Blue Smoke

[Mark Elder]

Nothing like as bad as I'd first imagined!

I was blasting around a small track on Teeside on Friday and I suddenly noticed vast amounts of blue smoke out of the back of the car. Pulled into the pits and the car was almost engulfed in it. Turns out it was just oil getting out of the oil filler cap and running down on to the silencer.

The oil level on the stick was (after the incident) showing about 10mm over the top of the max point - so presumably rather more before it overflowed.

Is it normal for over filled oil to spill out via this route? Was serviced about a month ago and it must have been like this since then - but the track session was first time I'm been redlining her since the service. Would it have been the high revs or the high lateral acceleration on the corners that caused the overflow?

 

[John Maddox]

It must have been very overfilled to cause oil to come out of the filler. Luckily we are dry sumped or it could have contaminated your clutch. Whilst only an indication did your oil level gauge give any warning ?

 

[Dave Wilkinson]

Mark,

It was almost certainly caused by your "giving it the beans". There is a tendency for most garages, when doing an oil change, to top up the oil to the full mark without getting the oil really, really hot. Because the system holds close to 12 litres of oil, even a relatively small percentage increase in volume caused by elevated temperature will result in a considerable overall increase - hence the level over the top mark.

It's for this reason that many of the track day junkies run with the oil level only at the half way mark on the dipstick - this allows for the thermal expansion of the oil whilst still keeping below the top mark.

You may be lucky in some ways that your oil filler cap is a rotten fit (as most are) since without it's opportunity to leak out here the excess oil would have vented through the induction system and almost certainly would have compromised the ISV operation and you'd now be complaining of a poor tickover!!!

Regards

Dave

 

[Mark Elder]

Thanks John and Dave. I was thinking of replacing the seal on the filler cap to get a better seal - I'll not do that now!

This also matches what happened because the problem did not occur on the first two runs (where I'm sure I was pushing just as hard as the third run) - but of course it now makes sense that the oil would have been getting hotter each run.

John - the dashboard oil level indicator was just showing at max - but that's what my gauge does when the stick is at the max mark. But with hindsight I now remember thinking "gauge seems to be working when I'm driving" - normally it's down on red when I'm driving with a bit of a positive reading if I'm on a very steady 2K rpm. But since the service I've seen it up in the white area just in normal driving - will make a mental note that this means "oil overfill".

 

[John Maddox]

No harm done that's the main thing.