Rb25Det Blowing White Smoke After Track Day

[LANDSCRIBBLE]

Yes, sorry this has been covered before but i thought i would ask for more opinions/thoughts. Compression test warm is between 106 and 120psi. Light smoke coming out of the oil filler cap and air filter. I saw it smoking after hitting boost on the drive home, even when gently accelerating theres smoke coming out the back when i change gears. The catch can is empty and the turbo sounds different im sure. I noticed a bit of wet oil in the crossover pipe, still have to check the turbo outlet/inlet for oil... Does this sound like piston seals to you guys? .. The car had been running 23psi and oil temp at 113C max with a 10w60 oil. The car idles and runs smoothely, but smokes when accelerating.

[tranman]

I hazard a guess and suggest you have a possible headgasket failure, but that ultimately depends on the colour of the smoke you are referring to. Not sure of your mechanical knowledge so apologies if this is all common sense to you below:

If you are faced with white smoke: Indicates coolant leaking out from the engine galleries past the headgasket and being burnt in the combustion chamber. Your low compression results indicate this also (weak combustion seal due to compromised headgasket).

Alternatively if your smoke is blue: Oil being burnt in the combustion chamber due to poor seals in either: Piston rings (poor oil control i.e. scraping oil off the cylinder walls and being burnt off) or valve stem seals (allowing oil from the head to leak past the valve guides). Can generally tell between the two if it burns blue smoke only during initial start-up = valve steam seals. Otherwise it's the piston rings if smoke is reduced when car is warm and blows smoke under acceleration etc.

General rule of thumb:

White smoke = blown turbo seals, or headgasket

Blue smoke = burning oil in the combustion chamber

Black smoke = Carbon deposits and rich fuel mixture

A blown turbo will generally blow white smoke ALL the time.

If Piston rings were to be worn that much and result in such low compression, then you would surely face excessive blow-by resulting in having oil in the catch can. Since there is none, we're left with the headgasket. So to check, tick ANY one of the symptoms below:

1. Check oil dipstick to see if there is any evidence of water/coolant being mixed through it. Severe headgasket damage can reveal coolant in the oil. Look for abnormal colour discoloration including milkiness.

2. Check your coolant level. Is it down on coolant? Having to top-up indicates coolant loss through combustion chamber or overheating that has caused it to spill out from the overflow bottle. It's a closed system, you should never have to top-up unless either two have occurred.

3. With the car off, take the radiator cap off. Do you notice any excessive hissing (like opening a coke bottle ?). This indicates residual combustion gasses that have escaped past the headgasket and have been left in the cooling system after a drive. (obviously don't open when hot)

4. Start the car with radiator cap off. If bubbles are coming to the surface this demonstrates combustion gasses leaking past the headgasket and into the cooling system

5. Low compression, down on power.

Hope that helps, Good luck.

[LANDSCRIBBLE]

I've checked the dipstick and coolant, the levels and appearance are normal. I'll have to confirm what colour the smoke is by watching it from the outside. I dont remember a hissing sound from the radiator, although there is a gurgling/bubbling sound coming from around the plenum when the car is off after a drive. I'll do those other things you mentioned. Greatly appreciate your post man! I would imagine it would have taken a little longer to type that up, so thankyou.

[tranman]

Hmm,

OK re-reading your post, smoke coming out of the air filter and oil filler cap. That's different.

I assumed compression was low, but that could just be your instrumentation. Are you actually down on power? I'm talking obvious power loss and/or possible spluttering misfiring?

Back to your original post, piston rings could be valid. Alternatively;

Worn Pistons Rings (as per your post),

Valve Stem Seals,

Turbo Seals.

The general idea is that something isn't doing it's job sealing and resulting in a liquid from being burnt, the list above is all oil related. As per the three color smoke guide, it ties directly back to the liquid being burnt: coolant, oil and fuel.

Once you find out the color, we can move on to trace where the possible source comes from.

[GTScotT]

Leak down test!!

If the leak down test results are poor that would suggest the rings are worn.

You can also do a co2 test on the radiator to see how much carbon is in the water, it will give you an indication of if the headgasket is goneski.

You should definitely tell us the colour of the smoke though, before we make too many assumptions... White, blue, black. You may need a friend to help diagnose.

[LANDSCRIBBLE]

Up until i saw smoke in the rear view mirror, power was fine, no spluttering or anything.

Leak down tester is on the way kudos to ebay.

Hopefully ill be able to check the smoke out tomorrow if it stops bloody raining!

So aswell as oil, it is possible for coolant to leak out the turbo?

[hypergear]

it shouldn't as the turbocharger doesn't use any water, water flow through out an different layer of the casting. If the layer broke for what ever reason the sump should be filled with water. you can test it by pressursing one end of the water line to the turbo while block up the other.

If the turbo don't have any abnormal shaft play then it is probably also ok.

[Chris32]

Is the catch can vented to atmosphere or plumbed back in (sealed)?

[LANDSCRIBBLE]

Ok thanks for clearing that up Stao. Its vented to atmo Chris.

[Chris32]

I had a similar prob years ago with my rb20, I'm not sure if the breathers were blocked but changing it to a sealed catch can setup (steel wool in a stocking stuffed in the catch can) fixed it entirely.

I used to run quite a high oil level due to a oil cooler and this fixed the problem.

The engine is still banging out 230 at the wheels 10 years later

I'd look at the basics before jumping to the worst outcomes

[LANDSCRIBBLE]

Ok pretty sure its a light blue coloured smoke coming out the exhaust, it wasnt up to full temperature but only seemed to puff when its under load or changing gears. Going to give it a leak down test on the weekend.

Unrelated but i noticed a tear on the 90 degree silicone elbow coming out the turbo although i couldnt poke my finger through it. Also theres no oil at all in the pipes coming out the turbo and there is no excessive shaft play.

Chris, do you mean by routing a hose from the catchcan to the turbo intake pipe, or having a filter on the rocker cover instead - then stopped oil being burnt?

[hypergear]

Disconnect catch can and let breathers breath freely into atmosphere.

[Chris32]

The connector from the rocker cover to the intake pipe, you can put a sealed catch can there. It works really well, as it still sucks pressure out of the crankcase under boost.

If you setup a sealed system with steel wool in stockings, it scrubs the oil out of the air going back into the inlet.