On a 7mgte, when do you need to increase the diameter of crankcase vent lines?

[MarkIII4Me]

I have a 7mgte that I'm nearly certain needs new valve stem seals since the spark plugs get oil soaked fairly quickly. Compression and leakdown #'s are good and I removed my catchcan since it was only collecting water (car sits for months at a time). Exhaust has blue smoke when engine is under heavy vacuum. I'm running both valve cover crankcase vents T'd to one line running to the intake pipe. There is no oil present in the pipe or on the compressor wheel. At what point do people run separate lines off of each valve cover or feel the need to drill them to a larger size?

 

[supraguy@aol]

The primary vacuum supply for the pcv system is to the intake manifold(at the throttle body), not the intake pipe. This is especially true on decel, where the greatest vacuum pressure is present there.
If you don't have the valve covers tee'd into the TB, you risk excessive crank case pressures.
As for oil on the plugs- have you checked the spark valley for oil contamination? If the valve covers leak, you will get oil all over the outside of the plugs, which will also eventually wyck down the threads into the combustion chambers.

 

[Nick M]

And Toyota lists 3 different gaskets, including "cylinder head cover number 3" or something like that. The large metric allen bolts can allow oil to pass also. They were installed with FIPG. At least one here used O-rings instead.

 

[gsxr141]

I had my two front bolts for the intake cam cap come loose. I was chasing valve cover leaks for a week till I found the problem.
that said, I now have -12 lines going from my valve covers to a catch can, then a line going to my exhaust. needless to say my fabricator/tuner likes to go all overkill on everything...
you should be fine with -10, but you still need a way to pull vacuum like everyone is saying.

 

[MarkIII4Me]

I really don't believe it to be the valve cover gaskets. I have not only replaced them and added rtv at the front corners, but have installed new isolator washers as well. I originally had the pcv system setup correctly with a check valve installed between the intake manifold (ffim) and valve covers and then T-ed into the catch can and charge pipe (per IJ's diagram). On my first dyno pull, there was blue smoke on decel, but the turbo was leaking out of the compressor into the intercooler. I sent the turbo off for rebuild and this resolved the oil coming from the turbo, but I still had smoke on decel. I removed the catchcan, since all it was catching was moisture,removed the pcv setup and simplified it by T-ing the valve cover lines and running them directly to the charge pipe. There is now zero oil in the charge pipe, but my plugs get oil soaked after a single drive cycle. There is oil present on their threads, but the wire boots are all dry. Since I rarely drive the vehicle, and letting it sit for more than a couple of weeks causes surface rust to build on the cams, I pull the EFI fuse around once a week and crank the engine until there is oil pressure to keep the internals nice and lubricated. I don't like to just let the engine idle cold and dump fuel in the cylinders since my EMS is currently tuned to run pig-rich on warm-up. I can't see this being a problem other than excessive wear on the starter. However, if the valve stem seals are split and oil is leaking into the cylinders when it rests, perhaps the cranking of the engine is forcing the oil up into the plugs' threads?


Here are pics of each spark plug upon removal (less than 200 miles on them):





















The top of the pistons are all black and shiny (basically caked with carbon and oil). I'm surprised that the plugs don't foul and misfire, but the engine actually runs great. So what's more likely, split valve stem seals or excessive crankcase pressure?

 

[MK3pizzadriver]

Could be tired/caked piston rings. A compression test could confirm that. I think if it was your valve stem seals, you'd see more smoke at start up, after the car has been sitting a while. To rule out crankcase pressure, maybe you could -temporarily- run open hoses off your valve covers. Like some 3 foot hoses routed off the side of the motor, pointing at the ground. But yeah, bad rings could be creating that crankcase pressure, so might as well do that compression test now.

 

[MarkIII4Me]

Compression and leakdown #'s are good

 

[gsxr141]

my plugs looked like that until I found the leak at the cam cap. do you have any oil in the alley, or just on the plug threads?

 

[MarkIII4Me]

Valley is dry.

 

[MarkIII4Me]

my plugs looked like that until I found the leak at the cam cap.

I don't understand how that would get oil on a plug, let alone all plugs. I must not be thinking of the same thing. Can you further explain this leak and the repair?