White Smoke when Decelerating ?

[1bigb1]

Need some advice ,do I look at my Turbo OR do I look at my Head ?
I have a Volvo v70xc AWD Auto 2002 ,When Driving normally I do not have Smoke coming from exhaust ,But when I accelerate Hard and then Release / decelerate , my foot from fuel then I see white smoke coming from my exhaust ..
Any body got some ideas..???? Please ?

[abscate]

Turbos on these cars are solid - made my Mitsubishi.

I would guess valve guide seals before turbos based on your symptoms

[Botbasher]

Hey BigB....

Could be either one. You didn't mention how many miles on the car?

Smoke on decel is usually from valve guides in a non-turbo car (Accel smoke is rings, decel smoke is guides) The vacuum in the manifold pulls oil past the guides and burns it.

When you have a turbo, you also have the turbo bearings that can leak oil into the intake track under similar conditions. A little is somewhat normal, but enough to smoke is not.

You may be able to differentiate between them by opening up the intake just before the inter-cooler and see how much oil is there. Mine, an 03 with 60k on the motor, has a slick of oil in the pipes, but nothing that will drip and easily wiped off the inside of the pipe.

If you find it relatively clean in there, then the guides would be suspect, but not a sure thing. To dig deeper if needed, I would drop the exhaust down-pipe before hanging any one criminal. 3 nuts and you'll be able to manipulate the shaft with your fingers. Move it side to side and in and out. You should have some side to side and next to nothing for in/out.

This would be my suspect... oil on the back side of the compressor wheel, being atomized in the intake track after a hard accel (high oil pressure). A slightly thicker oil next change can help tell you if it's simple wear (bearings or guides) or a bigger failure pending but it's only a mask for the inevitable failure.

Good Luck,

K "smooth criminal" S

[jonesg]

Hey BigB....

Could be either one. You didn't mention how many miles on the car?

S To dig deeper if needed, I would drop the exhaust down-pipe before hanging any one criminal. 3 nuts and you'll be able to manipulate the shaft with your fingers. Move it side to side and in and out. You should have some side to side and next to nothing for in/out.

This would be my suspect... oil on the back side of the compressor wheel, being atomized in the intake track after a hard accel (high oil pressure). A slightly thicker oil next change can help tell you if it's simple wear (bearings or guides) or a bigger failure pending but it's only a mask for the inevitable failure.

Good Luck,

K "smooth criminal" S

Removing the downpipe leaves you looking at the wastegate. Its a bit of a reach.
It might be easier to get to the shaft by pulling the inlet tube from the front of the turbo. No gasket replacement to bother with.

When my turbo shaft let go I had white smoke and then blue on startup.
Either way the turbo shaft started rattling very soon after.

[chrism]

When you experience white smoke, not blue or black, then I start thinking water - as in coolant being sucked into the combustion chamber(s).

A compression test may be a good move. Going a bit further, while the plugs are out, pressurize the cooling system and see if you get any leakage into a cylinder.


bigb, is your coolant level dropping?

[JRL]

Naw, valve guides

[jonesg]

Compression is a lot higher than coolant at 15 psi so exh gas would be present in the coolant, block tester fluid from NAPA can show this,
it turns blue to yellow when hydro carbons are in coolant. $7 a pint.

THeres an easier way,
pull the small overflow tube at the coolant bottle.
Raise the loose open hose from rad to prevent it syphoning coolant onto the ground. Plug it with a bolt for now.

Put a tube (from the hardware store) on the coolant bottle overflow nipple and place into a bottle of water, submerge it in the water.
Cold engine, coolant bottle pressure cap installed.
Now fire it up and watch the speed of the bubbles.
If bubbles increase and decrease consistently with engine rpm the head gasket is blown.
It only take a minute or two to find out.

You can use block tester fluid in the bottle, it will change color but the rate of the bubbles tells ya all ya need to know so why bother.

THe compression test is only better in that it more accurately locates the gasket leak, but the mere fact it leaks would be enough for me.

[Botbasher]

Removing the downpipe leaves you looking at the wastegate. Its a bit of a reach.

Umm Jonesg.. It ain't that far..

2016-12-26 11.34.28.jpg (262.08 KiB) Viewed 7533 times

K "big fingers" S

[1bigb1]

thanx all for your input ,I'm not a mechanic and don't have all the tools to dismantle,
I did a test today if I Accelerate 50% of throttle and then decelerate the amount of smoke from the exhaust is allot ,But if I accelerate 100 % and then decelerate the amount of smoke is much less ...any more ideas ?

[Botbasher]

Valve guides....JRL called it, but I was covering the spread!!!

50%.... You have less boost in the manifold and the oil is pushed past the guides by positive pressure in the head.

100%... You have more boost.... Pushes back the oil.

Try a thicker oil for a temp fix.

K "guided" S