Cause of Triple Seals Failing in 94 348

I cant speak for your situation, but if my 355 sits for a long period of time I will see a drip or two. After it gets driven a few times the seals must swell and I get no drips. Driving it often is the best prevention for me.

 

How can you tell it's the triple seal or the throw-out bearing seals that is leaking?

 

The triple seals do not prevent oil on the floor, they prevent oil from entering the flywheel cavity. If you have oil on the floor it is for another reason.

And the triple seals? They were a terrible idea that just barely work on their best day. If it was a good design only one would have been needed.

 

Is it gear oil or brake/clutch fluid?

 

Brake fluid will evaporate (slowly).

 

They were wrong. Triple seals seal the coaxial shafts from each other. They keep gear oil out of the flywheel period. When the flywheel gets completely full the O ring on the clutch shaft keeps it from dripping on the floor. If you have gear oil dripping out it is from the clutch shaft seal.

 

Trying to understand your explanation I am looking at it in reverse order. If the gear oil is leaking from the O ring (which then is defective) because the flywheel has filled with gear oil from failing triple seals it appears that is the initial cause of the problem. Is this a correct assessment? Just trying to understand the proximate cause. Thanks.

 

As explained earlier, the gearbox oil can escape out if the black o-ring (pointed at by the red line on the pic) is bad. This o-ring is easily damaged by the clutch disc splines that go over it during installation of the clutch/flywheel assembly if great care is not taken.

Your triple seals and the o-ring are possibly not 100% but still holding during moderate driving. But during spirited driving, when the transmission oil heats up more and gets thinner (and is thrown around more violently), some of it manages to pass the seals. I guess these are the early signs that the time is coming for your flywheel re-grease and seal replacement. A sign of oil having entered the flywheel is a brief rattle from the back on engine switch off.

When I did the mentioned flywheel work on my 348 a couple of years ago (because I had the rattle), I found that the transmission oil had traveled as far back as the large flywheel nut. My black o-ring was like bakelite and the oil had contaminated the clutch discs.
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If the flywheel is full of gear oil you will have far worse symptoms than a couple of drops of oil on the floor. This conversation would not be happening.

 

Probably because it has a bad seal. This is analysis paralysis. Take it apart, find the leak then replace every seal in there anyway. If there is gear oil in any amount in the flywheel, take it apart and service it. Problem fixed.

 

Not without tearing it apart to see what's going on in there

 

That is actually false.

The majority of leaks that I have read about were due to the seals in the TO bearing (brake and clutch fluid), and not the triple seals (gear oil)

Check this thread.

http://www.ferrarichat.com/forum/348-355-sponsored-bradan/296614-leak-underneath-clutch-help.html

 

Parts #16 & #18 are another place where you should look. The brown seal isn't a real tight fit and I've seen them get crooked and leak.
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The clutch shaft seal I spoke of.

 

What is the F number of this particular O-ring
I believe this is the one that is causing the leak in my car
But cannot find it on the diagrams

Sorry to hijack the thread

Frank

 

Your "F" is for Ferrari, I believe. It is 104984. Eurospares do not have it in stock (and may not sell it at all), I bought it from Superformance.

 

Thanks Miroljub

The diagrams are not very clear
But I believe you are correct
I will order here at the dealer, not so expensive
I replaced this O-ring last year together with the triple seals but the leaking continued
Must have damaged the ring while assembling the clutch
Will have to be more careful next time

Frank

 

I hate 131651. It's a $50 part from Ferrari that needs care to install in the TO bearing housing. I destroyed one by not being careful. There is a good instruction thread in this section I think. Ernie did it?

The O-ring is duck soup by comparison.

 

First picture: o-ring damaged by the clutch disc splines.

My installation:

Second picture: rounded off and smoothened the sharp corners of the splines (red marks) on the side that attacks the o-ring

Third picture: used guide-studs with shrink tube over them to eliminate the play in the bell housing holes and keep the assembly centered

Fourth picture: kept the assembly supported on a scissor jack and fine-adjusted it so that the weight if the assembly does not hang on the guide-studs; went in nice and easy with the help of the spring pushers; when it stopped at the point where the two splines start engaging, I just turned the flywheel through the top window by about an inch and it slid in
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It went easy in my case - I used a suitable disc from my oil seal installation tool kit but did not try to hammer it in; instead, I used a long bolt and nut through the installation disc to slowly "screw" it in.

 

The pictures show the splines of my new clutch disc before and after rounding-off of the spline edges. The edges are almost razor sharp and, if not rounded, they can easily shred the o-ring even if the clutch assembly is well centered as the splines pass tight over the o-ring.
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No more so than any other seal.