around.

So I'm finally getting somewhere and I have everything in place to get it fixed either way (heads or block). The motor this guy is selling is complete (turbo, alt, starter, ac, the whole thing) also out of a 98 but a 3/4 ton and it has 197k kms on it which is 50k kms less then what is on mine now. If I end up with it all have all the leftover bits to sell to make some money back.

Dave
 
At this point, you need to pull the pan and inspect the mains. Cracked main web can allow coolant into oil and is more common that I care to admit. I have found lots of blocks with cracks in the main web area, but you never know when the crack will run far enough to get into the water jacket.
 
Hey Guys,

Just a little update. After the mechanic power washed the heads he could clearly see that they were badly cracked in several locations. So it looks like the problem is the heads and not the block. I've got new aftermarket castings on order vs. reman GM. They are a little more money but apparently a much better casting that is not prone to cracking like the current GM casting.

So it looks like the problems that I've been dealing with since Feb. will finally be coming to an end.

Dave
 
At this point I would check the block too. I would hate for you to have had both the heads and the block cracked at the same time....just advice from someone who has been there and done that...
 
chrisk1500 said:
At this point I would check the block too. I would hate for you to have had both the heads and the block cracked at the same time....just advice from someone who has been there and done that...
Click to expand...

Agreed.
Where are you getting your heads from Dave?
 
Heads are coming from a local supplier that the mechanic knows.

I would hate for the block to be cracked too but I think I'm going to have to roll the dice on this one. I'll talk to the mechanic and see what the says but I doubt that he is going to want to pull the engine to check the block. I'll make sure he checks the cylinders from the top as best as possible.

Dave
 
Dave, just out of curiosity, did he mention where the cracks were?

You wouldn't have any pictures would ya?

Glad to hear the ball is rollin' for ya.

Rich.
 
Rich,

No pics. I'm going to take some when I pic the truck up. Cracked in several locations but the only thing I remember telling me specifically is around the glow plug pre-chamber. I don't know if he's talking about the pre-cup or what.

Dave
 
Dave12 said:
Heads are coming from a local supplier that the mechanic knows.

I would hate for the block to be cracked too but I think I'm going to have to roll the dice on this one. I'll talk to the mechanic and see what the says but I doubt that he is going to want to pull the engine to check the block. I'll make sure he checks the cylinders from the top as best as possible.

Dave
Click to expand...

Ok, just curious where they were being cast (US, Canada, etc.)...
 
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