Previa valve cover

[pdgizwiz]

I haven't posted anything here in a long time, mostly because my '91 Previa hasn't needed a thing. I replaced my valve cover gasket a little over a year ago and it's been as smooth and trouble-free as any car I've towed home and patched up before.
But now my valve cover is leaking again. The tell-tale whiff of burned motor oil as I park and get out has been irritating me for a few weeks, and I've confirmed the cover as the source of the leak.
Any sage tricks here that anyone will attest to being sure-fire? I sealed it before with some RTV, but perhaps that was a mistake. Or maybe I didn't hold my tongue right when I did it.
Thanks

[timsrv]

The VC gasket is certainly a trouble spot on the Previa. Seems like I'm replacing mine every 3 or 4 years or every 30k miles or so. The distributor shaft can also leak oil. When that happens the oil runs through the distributor, drips out the cap, then onto the heat shield, then onto the header. This usually creates rough running too though, so if it's running smooth then it's probably just the VC gasket again. Personally I much prefer the Toyota FIPG (Form In Place Gasket) over silicone. It's a bit more money but IMO it's well worth it. It should be used sparingly. You should only use a tiny bit on the corners where the gasket goes over the "bump" in the back, then just a very small dab on the front where the "half moon" plugs mate with the head. Tim

[pdgizwiz]

Thanks, Tim-
I feel better now, knowing that someone with a dozen Previas gets three years out of a VC seal job. My one isn't bad for a first pass, I guess.
My old gasket had hardened and cracked, so it was clear why it was leaking. I haven't removed the new one yet, but after I do I'll report here what I find.
I'm not sure what RTV silicone I used. It's white, and may be something I brought home from a past job from the "expired" bin. I know to avoid the types with corrosive cure agents and cheap generic bathtub sealants, of course. RTV silicone comes in a host of formulations. I expect that the Toyota FIPG is one as well. I assembled a wasserboxer engine once and the gasket kit came with a tube of VW-issue black RTV for the head seals. It worked. I suspect that Permatex "ultra black" or "ultra gray" are similar, but perhaps I'll try Toyota's finest this time. Would that be P/N 00295-00103?
Since this engine lays on its side, getting a seal here is more critical than if the engine were of the conventional upright type. Oil pools right against the seam, and will ooze out of the slightest imperfection. I think that it's funny that Toyota placed a "gutter" underneath this joint, with a "downspout" directly over the exhaust collector where it will burn rather than fall to the ground. Was this a "solution" to a known leak problem? If so, someone in Japan is still chuckling to themselves.

[timsrv]

Lol, just ask the parts guy at Toyota for a tube of FIPG. They keep changing the part number so I quit keeping track of it. The stuff is probably a formulation of RTV, but yet different. It has a different "feel" to it and is much harder to clean off you hands than black silicone. I use a lot of different sealants in my line of work. The ones that are the messiest and hardest to clean up are almost always the best when it comes to performance and longevity.

During troubleshooting I've run Previas before with the valve cover off, and man let me tell you it's unbelievable how much oil sprays out. If you ever do that you're going to want plastic over everything. I even made some sheet metal shields to knock it down (otherwise it's like a garden sprinkler). Even then you're limited to just a few minutes or the engine will run itself out of oil. Considering that, plus the fact it's on the side (gravity issues), this can certainly be a problem area. Now just add a couple years of heat exposure and you have a recipe for leaks.

Since this engine lays on its side, getting a seal here is more critical than if the engine were of the conventional upright type. Oil pools right against the seam, and will ooze out of the slightest imperfection. I think that it's funny that Toyota placed a "gutter" underneath this joint, with a "downspout" directly over the exhaust collector where it will burn rather than fall to the ground. Was this a "solution" to a known leak problem? If so, someone in Japan is still chuckling to themselves.

Lol, looking at the design of that heat shield I've also wondered the same thing "is it really a heat shield.......or a gutter for oil? " It is kind of funny how it's the perfect angle for oil to travel front to back, then set up perfectly to drip right onto the distributor shield. The little lip on the edge is for strength, but it almost looks like it's a little trough intended to direct the flow. Then of course there's the little hole on the distributor shield right above the header........looks like a drain hole to me . Very curious indeed. Tim

[pdgizwiz]

I pulled the old one off and did a post-mortem. It looks like I used Permatex ultra-gray. It stuck fine to the head and the cover, but not very well to the gasket itself. I cleaned everything scrupulously, got a new gasket and a tube of Toyota's black FIPG. It is sealed for now.
As to whether or not the heat shield is intended to be serve as an oil leak management system, I don't think there's any doubt. The hole at its low (rear) end drips into a feature stamped into a stamping welded to the header which neatly routes the oil over the side and down. The phrase "intelligent design" comes to mind.
PrevOilDrain.jpg
So I'll report back on this thread if and when this after-burning system goes back into action. Until I do, assume that my gasket is still holding oil.
Paul

[wirewrkr]

So, Paul, inquiring minds need to know..... What is the current part number for the FIPG ?
I need to order some online and would love to have the current part number.
Closest dealer is way too far. I live way out in the middle of Nowhereistan.
Thanks,
Robert