Crankcase pressure problems?

D

dproberts05

Member
Joined
Oct 12, 2005
This past summer I put a new engine in my 86 T, built shortblock with ported and polished heads and other supporting mods. After putting some break in miles on the car I noticed that under boost it would blow the dipstick off about an inch or so and blow some oil by also. The engine has a set of those new cast aluminum tall valve covers that say BUICK on them (or GN1). The vavle cover breathers are those chrome push in style that don't have an open element all the way around like some, just holes in the bottom side. I currently don't have a check valve in the PCV line if thats of any relevance. Any input on why this happens or how to correct it would be appreciated. Thanks, Dan
 
Dan,,

First you want to verify the motor is assembled correctly and the rings are seated. After that install a check valve before pcv to insure the system is not being pressurized. If problem is still there then:

I have/had a very similar experience this past summer. I installed my new motor with many-many mods. Heads, new champion intake, front mount, alky, 6776 dbb turbo,on an on from there. I also have the same Champion valve covers. After much research and speaking to vendors and other members heres what I believe is the problem.

The stock system has a Pcv valve and a vacuum pump, when the system goes under boost. What I mean by this is, the turbo inlet pulls vacuum from the crankcase, (passenger valve cover,) under boost. During this time the PCV valve is shut. Once you come out of boost, the vacuum from the turbo is no longer enough to pull any vapors and the PCv valve takes over.

Solution:

Install an evacuation pump, and/or smog pump. There are many systems out there varying from 30.00 to 1000.00. But the best bang for the buck is the electric pumps out of 01-04 Chevy s-10 blazers. Used with the racetronics wiring. Below is a long detailed install by a member named Pablo.

Hope this helps you.

Evaddave

http://www.turbobuick.com/forums/general-turbo-buick-tech/234420-crankcase-evacuation-lt1-smog-pump-how.html
 
Are you sure you have the correct PCV? The one for the Turbo Regals is very specific. You CANNOT use a generic Regal PCV
 
+2 on the pcv. Been there. I was getting boost into the crank case. I bought the correct one and installed a check valve. And I hate to say this but I ended up useing the handle from a ford on my GN dipstick because the ford one has a oring to seal it off.
 
Evaddave 87gn said:
Solution:

Install an evacuation pump, and/or smog pump.
Evaddave
Click to expand...



WRONG. Problem isn't solved with a band aid.


Fix what's causing the problem...plain and simple! A bad PCV system will cause crankcase pressures under boost. Make sure that is working 100% first. If you've already got that PCV system working as good as possible then you must have other issues.

Piston rings: They need to seal very good to eliminate blow-by. If they don't seal properly high cylinder pressures blow past the rings and into the crankcase causing pressure. This forces the oil out of the breathers. To help cure this you'll need to install gapless piston rings or make sure the rings in your newly rebuilt engine is seated or installed properly.

Valve Guides and Seals: Another cause of pressure in the crank case is worn out valve guides and valve seals. Since there is positive pressure in the intake, the pressure can travel up the intake valve stem and past the seal into the crankcase. Remember, 20psi of boost can leak past a worn guide/seal quickly. This is especially true on the exhaust. Since the exhaust pressure is usually almost twice as much as the boost pressure, burnt gases from the exhaust can enter the crankcase through worn valve stem seals.

Head gaskets: Leaky cylinder head gaskets. High cylinder pressure can leak past the head gasket and into the crankcase also. Obviously, this is probably the majority of where all the pressure comes from in a higher mileage Turbo Buick engine that's been pounded to death.

Misc: Most likely not the cause but worth mentioning. Leaking intake gaskets, a crack in the intake manifold or head. Even the turbo could be causing some but again it's a possibility that could be true. Got to cover everything...

If you don't cure these first you will ALWAYS have excessive blow-by more than normal.

You're not going to get rid of back pressure 100% but it's nice to know that you took all measures to try.


I don't care if your engine is rebuilt or brand new and has less than 200 miles on it you have at least one of those problems listed above. If all of those problems above are in good working condition YOU DO NOT NEED A VACUUM PUMP TO GET RID OF EXCESS CRANKCASE PRESSURE!!!
 
Ah what?

HTML: 
WRONG. Problem isn't solved with a band aid. 


