Blue smoke on overun & downhill

[coullstar 0]

Ive noticed that my VR puts out blue (oil) smoke from the exhaust but only in certain circumstances.

 

It only seems to happen after coasting downhill for a decent amount of time (5+ sec) and then applying the throttle. Any other time the car is perfectly ok.

I do have a slight oil leak but ive not yet traced it.

 

Anybody any ideas on what it could be? Oil into the breather system? Currently sitting at 3/4 full.

[Lufbramatt 0]

sounds like the valve stem oil seals getting worn out- when the throttle butterfly is closed the vacuum created by the coasting engine sucks oil from the head via the stem seals.

[coullstar 0]

Shouldnt be as the head has been polished with new guides, seals and reseated valves. Surely it should do it all the time off throttle. Its only happening when going downhill.

[dr_mat 0]

The reason he says that is that with dodgy valve seals there is a constant supply of oil seeping into the cylinder, but under wide throttle opening there's lots of flame and it all gets burned off. If you coast for a while you'll not burn it off and it'll build up in the cylinder .. until the next time you open the throttle, where a lot burns off at once, making it really obvious.

 

If you had blue smoke constantly on overrun then we'd say your piston rings are knacked and it's sucking oil past them, but you say you don't, only when you get back on the throttle after coasting.

 

Or something like that ...

[coullstar 0]

I understand that but it doesnt happen when its on the flat, only on a pronounced downhill section of road.

 

Its using very little and TBH doesnt happen very often. I will check the plugs to see what they are like.

[dr_mat 0]

I understand that but it doesnt happen when its on the flat, only on a pronounced downhill section of road.

 

Its using very little and TBH doesnt happen very often. I will check the plugs to see what they are like.

 

You don't coast on the flat, you have to consume fuel. You only 100% back off the throttle when you're going downhill.

 

Anyway, this is just speculation unless you want to either check the state of the plugs or take the head off and have a look.

[coullstar 0]

Right this was occasional but now pretty much everytime I go down a hill it does it. The car has a new brass guides and stems seals so I dont think its that. Only other thing I can think of is piston rings but should it not be doing it all the time with the rings?

 

Not had a chance to get the plugs out as I dont have a lead removal tool yet.

[boost monkey 0]

Down hill = oil in valvetrain moving towards front of engine i.e. inlet valves and stem seals.

 

I'd start your investigation there :salute:

[coullstar 0]

Just spoken to a knowledgable guy I know and put some more light on this. Ive just recently put a standard airbox on in place of a cone filter and its been more pronounced since then. I did get a puff of smoke when sitting still and revving to 5500rpm.

There is a slight ticking noise under load for the first minute or so when driving.

 

Didnt rule out valve train but sounds more like bore ovality or maybe broken compression ring. Its a 2nd car and I did have plans for a 24v so I might just drive it till it pops. Replacement 2nd hand bottom end will just end up going the same way no doubt.

 

Will try and check plugs etc tonight and get a compression test done first.

[Kevin Bacon 5]

Dr Mat was spot on.

 

On overrun, the injectors are off completely, so there's nothing to burn. At the bottom of the hill, you apply the throttle, injectors switch back on and the oil collected in the piston bowls by the vacuum will be burned off.

 

Also on over run, the piston rings aren't being pushed onto the cylinder walls by blow by gases, so that's the next weak link along the chain.

 

It's going to be bore or head. Only a leak down test will determine which without stripping the engine.

[coullstar 0]

Well I think this tells the tale. All plugs are ok apart from...... No1 & 6. Assuming 1 and 6 is top left and bottom right when viewed from the front.

 

Also Im assuming that the wire type gauze should be in the breather pipe?

[Toad 0]

Nah, pull the gauze out., that's not a good sign that someone has fitted that...

[Critical_Mass 10]

Nah, pull the gauze out., that's not a good sign that someone has fitted that...

 

Dont all VRs have that, what ever it is? Sure mine does.

