Turbo oil leak - I seek knowledge and wisdom
Discussion
My 993 turbo has been in secure storage for the past six months while I've been away on contract. Received a message yesterday to say that a small pool of oil (about half a litre) has appeared beneath the left side of the engine. Car hasn't been run, and was dry as a bone when it went into storage.
I'm guessing a valve cover gasket?
Do they 'dry out' and fail when unused, or might it be more serious? Should I be preparing to remortgage to repair this?!
My knowledge of these engines is not huge, but I can't think of any parts of that side of the engine where a large volume of oil might reside....
I'm guessing a valve cover gasket?
Do they 'dry out' and fail when unused, or might it be more serious? Should I be preparing to remortgage to repair this?!
My knowledge of these engines is not huge, but I can't think of any parts of that side of the engine where a large volume of oil might reside....
This is not all that unusual with a 993tt. The cause can often be oil draining from the dry sump tank, backwards through the scavenge pump and into the small sumps on each turbo. Significant contributors can be the wrong oil (too thin), an overtightened small oil filter and/or the wrong oil filter. Overfilling is also a cause.
The oil overflows the turbo sumps and it seeps past the turbo's seals. Running the engine in this state can put loads of oil through the exhaust and possibly the intake as well - this should be avoided if at all possible.
Some questions:
When was the oil last changed and what oil was used?
Are you confident that the oil change was done by someone who understands how to check the oil level (engine hot and running at idle and car on level ground is the only way)
What brand of oil filter was used? It seems that only a genuine Porsche filter has the correct anti-backflow valve. Even a Mahle filter should not be used on a 993tt. That said the valve in the Porsche filter can be damaged if the filter is overtightened.
If this were my car I would try to get answers to the questions above. And then before starting/running the car I would remove the drain plugs from each of the turbo sumps (6 or 7mm hex key) and drain them. If a Mahle filter is installed I would change it to a Porsche filter before even starting the car. If the wrong oil was installed I would change it ASAP.
I ran a 993tt for 6 years and had the exact problem you're seeing. Sad thing was the wrong filter and wrong oil were used by a well known Porsche Specialist!
The oil overflows the turbo sumps and it seeps past the turbo's seals. Running the engine in this state can put loads of oil through the exhaust and possibly the intake as well - this should be avoided if at all possible.
Some questions:
When was the oil last changed and what oil was used?
Are you confident that the oil change was done by someone who understands how to check the oil level (engine hot and running at idle and car on level ground is the only way)
What brand of oil filter was used? It seems that only a genuine Porsche filter has the correct anti-backflow valve. Even a Mahle filter should not be used on a 993tt. That said the valve in the Porsche filter can be damaged if the filter is overtightened.
If this were my car I would try to get answers to the questions above. And then before starting/running the car I would remove the drain plugs from each of the turbo sumps (6 or 7mm hex key) and drain them. If a Mahle filter is installed I would change it to a Porsche filter before even starting the car. If the wrong oil was installed I would change it ASAP.
I ran a 993tt for 6 years and had the exact problem you're seeing. Sad thing was the wrong filter and wrong oil were used by a well known Porsche Specialist!
AW10, thanks for the reply, very thorough and I think you may be psychic! The guys storing the car have put it up onto the ramp and had a look. The large quantity of oil is leaking from the left turbo, and there is also, apparently, a very small leak from the oil pipe which enters the left side of the bottom of the crankcase.
The last service was done at Precision Porsche, who I believe use only genuine parts (but I'll check). Not certain of the grade of oil used.
I'll try to attach a photo, but it may be too large.
When I return, would you suggest draining the turbo oil sumps and then running the car as normal? What else should I be looking out for or doing?!
Thanks
TM
The last service was done at Precision Porsche, who I believe use only genuine parts (but I'll check). Not certain of the grade of oil used.
I'll try to attach a photo, but it may be too large.
When I return, would you suggest draining the turbo oil sumps and then running the car as normal? What else should I be looking out for or doing?!
