View Full Version : Valve cover oil leak

06-22-2005, 03:49 PM
Despite my best attempts, I cant keep oil off my valve cover and the little channel where it meets the head(TR6). Granted, it's a fresh engine (about 600 mi.) with high OP but this is annoying. Can't figure if it's coming from the bolts or cap. Do the caps ever leak? The cover has the typical distortion. What are your feelings on the alloy covers?

06-22-2005, 03:57 PM
Shouldn't be any leaks coming from either the bolts or the cap since the system is designed to pull a slight negative pressure in the rocker area via the PCV hose to the carbs. This ensures any gases getting by the valve guides get reburnt.
The leaks could be happening because of the cover distortion if it's been pulled up too tight sometime. It could be caused also by not having the PCV system working properly, ie plugged up or disconnected thereby pressurizing the rocker cover and forcing oil out.
I don't have a nice alloy cover, wish I did. It should work better in that there would be less ditortion and you could pull the bolts up a bit more.

06-22-2005, 04:43 PM
These valve covers get slightly bent from age and over-tightening the screws on them.

Put your valve cover on a hard, flat surface and see if it sits flush with the surface. If not, gently whack the edges with a rubber hammer (or put a block of wood or hard rubber between the hammer and the cover) until it sits flat on the table.

Worked for me. Just don't damage the valve cover with the hammering! /ubbthreads/images/graemlins/hammer.gif

Good luck!

06-22-2005, 05:45 PM
I've been eye-ballin' the silicon valve cover gasket. It's very pricey though (45 + 6 s/h). The hype is that is seals like nobody's biz and it's intended to be re-used over and over. Has anyone tried these?

Thanks, Achtung

06-22-2005, 07:09 PM

I agree with the previous suggestions.... Leaks at the bolts or cap are rare if internal vacuum is correct. You might check your PVC valve is working properly.

Do you have a bypass oil feed sending more lubrication to the valves? If so, you might need to restrict it to reduce the amount of oil flowing up to the top end.

There are hard "fiber" or hard rubber washers that can be used under the nuts, to help prevent any leaks there. Nylon washers might be easier to find and also might do the job.

More likely is leaks from the gasket. As already suggested, first check that the cover is "square" and hasn't been over-tightened (also a common cause of leaks on the sump pan).

The silicone gasket is great. If you want to keep using the original valve cover, one of these might be just the ticket. Keep in mind that there is no sealer necessary with these and you can use one over and over, so consider the price of maybe a half dozen or more standard gaskets for true cost comparison. More info at https://www.jmwagnersales.com/T6SiliconeGasket.htm

Unfortunately silicone gaskets are only being made to fit the original, stamped steel valve covers. They won't work with the alloy valve covers.

The alloy valve covers seal well, too, thanks to their rigidity. They also help dampen valve noise, and at least theoretically should help the engine shed a bit of heat.

Either type of cover might be helped by installing a new cork gasket, if you don't want to spend the money for the silicone gasket.

Try soaking the cork gasket in warm water for an hour or so, before installing. That helps it conform to the head and cover better. Any moisture is "cooked off" as soon as you start the engine and warm it up.

You can also use something like Hylomar sealer on one side of the gasket. It will seal very well, but it's a bugger to get apart and completely off, when the time comes.

Perhaps use RTV sealer on the other side, or both sides, of a cork gasket to make disassembly easier and possibly be able to reuse the gasket once or twice.

If you use a sealer, be very sparing with it. Just a thin coat is all that's needed. You especially don't want it forming a ridge on the inside, eventually flaking off and possibly working it's way into the oil passages and such.

Hope this helps.


Alan Myers
San Jose, Calif.
'62 TR4 CT17602L

Geo Hahn
06-22-2005, 07:57 PM
...You can also use something like Hylomar sealer on one side of the gasket. It will seal very well, but it's a bugger to get apart and completely off, when the time comes....

[/ QUOTE ]

If you mean the Blue Hylomar that is what I use (on both sides) and I get several uses out of the gasket. For me it stays very soft & gooey and is easily wiped off even a year or more later.

I would be wary of RTV or any sealant that 'sets up' as it might send a bit of loose excess into the oil and clog something important.

Some use contact cement to glue the gasket to the cover but I have never found that necessary.

06-22-2005, 08:47 PM
If you cover has been overtightened, deformed or straightened in the past, get an aluminum cover. Stopping leaks around a sprung cover is difficult at best, even if you straighten it.

I had the same problem with my TR6. I opted for an aluminum cover and I am very pleased with the no leak situation. I have removed the cover a couple of times to check valve clearances, and re-used the same gasket (cork).

I used a skim coat of Permatex sealant between the cover and the gasket but none on the head. This keeps the gasket squarely in alignment during the installation process. The aluminum cover has a larger flat sealing surface than the original cover which I think is a plus.

The instructions that came with my cover said to torque the mounting nuts to 3-5 lbs. I was a little skeptical of the lower limit. I found that 4lbs was fine on the original installation, but I am currently at 5lbs after a couple of removals.

Several of our club members have opted for the silicone gasket setup, but they are using straight (chrome plated) covers - they really look nice. They have not mentioned any cover leaks. But I probably wouldn't mention any leaks either, if I spent that much on chrome plating and a silcone gasket!