Quite oily exhaust port...

[gridgway]

Whilst I was faffing under the car today failing to sort my driveshaft problem, I noticed that there was actually a drip of oil coming off one of the exhaust studs. When I took the knackered heat exchange off a few months ago, I saw the port was oily, but was surprised to see an actual drip today. See the pic. That was taken after I had wiped the drip off with my finger to prove to myself it was an actual oily drip!

I presume that it must be coming down the valve guide - is that likely to be right? Anywhere else it could come from? How worried should I be?

IMG_20200202_152924 by graham Ridgway, on Flickr

[wildtexas]

Graham, this is where my cheapy eBay boroscope would come in handy.


Connect to your smart phone and insert the camera up your exhaust port! ( opportunity for Bootsy and KS to get smutty there).

You might be able to see some oil on your exhaust valve?

ITs also very good for sliding down the spark plug hole to look inside the cylinder.

Have you any compression readings or leak down to compare this cylinder to the others. That might indicate valve guides or rings.

For example I had no3 cylinder 15% (20psi) down on the others. Ended up being a broken top compression ring, oily cylinder and the valve guides were fine. Leak down revealed no hissing past the exhaust port.


Matt

[gridgway]

Good point, I do have a bore scope which I'll insert when I'm next in the garage. This cylinder did have some history. It was down on compression from the exhaust valve. Valve clearance was adjusted and we got compression back. I did a leak down last summer and it seemed to be ok still, but I'm not sure I really trust it!

I'll get my borescope up there!

Graham

[wildtexas]

Is it definitely oil or could it be fuel and carbon?

If you look inside the cylinder and there's no sign of oil, then maybe that cylinder is too rich? How does the plug look?

[gridgway]

It's definitely oil as the drip is clean, freshly changed oil.

[911hillclimber]

My 10p is on a worn inlet oil seal on the valve guide letting oil to the chamber and then to the open exhaust valve thus clean neat oil flowing by gravity.
The ex valve points upwards in the engine so the oil cannot get 'out' under gravity, the inlet gets an oil pool around the stem seal so if that is worn (I've had one come clean off!) the oil will wick down the inlet stem and to the chamber if the valve is open to some degree.
Do you get heavy smoke on start-up?

I only express this comment as it has happened to me on my 3.2 in the racer, my fault when I drifted the new seal on not far enough.
If you try hard enough you can change the seal with the heads etc undisturbed, but with the engine out on a stand.

[gridgway]

Had to read that twice Graham, but got there in the end.

I do get some smoke on startup which I took just to be normal.

What's the effect of an oil seal off or badly worn? Does it produce a lot of oil smoke when running? Use a lot of oil?

Graham

[gridgway]

Had to read that twice Graham, but got there in the end.

I do get some smoke on startup which I took just to be normal.

What's the effect of an oil seal off or badly worn? Does it produce a lot of oil smoke when running? Use a lot of oil?

Graham

[911hillclimber]

On my hillclimb 3.2 it smoked quite badly (white/blue) and enough to raise alarm bells. Used little oil but a hillclimb is VERY short.
The seal has a small clamping ring fitted to effect the seal on the actual valve stem and on my errant seal the spring was off the seal and around the valve stem and the body of the seal off the valve guide.
Problem is it is very hard to see due if it is dislodged due to the dual coil springs of the valve design.
I had a lot of grief with the valve guides when they were all done by a pro shop very well respected on this forum and did not trust the guides they used, a long sorry story.

Oil will not 'pour' into the engine barrel if the seal is off, the puddle of oil around the dual springs is not large but when running a lot of oil gets to the valve rocker areas and will flood around the valve stem. If bad then blue smoke will result, BUT as said by another, compare the plug from the 'oil' cylinder to the others.
If leaking badly the plug will be very black in comparison.

A full leak-down test is a good place to start though as it tells you so much.

[gridgway]

The plug is quite oily as is the exhaust port. They other 5 are dry. At last check the leak down was ok. Oil usage is high but it's not really smokey apart from some at startup. Once I get the driveshaft done, I'll carry on and see what happens. I'm certainly not in the mood to pull the motor and have a go at it or get someone else to.

I'll have a poke around with my borescope to see if there's anything else to see!
Graham

[911hillclimber]

Good plan; a leak down will not show a valve stem seal failure but will eliminate everything else.