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Causes and solutions of blow by

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ZJTurbo

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Discussion starter · #1 ·
I went to get my car tuned today (DSG) Awesome guys very proffesional amazing work but had some car issues. From what I saw and was told I was having serious blow by issues with oil being pushed back up in the combustion chamber. One every pull the dip stick would pop off and oil would come through the valve cover gasket. I have done a compression test two times now. It is steady 155-165 across all 4. The motor has 160k:eek: . I am just wondering is it the rings/ ovalized walls? Or is it to much pressure in the crank case??? Just confused. I was thinking about haveing two bungs welded on the valeve cover and run them to a catch can to aleviate the problem just wan to make sure that is the issue. Need input. As of right now I am putting in a new valve cover gasket putting in some fresh oil and taking my valve cover to a friend of mine to weld in bungs.

Here is my setup if it helps?
14b/ 16g hot side
3'' turbo back
fmic
2gmaf
255wally
720cc RC
Link
COP
External wastegate on o2 housing (40mm)
FPR on rail

-Ben
 
#2 ·
blown PVC valve
bad rings could do it, but your compression seems good.
I also like to run a line from the valvecover to the intake so the suction of the turbo pulls a slight vacuum in the crankcase, which helps seal the rings a little better. Naturally, I have a catchcan inline with the valvecover hose so oil doesn't get into the intercooler and the rest of the intake tract.
 
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#4 ·
how many miles are on the motor? It almost sounds like cylinder wall taper. This happens because the most wear on cylinder wallers is at the top of piston stroke so over time the walls look like a a V.

Basically so at high RPM the rings cant expand and contract fast enough to follow the cylinder wall.
 
#5 ·
Get a new pcv, oil dipstick, valvecover gasket, and setup a catchcan with vacum. You might have to hold the dipstick down with wire and a hose clamp if all else fails and you dont feel like a full engine rebuild
 
Discussion starter · #7 ·
tikigod1539 said:
how many miles are on the motor? It almost sounds like cylinder wall taper. This happens because the most wear on cylinder wallers is at the top of piston stroke so over time the walls look like a a V.

Basically so at high RPM the rings cant expand and contract fast enough to follow the cylinder wall.
Click to expand...
Ok my question to that is if it tapers or is ''ovalized'' wouldn't I get bad crompression #'s? There is 160k been rebuilt ''supposedly''. So Far I found that my pcv which is supposed to be a 1 way valve was bad and was allowing are in and out which I am guessing was causing my ''boost'' to enter the crankcase via the valve cover and cause the blow by. I also put a new valve cover gasket and changed the oil and oil filter to be on the safe side. Drove the car and Now my knock sensor is lighting up. How will I know if I am not getting blow by? or not. Car has never smoked has good comp? Is there any way to proform a test and find out if I still have blow by. Or just go back to DSG and have them retune. Please any input helpful
 
#9 ·
To the original poster; Does your oil color change after driving for 2 weeks?
Does it burn oil?

Well i have a thread open for this too. Constantly getting around 20+ counts on higher rpm's. My compression is 185psi on all 4 cyl.
 
#11 ·
ZJTurbo said:
No knock up top just before and threw the begining of boost like 3200-3700 I get knock
Click to expand...
Likely when the turbo is spiking...
No wait you said you have external waste gate.
Pull a deg of timing were ever the knock is to see if it goes away.

My 6bolt bottom end has over 100k on it also and my compression is all within 160-150 across all fours. I have a ton of blow by under boost also.
It is just natural for an older motor to do. You have to get used to it or just re ring it and re hone the cylinder walls.

I burn about 2 quarts of oil before every 2500 mile oil change.
My oil is black before 400-500 miles. I run mobil 1 15w50 full synthetic
and i still change oil sooner than normal because oil will break down faster in a older engine due to contamination of the oil.

A few suggestions that may help your problem before you go out of the way looking too much into your cylinder walls being at fault,

Perhaps use thicker oil, and or find the proper engine restore that can help re seal rings. I dont know what works and what doesnt.

Do a proper catch can set up... If you have the mind and patience to go thru all those catch can threads good luck. A second bung on the valve cover can only help...

Make sure your turbo isnt bad
Also make sure your tubro return tube isnt blocked...

If those things check off then its your lower oil rings.

There are different tricks that will prevent the dipstick from blowing out.
Mines is crushed in a little and it doesnt ever blow out.
 
#13 ·
Thats the time about the tapered cylinder walls, because the way the rings expand and contract in the bore at high speed they can't conform to the wall. Thus causing low compression. When you do you compression check you remove that high speed contraction varability. This shows you have a higher compression than you really do.

Only way to really check this out though is tear it apart. =/
 
Discussion starter · #14 ·
Leak down test any good? Also I have ben wanting to put a new head on for a while. Throw some arps in there, mls. Some mild head work. What would Let me know if my bottom end is past due.
 
#15 ·
tikigod1539 said:
Thats the time about the tapered cylinder walls, because the way the rings expand and contract in the bore at high speed they can't conform to the wall. Thus causing low compression. When you do you compression check you remove that high speed contraction varability. This shows you have a higher compression than you really do.

Only way to really check this out though is tear it apart. =/
Click to expand...
Good thing compression isnt such a big factor in a turbocharged engine when it comes to making power.
 
#16 ·
ZJTurbo said:
Leak down test any good? Also I have ben wanting to put a new head on for a while. Throw some arps in there, mls. Some mild head work. What would Let me know if my bottom end is past due.
Click to expand...
Yes do a leak down test, and do all the things i mentioned in my other post and you will find something after you;ve done all that.
If your going to do a head job and have the money, id suggest doing the ARPs and head gasket like you mentioned...
Hell if its out build it up, drop some cams and new rings and pistons at least.

But honestly,
You dont have to do anything about it regardless if it smokes a little bit.
Your compression test was well within service limit and if its not costing you any noticeable power or making you burn oil excessively then just ride it out and save money so that when it is apart its built right.

Thats just my opinion though.

Why fix it when its not broken right...
 
#17 ·
don't weld fittings on your valve cover to cover up an issue with your motor. The 4G63 was designed to run @ boost without those kind of side effects, fix whats wrong.

Guys running 700hp and race motors with crazy clearances can do what they want, you don't need it. That is for sure.
 
Discussion starter · #18 ·
Black_ bullet said:
Yes do a leak down test, and do all the things i mentioned in my other post and you will find something after you;ve done all that.
If your going to do a head job and have the money, id suggest doing the ARPs and head gasket like you mentioned...
Hell if its out build it up, drop some cams and new rings and pistons at least.

But honestly,
You dont have to do anything about it regardless if it smokes a little bit.
Your compression test was well within service limit and if its not costing you any noticeable power or making you burn oil excessively then just ride it out and save money so that when it is apart its built right.

Thats just my opinion though.

Why fix it when its not broken right...
Click to expand...
\

Was thinking the same thing. I figure I will change a few things. Get it running a little better then just save some cash till' I can afford a full build. Thank will let you know how I make out. Thanks for all the responses,

-Ben
 
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