fpoli75490

Hi,

I've had ongoing issues with the head cover gasket of my '88 non-turbo manual supra. Oil leaks into the spark plug compartment. Someone told me that all supras have a head cover gasket problem but that Toyota isn't willing to admit that they made a design mistake. I was told that the engine should be torqued to about 80 (originally Toyota only torqued to 56 which allowed for looseness). Does anyone have any information about this or can anyone shed any light on this topic?

bgrieger

You're confusing 2 issues. The valve cover gaskets dry and get crusty over 20 years or so of use, and are a normal part of maintainence of any older engine. There are 3 of them to replace. They use philips screws to secure the usual 2, and then a large (12mm I think) allen wrench or socket to replace the centre valley one. Replace them all at once and forget about it for several years again. Some will change to a hex head bolt to allow them to put a little more torque on them, it is generally not needed or recommended as you can easily overtorque and damage the head or valve covers. I guess if the covers themselves warped a little or the mating surface was damaged this might help, but it's just as easy to get another set of covers from a part out sale.

The headgasket is a weak link in the engine, but does not cause the oil in the valley problem. The increase in torque of the head bolts ON REPLACEMENT OF THE GASKET usually ends the issue. Even stock gaskets are fine if the boost does not get turned up significantly if the torque is set higher. There is a wide variety of opinion on the correct value, but the range usually quoted is from 70-85 ft/lbs. Some suggest increasing the torque on the stock bolts without replacing the gasket, but this often leads to the gasket that was previously sealing suddenly failing. Toyota did not recall this part as the cars were almost all out of warranty when the reports were coming in at a high rate, and there was no safety issue related to it. They redesigned the gasket a bit in the mid 90's, but did not change the torque rating.

fpoli75490

Hi Bob,

Thank you so much for the information. Just so that I understand, I should change the valve cover gasket if oil leaks into the spark plug compartment, right?

Also, how do I know if it makes sense to change the torque on the head bolts on my particular '88 supra? I know you mentioned "weak link in the engine" but wWhat problems should I be experiencing?

Jeeves

That's correct.

Valve covers are these guys:


While the head gasket actually separates the top section (the aluminum part), from the bottom (which is iron). Head gasket failure symptoms commonly include: Overheating, loss of coolant (there's a dash light that often comes on indicating low coolant), white smoke out the tailpipe (LOTS of it), milky looking oil, a sound like a 'waterfall behind the dash' often accompanies the low coolant because of the air pockets that develop.

If the head bolts have never been changed it is a BAD idea to go and attempt to re-torque them now. Doing so is likely to give yourself a blown headgasket rather than keep yourself safe. The only 'safe bet' is to machine the block and head, install a metal head gasket and ARP head studs when the head and block are apart. This isn't an easy or overnight task.

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