Oil Burning

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Page created by T Jan 20th 2008:

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A carboned up PCV Valve can cause Oil Burning by allowing the wrong airflow for the Throttle setting. Photo by T. Click to enlargen.

Oil Burning:

There are many causes of Oil Burning and not all them are expensive to fix. 

The Lower Piston Ring:

The Lower Piston Rings must be installed with their inner Chamfer facing down so that the Ring will Gas Pressurise on the Intake Stroke. If it is installed upside down it will not seal properly and allow Oil to be drawn up around it during the Intake Stroke.

Blocked Piston Ring Grooves:

Improper running and poor maintenance can cause the Piston Ring Grooves to block up.The symptoms are the same as those of a worn out Engine. Piston Ring Pressurisation Steaming the Engine through cures it. See Clearing Piston Ring Grooves

Dirty Oil:

Clean Oil is a must for getting the best from the car. Dirty Oil is its worst enemy and blocks Piston Ring Grooves among other things.

Engine Oil
Red/blue/black 6 Cylinder PCV Valve.  Photo by T. Click to enlargen.

Rocker Oil Not Draining:

Oil should drain out of the Rockers after a shutdown. Oil that can't drain away from the Rockers will be thrown up and into the Baffle Plate during a Cold Start and cause the Exhaust to blue smoke.

Rocker Cover Baffle Plates:

It's the job of the Rocker Cover Baffle Plate to separate Oil from Crankcase Fumes and only allow the Fumes to travel out through the PVC Valve to the Inlet Manifold. If the Baffle Plate becomes layered with Carbon Sludge, any Oil becomes stranded and cannot drain back into the Head.The result is a cloud blue Smoke. This can occur on cold starts.

PCV Valve:=

PCV Valve Insertion:=

Hi All;Just a heads up re PCV valve. Had problems with a new re-co 186 donk chewing through oil big time- it was going up PCV pipe. I noticed the newer PCV valve seemed to be a tad longer than the original. If you push it right in, I think it actually sits right on the baffle plate in rocker cover, and constantly hoovers up oil. I pulled the PCV valve back a bit and secured it- it seems to be not using oil. I'll let ya know if it changes.
CheersRod Smith
This PCV Valve was exposed to an aftermarket product for stopping Oil Leaks. The product is rubbery which not even Carburettor Cleaner could remove. Photo by T. Click to enlargen.

PCV Valve Leaking:

A PCV Valve that does not seal off properly will cause noticable blue Oil Smoke on Startup.If the PCV Valve is carboned up it will allow the wrong airflow for the Throttle position.The reason is that airflow through the PCV Valve must be regulated because the pressure it sees is the opposite to the flow needs.There should be minimum airflow at Idle. This is when Inlet Manifold Vacuum is highest.There should be medium airflow at mid Throttle. This is when Inlet Manifold Vacuum is medium.There should be maximum airflow at full Throttle. This is when Inlet Manifold Vacuum is least.

Sludged Up Baffle Channel:

If the Engine has accululated a lot of Sludge, Oil will remain in the the Baffle Channel rather than draining back into the Sump. This will cause Cold Start Oil Burning. Changing the Oil and correct running will cure the problem after the PCV Valve has been cleaned out. Alternatively, remove the Rocker Cover(s) and clean the Baffle Channel. 

Testing the PCV Valve:

Examine the PCV Valve for cleanliness and wash it clean in Petrol or spray it clean with Carburettor Cleaner if it's dirty.When it's working properly it will not allow Air to flow into the Plastic Pipe (Inlet Manifold end), but will allow air to flow out of the Plastic Pipe.If you push the Inner Valve with a small Screwdriver, it should spring back into place and seal tight. If the Spring is weak the PCV Valve will need to be replaced.  The PCV Valve has to form a seal when it is in the closed position (downmost) and it must form a partial seal in the fully up position.There is an expanded explanation in the Link section in Myeh's Shed. This covers Partial PCV.
A carboned up PCV Valve can cause Oil Burning by allowing the wrong airflow for the Throttle setting. Photo by T. Click to enlargen.

