how to check for case leaks?

[jtamborra]

Hello,

I currently have my 930 motor top ends removed for machining... I'm looking at the case (in which the crank rolls like sweet-sweet butter, so I don't want to rebuild) and trying to decide a good method for checking it for leaks at THIS stage. I'm really most interested in checking the lowest seam for leaking because the upper and side seams were dry/clean, and I was thinking maybe pouring some thin colored oil-type fluid into the case to a depth below lowest opening (the oil return ports I believe) and watching for a few days to see if anything weeps out. maybe ATF since it's red? Has anyone seen a better method? Will ATF do something bad to case metal?

Thx-
john tamborra
hacked upon 1985 carrera cab w/ 3.3 turbo shoehorned in...

and boy, oh, boy were these pistons/heads dirty!

[Bob Kontak]

Welcome!

I like your idea but would default to the thinnest dino oil you can find vs Auto trans fluid - only because there are a lot of additives in ATF that I have not a clue about. Seal swelling agents included.

Can you provide some data about the leak condition before the case clean? Was there seepage or was there a large build up of oil and dirt at the case seam? Given the huge (time) investment to split the case and re-seal, I would live with a bit of seepage.

Additionally, you probably know plenty about these engines, but feeling like butter is not an alternative for pulling a rod and examining a journal/bearing for scoring and using plasti-gage to check clearance. You have to replace the stretch bolts - but for $30 or so it is worth the spend for comfort.

[john walker's workshop]

those pistons show a ton of oil use. (the clean areas). don't you want to check the rings?

[JohnJL]

Looks like 456 came off. How were the rings?

[jtamborra]

Thanks for the responses, I have sent the cylinders to EBS to be honed and replated w/ Nikasil. The rings seemed in good shape, but obvious scoring on the cylinder walls (cylinder floor? as it was the downfacing cylinder walls that have sustained damage.) I would guess from carbon falling off piston face into cylinder... New rings ordered from our host, hopefully a sweet fix!

New issue tho, while pistons were at the machinist to be cleaned, he found a few very small cracks in the piston skirt area. See pic, anyone else had this? Anyone have three 3.3l turbo pistons they'd like to sell me???? Can they be welded? Am I crazy to consider using these things again?

[88911coupe]

This is a good question, however let's assume you find a leak on the lower seam...is there a reliable process for sealing it up? I assume it's not under a lot of pressure so maybe something could be applied to the seam after a good cleaning?

[Rot 911]

Originally Posted by 88911coupe

This is a good question, however let's assume you find a leak on the lower seam...is there a reliable process for sealing it up? I assume it's not under a lot of pressure so maybe something could be applied to the seam after a good cleaning?

Dow Corning ® 735 Oil Resistant
Sealant is a one-component, ready-touse,
nonslumping silicone material
that reacts with moisture in the air to
cure to a tough, rubbery solid.
• Easy handling with no mixing,
heating or solvents; easy repair
by cutting away old material and
replacing with fresh material
• Service temperature range from
-80 to 400°F (-62 to 204°C) for
extended periods, and up to
450°F (230°C) for shorter
periods
Applications
Dow Corning 735 Oil Resistant
Sealant can be used for sealing
general industrial equipment where
resistance to oil, coolants and other
lubricants is required (oil circulation
systems, machine housings, conveyor
guides and guards, oil containment
troughs or barriers, piping).
Dow Corning 735 Oil Resistant
Sealant can be used as formed-inplace
gaskets for gear boxes,
engines, pumps and flanges.

[mreid]

That Dow sealant is not meant to be applied outside the case seam.

You can purchase a dye made for oil. Add a little to your oil and it becomes very clear where the leaks are under a black light (ultraviolet light). I would much rather see you use this than a foreign substance in your sealed case. The only concern I have is that often case leaks only show up when the oil is hot and yours is not going to be for a while. Good luck!