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  Feb. 28, 2010 8:02 p.m. aussiesmg UltraDork

  Can you guys identify this issue with a family members Chev van.

  3400 engine, driving down the road overheats suddenly.

  Oil is clean, waited for it to cool down, started up and drove about 15 feet, clouds of white smoke (coolant) out the exhaust.

  I know it is a head gasket, but is it the usual leak under the intake manifold, can you tell before a pull down.

  Steve

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  Feb. 28, 2010 8:07 p.m. John Brown MegaDork

  Tear it down, make sure to mark the pushrods so they can go back in the correct holes.

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  Feb. 28, 2010 8:30 p.m. Jensenman MegaDork

  Not very likely it's a head gasket. It's probably the usual intake gasket barf. But you can do this: stick a cooling system pressure tester on it and kill the ignition (unplug the module), then spin it over and look for sudden spikes in pressure. Spike = compression into the cooling system.

  Like JB said, make sure not to get the pushrods mixed up.

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  Feb. 28, 2010 8:43 p.m. Knurled New Reader

  It's physically impossible for the intake gasket to leak coolant into the intake ports. The gasket surface is non-contiguous.

  The pushrods are easy - the long ones go to the exhausts and the short ones go to the intakes. Intake rockers are closer to the valley, like you'd expect.

  I've done a few of these... per month...

  I've seen a few blown head gaskets on these engines. What seems to happen is the coolant develops an air pocket around the first cylinder on the rear bank, and it's next to impossible to bleed the air out. Every one I've had to do heads on was blown on that cylinder. It's a tricky cooling system to bleed out anyway, even without that shortchanged section.

  Incidentally, every instance of a rocker arm pulling the threads out of the head was on that cylinder as well. Coincidence?

  If you're going to do this job, do yourself a favor and spend the $15 or so for the pushrod removal tool. Those rocker bolts, technically, are torque to yield, and it seems like it is the head that yields rather than the bolt, so anything you can do to avoid disturbing the bolts is Good.

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  Feb. 28, 2010 10:23 p.m. aussiesmg UltraDork

  Great stuff and thank you, we will pull them tomorrow, will advise.

  Is there any odd parts I will need to pick up apart from gaskets

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  March 1, 2010 7:35 a.m. patgizz SuperDork

  its not too bad a job. not sure how accessible the rear head is in the van, but the exhaust manifold in the back usually can stay connected to the exhaust and just shoved back out of the way to access the head bolts.

  the easiest part of the job is the non adjustable rockers, not having to adjust things after assembly is a good thing in this case.

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