Failed Oil Cooler

[HarryD]

for years the back (clutch end) of my motor has been damp with a slight drip. Not enough to make me want to do any heroics but still annoying.

About a month ago I decided to figure out what was going on.

Thinking it may be that the "triangle of death" has reared it ugly head, I took some pictures of the area and noted it was oily. I also noticed the drain hose from the air box was terminated by laying in this area. A few months ago I had a slight overfill that resulted in free oil in my air box. At that time I cleaned the air box but assumed the oil went to the ground. I cleaned the Triangle area with brake cleaner and engine cleaner. Took it out for drive after verifying it was dry. On return, it was oily again.

I then thought it may be that the parts back there were loose. With a friend, we found that we could turn the fasteners about 1/16-1/8 of a turn. I also extended the air box drain to below the motor as the factory drain line extension was missing. I cleaned the area again and took it for a drive. Still oily after the drive.

A few weeks ago, I was at a HPDE and I went through a quart of oil in a 20 minute session. This seemed extreme. I went home and inspected the car. With the rear elevated so I could inspect and the motor hot, I had my wife rev the motor to 4-5000 rpm. Oil came pouring out. the next morning, with the motor cold (thermostat closed), I repeated the test. No visible leak.

At this point, I decided it was a leak somewhere between the thermostat and the oil cooler. We removed the oil cooler, inspected the area, connections and oil cooler seals to verify they were intact and functional. The seals were soft, pliable and not deformed. At this point I ordered a replacement cooler (be seated when you see the price), and upon arrival installed it with new seals.

It has been about 100+ miles since the cooler was installed. I have driven the car with both high and low rpms. No oil leaks are visible!

I will be attending a Hillclimb next week for the final test but looks like I got the problem solved.

[NorthernThrux]

I have something similar going on. Definitely some oil around the bottom of the cooler that drips onto the bottom-front part of the sealing rib of the case. It tested fine (cold), but I only see this after long drives. Where did your cooler leak from, can you tell?

The Porsche Classic part is about CAD 1300. Yikes.

Ravi

[uai]

a good method to find hidden leaks is to pressure wash and then use french chalk / baby powder or similar to dust everything. After a short drive you'll see where the leak is.

[HarryD]

I have something similar going on. Definitely some oil around the bottom of the cooler that drips onto the bottom-front part of the sealing rib of the case. It tested fine (cold), but I only see this after long drives. Where did your cooler leak from, can you tell?

The Porsche Classic part is about CAD 1300. Yikes.

Ravi

Ravi: There were no obvious defects.

I spoke with Rothsport about getting a used one. they reported the failures are usually internal. They have a pile of failed ones they have yet to find someone to repair. After that discussion, I decided to get new.

I suspect mine had failed a while back and the HPDE I did made it obvious.

And yes, you are in the ball park of what I paid.

[tom1394racing]

I had a similar issue with my '73 RSR hot rod a couple of years ago. It was fairly easy to remove the cooler and pressure test it for internal leaks. The Stromski tool is inexpensive and works reliably. Found that mine was leaking. I replaced it with a good used cooler and all is well.

[myflat6]

One area that can leak is actually a thin, vulnerable area of the case that has been known to weaken and then weep oil. Because it is behind the oil cooler, it can appear that the cooler is leaking.

Here is a photo of my case with the cooler not yet installed.



Here is a phot zoomed in to highlight the area of the case that can weaken and weep oil. Some shops proactively cover this area with material such as JB Weld during rebuilds.

[HarryD]

One area that can leak is actually a thin, vulnerable area of the case that has been known to weaken and then weep oil. Because it is behind the oil cooler, it can appear that the cooler is leaking.

Here is a photo of my case with the cooler not yet installed.



Here is a phot zoomed in to highlight the area of the case that can weaken and weep oil. Some shops proactively cover this area with material such as JB Weld during rebuilds.

That would have been nice but in my case that area was dry. I think this in issue for the later aluminum cases not the early mag case like mine.

[HarryD]

I had a similar issue with my '73 RSR hot rod a couple of years ago. It was fairly easy to remove the cooler and pressure test it for internal leaks. The Stromski tool is inexpensive and works reliably. Found that mine was leaking. I replaced it with a good used cooler and all is well.

I would have gone used but after talking to Rothsport I decided I did not want to waste a bunch of time during the driving season to find a good used unit.

[NorthernThrux]

Yeah, there are some used ones even in our Classifieds, but the new one looks identical, and you get something that has a Porsche warranty and should last for another 50 years.

Porsche had a Technical Bulletin about those weepy later cases, but maybe not relevant to our mag case cars. I'll pull it apart this winter and see what the source is, including checking that little depression. Gonna install some RSR rocker seals and Turbokraft rocker shaft locks to fix a few drips, silicone valve cover gaskets as well as a couple of gaskets on the MFI pump. Nothing serious but I'd like to get the motor as clean as I can. I use 1 litre of VR 20W50 every 1000 miles, so I think I'm doing OK on oil consumption.

Ravi