[Toad 0]

Nah, pull the gauze out., that's not a good sign that someone has fitted that...

 

Dont all VRs have that, what ever it is? Sure mine does.

 

Hmmm do you have a metal rocker cover? and a straight pipe for a breather, rather than that pcv valve thing?

 

I wonder if the early cars have them then? In which case, I'm massively wrong :oops:

[CorradoVR6-Turbo 0]

that gauze should be in the rocker cover,and peeps always point the finger at the steam seals,but on VR's they suffer bore wear more so than most other engines,oil will be drawn up past the rings more so than the steam seals,few of my 100 k plus engines burnt oil as your engine does,rebuilt the head plenty of times,still the same,new rings,rebore...no more oil burning.

[Critical_Mass 10]

Nah, pull the gauze out., that's not a good sign that someone has fitted that...

 

Dont all VRs have that, what ever it is? Sure mine does.

 

Hmmm do you have a metal rocker cover? and a straight pipe for a breather, rather than that pcv valve thing?

 

I wonder if the early cars have them then? In which case, I'm massively wrong :oops:

 

Yup straight pipe with a plug in the middle, no PCV

[Toad 0]

Hmmm do you have a metal rocker cover? and a straight pipe for a breather, rather than that pcv valve thing?

 

I wonder if the early cars have them then? In which case, I'm massively wrong :oops:

 

Yup straight pipe with a plug in the middle, no PCV

 

In which case, I'm a massive weasel...

[coullstar 0]

My car is a 94 M coilpack version so therefore it shouldnt have the wire filter then going by what your saying although the head was from a different car (been polished and ported with new guides/stem seals etc).

 

I take it Im basically looking at either a new 2.9, 2.8rebore or some other options like the 24v?

[Critical_Mass 10]

My car is a 94 M coilpack version so therefore it shouldnt have the wire filter then going by what your saying although the head was from a different car (been polished and ported with new guides/stem seals etc).

 

I take it Im basically looking at either a new 2.9, 2.8rebore or some other options like the 24v?

 

mine is 93 but with coilpack. Sorry thats not helping much :lol: cant the 2.9 be rebored?

[coullstar 0]

2.9 rebore would most likely require new pistons which are mucho expensive.

 

2.8 rebore then I should be able to use my piston, assuming there ok, with new rings.

 

I just feel that if Im going to much about like that then Id like to get away from the 12v however I cannot justify spending £2k+ on the car.

 

Might even just break it :( .

[Toad 0]

Buy Karls engine for £500??

[coullstar 0]

To late, twas sold yesterday.

 

Showed the photos to my friend and he pointed out the plugs seem odd with regard to the electrode in that it appears to have a thick shroud.

 

I cleaned them up and brought the car into work and there was no oil smoke. Going to change plugs and take it from there. Im pretty certian the bores are oval to some extent and I was going to change the engine at some point. Not overly bothered so I'll just run it till it gets really bad and look out for a 24v be it a 2.8 or R32.

Would love to tacke it myself but I dont have a garage or access to one and I have the Golf as a daily so its not too bad.

[k551 0]

I'm having the same problem with my VR smoking on overrun but I would say my smoke looks more white than blue.

 

Same cause??

[coullstar 0]

Is it completely white? Mine is mainly white but you can see the blue tinge to it.

 

Is it using any water? Just do what Ive done and inspect the plugs first.

[was8v 0]

I wouldn't worry about it too much at the moment, you won't be noticably down on power.

 

Eventually the plugs will start fouling worse and then missfiring. Then you will find you have to start carrying spare plugs.

 

As others have said most likely is the classic VR bore wear due to the poor cooling of 1 and 6, but don't rule out the head until you have done a leak down test.

 

 

 

Easiest is just to swap the engine for a known good one, then break yours selling the good head etc.

 

Cheapest is to get a 2.8 bottom end from a sharan/passat, might be hard to find a corrado one.

 

Re-con engine or 24v swap if you are feeling flush!