Thread: Blowby

I recently noticed some oil residue on the engine oil dipstick (outer casing ) of my 4bd1t. The dipstick grommet is a fairly tight fit.

After a long drive over mountainous country and driving it fairly hard, I popped the hood to notice some oil on dipstick. I then removed the oil filler cap with the engine running. I noticed a discrete puff of greyish gas immediately upon removal then nothing, apart from the occasional oil flicker.

This has never happened before however to me it suggests high pressures in the crank case.

I'm running a provent connected to the side crank case port through a series of 1 1/2 / 1 3/4" rub flex hoses. The valve cover is the 4bd1 type with ~1/4 - 1/2" line connected to the intake (pre-turbo). I've had the provent connected for approx 8000 km and there's about 20 ml of oil accumulated (i.e. bottom of filter still clean).

Engine starts first pop (always has) and no noticeable decrease in power.

I hope this is simply due to inadequate cc ventilation and not worn internals. Any thoughts on this and what my options are i.e. does it require immediate attention?

Much appreciated for your comments.

Cheers.

Originally Posted by 110Landy86

I recently noticed some oil residue on the engine oil dipstick (outer casing ) of my 4bd1t. The dipstick grommet is a fairly tight fit.

After a long drive over mountainous country and driving it fairly hard, I popped the hood to notice some oil on dipstick. I then removed the oil filler cap with the engine running. I noticed a discrete puff of greyish gas immediately upon removal then nothing, apart from the occasional oil flicker.

This has never happened before however to me it suggests high pressures in the crank case.

I'm running a provent connected to the side crank case port through a series of 1 1/2 / 1 3/4" rub flex hoses. The valve cover is the 4bd1 type with ~1/4 - 1/2" line connected to the intake (pre-turbo). I've had the provent connected for approx 8000 km and there's about 20 ml of oil accumulated (i.e. bottom of filter still clean).

Engine starts first pop (always has) and no noticeable decrease in power.

I hope this is simply due to inadequate cc ventilation and not worn internals. Any thoughts on this and what my options are i.e. does it require immediate attention?

Much appreciated for your comments.

Cheers.

Try cleaning your provent element using the method I have described elsewhere.

You can also pull the provent element and see if the problem goes away.

However it doesn't sound bad - some breathing is normal. The extra pressure drop across the provent element will find any seals that aren't 100%. Is the leak from the top of the dipstick tube or the bottom where the o-rings are?

Thank you, I do plan on trialling a few options on the we. Cleaning the provent with petrol should be right...I will then removing it temporarily just as you suggested and see if there is an improvement.

Oil is coming up and out of the top of the dipstick tube. There doesn't appear to be any oil at the base.

I would have thought there would be more blue smoke and harder starting if it were something major?

Originally Posted by 110Landy86

...Cleaning the provent with petrol should be right...

NO - I would advise against cleaning it with petrol. I have posted how to clean them using compressed air - the thread is in the good oil I believe.

Just to wrap up this thread.

The crankcase pressurising problem under high load was solved by a bigger breather setup. I went to a provent but then had problems with the provent sucking oil out the sump and feeding the engine.
I reversed the flow of the provent to keep the oily and clean sides further seperated and this is now working very well. But I still have to repair the damage from injesting a lot of oil (enough for it to run on it's own oil several times).

I'll be making a new catch can setup at some stage to fit in the original location (provent with reversed flow is too big and inlet/outlets in the wrong places) but with 1" hoses going in and out.

I'll also be going to back to factory matched piston/liner/ring sets which should have a slightly tighter ring-gap than the aftermarket items I'm currently using.

What size breathers did you change to Dougal?

Originally Posted by Judo

What size breathers did you change to Dougal?

I stepped straight into 1" from the rocker cover. But this size doesn't fit well past the throttle linkage, next time I'll keep 16mm from the rocker to the catch can but make sure the fitting on the can has the biggest internal bore possible. I'll do 1" from the can to the intake.

Originally Posted by Dougal

I stepped straight into 1" from the rocker cover. But this size doesn't fit well past the throttle linkage, next time I'll keep 16mm from the rocker to the catch can but make sure the fitting on the can has the biggest internal bore possible. I'll do 1" from the can to the intake.

Just the one breather? No side cover breather then?