embarasing blue smoke on overun

[quicky1980 0]

It may be down to too much oil in hte engine (not had time to drain it). But what else could cause the engine to give off blue smoke on over run (ie slowing down in gear). It doesnt always happen, but when it does, the engine seems affected and hesitates as it clears the oil out through the combustion chamber.

 

Im thinking the rings may be shot? But Im hoping oil is so high its forcing itself down into the chambers through the valve seats.

 

which is the best way to check oil too? cold engine sat over night, hot engine straight after turning engine off or (which i do) wiat for ten min's after turning hte engine off to give oil chance to flow back into the sump.

[flusted 0]

cold engine on flat service best way to check

[Valerian 0]

cold engine on flat service best way to check

 

On a flat surface is even better :lol:

[Valerian 0]

Valve stem seals tend to go rock hard on Valvers.

Which engine are we talking about?

[quicky1980 0]

its a vr, with no history on the engine. i think its done less than 100k

[HiAsAKite 0]

Is it particulary pronounced after a long period of engine braking (eg going down a long hill using the engine to control your speed) -- when you get to the bottom, if you floor it do you get a plume of blue smoke out the back? (and possible a slight falter before the smoke comes out- once its out the cars fine again?

 

If so, I suspect your stem seals need doing..

 

If you do get the above, I suggest you use your brakes more rather than engine braking until you can get this remedied, as if you get too much oil onto the plugs you'll 'cook' them and need new plugs...(you'll know if this happens as it will sound like its running on 5/4 cylinders etc and feel rough, unbalanced and down on power) - as I found out on a Saturday afternoon in the South of France.. ever tried to find a mechanic/somewhere that sells plugs on a Sat afternoon in France? :brickwall:

 

All the best,...

[quicky1980 0]

Is it particulary pronounced after a long period of engine braking (eg going down a long hill using the engine to control your speed) -- when you get to the bottom, if you floor it do you get a plume of blue smoke out the back? (and possible a slight falter before the smoke comes out- once its out the cars fine again?

 

If so, I suspect your stem seals need doing..

 

If you do get the above, I suggest you use your brakes more rather than engine braking until you can get this remedied, as if you get too much oil onto the plugs you'll 'cook' them and need new plugs...(you'll know if this happens as it will sound like its running on 5/4 cylinders etc and feel rough, unbalanced and down on power) - as I found out on a Saturday afternoon in the South of France.. ever tried to find a mechanic/somewhere that sells plugs on a Sat afternoon in France? :brickwall:

 

All the best,...

 

that sounds just like the problem. ok, will get on the case of rebuilding a head ready for the old one to come off. thanks

[boost monkey 0]

Definitely concur on valve stem seals.

 

Do you get a small puff when the engine starts? This is normally a tell-tale sign of VSS wear.

 

Piston ring wear would show more as excessive smoke when engine under load, and also at idle if the rings are _really_ shot.

[CorradoVR6-Turbo 0]

Ive had the same poblem in my old vr and in my mates jetta VR and ive rebuilt both heads bla bla and they still smoked on overrun,just remember that oil will get drawn up past the rings if your bores are worn and being a VR will be worn.

 

I rebuilt my bottom end ,not just rings but rebore and fitted back on the head that was rebuilt before and it stoped smoking.

 

Try the stem seals first,but check the bores when the head is off.

[dinkus 10]

The 2.9 VRs are sadly notorious for irregular bore wear on cylinders 1 and 6, so you get oval-shaped cylinders and the oil blows past the rings. Only real solution is to bore it out or swap the block :(

 

So well worth checking that before you go forking out loadsa dosh on a rebuilt head.

[Kevin Bacon 5]

You can buy some time by doing the head and using a thicker oil. That worked for me. Mine was still smoking on the over run after a stealth head rebuild on my original block, so I stuck some 10W/50 oil in it and it stopped smoking completely.

 

If I was faced with rebuilding another VR6 engine now, there's no way I'd waste the money tbh. I'd fit a 24V. Mechanically it's a far, far superior engine; in every way.

