Stopping oil blow-by - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 03-10-2000, 03:16 PM
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Stopping oil blow-by

I have a 93 Bronco with the 351 Windsor engine. At high RPM (> 3000rpm) there is lots of oil blow-by. It soaks the stock breather filter in the filter box. I eventually removed the stock setup and put an aftermarket breather over the hose end. Now the engine compartment gets filled with oil from the vapors passing the aftermarket filter. It has a new PCV (the old one worked fine). Lately it has worsened to passing about 1 quart every 500 miles (uphill miles in the mountains). Being a "real genius" I plugged the breather to stop the oil from covering my engine compartment. The first sign that something was wrong was the grey/blue cloud of smoke I created at 3000 RPM. The oil passed everywhere else including my dipstick and rear main seal. (Please don't comment on my stupidity).
I really don't want to rebuild the engine yet. It runs great otherwise. Does anyone have a quick and easy solution that doesn't cost an arm-and-a-leg?

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post #2 of (permalink) Old 03-10-2000, 04:41 PM
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Re: Stopping oil blow-by

I think there's a Ford technical service bulletin about some engines with a missing baffle in the valve cover, which allows oil to get into the filter box. Did the problem just begin recently, or as long as you've owned it? I'll look for the TSB.


NormSpeed
post #3 of (permalink) Old 03-10-2000, 04:48 PM
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Re: Stopping oil blow-by

Blow by is caused by pressurized air leaking past piston rings and valves. That air pressure builds up in the crank case. Now under normal conditions there is little air leaking past the valve and rings. What does, is evacuated through the PCV system. When more air pressure builds up than the PCV system can deal with, ventilates through the breather. As an engine wears out, more air is able to leak past rings and valves, causing more air to evacuate through the breather. Now so much air is blowing out the breather with more force, that it picks up droplets of oil with it. This in turn soaks down the filters and eventually gums up the carb or throttle body. If the PCV system is working properly, then its time for a rebuild. At least a head job and re-ring it. Once you've gone that far, you might as well rebuild it though.

What I did to buy time until I could rebuild my engine was to take a bicycle water bottle and drill a bigger through hole in the nipple. I then drilled several smaller holes in the cap for air to escape. I then placed a large wadding of course steel wool in the bottle and ran the breather hose from the valve cover to the bottle and stuffed the hose over the nipple. Now the bottle will catch the oil and air is able to vent through the small holes in the cap. I also mounted bottle carrier to my core support. Then I just had to pop the cap off and empty the bottle every now and again. Something to think about.

Eric R. Tachell

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post #4 of (permalink) Old 03-10-2000, 05:02 PM
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Re: Stopping oil blow-by

NormSpeed: I only noticed it in the last year, it could have been existent for a while. I only started the heavy mountain driving lately. I will check for the missing baffle. Let me know about the service bulletin. Thanks!

Eric: I haven't checked the compression yet (spark plugs too hard to get to) but I am assuming that the problem is both valve guides and piston rings. The engine has only 110,000 miles on it. It is real unfortunant for such a young engine. Just pulling the heads off the engine is a major task because of all the hoses and wires that need to be disconnected and reconnected. I will try your bottle solution (sounds like a good idea). Thanks!

Curtis


post #5 of (permalink) Old 03-11-2000, 12:23 AM
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Re: Stopping oil blow-by

Well, forget the missing baffle, the TSB doesn't apply to your year. Good luck....Norm

NormSpeed
post #6 of (permalink) Old 03-13-2000, 10:32 AM
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Re: Stopping oil blow-by

I ran that bottle trick for two to three years and put 40,000 miles on it. When I decided to rebuild the engine it wasn't because of that, I noticed that my power wasn't what it used to be. When I first bought the truck, I could run up a pass at 60 mph. Just before I rebuilt it, I dropped clear down to 45. My wife actually told me to do it then.

post #7 of (permalink) Old 03-13-2000, 12:47 PM
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Re: Stopping oil blow-by

Thanks Eric, 40,000, that is good to know. I too, can run up the passes at 60mph. It still has a bit of power left in it.
I just heard that K&N makes a breather that will pass the vapors but not the oil. The photo I saw showed a filter and a reservoir to collect the oil and a drain plug to drain it. I will have to check into it.
Later,
Curtis

post #8 of (permalink) Old 03-13-2000, 01:26 PM
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Re: Stopping oil blow-by

Found this photo on the jeep forum (no, I am not defecting, never will either).
Now I am not sure who makes this, but the post says that it is similar to the K&N.
The K&N setup fits on the PCV port, which is buried under the intake. There is no application for my setup, but I think I can modify it to fit.
Curtis

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post #9 of (permalink) Old 03-13-2000, 03:55 PM
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Re: Stopping oil blow-by


I saw the same thing on the Jeep board and I plan to give it a try.

post #10 of (permalink) Old 03-13-2000, 04:02 PM
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Re: Stopping oil blow-by

Any idea who or where the (pictured) filter comes from?
_______________________________________________

Must have hit the maximum number of threads, I am unable to reply in thread order. (This is a reply to the following post on the filter.)
GeeAea: Thanks for the location and product info.
As far as the crankcase under full vacuum, I don't think the PCV works under engine load, I think the vacuum is only at idle, but I am not sure. I will give it a whirl. Thanks again!
Curtis
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