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Old 07-27-2007, 02:31 PM   #1
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What's the procedure for testing for blown/leaking head gaskets?

Does anyone know what I should be looking at in terms of paying to diagnose my potential head gasket leak? What's the procedure for testing this?

I was pointing at the AOS but because of all the white smoke all of a sudden while driven on the highway, the mechanic thinks it could be the head gaskets.



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Old 07-27-2007, 08:15 PM   #2
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Is there any evidence of coolant in the oil or vice versa?

The AOS is typically the cause of sudden smoke from the exhaust. Since it costs barely $100 and a couple hours of your time, it's worth doing before digging into serious head gasket inspections.

As for the actual diagnosis of a blown gasket, the coolant oil mixing is one indicator, as is overheating. A white buildup or heavy black sooting of an individual spark plug is another indicator. A leakdown test could be performed which pressurizes each cylinder individually, then you look for evidence of coolant bubbling or air hissing through the oil filler pipe.

The coolant system can be pressurized as well, tehn a borescope inspection done on the individual cylinders to look for the presence of coolant.

Do the AOS first!

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Old 07-28-2007, 07:57 AM   #3
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One mechanic made it sound like it was a difficult job so I wanted to have some kind of idea what he meant.

I had a suspicion that it was the AOS but I also knew of a pre-existing coolant leak (it was leaking on the ground), but the car never overheated or even went unusually hot. There were a few problems that all happened at once. Bad luck for me

Thanks very much for the explanation.

take care,

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Old 07-28-2007, 12:01 PM   #4
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As mentioned, there are several ways to pinpoint your issue. A Leakdown Test and Coolant Pressure Test are essential to determining a Headgasket leak with any certainty. Also, looking for emulsified Coolant/Oil on the Dipstick (if you have one, draining the Oil if you don't), it'll look like someone threw a Latte' in your Crankcase. And, you can fairly easily perform these tests yourself for under $100 worth of equipment (even less if eBaying the stuff used).

Throwing fixes willy-nilly at the issue can run several hundreds of $$ and may not even solve the malfunction. But certainly, living with a Coolant leak (no matter how small) without correcting it will only compound your problems.

Pinpointing the cause and then applying that specific solution is the best (and perhaps the cheapest in the long-run) way to go. Hope this helps...

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Old 07-28-2007, 03:33 PM   #5
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If your mechanic thinks replacing an AOS is difficult, wait until he reads the procedure to replace a head gasket!!! Not to mention the "special" tools.

Although I agree with the leakdown and pressure tests, sometimes a simple compression check is enough to id a blown head gasket. In any case, they rarely blow in pairs.

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