[dr_mat 0]

You can always just ... not worry about it and thrash the crap out of it till it dies .. !

After all, no point looking out the rear view if you're accelerating all the time..! ;)

[quicky1980 0]

Thanks guys for your answers. If there is a chance that the bores could be at fault I think I may go for the 24v option. Its not that bad at the moment, but Im not sure if the engine is using any oil because of it.

 

if i can be bothered ill take hte head off and change it but I reckon I'll carry on as planned and have a bigger engine fitted sooner than expected.

[CorradoVR6-Turbo 0]

the 24v bottom end will wear just like the 12v in time.

[Kevin Bacon 5]

After all, no point looking out the rear view if you're accelerating all the time..! ;)

 

That's the American way of tuning cars :lol:

 

the 24v bottom end will wear just like the 12v in time.

 

You'd be surprised.....

 

I've seen quite a few stripped 24V blocks and they're nothing like as bad as the 12V for wear.

 

There are a few 200K+ R32s out there still going strong and hundreds of boras / golf 4 motions way past 150K with no increase in oil consumption or chain parts replaced.

[CorradoVR6-Turbo 0]

no doubting they are a better engine and the better designed pistons will make for less wear,ive also stripped a few low to high mileage 24v and 20v and the bore wear is similar to the 12v...

 

Come on Kev you lost all the love for the donkey engine :lol:

[quicky1980 0]

if it could be bore wear, can I do a compression test to check? or will this not prove anything. Im having trouble figuring out which route to go ie 12v part rebuild/12v full rebuild or 24v

[CorradoVR6-Turbo 0]

compression test will tell you the current state but not which part to blame,leak test is the best way.

[Kevin Bacon 5]

no doubting they are a better engine and the better designed pistons will make for less wear,ive also stripped a few low to high mileage 24v and 20v and the bore wear is similar to the 12v...

 

It's not just the blocks, the heads at 150K have negligable valve rock compared to a 12V.

 

Come on Kev you lost all the love for the donkey engine :lol:

 

No, I'm just ready to move onto better things. The 12V's had it's day :lol:

[quicky1980 0]

compression test will tell you the current state but not which part to blame,leak test is the best way.

 

how are leak tests carried out? is it something a local garage can do?

[HiAsAKite 0]

Hold on a minute- before you start getting the heads redone, rebores or swapping out for a 24v block- how much oil is your engine actually using (eg how many l/500 miles), and how much blue smoke is coming out the back?

 

Just because there's a little bit of blue on the overrun sometimes doesn't mean your engine won't go on for another 20,000 miles without significant drop in power...

 

How bad is it?

[quicky1980 0]

Hold on a minute- before you start getting the heads redone, rebores or swapping out for a 24v block- how much oil is your engine actually using (eg how many l/500 miles), and how much blue smoke is coming out the back?

 

Just because there's a little bit of blue on the overrun sometimes doesn't mean your engine won't go on for another 20,000 miles without significant drop in power...

 

How bad is it?

 

its not bad, just a puff of smoke once in a while. im still hoping its cus there is too much oil in the sump and its hard to say if there is too much or not because im sure the dipstick tube that came with the vr engine isnt the right type. so will be sourcing a replacement soon

 

power is still good, i just dont like seeing a trail of smoke. will see how the next few months go. but i am interested in maybe carrying out a leak test, hopefully this will point to the problem.

[Critical_Mass 10]

Firstly why dont you drain some of the oil. Secondly get the correctly dipstick tube so the level can be measured accurately - is this why there could be too much oil in the engine? Also too much oil will cause more pressume and could cause more problems.

[CorradoVR6-Turbo 0]

It's not just the blocks, the heads at 150K have negligable valve rock compared to a 12V.

 

now thats something i agree on fully! :lol: its a old engine but still halls ass!

 

how many miles have you done on your current engine Kev?

[CorradoVR6-Turbo 0]

compression test will tell you the current state but not which part to blame,leak test is the best way.

 

how are leak tests carried out? is it something a local garage can do?

 

You would need to go to a garage for that yes and even then they probably don't have the gear...