David Salama

If your car is like mine, you probably smell like burnt oil after a spirited drive. Sitting at stop lights can be nauseating. I, like many of you have a few leaky gaskets. I blew out two cam housing gaskets recently I believe from piston ring blow by with my mods, and positive crankcase ventilation that overwhelms the normal recirc PCV system. This week, I discovered a great way of venting my crankcase to minimize positive pressure spikes which may worsen my oil leaks. I have taken off the oil fill cap, and replaced it with a one way check valve from Lowes (sump pump check valve $4.50) I attached it with a short segment of rubber tubing. The crankcase now has the ability to still generate negative pressures (vacuum) which potentially has hp benefits, but does not allow high positive pressures from developing since the check valve would open. The car is running great and not only that, but I don't have that oil smell anymore. I drove the car really hard today, sat a stop lights several times with my windows open, fan on, and had no oil smell. Is it possible that I have stumbled onto something great ?? I would like for some of you to try this simple mod to see if it works for you. Let me know what you think !!
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jordanolder

could be useful, can you outline it again?

Olli Snellman

David,
that's sounds great.I have had the same kind of smells as you have.I must try this with my own car.

Olli
'88 951

Steve Lavigne

Do you still have the air/oil separator vented to atmosphere? Venting this to the intake with the stock system should be able to provide significant vaccum, especially at high rpm/boost levels. Though the oily air alone wouldn't help engine performance, the vaccum in the crankcase *may* offer a performance enhancement. Additionally, having the oil go back into the intake should eliminate the oil burning smells you were experiencing.

Danno

I think he tried venting his air/oil separator to a K&N filter or a catch can and it made the situation worse. I think David's problem is that he's not getting a good seal on his cam-housing cap. I fought this problem for 4-months and tried the whole air-oil separator venting thing and ended up driving with my oil-filler cap completely off for a couple of weeks. Yes those mods did reduce the dripping, burning oil symptoms. BUT they were just that, fixing the symptoms and not the real problem.

David Salama

Thanks for the feedback. Yes, I agree Danno that I am treating the symptoms and not the cause. I really believe to fix the cause in my case would be a complete rebuild (new piston rings). My car is running way too strong to do that. I can live with the blow by if I can prevent major gaskets from blowing out. This is what I am trying to do. I don't think my problem is limited to the cam housing seal only. My balance shaft rear plug has been dripping oil as well since my "big mods". I don't like the idea of having the oil fill tube being left wide open, and I really like the idea of still being able to create a vacuum in the crankcase. The one way check valve works great. If I can fit it under the hood, I plan to add a small K&N to the top of the check valve as well to catch any possible oil splash. So far, it is completely dry by the check valve.
Yes, I did previously try to vent my stock PCV valve to atmosphere. When I was at the track, the oil dipstick shot out of its tube and sprayed oil all over my engine. Obviously, that system did not adequately vent the crankcase. Just given the large diameter of the oil fill tube, any build up of pressure can easily be vented.
Danno, glad to also hear that you had an improvement of your oil drips and smell when your cap was left off. That evidence supports my theory that increased crankcase pressure increases the oil leaks through the gaskets.
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RJP 951

David, sounds like something I need to try too.

Do you have a photo you can post showing the completed installation, or provide a manufacturer's part number for the valve? Did you need any type of hose to attached the valve to the fill tube?

Thanks
Ron

David Salama

I'll look at the valve tomorrow for a possible part number and manufacturer. You may want to do what I did which is go to your local Lowes, or Home Depot to the plumbing section and look through their collection of sump pump check valves. The one I got came with theads on both ends, is plastic, and has a rubber flap in the middle. The overall shape was narrow cylinder, wider cylinder, widest cylinder, and the mirror image on the other side. I hack sawed the threads off the top side. The widest cylinder is the only part that is wider than the oil fill tube, so the second cyinder fits inside. I used a piece of rubber hose that snugly fits over the oil fill tube and hose clamped it to the valve at the level of the medium cylinder. Confused ?? I will try to post a picture tomorrow.
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Thaddeus

A pic would be great... I can't visualize this...

RJP 951

I bet it's something like this....



I found this on the Lowe's web site.

Ron

David Salama

Thank you. Yes, the valve looks similar to the one in the picture. The rubber hose needs to fit over the next ridge, however, so that it can sit further into the oil fill tube. I also must confess that the smell came back. Sorry guys, but I guess when the wind direction blows the exhaust fumes back toward the car, then it inevitably smells. Still, the underlying reason for placing the valve was to decrease spikes in my crankcase pressure to help with gasket leakage. Only time will tell.

Alan C.

Is that valve compatible with oil? IF not it may be a frequent replacement item. Just a thought.

Also on the issue of blow by. My engine was previously built with a set of standard rings on first over pistons, thank you BodyMotion, and I had up to 50% leakdown. The strange thing is that I never blew a gasket. The car did have an external catch tank and filter.

Alan

David Salama

Alan,

When you say external catch tank, I assume you mean the crankcase was ventilated to atmosphere with a catch tank to catch any possible oil out the vent. How was that hooked up to your car? Was it through the standard PCV pipe? Did you get any oil in your catch tank? Thanks. My car had a miserable leak down (80%) in pistons 1 and 4. Hard to believe since the car is still scary fast ! I'm holding out on the rebuild until the car performs poorly, or I can't stand replacing gaskets any more.

RJP 951

Just thinking out loud... how much volume is needed to adequately vent the crankcase?

That check valve is a creative solution, but I also assume it's huge overkill from a size/flow-volume standpoint. I.e., could a much smaller valve be installed somewhere else and still perform adequately for this purpose?

Ron