We've got a small oil leak at the front of the engine on the Charleston. It's using a tiny amount of oil (covered ~500 miles since I noticed it and the level has only just moved between the two marks on the dipstick), but it's being blown around by the fan and is making a bit of a mess! As far as I can tell, it's only happening when the engine's being worked hard on motorways or dual carriageways.

I've tried removing the fan, cleaning everything up, and running the engine to see where it's leaking, but with it sat on the drive, I can't persuade any to come out! There was some oil around the front crank seal area, so at the moment that's my main suspect, as I'd expect to see oil coming from anywhere else even when the engine was sitting at idle.

I'm not sure whether the breather should be creating enough of a crankcase vacuum to be keeping the oil in, or if the pressure will tend to go slightly positive with the engine at full chat?

Luke,
under *full load/high rpm*, there will be a lower level of vacuum in the crankcase, so more tendency for oil to leak out of the front crankshaft seal.
It's not difficult to replace the seal.

* It's impossible to replicate these conditions in the comfort of your own home, unless you've got a rolling road on the driveway... *

ken

That's what I was thinking/hoping. Thanks, Ken! Any idea of the seal size, offhand?

I would check vacuum before you change seal -3 minutes work... and worth it to know if breather working OK

Thanks. That was my first thought as well, although considering I'd actually have to find all the bits to make a manometer, I think it would take rather more than 3 minutes!

The problem is that it's currently only leaking when the engine's really being worked (the problem didn't really show itself until we did a 70+mph trip motorway trip to Cornwall and back last week) and, as Ken says, I can't see a way to check the vacuum under those conditions...

That said, it would be interesting to check, even at a lower RPM on the drive, just for peace of mind, so perhaps I'll have a go at some point...

All you need is a glass of water, piece of clear pipe and some insulation tape. Just make sure water level is lower than around 50cm from breather. Once started measure from water level to level in pipe - nothing special and does not have to be acurate. Around 40cm difference is good @ tick over.

If you use LHM instead of water it's less of a problem if it ends up in your crankcase. And it's more visible.

also look at the timing as even if its a bit advanced then it'll blow oil even if its not yet pinking.

Yep, I will have a go at it at some point, but unfortunately there isn't that much clear pipe amongst all the rubbish piled up in the shed!

I'll double check the timing Sean, I hadn't thought of that. As it's come on all of a sudden though, and is only leaking from the one place, I suspect the main issue is just a knackered seal!

There's also a minimal amount of oil being blown into the air cleaner (certainly compared to my old Dyane, which RT has now found has compression issues..!) so that would lead me to suspect there's very little blowby. Sound plausible?

I've found the size for the seal now (30x42x8 if anyone needs it and can't be bothered to look it up either) so will get one ordered and fitted ASAP.

I believe you mean 40mm.