Oil Blow-by

[nitrofarm]

Hey guys,I want to run a theory past you.Its an open ended question. If your B3 has lots of blow-by. And it has a substantial oil leak.@ oil pan/Dizzy O-ring/Cam seal or oil pump seal . Couldnt the blow-by be a symptom of the absence of a good crankcase seal? If the leak is large enough(like the one on my ATX). How is the Crankcase ever gonna see vaccum?

[gauge_half_inch]

It is more than likely the complete opposite of that. The blow could be causing the large oil leaks caused by excessive crank case pressure forcing past the seals, not having enough vaccum to compensate for blow-by. Perform a compression test, if any are low, I'm guessing they will be, perform a cylinder leak down test to conferm the rings/walls are worn.

[nitrofarm]

It is more than likely the complete opposite of that. The blow could be causing the large oil leaks caused by excessive crank case pressure forcing past the seals, not having enough vaccum to compensate for blow-by. Perform a compression test, if any are low, I'm guessing they will be, perform a cylinder leak down test to conferm the rings/walls are worn.

OK,sounds good,I'll report back. Its leaks like a seive when running at idle.Shut it off and it stops.

[Movin]

Gauge gave it to you right on! Blow by makes pressure in the engine . Gaskets and seals
are not designed for pressure or vacuum, ventilation of fumes is what you are looking
for, this prevents internal rust and break down of the oil. A small amount of blow by is normal.

[nitrofarm]

So the crankcase isnt under neg press with a good working PCV system?

[gauge_half_inch]

Correct, the vaccum should be relatively equal to the blow-by created by a healthy engine.

[getnpsi]

Simply going to synthetic oil and boosting a leaky engine actually helps. It sounds like the worst idea but I've done it myself to fords and other people with mazda engines have experienced this. It depends on which rings are bad anything or just dirty. If it's a top end issue nothing will change. Always check that the pcv valve good, wait don't check it just buy a new one. I hate the rattle test.

[blkfordsedan]

Even with a properly operating PCV system, it's drawing it's vacuum from the intake manifold. When you're under WOT, you have zero vacuum since everything is at equilibrium. If you have blow-by issues, high cylinder pressures @ WOT make the blow-by the greatest at the time when you have no vacuum. In addition, the fresh (and metered) air inlet that goes from the air intake tube to the valve cover should reduce any vacuum created in the crankcase to a minimum....just enough to create air flow circulation in the system. If you plug the fresh air inlet and pull a vacuum on the crankcase, the motor will usually run like crap.

[Movin]

Even with a properly operating PCV system, it's drawing it's vacuum from the intake manifold. When you're under WOT, you have zero vacuum since everything is at equilibrium. If you have blow-by issues, high cylinder pressures @ WOT make the blow-by the greatest at the time when you have no vacuum. In addition, the fresh (and metered) air inlet that goes from the air intake tube to the valve cover should reduce any vacuum created in the crankcase to a minimum....just enough to create air flow circulation in the system. If you plug the fresh air inlet and pull a vacuum on the crankcase, the motor will usually run like crap.

LOL !! A guy did that to his jeep the other day. The IAC and O2 were
going nuts trying to keep up with it!! After about 20 minutes the oil would
get hot enough to boil off the gasoline fumes and it would kill it! It wouldn't
start until it cooled off then it would run fine again!! LOL if I wanted a jeep
wrangler I could have had one for cheap!!

As usual, he had replaced almost all of the ignition system and put in
several new computer parts...A little over $1000 of just parts...Love the
look on their faces when just after their story you tell them what the
problem is...