Checking for cracked head or block


Old 09-07-10, 08:04 AM
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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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Old 09-07-10, 03:50 PM
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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.

Old 09-07-10, 05:34 PM
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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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