engine blow by

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Dec 16, 2010 | 09:28 PM

reinmb

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engine blow by

I have a 1986 f150 with a efi 302. I'm not much of a mechanic but love to jack with this old truck. I have oil blowing from the engine fill cap into the air filter housing. I believe this is called blow-by. The truck seams to run ok, starts right up, no blue or black smoke but dies when I pull up to a stop(only when its warmed up) When its cold it doesnt die. It seems to build a lot of pressure in the valve cover. If I hold my finger over the hole in the engine fill cap air (oil mist) blows out from underneith of the cap. What should I do to troubleshoot this? Thanks for your help.

Dec 16, 2010 | 10:00 PM

ctubutis

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From: Denver Metro Area, CO

Welcome to FTE.

A certain amount of blow-by is expected but will ge worse with age (especially in not-well-
maintained engines).

First, make sure your PCV system is working correctly - there should be a rubber hose
going from the air cleaner to the rear passenger-side valve cover, and the PCV valve that
goes into the oil fill cap and generally attaches to a bigger vacuum port at the base of the
carb area.

Outside of that, it's most likely a worn-out engine - worn piston rings, valve guides,
broken piston, cracked head or block, etc.

Do a compression test and post the results.

Hey, BTW, fill out the rest of your profile (User CP -> stuff in LH column) so we can see
where you're from, OK? Thanks.

Dec 17, 2010 | 05:38 PM

reinmb

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i was affraid of that. This motor hasnt been taken care of. My grandpa bought this truck new and drove it about 3/4 of a mile at a time. From one farm to the other. When he passed on, I got the truck and had the body redone. I have driven it off and on for the past 10 years and it now has 80,000 miles. I have taken care of it, but you know how old farmers are. This truck didnt even get washed unless it rained. Thanks for the advise. I will do as you suggested. I already have way more money in this truck than it is worth but cant seem to let it die.

Dec 17, 2010 | 05:43 PM

Sw1tchfoot

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From: Missouri

It probably has 180 or 280k miles.

Dec 17, 2010 | 05:51 PM

reinmb

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84,541 to be exact. this truck was just never driven. When my grandpa bought it new in 86 it replaced his 65 f250 which to this day has less than 100,000 actual miles more like 65,000. the miles dont add up very fast at 3/4 of a mile at a time.

Dec 17, 2010 | 05:57 PM

Rogue_Wulff

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From: Lost

I'd suspect the PCV valve and/or hose is plugged with crud. Cleaning that out, and maybe a new breather filter (not to be comnfused with the main air filter) should help quite a bit.

Personally, I'd almost kill for a 1965 model pickup with less than 100K actual miles......

Dec 17, 2010 | 05:59 PM

ctubutis

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From: Denver Metro Area, CO

Quote:

Originally Posted by reinmb

I already have way more money in this truck than it is worth but cant seem to let it die.

I and a lot of guys here are in the same situation so don't feel bad, I think we all
do it just cuz it's fun. I spent about $4,000 rebuilding the 400 in my rusted-out
'81 F350, I now have a jewel in a turd.