Fix what's causing the problem...plain and simple! A bad PCV system will cause crankcase pressures under boost. Make sure that is working 100% first. If you've already got that PCV system working as good as possible then you must have other issues.

HTML: 
First you want to verify the motor is assembled correctly and the rings are seated. After that install a check valve before pcv to insure the system is not being pressurized. If problem is still there then:

Apparently reading comprehension is not one of your strong suits. Think I covered all you rhetoric in my first two lines. I could go on and explain what I have written to you, however, I believe it to be a waste of my time. Judging by your arrogant rantings on other posts.

Evaddave
 
Evaddave 87gn said:
HTML: 
WRONG. Problem isn't solved with a band aid. 


Fix what's causing the problem...plain and simple! A bad PCV system will cause crankcase pressures under boost. Make sure that is working 100% first. If you've already got that PCV system working as good as possible then you must have other issues.

HTML: 
First you want to verify the motor is assembled correctly and the rings are seated. After that install a check valve before pcv to insure the system is not being pressurized. If problem is still there then:

Apparently reading comprehension is not one of your strong suits. Think I covered all you rhetoric in my first two lines. I could go on and explain what I have written to you, however, I believe it to be a waste of my time. Judging by your arrogant rantings on other posts.

Evaddave
Click to expand...

Don't suggest band aiding as a solution to his problem and I won't go off on one of my "arrogant rants".:rolleyes:
 
First of all, we need to put the proper part on the engine before we can get to the source. He must install the proper pcv to keep boost out of the engine first. Make sure the breathers are flowing freely.


Most the people looking for info should be told to get the proper parts installed first. There could be several problems here and should take steps to help anyone one. He stated he may have the wrong pcv, so it sounds like it is most likely the cause. I hate to freak someone out about all kinds of things like rings or such.

And unless the car is in your sight, you can only give a guess, so anyone of us could be wrong. So lets try to help, not fight. How good does our advice seem when we fight about it??
 
Food for thought.

I suppose we all know or think we know how the pcv valve works, however I’d like to throw out a few thoughts.

The pcv is a one-way valve. The unit is closed until a set vacuum is applied to one end which will draw up a weight/ball/cone against a spring at a set tension. As long the predetermined vacuum is applied, the gasses inside the crank case are pulled through and ignited. Once the vacuum is exceeded or withdrawn the valve closes. In a forced induction system such as ours, the unit will, (or should,) slam shut as soon as boost is applied. This in turn stops ‘boost’ from pressurizing the crankcase.

Now to my point, any motor is basically a giant air pump. By altering the amount of air being displaced we are also altering the amount of vacuum the system is producing. (Such as a cam, heads, intake, turbo, etc….) So the ‘correct’ pcv may or may not be the right choice. For our application it is more important to ensure no boost is passing the pcv. The best way to ensure this is to install a check valve.

In a perfect and highly efficient engine no gasses would leak passed the rings and into the oil. However, all four cycle engines are extremely inefficient, and gasses due leak by. I know, “the gapless rings don’t." Well if that’s the case smell your oil on your next change. Better yet have the concentration of hydro-carbons tested. (Now granted it should be lower than a standard set. But it will still be there.)

Finally, my only reason for posting was to offer information that I gathered when I had a similar problem. Not to argue a reoccurring point of view. I, like everyone else only intend to offer information that I have in hopes to solve the problem. As with any advice, due your own research, contact any that can help. But you must make your own decision.


Evaddave
 
Same thing happened

Friend's engine would do the same put a checkvalve and a new PCV valve and relieved the pressure. He used to put a bungie cord on the dip stick to keep her inplace.
 
this is about learning*

I thought many race engines have long used vacuum pumps to help increase the rings seal in the cylinder.

And then the factory started using vacuum pumps.

This does not sound like a band-aid to me. Indeed, the check valve added to the PCV sounds like a band-aid====>NOT TO SAY it is a bad idea.

Wonder what would happen if valve seals were used on the exhaust? - Think they would get pushed up and then just ride up and down on the valve stem?

