You didn't say which engine you have. If yours has cast iron cylinder heads, a leaking head gasket would be very uncommon. How did you diagnose this and what are the symptoms?
The main thing with head gaskets is to determine why they leaked. If the engine overheated, the head may have warped, particularly aluminum heads. All heads should be checked for flatness at an engine machine shop. Unless specified otherwise, .005" is the maximum allowable warpage in any direction.
If the head gasket has a spot that corroded through, the engine coolant may have had too much acid in it. That is a real big problem on GM engines. To identify that, use a digital voltmeter with the negative probe grounded to the battery or engine block, then stick the positive probe in the coolant. If you find more than a couple of volts, the coolant should be flushed and replaced. Two different metals and an acid are what's in a battery. There's many different metals in the engine, and the acid in the coolant leads to corrosion.
Head gaskets aren't very expensive but some engines use "torque-to-yield" head bolts that are designed to stretch when they're tightened. They only do that once so you're not supposed to reuse them. Replace them with new bolts and be sure to follow the tightening procedure in the service manual. On all engines the bolts must be tightened in a specific order, but never all at once. Tighten all of them on one head 1/3 of what's called for, then all of them 2/3, then all of them the full amount to maintain even clamping forces. The guys at the engine machine shop will tell you if new head bolts are required.
A lot of newer engines need a "torque angle meter" to tighten the head bolts. If you use a torque wrench, the bolts will just keep on turning without getting tighter until the threads peel out. This procedure involves tightening the bolts to a very low value with a torque wrench, then an additional number of degrees.
Thursday, October 10th, 2013 AT 11:42 PM