Oil Consumption

[Blwn87]

Alright I have what everyone says around here is , A BIG PROBLEM. My very modded GN goes through a quart of oil about every 100 miles (highway or cruising miles doesnt matter). Here are the things that are the problem and things that have been looked at.

Thought it could have been a bad turbo seal but there seems to be no oil residue in the intercooler or throttle body.
Motor has been leak checked, Seals checked, and compression test checked (#'s on compression test, Cylinder #1 150psi, #2 160psi, #3 155psi, #4 150psi, #5 155psi, #6 150psi) by respectable GM Mechanic (Mechanic says engine is very sound).

So what could eat a quart of oil every 100 miles?

 

[John Larkin]

It's either going on the ground or out the exhaust. That you can bet on. After it idles for a bit, pull off the vacuum pod on top of the TB and see if oil oozes out. That would indicate a PCV problem. Check spark plug color and look for signs of oil burning. How does your vacuum gauge look at idle and cruising? Any movement/wavering/erraticness?

 

[Blwn87]

reply

There is no oil under the car. Plugs look a slight bit darker than "normal". I replaced the PCV and hose twice in 2 years just because it was cheap. Leakdown performed 4 weeks ago at a sped shop had no issues. Intercooler outlet or inlet (FM) had no residue of oil. Delta gate on crossover has no oil on the dump, other deltagate on the turbo intake goes directly into exhaust so I cannot tell. I will pull the vacuum manifold tomorrow after work and check for oil.....what if there is some?

 

[Blwn87]

Pulled Vaccum manifold

Now i have a problem that i dont know what to do about. I pulled the vacuum manifold this morning and found oil residue. The top of the gasket had some oil on it and there are two holes in the vacuum manifold. The one farthest back has a goo amount of oil residue on it while the one in front only has alittle. I cleaned the entire surface off and ran the car at idle for about 5 min. Checked it again and it seems that most of the oil residue is at the back hole and not really at the front. Where is the oil coming from and how do i fix this problem.

 

[John Larkin]

You have the same problem as me: a leaky or overly aggressive PCV. I need to buy another one and see if it helps. Mine isn't drinking that kind of volume but apparently yours is. I guess it's possible to have it in backwards? Might check that first. Also, how are the breathers in your valve covers?

 

[Blwn87]

reply

OK i will replace for the 3rd time in 2 years. i will verify direction after i inspect the PCV valve on my other GN. I have breathers on BOTH my valve covers.

Where else can the vacuum draw oil from other than the PCV valve? The vacuum line from my master cylinder goes to the vacuum manifold but there is a check valve to prevent reverse flow.

 

[fc227]

Do you have "ash" deposits on the spark plugs?

 

[Mark E.]

If you are not using the valley pan intake gasket, your pcv could be sucking up oil from the galley. I went through this on my car years ago and even re-ringed it. DOH! I made a partial valley pan to cover the pcv and used the fel pro indivisual gaskets to seal the ports. Try driving without the pcv for a few days and see if it helps. I do not recomend removing the pcv for good, although I have heard some people do it. Good Luck,

 

[Scott Atk]

If your PCV is sucking oil you should be seeing smoke out the tailpipe, most likely at idle (when vacuum is high). I would also recommend just unhooking the PCV and capping it off for a couple of days and see what happens. Good Luck

 

[musclecar neal]

many times oil gets in the pcv system when the engine is running higher RPM's as the amount of oil vapor in the valve covers is much higher then at idle. the amount of vacuum has something to do with how much oil is pulled in the system but the volume of oil vapor is the real issue. On street cars with a non restricted oil system you find this all the time. to solve this we baffle the valve covers in a way that oil can never directly get to the pcv valve. We place the PCV in the front part of the cover and make the baffle end point toward the rear of the over so there is no chance liquid oil gets to the valve. It has worked for us for many years. we also use a valve that has a smaller orifice to cut down on flow and a very good size breather on the other cover.


hope this might help.

 

[Blwn87]

reply

I can honestly say I havn't seen redline in third or fourth yet this year (I usually made my point to the other car by then, mostly wanna be fast mustangs or ricers that only have speed in their dreams). I do have whiffs of blue smoke at low rpm's after start up and drive aways, like back-up the driveway and shift to 1st.

Help me through the logic. I have always thought the pcv was intended to relieve the crankcase pressure by diverting the vapor to the intake side of the engine for re-burn. If I remove this valve won't I be increasing my crankcase pressure? This brings me bake to my querry of last week. Has anyone used the Moroso vacuum crankcase pump for relief of the dipstick rise I'm seeing?

 

[ThikStik]

PCV is used as an emission control. It was the first emiss control and it debuted back in the early 60's. Before. th ere was just a draft pipe which let the gases just vent out to atmosphere. PCV is also good for keepin oil clean, burns off water which build acids in c.case.
It can help a car have engine leaks when not running pcv as pressure builds in the c.case. This, I guess is more so for our turbo cars.
Doesnt Red run pcv-less? I sure agree that running without for a few days would determine problem and not hurt a thing.
hth

 

[Blwn87]

PCVless

Alright i blocked the PVC valve today and it seems to be working for right now (not as much knock during acceleration but still have to see how much oil i am going through). Know we blocked the PCV red neck style (its a dont ask, dont tell kinda thing). How are you running PCV less. We put a crankcase breather at the end of the tube coming out of the PCV valve. What are you running to block the side that comes from the vacuum manifold? What other ways are you running a PCVless system?Thanks to everyone by the way for all your input and i hope things get better from here.

 

[John Larkin]

I have been toying with the idea of putting the PCV in the valve cover. Originally I wanted to put it in the backend of the driver's side valve cover but it's just too tight between the firewall IMO. I have some spare heads and a set of VCs in the barn. I may mockup something this weekend and see if there's enough clearance around the valvetrain to put one in the passenger side. Of course to do this you'd have to mill a flat spot down in the VC fins to install a grommet or use one with a really long neck. This is how n/a cars usually do it; don't see why it wouldn't work for us. There's very little oil in there to suck up.