Thanks
TM
AW10 said:
...an overtightened small oil filter and/or the wrong oil filter. Overfilling is also a cause.
What brand of oil filter was used? It seems that only a genuine Porsche filter has the correct anti-backflow valve. Even a Mahle filter should not be used on a 993tt. That said the valve in the Porsche filter can be damaged if the filter is overtightened.
Sad thing was the wrong filter and wrong oil were used by a well known Porsche Specialist!
Apologies for picking-out bits of your reply - I just wanted to highlight that my understanding of this issue is that it was a better solution to fit an 'aftermarket' non-return valve between the small filter and housing?What brand of oil filter was used? It seems that only a genuine Porsche filter has the correct anti-backflow valve. Even a Mahle filter should not be used on a 993tt. That said the valve in the Porsche filter can be damaged if the filter is overtightened.
Sad thing was the wrong filter and wrong oil were used by a well known Porsche Specialist!
Then
a) you can use a better filter than the one currently Porsche-branded
b) overtightening isn't such a big issue any more?
Obviously you can use a decent filter on the reservoir regardless.
Edited by Orangecurry on Tuesday 16th September 17:09
I need to make a correction/expansion in what I wrote above. Oil can get into the turbos when the engine is off via two different ways:
1. Oil flows from the oil tank, through the filter, through/past the pressure pump's gears and into the turbos via the oil feed lines. This is probably what's happening in the OP's car. There's valve in the genuine Porsche filter that prevents this but it's easily damaging by overtightening. I had this on my car after an oil change by a well known specialist and oil drained continuously from one of the turbo sumps - I think I got to 1.5 litres in 24 hours before I fully realised what was going on and changed the oil and filter at home.
2. Oil can be siphoned back into the turbo sumps from the scavenge pump via the hard pipes that are used to scavenge the sumps. This seems to be rare - the only solution would appear to be an oil line that has a vertical loop that breaks the siphon. The good thing is that the amount of oil is limited by what's remaining in the scavenge pump
Running the right oil and filter is the best solution and simplest/cheapest. It's also possible to install valves (It's a 996 turbo part) in the turbo's oil feed lines that only open under pressure - this prevents the first problem. The kits cost about £500 ( here's one link) and a couple hours of labour to install. They're a bit of a bugger to install on an older car though as the valves use the turbo's body as part of the sealing surface but with the passing of the years and rain and road salt that surface is often pitted making getting a good seal difficult.
1. Oil flows from the oil tank, through the filter, through/past the pressure pump's gears and into the turbos via the oil feed lines. This is probably what's happening in the OP's car. There's valve in the genuine Porsche filter that prevents this but it's easily damaging by overtightening. I had this on my car after an oil change by a well known specialist and oil drained continuously from one of the turbo sumps - I think I got to 1.5 litres in 24 hours before I fully realised what was going on and changed the oil and filter at home.
2. Oil can be siphoned back into the turbo sumps from the scavenge pump via the hard pipes that are used to scavenge the sumps. This seems to be rare - the only solution would appear to be an oil line that has a vertical loop that breaks the siphon. The good thing is that the amount of oil is limited by what's remaining in the scavenge pump
Running the right oil and filter is the best solution and simplest/cheapest. It's also possible to install valves (It's a 996 turbo part) in the turbo's oil feed lines that only open under pressure - this prevents the first problem. The kits cost about £500 ( here's one link) and a couple hours of labour to install. They're a bit of a bugger to install on an older car though as the valves use the turbo's body as part of the sealing surface but with the passing of the years and rain and road salt that surface is often pitted making getting a good seal difficult.
Orangecurry said:
Apologies for picking-out bits of your reply - I just wanted to highlight that my understanding of this issue is that it was a better solution to fit an 'aftermarket' non-return valve between the small filter and housing?
Then
a) you can use a better filter than the one currently Porsche-branded
b) overtightening isn't such a big issue any more?
Obviously you can use a decent filter on the reservoir regardless.
