I've had repeat failure of both the oil return line AND the oil cooler manifold. I suggested to my mechanic that they measure oil pressure before dropping the engine again (this is drop #3...). Has anyone else had issues like this?

Thanks,
Larry

 

Finally got pressures measured:
Cold start up: 92 - 96psi (6.2-6.6 bar), cold idle (5 min running): 86 psi (5.9 bar), hot idle (90 c): 20 psi (1.4 bar)

Anyone have an opinion on these values? Cold start seems pretty high to me considering ambient temps aren't particularly cold.

-Larry

 

Weird issue...I'm sorry I don't have a TON of insight but I'll try since this hasn't had much attention. I've never measured pressure other than looking at the gauge on the dash...which I continually think is likely wrong.

BUT...from what I see on the dash those values don't really seem off Mine is pegged at 5 bar for quite some time after cold start and I rarely see it below 2 bar.

What oil are you running? Thicker than the Mobil 1 water that is factory fill?

Have you had the oil cooler off the car, possibly for welding the coolant lines that go into it? is it possible to put it on backwards and have flow going the wrong direction. Off the top of my head I think it *could* happen but I may be wrong.

 

I'm running Mobil 1 0W-40. Oil cooler has been off for pinning coolant lines- not sure if it can go on backwards, but I'll check. Wonder if it's possible for the cooler to get partially blocked...

At least it's something to look at- I really don't want to put it back together and have it fail a 3rd time!

-Larry

 

Engine is out, and it looks like oil is leaking from between the oil cooler manifold and the block. Apparently there's no gasket there, just a special sealant that needs to be applied exactly right. I'll be replacing both the manifold and the oil cooler itself, along with all of the o-rings.

BTW, it is NOT possible to mount the oil cooler backwards, there's a fitting on top of the cooler that only goes one way.

 

While I have no data for what cold oil pressure should be or what's reasonable -- in the 996 Turbo/GT3 factory manual Porsche only calls out the hot (90C) oil pressure (approx. 6.5 bar) at 5K RPMs -- 6+ bar sounds about right. Hot idle of 1.4 bar is well within the ballpark.

My 2003 Turbo hot idle oil pressure -- using the dash gage which is a crude instrument at best -- is in the 2.0 bar (or a bit lower if ambient temperature is quite high) and this with 5w-50 oil (not a typo for 15w-50!) in the engine.

Might add that from the hot idle oil pressure I can't tell if the engine has 0w-40 or 5w-50 oil in it.

If there was something wrong with the oil pressure regulation, or something in the oil passages, I think hot idle oil pressure would be high.

Reading your more recent post it appears you have found the culprit, the reason for the leaks. An improperly sealed oil cooler.

 

Thanks for the feedback, it sounds like my pressures are in the normal range, even though they're higher than the stock gage can read. One thing this data highlights is the need to let everything warm up fully before running it hard.

I really hope that properly sealing the oil cooler will solve this once and for all!

 

I'm interested in what you find here. Here are some pictures I took of that stage of assembly when I assembled my engine, in case they are useful for you (or others) to help you think about this. This engine is not exactly like yours, because it's a 2001 race engine, but it's very similar. The large oval opening between the oil cooler manifold and the engine case (that has no paper gasket) is the breather, and of course would not be subject to oil pressure, per se. But there's a lot of potential for a leak if it's not sealed. I'd check the flatness of those surfaces, especially across the parting line of the engine case. And there are many O-rings in that installation for the oil cooler as you know. I assume you lubricated them appropriately? Too bad you can't run the engine while it's out of the car and watch for the source. Good luck.

 

One more thought: I'd be really surprised if you had a problem with the oil cooler manifold itself, especially if there was no leak before you took things apart. Same for the engine case. I'd be most suspicious of the O-rings and sealing process. I've never heard of an oil cooler on a GT3 that leaked externally (as the old air-cooled oil coolers commonly did), but I have heard of them failing internally, and I had one that mixed the oil with the coolant and wreaked havoc. You might pressure test your cooler to see if there's a problem with it. Also, note that on the race engines, there's no welding or pinning of fittings needed on the various manifolds -- they used threaded fittings. Too bad the street cars didn't get this treatment!

 

Thanks Rob! Are these pics of a Cup engine, or something different?

The oil cooler manifold was replaced two years ago due to a crack, and we're replacing both the manifold and the oil cooler this time- just to be absolutely sure there's no issue. My mechanic is being extremely careful about sealing it properly, and is replacing all of the O-rings as well.

I agree with you on the fittings, you'd think they would have updated the fittings over time once they became aware of the problem. There are many other parts that got updates, so it's not like it would be setting any sort of precedence...

 

Wow, the oil cooler manifold was replaced because of a crack? How did that happen?
My engine is a factory 2001 GT3 RS race engine -- similar in many ways to a Cup engine, but one or two notches beyond.

As for the threaded fittings, it's obviously more expensive to use threaded fittings instead of glued. But it's the perfect solution. I wonder what the price difference would have been for Porsche to use this method for their production street engines, especially when they obviously had the technology to do it for their race engines. My guess is that the cost increase would have been well under $100 per car. In retrospect, I'm sure Porsche wishes they'd done that. Imagine how much better it would have been for all of us. I've also wondered if any of the race parts could be purchased and used on street cars. I've never done a comparison to see if they'd be compatible. It's easier just to weld and be done with it.

A couple years ago someone on Rennlist posted his method for doing custom aftermarket threaded fittings. They were beautiful, but very labor intensive and hence expensive.

 

Not exactly sure how the manifold cracked, my guess is that it was damaged when the fittings were drilled and pinned, but that's just a guess.

Good question on whether the race parts would swap over. My guess is that many of them would, but it would be extremely expensive and not noticeably better than pinning or welding.

 

i would check pressure limiting valve (item 7 in the attachment). Seems like your oil pressure is high when cold as if this valve is stuck. What pressure do you see when warm at higher rpms?

 

The car is back together, but hibernating for the winter. I'll check the hot oil pressure when I pull it back out in the spring. Do you know where that valve is located? Is it accessible with the engine in the car?

 

The pressure relief and safety valve are accessible with the engine installed. see the attachment showing their locations. The attachment is for a 993 however i believe it is representative for the GT3 case.