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Checking for cracked head or block

bwilker's Avatar

Join Date: Nov 2004
Posts: 77

09-07-10, 08:04 AM   #1  
Checking for cracked head or block

I have a 1987 3.0L Mercruiser engine that I have torn down to where I have the head off the engine. The head is a GM head. I have a problem with water getting in the oil so I thought I might have a blown head gasket. The gasket looks good and doesn't look like any water has been getting past into the oil passages so I'm wondering how I can check if the head or block might be cracked. I've done a visual check but don't see anything. The piston tops and cylinder walls look real good with no evidence of water.

I'm taking the head in for a flatness check tonight but again if the head was warped shouldn't I see evidence of water getting past on the head gasket?

Any help would be appreciated.

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GBR in WA's Avatar

Join Date: Mar 2009
Posts: 1,167

09-07-10, 03:50 PM   #2  
When I rebuilt diesel heads, I used a large magnet on the bottom, sprinkeled metal shavings on the surface and watched for them to form the crack line. Don't do his if partially assembled. I believe there is a stain for showing cracks used today..... Yes, you should see a water-line, if it was leaking for some time.


samuari's Avatar

Join Date: Jul 2008
Posts: 541

09-07-10, 05:34 PM   #3  
All of the 3.0's I have seen crack do it externally under the manifold and they will also crack at the bottom of the manifold. Check the riser gasket on the exhaust, if the motor got hot at some time it could have burnt this gasket causing water to get into the motor.

The riser and the head are the only 2 gaskets that I can think of that have a possibility of contaminating oil with water.

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