Minor Smoke Problems

[240Z_Master]

Okay, I've got a slight problem. The car runs fine, strong and what not. After a few hot laps around the neighborhood or whenever the car warms up to temp, a vapor cloud seems to make itself known from my tailpipe. More gas I give it, the more it seems like I'm a stunt plane laying down a trail of smoke.

 

Now, I've tried searching desparately for an oil leak, water leak, nothing. Just a few drops of oil on the floor over time.

 

I'm trying to add a can of stopleak to the fuild system after a radiator flush, then maybe some Lucas Oil treatment on the oil side. The smoke is whiteish, not blue like you would expect oil.

 

Now I'm just dumbfounded. Any help, suggestions, ideas? I'm not the brightest mechanic, but this freakin sucks as the Japanese Classic Car Show is on Sunday!

 

So I'm wondering if I should just do a damn rebuild (maybe a bigger turbo too).

[Careless]

oil catch can? pcv valve stuck open?

im deleting the PCV valve hose to my intake on my z31, i saw what it does to the entire intake tract. It basically works it's way down to the turbo if it's not been changed for 21 years. Turbo is clean. Burned a bit of oil.

 

Sounds like your PCV is opening at high rpm, or if it's indeed oil, you may have a ring leak.

 

Don't want to alarm you, but sometimes gaskets only show their cracks at high rpm when they tend to split/expand.

[triple B]

what color is the smoke?

 

if its blue its oil if its nice and white its coolant.

 

you could be getting blow by. as careless said the PCV could be sucking oil.

 

i would try a compression test of the cylinders first to elimnate the ring issue and then try a new PCV or just eliminate it if you can manage it

[240Z_Master]

I just realized none of this happened before when I had my other radiator cap. The new one I'm using right now is 18lbs. Does this have anything to do with it?

 

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***Update***

 

So now I'm realizing as I'm tinkering around with it a bit more, the smoke does have a blueish hue to it. Basically when I rev, and let off the gas, the smoke show begins, then stops until I rev it up some more. In other words when I let off the gas the motor slows down the cloud appears.

[ZDrifter]

I would start with some easy diag. Pull your plugs and see what they look like, they are like a high school girl, they tell a lot If they have a white residue on them I would start thinkin about pullin your head and replacing the head gasket. If they are wet with oil might be time for a rebuild. If the plugs look fine then its time to do a leak down test and compression test. Hope this helps you out.

[Careless]

Pull your plugs and see what they look like, they are like a high school girl, they tell a lot

 

I think you have it backwards. They make you want to pull the plug after you've found out what's wrong with them.

[Z24O]

i had a similar problem when i repowered my 240 with an RB30ET,was told the turbo seals were probably us and were allowing oil through to the intake side under boost.....so i went ahead and rebuilt the T3,the turbo guys said they had seen much worse seals that showed no signs of leaking.....sure enough i put it back together to find the problem was still the same

finally i worked out that because i had doubled the boost,the breather in the rocker cover was causing pressure to build up....solution...fitted a catch can with obversize fittings and hose

you could confirm if this is your problem by removing the oil filler cap,taping a rag over it to stop oil flying everywhere and taking it for a short drive under revs....if there is no smoke then you have found the culprit

good luck and let us know what you turn up

[Careless]

i had a similar problem when i repowered my 240 with an RB30ET,was told the turbo seals were probably us and were allowing oil through to the intake side under boost.....so i went ahead and rebuilt the T3,the turbo guys said they had seen much worse seals that showed no signs of leaking.....sure enough i put it back together to find the problem was still the same

finally i worked out that because i had doubled the boost,the breather in the rocker cover was causing pressure to build up....solution...fitted a catch can with obversize fittings and hose

you could confirm if this is your problem by removing the oil filler cap,taping a rag over it to stop oil flying everywhere and taking it for a short drive under revs....if there is no smoke then you have found the culprit

good luck and let us know what you turn up

 

Z24O may have hit the nail on the head here.

 

I found that my PCV valve was NEVER changed on my Z31. It was so badly clogged or worn that my Driver's side head/vc with the vaccuum line was varnished with oil as normal... nice bronzing... but the Passenger side head with the pressure line was completely covered in a sooty oily residue.

 

The manifolds were soaked in oil. I think the pressure buildup in the head caused the PCV valve to be stuck open at times and just squirt hot shots of oil into the intake tract. The throttle plate had so much build up behind it, and it worked it's way all the way back down the intake tract and covered the entire turbocharger compressor plate in oil and clogged my actuator.

 

Funny enough, the front of the throttle plate was perfectly clean, and it seems as if there was enough vacuum coming from the turbocharger off boost that it started to pull the oil back down into the compressor housing little by little.

 

I'm taking apart the turbo tomorrow to see how it really is. I just bought a 2 pack Thermos and Hot Cup storage pack. Stainless steel for 9 bucks. So now I have something to make a catch can with that is solid, and I have something to keep some nice warm soup in for the drive to work.