davis303

I have a 1994 f150 with 250,000 mile on it.. and here lately its had pretty bad blowby ( i think ). I'm getting oil in my air filter box,and all over the top of the inner wheel well. Ive changed the pcv and check the vacuum line for it and check the compression. All cylinders check 170-150 And i cant find why its doing it. I know with that many miles its going to have some but i would think it wouldnt be that bad. And i notice while doing the compression, when i pulled the plugs out they had carbon on them. So i ran seafoam through the gas tank and pour a can through the vacuum line for the brake booster. Any help would be appreciated.

sdmartin65

Inline engines are prone to have blowby as they age, Jeep 4.0 will also do this. Only fix is new rings.
On my 95 4.9 I routed the breather line above the air box. It still has the blowby it just gets burned in combustion vs making a mess on the driveway. Google search for pics of a 96 F150 4.9 engine. The 96 is the only year the breather tube attaches to the air intake tube not to the bottom of the air box.

Chris_1

iTrader: (1)

If it's pumping oil up the breather hose, the PCV system still needs attention. That breather hose should have negative pressure (in a perfect world).

davis303

I check the vacuum line for the pcv to make sure it wasnt clogged up. And check it for cracks, and check it with the vehicle running and put my finger over the pcv valve and it seems to have a good vacuum.

Chris_1

iTrader: (1)

What about at the breather hose ? Is it still pulling vacuum all the way to there ?

sdmartin65

So you see what Ford did in 96, no more breather filter. Breather line goes into the air tube, so if a 96 gets blowby it just gets burnt off.

davis303

I haven't check the hose that goes to the breather yet. I see what you are talking about as far as the 96 models. But i would think either way how the hose was routed that it shouldnt have this much blow by.

sdmartin65

Here's a pic of my setup. Drilled a hole in air box above the filter, attached two 90's to it with a short piece of hose going up the air tube. No more oil in the driveway. When my 4.9 started getting blowby it had a lot of oil coming from the air box. With this fix I get zero oil in the air box. You can try to chase the reason for the blowby but trust me you won't find it. Well not without an engine tear down. I've had my intake off to change valve cover gasket and had no major build up that could cause the blowby.

One thing I should mention my truck still has blowby it just gets sucked into the intake and burnt off.

Matthew Burr

i got sick of oil collecting in the air filter of my carb so i disconnected the breather tube, still has the pcv valve to pull air out of the engine if it wants to, but depending on rpms of the engine increasing or decreasing the breather can have flow going in or out. not a huge deal what you do with it, but yeah sending it down the intake will keep your engine clean