After Market Rocker Covers:

Often these have internal Baffles that permit Oil to be drawn into the PCV system and from there into the Inlet Manifold. PCV 

Inadequate Crankcase Ventilation:

Even a perfect running Engine generates pressure inside the Crankcase. The pressure buildup has to be allowed to escapeor the excessive pressure can force Oil down the Valve Guides and around the Pistons. PCV 

Valve Stem Seals:

Valve Stem Seals can be replaced with the Head still on the Engine and the Engine still in the Car. Check for adequate clearance between the Body and the Valve Stems on models such as Commodores and Toranas. Valve Stem Oil Seals

Worn Valve Guides:

After the above items have been checked the problem can be caused by worn Valve Guides. This involves a Cylinder Head removal and a rework. Naturally this is involves expense.

Worn Piston Rings, Piston and Cylinders:

After checking the easy free things, this means a full reconditioning of the Engine. Naturally this is involves expense. 
A carboned up PCV Valve can cause Oil Burning and poor running  by allowing the wrong airflow for the Throttle setting. Photo by T. Click to enlargen.
A new PCV Valve. Photo by T. Click to enlargen.
A new PCV Valve. Photo by T. Click to enlargen.
Original VB Rocker Cover showing the Full Length Baffle Plate. The Baffle can fill with caked on Carbon and prevent Oil from draining properly. The lodged Oil gets drawn through during a Cold Start producing a Cloud of blue Smoke. Photo by Lovemyholden. Click to Enlargen.

Excessive Bearing Wear:

Excessive Oil spilled from worn Big End Bearings can be thrown up onto the Pistons. Oil burning results.  

After Market Rocker Covers:

After market Rocker covers - A word of warningSubmitted by Lovemyholden on Fri, 23/12/2005 - 02:32.
This might have been brought up before,
but I thought I'd mention my experience with these chrome "off the shelf" rocker covers you buy around the place.

Whether it's because you put on roller rockers or just like the look of the taller chrome covers, BEWARE! In my case I put on the Street Terra roller rockers, no worries there, but I purchased a generic after market rocker cover with 202 nicely stamped into the top of it.
Looks great, put it all together and all was happy. Or so I thought! Over several thousand K's I noticed my car started to ping under load. Strange, I checked timing, all ok! After a while it got so bad couldn't even do 100KPH without severe pinging. No alternative, take the head off and inspect combustion chambers. I found large sheets of thick carbon flaking off the pistons. I couldn't believe it. Motor is in good shape, good rings, guides etc, why is it burning so much oil.
I checked out the intake manifold and there was the answer, it had a thin coat of oil throughout it. What! where is this coming from? I traced it to the PCV feed into the manifold.  What it comes down to is this. The stock Holden 6 rocker covers have a full length baffle with a breather slit either end. The Chinese (or wherever they are made by) Rocker Covers have a bent bit of steel folded over and a couple of tack welds holding it up under where the PCV grommet and hence the valve pushes into the rocker cover. It can suck not only crankcase vapours, but any oil that happens to be splashing about, straight into the PCV line and down the motor's throat.
Doesn't take long for this to cause the massive carbon problem. My solution was to rivet an aluminium baffle of my own in (not ideal as rivets leak) and secondly added an oil catch can inline with the PCV line (which did work well) you've just got to remember to empty it from time to time. I hope this saves people some problems, I learned the hard way. Check out the image of the piston.End of submission by LMH.

After Market 2 Hole Rocker Cover. Note the Baffle Plate is much shorter than the original Rocker Cover and can be a source of Oil Burning through the PCV Hose to the Inlet manifold. Photo by HKing. Click to Enlargen.


Myeh's Shed and Partial PCV Info



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