I finally found the time to get my hands dirty and replaced the valves and gaskets on the head of my '91 Geo Metro a few months ago. After (carefully!) putting everything back together again, I was disappointed to find that she is leaking more and more oil every day.
A friend told me that he re-torques his head bolts after about 1000 miles because of “engine vibrations.” He is confident that my oil loss is due to this lack of re-torquing.
Even more distressing, I recently blew a radiator hose (it was just plain old) and discovered that I’m leaking plenty of engine oil into the radiator system! This seems like a direct result of head gasket problems, since the trans is manual.
Wanted to get a little more input on the subject before going to the all-day project of tearing the head off again.
(PS - I have also heard that it’s common to machine the faces of the head and valve cover to make them seat better after taking the pieces apart. I have never done this, and on a small engine like the 1.0L 3cyl it doesn’t seem too necessary. However, as prone as an aluminum block is to warping, I wanted to be sure I wasn’t wrong in glossing over this step!)
As always, thanks very much for your advice and help.
-Amad
It’s not vibrations that cause the head bolts to need retorquing; it’s because the gasket relaxes, head bolts alter their shape a bit from heating/cooling cycles, etc.
Whenever a cylinder head is removed it should always be checked with a precision straightedge (not meaning a garden variety ruler) along with the surface of the engine block, both manifolds, and both manifold flanges on the cylinder head.
Any part including cast iron can warp and this is especially true with overheating involved.
You know one of the most warp prone cylinder heads I’ve ever seen? Subaru. One would not think a cylinder head that is so short in length would be prone to warping at all but my rough guess is probably 80% of the Subaru head gaskets I’ve replaced involved having the heads surfaced due to their being warped out of spec.
(Rule of thumb on warpage is .002 of an inch maximum per 12" in length; .002 and less will usually straighten out when the head bolts are tightened)
Before tearing it all apart try retorquing the head bolts and see what happens. Hope that helps.
First determine the source of the oil leak. It may be that the aluminum block is warped, especially if the engine has overheated, but refacing the heads on either the block side or the valve cover side wouldn’t have helped much anyway. If the block is warped, you could expect the loss of enough compression (especially in a three cylinder engine) to insure that the engine would simply never run again.
I do sort of like the advise to retorque the head bolts, but as well make sure you are not losing your oil via the valve cover gaskets. If you used a rubber or silicone gasket sealer when you replaced the valve cover gaskets, then you added an unnecessary step more likely to result in a leak than not. Valve cover gaskets should be installed in most cars dry, and lightly torqued. That was not always the case, but I bet it is in yours.
Last, the fact that you have found oil in the coolant is not encouraging. It does indicate a head-gasket leak. I don’t want to tell you to buy another head-gasket kit and replace the work you just did, but also you need to be aware that damage to your just-replaced head gaskets is just as likely as it is that you simply need to retorque the head bolts.
two words, geo and metro, need I say more?