Leaky valve stems?

[mb450]

Hi

I suspect my valve stems are leaking. 1999 450 with 74k miles on the clock.
Symptoms are: smokey (blue-ish) on startup and more than normal oil use.

I've had a good look at the bores and they look ok - they still seem to have the honing marks from manufacture. Compression test is uniform an good (cant find figures right now) but from memory they didn't change significantly when I did the tests again with a few drops of oil in the cylinder.

I don't see smoke in the mirror when I'm out an about but I assume it's there an just not visible enough.

I've checked coolant and oil; and the clutch inspection cover and there is no Mayo or build up of oil, similarly there are no leaks that I cab find.

Any advice greatly appriciated.

Thanks

[spend]

I assume you mean leaky valve stem seals?

They can be replaced in-situ by either pumping compressed air into the cyl at TDC comp or inserting 'rope' to keep the valve up. There are spring compressors that allow you to remove the collars and springs so that the stem seals can be replaced.

I guess the extra heat of TVR engines shortens the life of stem seals, so 75K is probably reasonable?

If the valve stems are worn its a much bigger job, it's also possible to gauge if oil is leaking by looking in the ports but you would need to remove in/ex manifolds which seems to put a lot of people off

[bigdods]

The smoke on start up could just be the rich mix required when the engine is cold. You could be losing oil through a small leak ? . I was using ~ a litre per 1000 miles that turned out to be a small oil leak at the rear of the engine. It only leaked oil on the move. Seal was replaced when the clutch was done recently hasnt used any oil since (ok I've only done ~300 miles but no sign of the oil level dropping now).

Just a thought.

[mb450]

Hi bigdods

That's interesting: I wonder do you know roughly where your duff seal was? I'll have a look up the back of the engine tomorrow.

[bigdods]

mb450 said:

Hi bigdods

That's interesting: I wonder do you know roughly where your duff seal was? I'll have a look up the back of the engine tomorrow.

Underneath, somewhere near the gearbox (I never saw it myself). It was spotted during a service but I left it until I had the clutch replaced recently as it involved removing the gearbox to replace the seal so wasnt worth doing until the gbox came off for the another job,

[DavidLScott]

My seals went during 2007 (60k miles on a 97 450) and I polluted the world with stinking smoke after about a mile of driving. Oddly it didn't smoke at start up and didn't use too much oil as IIRC it only weeps when standing - didn't smoke if car was used very few days but did if left for a week or so.

Bit the bullet and had them done with the service in April and had the heads all nice and cleaned, valve seats done etc.
Whole service and work was about £1600 inc fitting the replacement stainless steel power steering bottom bend.

At least I now know the top end has been sorted and the manifold gaskets replaced.