Oil Blow Back

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Aug 15, 2005 | 06:51 AM

STACK86

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From: Salem, VA

Oil Blow Back

I have a 1986 F-150 with 302 (EFI) that is blowing oil back thru the breather into the Air Box. I have checked the obvious (PCV, replaced Breather Cap) and the condition still exists.

Anyone else have this problem? Any suggestions appreciated.

Thanks,
STACK

Aug 16, 2005 | 12:34 AM

Old-F100-Driver

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From: Chula Vista, CA

You either have too much oil in the engine or one or more broken rings or the rings are just worn out, if the pvc valve is ok-check the pvc hose and connection points for blockage-, remove the oil cap and put you hand over it to see if you have a vacumn or pressure/vacumn. A vacumn would indicate the pvc is working ok, pressure possible bad rings also look at the plugs for obvious oil burning.

Aug 16, 2005 | 01:27 AM

fmc400

MSEE

Joined: Apr 2004

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From: Austin, TX

I'd put a new PCV valve and a new breather filter on it; they're pretty cheap. Next make sure your PCV hoses are routed correctly and your oil filler cap isn't plugged up...I believe you can soak it in kerosene if it's full of sludge.

If that doesn't work, I'd say your rings are worn out. Does it burn any oil? My dad's old '79 F-150 with a 302 threw oil up into the air cleaner due to worn rings.

Aug 16, 2005 | 07:08 AM

STACK86

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From: Salem, VA

Oil Blow Back

I changed the PCV last night and checked the hoses. Changed the Breather Cap last week but still had oil collecting in the air cleaner. I will watch it for a week or so and if the problem still exists then I gues it is a ring problem even though the engine only has 116K miles and has had the oil changed regularly during it's life.

Thanks,
STACK

Aug 16, 2005 | 08:58 AM

Old-F100-Driver

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From: Chula Vista, CA

Your next step should be a compression check using a guage, one cylinder at a time, all cylinders should be close to the same and fairly close to the specs in the book for your engine. Any low (if all) reading cylinders should point to the rings. Bad valve can also give you a low reading but your not likely to get oil blowing out the breather. If you have oil leaking out the front or rear seals, this can also be a sign of bad rings.

Aug 16, 2005 | 02:58 PM

dbuck50

Tuned

Joined: Jun 2003

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how is the engine running? I had bad blowback on mine and drove it many miles that way until I put new rings in...Mine had about 100K when it happened...but I don't know how it was treated for most of its life.

BTW, check the #8 cylinder first...thats where all the PCV gases vent into and often cause that piston/rings many problems. Ford fixed it in later years. I rerouted mine from the end of the intake to the center of it.

Aug 16, 2005 | 03:40 PM

STACK86

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From: Salem, VA

Oil Blow Back

Thanks, I didn't think you would have ring issues with only 100K on the engine but when I checked the plug on number 4 (below PCV) it was covered in oil.
I guess that is the problem.