Freddie's Rear Main Seal Thread Revisited

[Turbobug]

My 59 Turbobugeye project has hit a speedbump. The engine is running great and the torque/speed is awesome (actually a little frightening).

I'm on my third attempt to stop a persistent rear main seal oil leak in the recently rebuilt 83 turbo engine. My first attempt was made using just RTV in the side grooves (Charlie's approach) with the engine on a stand. I let it sit two weeks before installing and another before I got it fired up. It leaked like Niagra Falls. I pulled the pan and cap and checked for problems. The RTV was sealed good on top but still uncured in the center of the cap groove and oil just blew by. It looked like it just came out of the tube!! How do you make sure this RTV cures?

I plan on following the procedure provided to Freddie via the subject thread.
Like Freddie, I noticed significant crankcase pressure (whistling from the dip stick tube). I stuck in a PCV and vented oil fill and ran them to unused inlets on the front of the carb. Didn't seem to impact vacuum. Does that sound legitimate? What is the normal vacuum source for the PCV?

Also, since a newly rebuilt engine is going to have significant blow-by until the rings seal, I'm thinking I may have significant leakage even if the rear main cap is sealed properly. Any idea how long it takes for rings to wear-in using break-in oil?

As always, thanks for the help.:biggrin:

 

[charlief1]

If I remember right you live in the northern climate so temps are a little cooler than where I live. RTV requires warmer temps to cure properly and if it's been getting below 50 then it didn't have enough heat to cure properly. When you install the rear you need to heat it up some after you put it together. I've used a MAPP gas torch to heat the block up when it's cold to make sure the RTV has enough heat to cure properly. Just heat up the block some but not the main. Leave the pan off while it's cooling and you should be good.

 

[Turbobug]

It was cold in the shop. Pot bellied stove while I was working on it, but freeze a-- cold after. I'll give it another shot today with heat.

Any thoughts on the break-in period?

 

[charlief1]

The main thing is that it needs time to cure because the chemicals need to evaporate. If you can, leave the pan off so it gets the most time for the VOCs to evaporate.

 

[Turbobug]

Thanks Charlie.

 

[LOT]

Anirobic (spelling) sealant

Means it won't cure without moisture. Sealed up will take much longer as Charlie has stated. I have never tried this but have seen it posted. Take a tooth pick and dip it in water--probe sealant with wet tooth pick numerous times to add moisture. Best of luck. Also as an added thing to do when redoing a rear seal with neophrene seal or any seal. Clean the grooves in the knurling. Knurling that has the grooves full is the same as no knurling. Some after market cranks are not knurled and I know of a few that leak.

 

[Freddie's Buick]

..Means it won't cure without moisture.....

Yep. Locktite 518 is Anaerobic and water is recommended with a toothpick. I believe it's in the service manual, (the Fel-Pro and Kenne Bell kit refer to this type of sealant). Pretty much any engine with this type of design should use it on the main seal.

BTW I was lucky in my situation. My seals stopped leaking ever since I vented the engine. I think that a good set of after-market valve covers that have the grommets allowing one to vent blow-by is the way to go.

What is the normal vacuum source for the PCV? :biggrin:

I would put a vent on each VC and leave the PCV attached via the intake manifold to the carb, (which is the OEM method of crankcase ventilation).

 

[dr_frankenstein]

I dunno if this is right or not...... but I have always used Aviation Form-A-Gasket on my rear main.... looks like a jar filled with poo, and never hardens, but works for me.

A.j.

 

[Turbobug]

Thanks for all the help. I do remember one set of instructions saying to wet wire the sealant, but I had no idea what that meant. Now I know!!!

I looked at the knurling and cleaned that area with a solvent the first time around. It looked pretty good. I'll double check when I redo it this time since there could be some sealant that wondered onto that area.

The info on the PCV hose to the carb helps. It's hard to tell where stuff should go when all you got is the engine to begin with.

As soon as it warms up a bit, I'll give all this a try. Thanks

 

[SNOWBIRD]

WHISTLE from dipstick tube would indicate to me that boost was going by intake or head gaskets into motor oil pan and blowing past rear main seal...It happened to me excessive pressure in pan due to a badly machined intake manifold caused 2 brand new rear mains to leak badly