alsaab

Hi,

as my 1996 TT has all of a sudden started to smoke on startup, I had to investigate. I already posted in the "Have your turbocharger failed" thread perhaps not the ideal place to do...
What I found out yesterday is that the dipstick was no longer seated, so there must have been enough pressure in the oil tank to push it out of the grooves. As I had to clean as much oil as possible, I also took the IC of and wanted to check the vent lines at that occasion. The line starts at the throttle body and the tank, the turbo reservoirs, the crankcase and the intake are connected to the line. I was looking for a check valve in this system but didn't find one. But this would mean that, under boost, the boost pressure would be present in all the connected parts, that should for sure not be the case.
So my question is : is there actually a check valve (or is the large fitting in the throttle body a check valve) or is there a mistake in my analysis and understanding of the system.

Many thanks for your help


Alain

sonny1

No check valve.

alsaab

Hi and thanks for your reply !
However, I still don't get it....
If there is no check valve, at 0.8 bar boost pressure we will have the same pressure in the reservoirs, in the oil tank, in the crankcase.....I cannot imagine this. The more I think about it, the more I fear this is a leakdown problem. By the way, is it possible for a turbocharger to leak boost pressure into the reservoir ?

Thanks again


Alain

NB Just heard a 993 lift off in front of the office..........mine is on ramps right now

Kevin

If you have crankcase positive pressure to the point of blowing out your dipstick > points to piston ring wear or a broken ring. A engine leakdown test is in order. Roll each piston to TDC and pressurize the cylinder with 100PSI.. Buy or borrow a leakdown gauge. A compression test will not pinpoint the failure. If you have leakage in a cylinder> pay attention to where you hear the rush of air.. Intake system, exhaust, or crankcase..

Kevin

It is possible to read high crankcase base pressure "IF" you have ring damage or accelerated wear.

alsaab

Hi,

first of all the easy part : the oil separator is also a check valve......and it holds 1,5 bar without any problem. So I can discard that one......

For us here in Europe, a leakdown test is not something usual. Most of the time I hear about it, I'm on a US site. Anyway : I know I'm dreaming but could it be something else ??? The car was working perfectly when I parked it in the evening, nothing unusual. I let it idle for a couple of minutes like always, and 12 hours later the huge cloud. Before that, never the slightest smoke, clean rear bumper, no oil consumption....Is it possible to damage a piston ring or to burn a valve w/o noticing anything ?

Also, after 2 days I have probably drained about 5 quarts through the reservoirs. Could my leak have damaged the filter ?

Thanks


Alain (panic mode now, seriously !)

Kevin

You aren't going to wake up and have this problem solved..

You have to rule out everything. Valve guides, bent valves.

My first recommendation is:

1) Pull the plastic inlet pipes to each turbocharger and check for oil. Clean the pipes.
a) If oil is present, remove your IC and clean.

2) We address your engine oil level. Must drop the engine level to the dipstick First hash mark.. Verify when warm. But if you are pulling out quarts of oil, the level is down.
a) If you are running 0W or 5W oil change it to a 10W or 15W..

3) Buy two Genuine Porsche engine oil filters. Spin on the engine filter. Do not over tighten. Spin on a 1/2 turn once it seats.

All of these recommendation need to be done all at once. Or you will be chasing your tail.

alsaab

Hi Kevin,

first of all, thank you for your help ! As I already wrote, I started this discussion in the "Have your turbochargers failed" thread which was probably a bad inititative, sorry for that!
What really worries me is that I follow the golden rules since always : 15W50 Motul, oil level as low as possible, genuine P-filters (including the 03 type for the small one), idle and cool down time to an excess........
My only hope is (and I don't expect to wake up and have it all solved, it's more of a nightmare) that all this happened so suddenly that I can't see what has happened, but it did !
I found about 4 tablespoons in the IC, almost the same in each plastic pipe. As I already wrote, after 48 hours I drained about 5 quarts out of the T-reservoirs.
It's not only that I don't wont to admit I have to face an engine rebuilt, I simply cannot understand what has happened between a really "tourist drive" the day before and the smoke explosion the day after. I realized the dipstick thing only after having read a post here on the forum.


Alain (sorry for my "Luxembourg" english)

Kevin

Verify engine oil level.. Spin on a new engine oil filter (Porsche).

If you still have oil movement, turbochargers will need to be looked at. I'd still be doing a leakdown test.

alsaab

Meanwhile this is more or less a chat we are having !
As I am not used to : does one do the leakdown test with a cold engine ? I will have to find a spark plug adapter but as I stripped already most of the parts, why not ?
Of course I would like to give it a second try and get away with it, but my oil level was already extremely low and both filters have been Porsche since always. So I don't expect any improvement from that side (unless the filter I changed 18 months ago is now at fault).
In the past, the car sometimes sat fore more than 2 months, never any smoke. Something very specific must have happened during the last drive before the smoke explosion. That's the reason why I was worried about the check valve in the throttle body but it's fine.
Final question for today : what's the role of the pressure relief valve on top of the oil tank ?
Right now, I would like to give it a try with a new filter, but I still did not understand what happened so I don't know what to do....


Alain

sonny1

Oil separator a check valve? that's is news to me., follow Kevins advice, I'll do the leak down test, warm engine is best, cold engine will work also but not that precise.
Cheers, Sonny.

Marcus S.

Alain, is this problem solved? If yes, what was the problem?

Regards!
Marcus