3.6 Case seam oil leak after rebuild?
 

NOT a case seam leak! OOOPS . . . yes, a very very small case leak just below the major leak in the intermediate shaft bearing O ring leak :eek: see my post on 7-21-2023. . . The shop will now do the vacuum procedure . . .

Thanks in advance for any feedback on this case leak issue after a rebuild.

Do any of you have experience with case leaks at the bottom case halves mating?

Engine builder says not enough sealant - will have to disassemble and reassemble
with a little more sealant . . . builder says they have seen this before when cases are
machined. we are planning to do the engine work in Aug-Sep - we don't race in the summer here . . . ha ha . . .

We ran a break in track run 2x20 minutes to seat the rings - - thinking maybe the heat would seal the leak - but it is now worse - and we did have a little oil on the rear bumper and rear deck after the track runs (only very small droplets)

Regards,
Roy T (Crew Chief - son's car)

Photos of where the leak occurs:

Hard to see oil leak because fresh new break in clear oil - oil runs down left to right
and then drips - -

http://forums.pelicanparts.com/uploa...1685807074.jpg

Spots on wood - one for each day

http://forums.pelicanparts.com/uploa...1685807074.jpg

I've solved this before, so method is sound:

First, clean the area and dust some baby power in the area. The leaking spot will become very visible. Mark the spot.
Next beg or borrow a vacuum pump and connect it to the breather port in the engine. 10psi should be more than enough.
Spray some BraKleen on the area to clean remaining oil from the joint.
Apply some LocTite 574 (or similar) to the leaking area and watch it get sucked in. Remove the vacuum AS the sealant is being sucked in.
Wait a while, perhaps take a nap... Leak is gone without disassembling the engine!
You're welcome!

Thank you for this great solution - we'll give it a try, may take a while to get to it . . .
But, I will follow up with our progress.

Regards,
Roy T

double and triple chaeck that it's not the through bolts

Thanks Bill for the great suggestion!
You are always a huge help on this Forum!

Regards,
Roy T

This is a great idea… I’ve done the exact opposite to find porous mag leaks. Definitely going to try this

The lack of glue or the type of glue always gets blamed for leaks. Never is it either. Its down to preparation and making sure the surfaces are flat and have no divots.

If the surfaces were perfectly flat and zero divots you would not need any glue. The case will never stick to itself like gage blocks can as there are open holes limiting a vacuum seal.

All you need is a few microns of thickness of glue, unless you have not prepared the surfaces properly. The rest oozes inwards and outwards. Some have the notion that some is good more must be better. I have seen photo's of cases assembled with copious amounts of glue outside of the case parting faces sealing nothing.

Remove the perimeter studs, lap the case parting faces and inspect for divots and surface irregularities.

Thanks Neil,
I really appreciate your insight into this issue - I'll be talking to our engine builder this week sometime . . .

Regards,
Roy T

Hi Neil, Is there a good tutorial somewhere or a source where one can learn the proper steps to prepare the case surfaces?

Although Niel is absolutely correct, achieving a "perfect" mating surface is tantamount to impossible. When it comes to the case, case through bolt torque and perimeter bolt torquing create forces that modify how the case halves mate. Clean and smooth are a great start but we are often working with 50 year cases subjected to hundreds of heat cycles. In the early days of the 964, the factory hid the fact that 4% of their "new" engines leaks on the dyno. Remember, 4% leakage with brand new parts, assembled by factory trained technicians.
The purpose of the engine sealing thread and my suggestions about sealing techniques are based on experience. They are designed to give the first timer the greatest shot at success. It is not the only way to do it and in no way suggests that preparation is secondary but after over 400 air cooled Porsche engines, this seems to work best for us.

michaelmount,

I talked to our engine builder and they really like your solution - they will work on the
car week of the July 10th - they have all the right tools and supplies to do the work -said
they could have used this on previous engines - they will do the dye in the oil also . . .
I'll follow up when we finish up and test the engine . . .

Thanks again for your contribution to my request.

Regards,
Roy T



First, clean the area and dust some baby power in the area. The leaking spot will become very visible. Mark the spot.
Next beg or borrow a vacuum pump and connect it to the breather port in the engine. 10psi should be more than enough.
Spray some BraKleen on the area to clean remaining oil from the joint.
Apply some LocTite 574 (or similar) to the leaking area and watch it get sucked in. Remove the vacuum AS the sealant is being sucked in.
Wait a while, perhaps take a nap... Leak is gone without disassembling the engine!
You're welcome!

Genius fix
 

This is such a great idea......

Don't use anaerobic Loctite 574, which has a tendency to set up before you get the case halves tightened. (shimming). Famous for causing leaks around the #8 nose bearing. If you torque the mains before the perimeter nuts, this could happen. My 2¢, take it or leave it.

Sucking glue into the gap sounds cool for a band-aid but if your engine builder is offering to repair it correctly, do that.

Jim,
Engine builder has offered to do both - if the "sucking" method doesn't work then they
will disassemble and reseal . . . really stand up guys and very long time Porsche Indi shop . . .
And . . . their father worked for Carrol Shelby a very long time ago . . . the brothers now own the shop.

Regards,
Roy T

John,
Thanks for the feedback - - they don't use LocTite on the case halves . . .

Regards,
Roy T

Neil and Henry,

Thanks for the added information - you are always great contributors to this Forum.

Regards,
Roy T

John Walker is right, as usual. We are using 574 Loctite to seal case halves on construction transmissions, we build roughly 100 of them every day. During my manufacturing engineering times I did a ton of tests with it and I highly doubt that there was not enough 574 which caused the leak. If it comes out of the seam you used too much is what we go by, mainly not to clog up test bench filters, point is it just needs to fill the gap. The stuff is absolutely great and will last BUT you must be quick, as mentioned by others, if the halves are together it starts to cure, when it starts to crystalize it is too late and if you then torque the bolts you will get a leak. I built a few 3.2's and used 574 and other sealants just to see what works best. It will all work if the prep is done right is my opinion.

What sealant do you recommend for that application?

1215 on nose bearing area. 1184 on metal to metal. The Threebond numbers change constantly, so call them 11 series and 12 series. The 12 series is thicker for formed in place gaskets (omit the gaskets), 11 series is thinner for machined metal to metal surfaces with no or very small gaps.

I'll likely get s**t for this, but when we had comebacks at the stealership, it was on OUR dime, the mechanic was paying. I never trusted whatever goop the Porsche (and other) factories were recommending because we'd see leaks on everything they used. UNTIL they started using Threebond everywhere. If you look at other manufacturers, they all now use some derivation of Threebond on metal-to-metal surfaces (if not o-ringed. and no gaskets unless they have built in o-rings). That goes for engine cases, cam housings/towers, various bolt-ons, transmission cases, etc. There's a long history of Japanese manufacturers using various Threebond products to seal engines and transmissions, and they would nearly always make it hundreds of thousands of miles with not even oil "seepage," or "weeping." Literally dry as foundry produced aluminum with nary a hint of oil anywhere.

The biggest thing to guarantee success was to get the surfaces surgically clean with alcohol or brake cleaner and NO old residue of anything before applying the Threebond.

FWIW, YMMV. Just a voice from a several decade professional.