Excessive crankcase pressure/PCV question
10-05-2010, 02:36 PM
#1
Excessive crankcase pressure/PCV question I have noticed since putting together my heads cam engine on 53k shortblock, that I have been having some crankcase pressure issues. First it was leaking from where the dipstick meets the block with the dipstick loose, and would leak oil onto the headers after WOT, fixed that leak, now yesterday I go WOT again and the dipstick tube apparently came out about 1.5" and sprayed oil all over the pass side and top of engine. So while idling, I take out the PCV valve out of the side of the intake, put my fingers over the hole in the intake, no vacuum. Place finger over the hose going to front of intake under TB, and has vacuum.
Now I have been reading that the vacuum side is supposed to be at the side of the intake while the crankcase air comes from the front of intake? If this is the case, what explains the reverse happening?
Now I have been reading that the vacuum side is supposed to be at the side of the intake while the crankcase air comes from the front of intake? If this is the case, what explains the reverse happening?
10-05-2010, 03:11 PM
#2
That actually is NOT the case. You should not have vacuum at the PCV valve. The port under the throttle body is connected to the intake plenum. If you take off your throttle body and look directly down into the intake manifold, you will see where that front port enters the plenum. It is here where blowby gases are pulled via plenum vacuum from the PCV valve to be combusted. The PCV system pulls metered air from the throttle body (via the fresh air supply hose) into the crankcase. This displaces the air in the crankcase up through the intake manifold tray (bolted to the underside of the manifold) and into a 3/4" slot, which is connected to the PCV valve. It is then sent to the plenum.
10-05-2010, 04:07 PM
#4
RamAir, that makes sense, that's what I originally thought, but was reading another thread, they must have explained it differently.
SpeedDemon, yes I still have stock TB, and hose going from it to valve cover, however, I have aftermarket covers that came with no holes, so I only have 1 hole which has an elbow in it, which happens to have a smaller opening than stock elbow, so has smaller hose over the elbow nipple which stock hose clamps on, then stock hose to TB.
Could this not be allowing enough pressure out at WOT? I'll upload a pic to show.
SpeedDemon, yes I still have stock TB, and hose going from it to valve cover, however, I have aftermarket covers that came with no holes, so I only have 1 hole which has an elbow in it, which happens to have a smaller opening than stock elbow, so has smaller hose over the elbow nipple which stock hose clamps on, then stock hose to TB.
Could this not be allowing enough pressure out at WOT? I'll upload a pic to show.
10-05-2010, 05:40 PM
#5
RamAir, that makes sense, that's what I originally thought, but was reading another thread, they must have explained it differently.
SpeedDemon, yes I still have stock TB, and hose going from it to valve cover, however, I have aftermarket covers that came with no holes, so I only have 1 hole which has an elbow in it, which happens to have a smaller opening than stock elbow, so has smaller hose over the elbow nipple which stock hose clamps on, then stock hose to TB.
Could this not be allowing enough pressure out at WOT? I'll upload a pic to show.
SpeedDemon, yes I still have stock TB, and hose going from it to valve cover, however, I have aftermarket covers that came with no holes, so I only have 1 hole which has an elbow in it, which happens to have a smaller opening than stock elbow, so has smaller hose over the elbow nipple which stock hose clamps on, then stock hose to TB.
Could this not be allowing enough pressure out at WOT? I'll upload a pic to show.
How much should one cost? I don't have an air compressor or leakdown tester. 
10-12-2010, 12:57 AM
#14
So I pulled the cover on top of the stock TB, and while there is some oil in there, it turns out that the piece that the airfoil screws into, sits in the hole that would otherwise allow more air through the PCV, so this could be my restriction in the PCV system, as it is not allowing air to flow well, causing pressure?
As far as the burning oil/blowby, I pulled all of the plugs, and saw NO sign of oil burning whatsoever. All of the plugs are clean with just a light brown color, not even an indication of a rich condition going on. SO, if the plugs show NO oil symptoms, then the smoke at WOT is probably NOT from blowby, right?
I did notice on the #8 plug, oil on the outside of the plug, and some oil around the bottom corner of the valve cover, so I pulled the cover, and it had oil on both sides of the gasket at the back of the cover. I didn't see any oil under the valve cover on the head itself, but that doesn't mean that a tiny amount isn't seeping into the exhaust port, right?
Cleaned it up, and replaced, making sure it was tightened down all the way, as well as the header tightened all the way.
My pass side underside of the car was coated with power steering fluid, which I have been losing a TON of daily, as well as oil/fluid around the pass O2 sensor and collector. Is it possible that some of the power steering fluid, which has coated the underside of my car, has leaked into the exhaust, through the O2 and/or collector/y-pipe connection, causing some of the smoke I see? Or would it be more likely that the valve cover leak could be causing the smoke at WOT?
I haven't done the leakdown test, but will do a compression test tomorrow and post results. Also, I don't know if it matters, but with the GM 'white' spring on the Melling pump, and only 54k mi on the engine, my oil pressure is usually in the 65-80 psi range, only dropping to about 50 when idling in HOT weather after driving around for a while. Not sure if that would cause any problems either?
