ccamut

I have owed the car for several months, it has 155 k miles. Does not leak a drop, however I have had three track days and oil blows out the filler cap. I first thought it was over filled, but ran it with oil just showing on dip stick, same problem.

I suspect there is a breather hose issue, can you suggest a few places to look?

Thanks for the help.

crg53

When you say reading the dip stick, that is with the engine hot and idling on level surface, right ????.
Below is a picture of the oiling system, part #44 is the tank breather hose, that could be plugged.

dutchcrunch

whooo. check oil cap maker sure inners seal of cap is there. properly filled, with g force could cause this and if the cap is not sealing like it should this could result

ccamut

The oil level is well below the dipstick actually, by at least a half quart, 30 min session, car is level and smokin hot and I still get the blow out. I first suspected the cap, but its clear there is an unusual amount of pressure.

Your diagram is helpful, the u shaped hose..... How do you get to it, and what does the other end connect to? Thanks again.

Steve Weiner-Rennsport Systems

If your oil level is correct and the tank breather is properly connected, you need to perform a leakdown test to see if there is a ring/piston problem..

Vandit

I've had my car blow oil out the filler cap during a Time Trial event (baby track event, 10 min sessions, lots of sustained high RPMs).

I wasn't tightening the filler cap too much at the time, but I've now made it a point to tighten it up w/ more force. I also haven't done another Time Trial event since that occasion, so unfortunately, I can't tell you if it was a cap problem or if it is a breather issue or more serious issue as Steve is alluding to.

ccamut

Thanks Steve, I considered excessive crankcase pressure, but wouldn't the car be leaking elsewhere? There are no leaks anywhere on the motor.

RSAErick

I hate to say it, but you seem to be having similar problems to what I was experiencing back in 2005. I started a thread about the troubleshooting process and discovery here: https://rennlist.com/forums/964-foru...i-find-it.html

Unfortunately, it indicated bad news. The oil system over-pressure was caused by 6 broken upper compression rings, which necessitated an engine rebuild. Amazingly, I thought that the car was running very well with 6 broken rings.

Anyway, I'll keep my fingers crossed that something else is causing your oil leak, but this sounds frighteningly similar to my previous experience.

Best of luck...

ccamut

Thanks Erick, that's my concern, surprisingly the car does run great, just dynod at 245.

If the broken rings are the problem, what is the risk n continuing to drive. Btw, no smoke at all under full acceleration or deceleration.


Thanks

RSAErick

Other than oil spilling in compromising areas, my concern would be that you could do much more serious damage to the pistons or cylinders with broken rings, or if you lost the lower compression rings. Other experts would know better than I, but my pistons and cylinders were still in good condition - probably because I caught it before the lower rings were also broken, and addition wear or damage occured.

Still hoping for the best for you.

rebp911

Hold on! I had a similar problem 5 years ago after I bought my 964. The area around the filler cap used to get very wet, until I changed the yellow cap itself. Problem was solved for £15!

CBR786

YES some people put a big jubilee clip on the oil cap and tighten that slightly as some of these 20 years plus oil caps do not seal properly on the threads of the oil filler neck hence the jubiliee clip on oil cap then thread it on neck so it makes a nice tight snug fit.

this has been mentioned before search the topic on here I am sure some one else had similar issues and advised the jubilee clip method.

FeralComprehension

=hose clamp according to Google.

kos11-12

as Steve mention do a compression test,
if your breather pipes are blocked or bend (so no breathing) it will probably spill oil around the breather gasket ....
I was just wondering if the breather system is big enough for track/ race use...
I recently had this issue at Spa with a bike engine ...until we found a bend pipe on one of the breather pipe (underneath the seat) what a mess, thank God no spill on back tire or track ...