*Remember, on-line our emotions are not as easily detected as if we were in the same room. Chop-busting and alternative ideas are NOT usually meant as an insult. IMO, it is good to challange ideas to get to the bottom of an issue and a challange to ideas is not an insult ;)
 
Evaddave 87gn said:
The stock system has a Pcv valve and a vacuum pump, when the system goes under boost. What I mean by this is, the turbo inlet pulls vacuum from the crankcase, (passenger valve cover,) under boost. During this time the PCV valve is shut. Once you come out of boost, the vacuum from the turbo is no longer enough to pull any vapors and the PCv valve takes over.

QUOTE]



well can you answer this question for me then? How come there are alot of buicks out there that don't have the stock pcv system hook-up on the non stock appearing turbo's or they have done away with the breather set-up from the pass side valve cover as this allows oil into the I/C. So there don't seem to be that many of these cars experiencing problems with the dipstick blowing out or oil blowing out of the breathers. so why is this now a problem for this application? seems to me that there is something else causing the problem.

i guess it's a new fad to have a e-vac pump on the TR's now?
Click to expand...
 
Not sure of your point...

SloGn

Not sure that I understand what you are asking. If you are saying that there are guys out there that remove and/or cap off the turbo bell port due to oil in the intercooler, then you are right. Most of this is due to the high mileage cars with worn parts. Basically the problems that you often go into detail over. In these cases you are right; a tear down is in order. That doesn’t seem to be the case here. Remember these are not the type of high-horsepower units, displacing large volumes of air that we are talking about here.

<<<A new fad?>>:confused:
Well one of the top vendor/innovators in the Buick world, RaceJace has been using this setup for four years now.

http://www.turbobuick.com/forums/general-turbo-buick-tech/184176-crankcase-vacuum-pump-options.html

As far as how our emission system works, I believed I explained it in very simple terms. Not sure what else I can say about it. I don’t think there can be any disagreement about that. If you believe me to be wrong then I would be glad to review any contrary information you have.


Evaddave

HTML: 
oh boy

LOL
 
Evaddave 87gn said:
SloGn

Not sure that I understand what you are asking. If you are saying that there are guys out there that remove and/or cap off the turbo bell port due to oil in the intercooler, then you are right. Most of this is due to the high mileage cars with worn parts. Basically the problems that you often go into detail over. In these cases you are right; a tear down is in order. That doesn’t seem to be the case here. Remember these are not the type of high-horsepower units, displacing large volumes of air that we are talking about here.

<<<A new fad?>>:confused:
Well one of the top vendor/innovators in the Buick world, RaceJace has been using this setup for four years now.

http://www.turbobuick.com/forums/general-turbo-buick-tech/184176-crankcase-vacuum-pump-options.html

As far as how our emission system works, I believed I explained it in very simple terms. Not sure what else I can say about it. I don’t think there can be any disagreement about that. If you believe me to be wrong then I would be glad to review any contrary information you have.


Evaddave

HTML: 
oh boy

LOL
Click to expand...



I'm not saying that your wrong here on how the STOCK PVC system works.

What i was referiing to is the many of turbo buicks out there that has had that system modded by the way of removing the beather from the pass side valve cover either cause they have 1 removed the stock appearing turbo or they were tired of the oil issues in the I/C ( thats a problem on a low mileage engine cause it's a ****ty way of doing it!).

but you make it sound like that since that has been disrupted that you need a vac pump to replace that system to keep the engine from having oil coming out of the dipstick tube or the breathers. That where i think your wrong since there has been tons of buicks that has removed that part of the PVC system with no ill effects. so i do think that putting a vac-pump on to help that problem is not fixing the actual problem.
 
thanks

Everyone's input is appreciated. Could anyone tell me the part # for the correct PCV valve? I'm confident mine was new but I could be wrong. Should I get a GM unit or pick one up somewhere like Autozone? Thanks, Dan
 
You must log in or register to reply here.

Similar threads

G
100,000 mile engine service - a few questions
Replies
11
Views
848
granitestategn
G
S
Vacuum Brake Conversion
Replies
10
Views
1K
TIMINATOR
TIMINATOR
williamsGN
Bent same pushrod twice
Replies
10
Views
963
TIMINATOR
TIMINATOR
D
PCV Help?
2 3
Replies
43
Views
3K
Clark6
C
N
Crankcase Evac
Replies
9
Views
2K
TIMINATOR
TIMINATOR
Top