Paul L

Getting ready to tackle the rear main seal in a week or so as I have a nasty leak back there. Making a mess of the driveway. The instructions with this GM seal speak of coating the rear main bearing cap adjacent to the seal ends and the cap's chamfered surfaces with "oil sealing compound." Does anyone know what GM is speaking of? What is this compound? It seems that it must be oil-resistant which makes sense if you want a good barrier to oil exit.

BTW, anyone want pics of this job?

*Edit*-Should I install a new GM oil pump and pick-up while in there. My pump is the factory-installed version (24-years-old). I am not having problems with it but I am tempted to say why not?




[Modified by paul79, 6:45 PM 7/16/2002]

The Dude

I've always put the rear seals in with their backs dry and haven't ever had a leak there.

You should, though, put a teeny little dab on the block and the rear main caps (NOT ON THE SEAL ENDS) immediately adjacent to the seal ends, though. Very little dab. Very thin. No excess to squeze out. Teeny bit. Just a little.

When I say, "should," I really mean that's the way I've done it and I tend to stick with what works.

mountainmotor

I use Hylomar.But not on the ends of the seals,just between the main cap and block.

Binnie77

Jack...When I bought my seal, it came with a small tube of sealant...it felt almost like a heavy grease. The seal I used came from NAPA.

The Dude

I've seen them installed with goop before. I just learned to put 'em in dry. That's kind of an extension of not putting any stuff on the seal ends themselves even if you use it on the backs of the seal halves--it could goosh out and get on the rear main journal when you install the cap and torque it down, "crushing" the seal into place. But this was back in the day when your goop coiuces were pretty much limited to RTV and/or silicone. If there's special stuff these days, go for it. Just don't get any on the seal ends where they mate together. Very important.

Paul L

These points are excellent! I always learn from the Forum. The instructions (large file attached) are very clear that the compound - whatever is used - must NOT go on the seal. My current rear seal is only three years old and I can only conclude that the local shop that did the work did not know what they were doing! Hence we get back to one of the basics with C3s: do it yourself or in my case, with local Corvette Club buddies.
http://temp.corvetteforum.net/c3/pau...struct_001.jpg

BSeery

I have always installed them so the seal seperation is offset with the main cap seperation. In other words, don't line up the split in the seal with the split between the cap and block.

Paul L

What is Hylomar? Is there a Permatex equivalent?

Paul L

Thought that over for some time and basically it makes sense. So in spite of the instructions, you offset the mating surfaces of the seals up-down a wee bit from the bearing cap mating points. That would seem to avoid any oil leak where the split seal/cap surfaces intersect: all lined up. Have I understood correctly?

john's '81 mouse

Paul79:

Yes there is a special sealant you should use on the metal to metal cap to block area when re-installing the rear main cap and new two piece seal. I replaced my rear main seal two years ago, along with new oil pump, and standard main / rod bearings and have no rear main seal leakage.

This special sealant comes in a red tube, available at auto parts stores and I believe is sold under permatex brand, but damned if I can remember what it's called right now. I do remember that it is for metal to metal sealing purposes, and it will not deteriorate from oil / petroleum products, so it is what you want to use, and yes, instuctions advise to use carefully, so as not to get any on the actual seal lips, and use sparingly so you don't squish it out when you tighten rear main bearing cap.

This sealant is good stuff, and I just used it to help seal the valve cover camshaft seal area on my wifes Dodge Caravan 3.0 V6, after I pulled the heads to replace valve guide seals on it............and like the vette, no leaks!!!

BSeery

Uh -- there are instructions saying NOT to do this ??

And yes, thats what I do.

john's '81 mouse

Quote: "Uh -- there are instructions saying NOT to do this ??"

Yep, instructions that came with my felpro seal said to install with seal lips of each half flush with bearing cap and block area.

Paul L

I agree. See the diagram in the pic link I posted above.

Paul L

I believe there is a Permatex Red. I will check at the autoparts store tomorrow.

*Edit*-I got into the Permatex web site and this is all I could find that would seem to be close.


[Modified by paul79, 5:39 PM 7/17/2002]

BSeery

I have done this with at least 5 small blocks and have not had any problems. I wonder why they say not to do so ??

The Dude

I have never offset the seal or tried to index it so the gaps in the seal didn't line up with the gap between the main beraring cap and the block. Never had a leak there, either. Dry and aligned for me, bay-bee. Why? Because the rear seal is designed to be "crushed" slightly by the main cap when it's torqued down. That's what creates the seal.

But, hell, if guys put 'em in cocked and they don't leak, more power to 'em. Whatever works, right?

mountainmotor

Quote:
"I believe there is a Permatex Red. I will check at the autoparts store tomorrow."

While you are there,,see if they also have Hylomar :) It is good stuff used primarily in the past in Aircraft,,now has made it's way into the Automotive world. Near every parts store here in my area has it. It is impervious to oil,unlike silicone.

Paul L

Thanks. I will try to find that product.

*Edit*-I have checked out the Hylomar web site. It is a silicone-based product also. I will go with Permatex 2-Form-a-Gasket: "resists gasoline, oil, kerosene, glycol, grease, propane and butane."


[Modified by paul79, 10:04 PM 7/17/2002]

Jughead

Paul--you always seem to have a pic and text of every GM replacement part. Do you have any info on the rearl main seal for a Mark IV BB? According to my manual, the package should contain a "shim-stock" tool to insert the seal? Text goes on to say that if one is not provided a tool will need to be fabricated.

Could you check for me? I tried GMPP but couldn't find a listing. Local GM parts guy is clueless.

Thanks
Len


[Modified by 1970 Stingray, 10:50 AM 7/18/2002]

Paul L

Len,
I am not familiar with BBs but I cannot imagine that the procecure is much different. Others will correct me if I am wrong. Here are the instructions from GM in a large file pic file so they can be read. The "tool" is simply that thin nylon piece on the calculator black pouch. That's all it is....??
http://temp.corvetteforum.net/c3/pau...altool_002.jpg


[Modified by paul79, 7:01 PM 7/18/2002]