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Old 01-31-2020, 10:25 PM
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Al Schober Al Schober is offline
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Let me add a bit to Dave's suggestions (all good). The block is a high nickel alloy and is somewhat corrosion resistant - the studs are not. The end of the stud exposed to raw water coolant will tend to go away. This also applies to the 3 studs holding the manifold. The only way to check them is to pull them. Consider this a plug for glycol coolant/heat exchanger.
As for sealant, what I use is Permatex 2A - this is the brown stuff with the consistency of peanut butter that comes in tubes.
The purpose of the studs is to be in tension, holding the head against the block. When you torque the nuts, the amount of corrosion affects the amount of tension developed. Rusty studs/nuts should be replaced or at least cleaned up. The ID of the nut and the face against the washer should be lubricated - I use the silver Permatex anti-seize (comes in a 4 oz tub with brush - lifetime supply). Some A4 owners go with stainless washers and acorn nuts - building a 'show quality' engine.
When cleaning the top of the block and the face of the head, don't try to get it too smooth - the gasket holds better to surfaces with a bit of 'tooth'. 60 grit is good, I wouldn't go finer than 80 grit.
Original head gaskets on the A4 were asbestos with a copper jacket - top and bottom. I've measured the original gaskets after removal, and found them to be a solid 1/16". Gaskets available today are 1/32" hence you need 2 of them. If the head/block have been surfaced, you might even need 3 to retain the original compression ratio.
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