I had this job about a week ago and thought it would make a good article. I’ve done many head gaskets over the years, and it becomes kind of a no brainer for me, but this is a common problem on the V6 engines so it deserves some recognition. The main problem on these engines when they do have a head gasket leak, is that they will normally leak at the back corner of the rear head. This is the most common place to see a coolant leak on these vehicles.
After getting the car in the air to do some diagnosing, I saw right away that it had the ‘usual’ leak in the back corner of the rear cylinder head. Now, this is a pretty big job as nearly the entire top half of the engine has to come apart to do this repair. Luckily for the customer, their Impala was still covered under the factory powertrain warranty so it would end up costing them nothing to get the car fixed.
Quite a few parts are needed to do this job as well, including a new head gasket set, intake gaskets, valve cover gaskets, coolant crossover gaskets, and a few others. New cylinder head bolts are required as well since they are known as ‘torque-to-yield’ bolts. This means that after a regular tightening to a specific torque reading, they require an additional tightening to a specific angle reading. A special tool, called a torque angle meter is needed to do this correctly. Please note that you should NEVER reuse the old head bolts.
I got the car apart pretty quickly since it’s such a familiar repair for me and found the leak was caused by a spot on the head gasket that was lacking some material. You can see in the included pic below that there is a blue material on the gasket and that it is worn away in the corner area of the leak. GM has redesigned the cylinder head gaskets for these engines that are a little beefier and better sealing. Always use the new design when doing this repair.
Some block and head clean up, and it was ready to go back together. These engines, for as long back as I can remember have used different length pushrods for the rocker arms on the intake and exhaust valves. Many times, people replacing the intake gasket or even doing a head gasket, end up getting these pushrods switched around. This causes an awful misfire condition and will usually have some odd noise as well. If you attempt a repair like this please keep everything where you’ll know how it goes back.
Using the new gaskets and new head bolts, it all went together just like normal and I didn’t have any issues getting the torque and angle readings right on the money. Installation of the intake manifold, coolant crossover assembly, and related accessories all came next and it was just about ready to fire. A quick oil change and coolant flush got it ready to run.
The car fired right up, which is always a good thing! It got to operating temperature, and I bled the air from the cooling system so it was good to go. Another big job down, and a satisfied customer! I’m sure I’ll be seeing another one like this very soon, as usual…
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