The valves go in the feed lines to the turbos - there's an image in the link in my post just above this one. I don't think there's much wrong with the Porsche filter; it's perhaps a bit too susceptible to over-tightening but that's never a good idea on any car.Then
a) you can use a better filter than the one currently Porsche-branded
b) overtightening isn't such a big issue any more?
Obviously you can use a decent filter on the reservoir regardless.
Edited by Orangecurry on Tuesday 16th September 17:09
Thanks for that clarification - you clearly know what you are talking about - every day is a school day.
I didn't realise the 'external' non-return valves cost that much or were that difficult to fit.
And what I mean about the poor quality of the Porsche-branded filters is the very thin metal, poor construction/design, and the chances of them failing due to rust, partially explained here:
http://rennlist.com/forums/993-turbo-forum/702507-...
I didn't realise the 'external' non-return valves cost that much or were that difficult to fit.
And what I mean about the poor quality of the Porsche-branded filters is the very thin metal, poor construction/design, and the chances of them failing due to rust, partially explained here:
http://rennlist.com/forums/993-turbo-forum/702507-...
Thanks for the reminder about that Rennlist thread. My personal thought is that the Porsche filter is still the right one to use because of the valve within it. There are two filters in the system - the large one that filters hot oil coming out of the engine and the small one filtering the oil being supplied to the engine. Plenty of filtering capacity! And if a filter rusts badly enough to weaken it it's been in service for far too long and I would worry about all sorts of maintenance/neglect issues throughout the car.
Here's a picture of the Porsche filter that was over-tightened, damaging the valve within it.
The disc fell out when the filter was removed.
Here's what the spring and disc in the filter should look like:
Here's a picture of the Porsche filter that was over-tightened, damaging the valve within it.
The disc fell out when the filter was removed.
Here's what the spring and disc in the filter should look like:
Well done Pistonheads, I sought knowledge and wisdom, and knowledge and wisdom was what I found.
993 turbo back-flow kit ordered from FVD, car now cleaned up (by the kind storage fellas - thanks!) Kit will be fitted with the next service at Precision when I return (along with genuine Porsche filters).
I'm sleeping soundly again!
Cheers all
993 turbo back-flow kit ordered from FVD, car now cleaned up (by the kind storage fellas - thanks!) Kit will be fitted with the next service at Precision when I return (along with genuine Porsche filters).
I'm sleeping soundly again!
Cheers all
ThirstyMoose said:
Well done Pistonheads, I sought knowledge and wisdom, and knowledge and wisdom was what I found.
993 turbo back-flow kit ordered from FVD, car now cleaned up (by the kind storage fellas - thanks!) Kit will be fitted with the next service at Precision when I return (along with genuine Porsche filters).
I'm sleeping soundly again!
Cheers all
Holy Thread Resurrection Batman!993 turbo back-flow kit ordered from FVD, car now cleaned up (by the kind storage fellas - thanks!) Kit will be fitted with the next service at Precision when I return (along with genuine Porsche filters).
I'm sleeping soundly again!
Cheers all
Thirsty, do you still have the turbo and did the filter and oil change cure the issue? Did you get the back flow kit fitted?
The reason for the questions is mine seems to have started doing something similar - Small leak from the l/h turbo sump.
We have drained both turbo sumps and got about 100ml out of the l/h and about 250ml out of the r/h.
On starting the engine there is a cloud of smoke from both exhausts for about 5 seconds.
The engine appears to be running fine apart from that.
It took a while but I solved the problem eventually. The back-flow kit helped, but didn't entirely solve the problem. I subsequently fitted ruf oil scavenge lines (raised loop as described in earlier post). Now completely dry again. It looks was though the oil was filling the turbo sumps from both supply and return sides. Cost of the whole repair was less than £1k including fitting.
I also had the turbos rebuilt a little later, but not because of this issue, just as a bit of general improvement therapy.
I also had the turbos rebuilt a little later, but not because of this issue, just as a bit of general improvement therapy.
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