Club 80-90 Forums

We have recently purchased our first VW T25 camper a 1990 1.9 dg petrol with 99k on the clock. Run's great with full service (vw) history from new. how ever we have noticed that on a down hill run on over run the engine smokes (white) then seems to clear after a while and all is ok again. No smoke on start up, No oil in the water or loss of water and no smoke on an up hill climb. Uses a little oil but not excessive. I would have said valve stem seals but i don't think it has any?
Can any one give us any leads and should i be starting to look for a new engine?
Great site full of information have lost many hours of my life on here

Smoke on over-run is (or was with Fjords) worn valve stem seals.

Ian

or valve guides

I take it thats an engine out, head off job then, or can you change the stem seals without removing the head?
Valve guides sound a little more involved do these have to be pressed in?
Haynes say leave to VW or machine shop.

Thinking long term may be best to find an engine and rebuild to leave ready in the garage to fit one day may be a nice 2.1 may come along.

I have replaced valve stem seals on dozens of VW and Audi engines for this exact problem. Replacing these seals was very common and an almost routine repair. These seals go hard and split allowing oil to be drawn down the guides on over run (when under vacuum)
I carn't honestly remember changing any on a flat 4 wasser (25 years is a long time) but if they are fitted then it seems very likely given your symptoms, that they are the problem.
We used to change them in situe by positioning each piston at TDC, putting the gearbox in drive and applying the handbrake, then with the use of a home made adapter (old spark plug welded to an air line adapter) pressurise the cylinder. VW special tools (valve spring compressor) push down the valve spring and remove the collets, extract the old seal with special VW tool OR snipe nose pliers, knock on new seal with special VW tool or home made tool (piece of copper plumbing pipe) refit valve sping and collets, move on to the next etcetc.
OK....lots of special VW tools but they can be home fabricated, not as dificult as it sounds.
martin

Red Westie wrote: We used to change them in situe by positioning each piston at TDC, putting the gearbox in drive and applying the handbrake, then with the use of a home made adapter (old spark plug welded to an air line adapter) pressurise the cylinder. VW special tools (valve spring compressor) push down the valve spring and remove the collets, extract the old seal with special VW tool OR snipe nose pliers, knock on new seal with special VW tool or home made tool (piece of copper plumbing pipe) refit valve sping and collets, move on to the next etcetc.
OK....lots of special VW tools but they can be home fabricated, not as dificult as it sounds.
martin

Yes I agree that this is the most likely cause of smoking on or after a period of overun as this is the time when the pistons are sucking on a closed throttle and down the valve guide is an available route for oil or oil mist. The other cause can be rings or bores but lets not talk about that just now. Unfortunatly my Bentleys manual section 15.17 doesn't show valve seals fitted although the valve guides are seperate and presumably could be replaced with the heads off so maybe someone else can say if they are indeed fitted or even if there is an aftermarket mod for seals. It could be though that by design some oil is needed to lubricate the guides.

As it happens I note that cracks between the valve seats are permissable up to 0.5mm or that the first coil of the plug retaining thread can have a crack so don't get too alarmed if you spot this. Incidentally I saw a tool which could be screwed in in place of the spark plug and revolved so as to support the valves while the (In our case posibly non-existant valve seals) are replaced. I also made one for my Mondeo with a see saw device at the end which could do the same job. If using the compressed air method I would leave a residual pressure applied in case of slow leaks. Don't panic as you have a working vehicle and time to assess the situation properly before you make your next move.
Good luck
Ken

There ain't any valve stem seals on't WBXs, they have machined guides instead. They are allegedly removable but it say's 'This must be left to a VW specialist or machine shop' in't Haynes.

Ian.

White smoke not blue?

That sounds more like coolant getting drawn in somewhere.
Is it losing any coolant over a long period?

Ian Hulley wrote:There ain't any valve stem seals on't WBXs, they have machined guides instead. They are allegedly removable but it say's 'This must be left to a VW specialist or machine shop' in't Haynes.Ian.

I guess a lot of us do stufff Mr Haynes would prefer to be left to the specialist. Sadly it isn'r mentioned in Bentley but I am sure someone will know the procedure.
If the new guides have a lip, taper or positioning feature then this will indicate the removal direction. The tooling would probably comprise a threaded rod (studding), a tube and nuts/washers. It may be necessary to heat the head at gas mark quite high before positioning  the (preferably cold) tooling and extracing the guide. Reassembly would be the reverse. I believe that this would be less risky than a press as the force is applied direct and close to the eaining aperture.  Anyone done it?Ken

I think the question needs widening out to those that know WBX's very well..

Do they 'do' their valve guides to this extent
If so....
At what sort of mileage
and how frequent is this sort of job done on WBX's ?

I'd not come across many accounts on here over the years, but I'm sure valve guides wear...

Links... exh valve guides

https://club8090.co.uk/forum/viewtopic.p ... ght=guides

I can't see Stem seals shown or mentioned in my manual either. i have changed them on a CVH with a tool which screwed into the rocker stud and then compressed the valve to remove the collets and replace the seals in place, was quicker and easier then a spring compressor.
The good news i surpose is the engine is working and no long term damage is taking place other than burning a little oil. i'll keep watch to see if anyone can confirm if ay stem seals are fitted?

could be a wored/broken ring , , do a compression test

Yes, when in doubt always do a compression test as t'man says, it's so easy...

Wiki quick guide to compression testing

Carried out a compression test today after a trip out results as follows:-
1 = 7.9 dry 8.5 with oil
2= 8.1 dry 8.5 with oil
3 = 8.0 dry 8.5 with oil
4 = 8.0 dry 8.5 with oil
all with throttle closed as no helper around all a little low but no great changes between cylinders should I be worried about rings?
or is it looking more like valve leakage.

Presume units are bars?

They look fine acropss the engine, but low, marginal.

Presume done as per spec above?

You could have hooked the throttle lever open with something maybe?

99,000, looks like a 150,000+ miler!
Wouldn't have thought valves though, too comsistent though a leakdown test may reveal something.

When last changed oil? What sort of oil? How hot was it when you tested?

Great site full of information have lost many hours of my life on here

I think that'd be a relative statement