As far as the burning oil/blowby, I pulled all of the plugs, and saw NO sign of oil burning whatsoever. All of the plugs are clean with just a light brown color, not even an indication of a rich condition going on. SO, if the plugs show NO oil symptoms, then the smoke at WOT is probably NOT from blowby, right?
I did notice on the #8 plug, oil on the outside of the plug, and some oil around the bottom corner of the valve cover, so I pulled the cover, and it had oil on both sides of the gasket at the back of the cover. I didn't see any oil under the valve cover on the head itself, but that doesn't mean that a tiny amount isn't seeping into the exhaust port, right?
Cleaned it up, and replaced, making sure it was tightened down all the way, as well as the header tightened all the way.
My pass side underside of the car was coated with power steering fluid, which I have been losing a TON of daily, as well as oil/fluid around the pass O2 sensor and collector. Is it possible that some of the power steering fluid, which has coated the underside of my car, has leaked into the exhaust, through the O2 and/or collector/y-pipe connection, causing some of the smoke I see? Or would it be more likely that the valve cover leak could be causing the smoke at WOT?
I haven't done the leakdown test, but will do a compression test tomorrow and post results. Also, I don't know if it matters, but with the GM 'white' spring on the Melling pump, and only 54k mi on the engine, my oil pressure is usually in the 65-80 psi range, only dropping to about 50 when idling in HOT weather after driving around for a while. Not sure if that would cause any problems either?
10-12-2010, 01:27 AM
#15
So I pulled the cover on top of the stock TB, and while there is some oil in there, it turns out that the piece that the airfoil screws into, sits in the hole that would otherwise allow more air through the PCV, so this could be my restriction in the PCV system, as it is not allowing air to flow well, causing pressure?
As far as the burning oil/blowby, I pulled all of the plugs, and saw NO sign of oil burning whatsoever. All of the plugs are clean with just a light brown color, not even an indication of a rich condition going on. SO, if the plugs show NO oil symptoms, then the smoke at WOT is probably NOT from blowby, right?
I did notice on the #8 plug, oil on the outside of the plug, and some oil around the bottom corner of the valve cover, so I pulled the cover, and it had oil on both sides of the gasket at the back of the cover. I didn't see any oil under the valve cover on the head itself, but that doesn't mean that a tiny amount isn't seeping into the exhaust port, right?
Cleaned it up, and replaced, making sure it was tightened down all the way, as well as the header tightened all the way.
My pass side underside of the car was coated with power steering fluid, which I have been losing a TON of daily, as well as oil/fluid around the pass O2 sensor and collector. Is it possible that some of the power steering fluid, which has coated the underside of my car, has leaked into the exhaust, through the O2 and/or collector/y-pipe connection, causing some of the smoke I see? Or would it be more likely that the valve cover leak could be causing the smoke at WOT?
I haven't done the leakdown test, but will do a compression test tomorrow and post results. Also, I don't know if it matters, but with the GM 'white' spring on the Melling pump, and only 54k mi on the engine, my oil pressure is usually in the 65-80 psi range, only dropping to about 50 when idling in HOT weather after driving around for a while. Not sure if that would cause any problems either?
As far as the burning oil/blowby, I pulled all of the plugs, and saw NO sign of oil burning whatsoever. All of the plugs are clean with just a light brown color, not even an indication of a rich condition going on. SO, if the plugs show NO oil symptoms, then the smoke at WOT is probably NOT from blowby, right?
I did notice on the #8 plug, oil on the outside of the plug, and some oil around the bottom corner of the valve cover, so I pulled the cover, and it had oil on both sides of the gasket at the back of the cover. I didn't see any oil under the valve cover on the head itself, but that doesn't mean that a tiny amount isn't seeping into the exhaust port, right?
Cleaned it up, and replaced, making sure it was tightened down all the way, as well as the header tightened all the way.
My pass side underside of the car was coated with power steering fluid, which I have been losing a TON of daily, as well as oil/fluid around the pass O2 sensor and collector. Is it possible that some of the power steering fluid, which has coated the underside of my car, has leaked into the exhaust, through the O2 and/or collector/y-pipe connection, causing some of the smoke I see? Or would it be more likely that the valve cover leak could be causing the smoke at WOT?
I haven't done the leakdown test, but will do a compression test tomorrow and post results. Also, I don't know if it matters, but with the GM 'white' spring on the Melling pump, and only 54k mi on the engine, my oil pressure is usually in the 65-80 psi range, only dropping to about 50 when idling in HOT weather after driving around for a while. Not sure if that would cause any problems either?
