Rear Main Leaking. Help a.s.a.p.!!

[Bad81bu]

I just put the 406 back into my malibu and wouldnt ya know it, the rear main leaks, not too bad but i hate oil leaks. Is there any way to replace it or repair it without taking the engine back out of the car????

Thanx
Brett

[scott83]

you can find a way to poor brake fluid on it.. brake fluid swells up rubber

[MrPbody]

Brett,

Are you certain it's the seal? Many oil pan leaks are blamed on main seals...

Was the block align-bored or align-honed? If so, was the "special" seal for the 400 that's BEEN align-bored used?

Yes, the rear seal can be replaced in the car. Get a service manual and it will describe the proceedure in detail. Chevrolet manual would be the best one.

Scott,

Bad idea to use brake fluid inside an engine. While it's true, it will "swell" the seal, it will also swell the o-rings and valve stem seals. It also will eventually evaporate, causing the parts to shrink more than they swelled. Best thing to do is just fix it...

Jim

[Bad81bu]

yeah when i rebuilt it last year i had it line honed and had the new seal, my machine shop guy said to add a "shim" to the seal as well so we did and it didnt leak last year, we took it apart this past winter and put a new cam in it, took the rear main cap off and replaced the main seal again and reinstalled the shim, i am thinking that since i dont have a pvc valve (as there is no vaccum port in my tunnel ram) that there is too much pressure in the engine and its causing the rear main to leak, if i put a pvc valve in it will the leak stop? or is it too late? once it leaks, it leaks? not real hip on the brake fluid idea, but thanx for the suggestion. i wouldnt put it directly into the oil but try to spray it on the seal???

Thanx for the tips i really appreciate it.
Brett B.

[MrPbody]

If you have no PCV system AND no breathers, then, yes, the thing will continue to leak. A PCV valve helps by evacuating the "nasty" out of the crankcase at low speed/high vacuum. Highly recommended for a street-driven engine.

Best of luck.

Jim

[MagicRat]

You need at least a crankcase breather to prevent crankcase pressure related oil leaks.

A PCV valve is nice as it sucks out all the partially burned hydrocarbons found in the blow- by gases. However a PCV valve on its own rarely has enough flow to prevent crankcase pressure related oil leaks.

If you do not have a PCV valve, you should change the oil more frequently than normal, and be prepared for the possibility of somewhat shorter engine life.

From personal experience, I have found that suck a leak is not necessarily permanent. Once the correct breather has been installed, the leak often stops.

[Bad81bu]

I was thinking of welding a couple bungs into my headers and running braided lines from the valve covers down into the headers, will that exhaust create enough vaccuum to do the job?

Thanx a Million
Brett B.

[MrPbody]

Brett,

With full exhaust, it's a very bad idea to install an evac system. Those are for race cars with open headers. Even though those systems have "check valves" in them, they fail quite regularly. We've seen massive crankcase pressure in engines when that happens. Talk about leaks... Niagra F'in Falls!

Your best bet is what Magic Rat and I have explained, about using breathers in conjunction with a PCV valve. Disregard any negative info you may have heard about PCV valves adversely affecting performance. Unless they leak vacuum, they have no effect at all, on overall performance.

Jim

[Bad81bu]

ok i wont do the bung thing but my tunnel ram has no vaccuum port and neither do my carbs. where do i hook the PVC to?? sorry im so ignorant. 1st time with this problem.

Brett
Thanx again guys.