Blow-by?
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Senior User
Joined: Nov 2000
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From: Calgary
Blow-by?
Hello.. I have a 1990 F-150 4x4 302 5spd, I recently performed an oil change at accidentaly put a bit too much oil in, but only about half a litre at the most. I thought nothing of it, until about 150 miles later when I noticed large amounts of oil leaking out from my air filter box. I oppened the box and noticed that oil had been coming out of the breather and totally saturated my air filter. Since then I drained all the oil and put the correct amount in and the same thing is still happening but to a lesser extent. For a test I pulled the breather out of the air-box so it was just hanging in the engine compartment and while driving there was an amazing amount of smoke coming out from under the hood (from the breather tube) normally this smoke would just go right into the intake and be burned, but i am not sure if that amount of smoke is normally expelled from the breather and am wondering if there is a bigger problem somewhere?
Any help would be greatly appreciated.
Jason
Any help would be greatly appreciated.
Jason
Postmaster
Joined: Jul 1999
Posts: 3,172
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Blow-by?
How many miles on your truck ? Check that the entire Pcv system isnt clogged . Sometimes the passages inside the valve cover become clogged & pressure builds up . If you havent done so in the last 20K miles or so replace the Pcv valve & its filter . Its possible the extra oil you added caused the problem & the residual amount that made its way to the Pcv is where the smoke is coming from .
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Joined: Nov 2000
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Blow-by?
I'm wondering if your PCV valve is stuck.. take it out and see if it rattles.. That's my guess.
Hope it helps.
LeRoy Wolff, original owner of
1984 Ford F150
300 six 3 speed with overdrive
optional dual rusted out fenders
truck's nick name "Old Red"
Hope it helps.
LeRoy Wolff, original owner of
1984 Ford F150
300 six 3 speed with overdrive
optional dual rusted out fenders
truck's nick name "Old Red"
Posting Guru
Joined: Sep 2000
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From: Linwood, N.J. USA!
Blow-by?
Yes, check the PCV valve. It could very well be gummed due to the extra amount of oil. It could also be the other, the dreaded thought of blow-by. I had an 86'f-150 that I wound up putting a piece of heater hose off of the valve cover vent and zip-tied it to the frame rail just to keep the smoke and oil out of the air breather assembly. This was not a permanent fix but it did keep the filter and carb clean. Engine still ran good. Good luck.
Jakegypsum // Ford fleet, soup to nuts.
Jakegypsum // Ford fleet, soup to nuts.
Thread Starter
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Senior User
Joined: Nov 2000
Posts: 243
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From: Calgary
Blow-by?
I checked my PCV valve today and it rattled so i don't believed it was to badly glogged (as i just replaced it a little more than a month ago) however I am going to replace it tomorrow and maybe get some results. Also if it was blow-by, then I would assume that I would see smoke from my exhaust, should I not?
Thanks for all the help
Thanks for all the help
Senior User
Joined: Mar 2000
Posts: 337
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Blow-by?
hate to break it to you, but it could be your piston rings, my truck did the same thing, i was told up on this site it could be the rings, and thats what was making oil come out my breather.
John Floyd
South Mills,NC
'86 F150 2wd 300 6
Crane Cam 260/272
stock manifolds, w/ staight pipe
John Floyd
South Mills,NC
'86 F150 2wd 300 6
Crane Cam 260/272
stock manifolds, w/ staight pipe
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Joined: Mar 2000
Posts: 337
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Blow-by?
also, you may not neccesarly see smoke from the exhaust, mine never smoked.
John Floyd
South Mills,NC
'86 F150 2wd 300 6
Crane Cam 260/272
stock manifolds, w/ staight pipe
John Floyd
South Mills,NC
'86 F150 2wd 300 6
Crane Cam 260/272
stock manifolds, w/ staight pipe
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Freshman User
Joined: May 2000
Posts: 38
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From: Channahon Il.
Blow-by?
I agree with Motorcraftsman, My 92 302 has the same blow by and oil in the air box problem and it didn't smoke. But after doing a compression check and #8 cyl. only had 20 lbs. I ordered a new long block. That will be here next week. Good Luck !!!
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Thread Starter
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Senior User
Joined: Nov 2000
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From: Calgary
Blow-by?
Is it hard to perform a compression test by myself? I have a compression tester and are there any tips that I need to follow? Also what should the correct compression be for my engine? Thanks