10-12-2010, 12:29 PM
#17
So with the car sitting for the past 3 days (cold engine - 70* temp) and 5 cranks:
Compression Test Results:
1 - 205 2 - 195
3 - 210 4 - 205
5 - 205 6 - 185
7 - 185 8 - 205
Average - 199.4 psi
So I know this isn't a leakdown test or a warm compression test, but I assume with these results, that I shouldn't be having major blowby causing the oil burning. Hopefully it IS just the power steering fluid leaking on the header (which has a light brown color baked onto it at the bottom) that is causing the smoke. Also, idling doing the 'dollar over the valve cover hole' test a few days ago, the dollar barely moved, only moving slightly with a hit of the throttle.
Compression Test Results:
1 - 205 2 - 195
3 - 210 4 - 205
5 - 205 6 - 185
7 - 185 8 - 205
Average - 199.4 psi
So I know this isn't a leakdown test or a warm compression test, but I assume with these results, that I shouldn't be having major blowby causing the oil burning. Hopefully it IS just the power steering fluid leaking on the header (which has a light brown color baked onto it at the bottom) that is causing the smoke. Also, idling doing the 'dollar over the valve cover hole' test a few days ago, the dollar barely moved, only moving slightly with a hit of the throttle.
10-12-2010, 01:27 PM
#18
From what you are saying, it appears the PCV is working fine.
You have suction at the fitting on the front of the intake under the big rubber elbow. The metal tube connecting the above fitting is connected to the PCV valve and is installed in its hole on the intake. And you have the tube from the right side valve cover connected to the TB. Assuming those two tubes are not plugged, your PCV system should be fine.
It normal to get a little oil in the top of the TB like what you found. The engine blows it back through the right side rubber hose at WOT just a bit. I fixed this on mine by installing a filter in the valve cover just before the rubber hose and no more oil in the TB. The filter can be had at any parts house.
I recently had an issue with lots of oil getting in the plenum of my intake which resulted in occasionally smelling oil burning. I determined that it was coming through the metal tube from the PCV and going in the front of the intake. I installed a catch can and now that problem is resolved. I also did a leak down and it came out perfect so blow by was not the issue.
You have suction at the fitting on the front of the intake under the big rubber elbow. The metal tube connecting the above fitting is connected to the PCV valve and is installed in its hole on the intake. And you have the tube from the right side valve cover connected to the TB. Assuming those two tubes are not plugged, your PCV system should be fine.
It normal to get a little oil in the top of the TB like what you found. The engine blows it back through the right side rubber hose at WOT just a bit. I fixed this on mine by installing a filter in the valve cover just before the rubber hose and no more oil in the TB. The filter can be had at any parts house.
I recently had an issue with lots of oil getting in the plenum of my intake which resulted in occasionally smelling oil burning. I determined that it was coming through the metal tube from the PCV and going in the front of the intake. I installed a catch can and now that problem is resolved. I also did a leak down and it came out perfect so blow by was not the issue.
12-13-2010, 10:41 PM
#19
I have just installed a air/water separator for an air compressor inline with the PCV on the driver's side, and driving around normally, no WOT, I have noticed that it has accumulated a slight bit of oil inside of it, so for now I will leave it on to keep oil from entering in that way.
As far as the clean air side, I still have the breather on, I went back to the stock valve cover to TB line for a few days, and blew the dipstick tube up again at WOT. I also noticed that it had some milkshake looking condensation in it as well. Took it off for the breather, no more condensation in top of valve cover, and no more dipstick popping out. However, after a while, the breather does leave an oily mist on the surrounding engine as well as the occasional oil vapor smell, so I would like to somehow get back to a sealed system if possible, maybe put a catch can/separator in the clean air side as well to keep oil out of the TB.
So my thought is that with the stock TB line in, that enough air is not flowing through the system causing the pressure to back up the dipstick. My theory is that the air foil in the stock TB may be restricting air flow, since it essentially blocks where the air is supposed to enter the PCV fresh air chamber at the top of the TB. Does this sound like a possibility? Unfortunately the weather here is not going to permit me to try this theory of removing the airfoil out for a while, so if anyone has any opinions/ideas, let me know.
As far as the clean air side, I still have the breather on, I went back to the stock valve cover to TB line for a few days, and blew the dipstick tube up again at WOT. I also noticed that it had some milkshake looking condensation in it as well. Took it off for the breather, no more condensation in top of valve cover, and no more dipstick popping out. However, after a while, the breather does leave an oily mist on the surrounding engine as well as the occasional oil vapor smell, so I would like to somehow get back to a sealed system if possible, maybe put a catch can/separator in the clean air side as well to keep oil out of the TB.
So my thought is that with the stock TB line in, that enough air is not flowing through the system causing the pressure to back up the dipstick. My theory is that the air foil in the stock TB may be restricting air flow, since it essentially blocks where the air is supposed to enter the PCV fresh air chamber at the top of the TB. Does this sound like a possibility? Unfortunately the weather here is not going to permit me to try this theory of removing the airfoil out for a while, so if anyone has any opinions/ideas, let me know.
12-13-2010, 11:10 PM
#20
I worked at a high volume Chevy dealer when these things were still under warranty. The LT1 cars with those stupid airfoils in the throttle body would come in for 10x more oil leaks than any other small block.