oil in exhaust

[77FordTruckMan]

My nephew just bought a 76 f-150 with a 390 and it has an oil leak. As far as we can tell, oil is leaking into the exhaust manifold on the one side. Does anyone know what could cause this? How do we determine what could be causing it? Thank you

 

[LEB Ben]

Valve seals or bad rings. Check compression and that'll tell you if it's rings or not.

 

[G.O. Stang]

Oil in the exhaust is never good. As said earlier, it could be valve seals or rings. How many miles are on the engine? I'd say its probably time for a rebuild.

 

[Blue Goose]

Because I've had this happen to me.....twice, I ask the following with explanation:

Is the truck equipped with an automatic transmission?

If so, is the transmission inexplicably losing transmission fluid?

If so, is the engine smoking out of the exhaust pipe?

Pull the vacuum line off of the modulator valve on the side of the transmission and see if there is a presence of oil. There shouldn't be any, that valve could be bad.

 

[77FordTruckMan]

Thanks for the tips guys, it has a manual trans. I did a compression test and its getting 120 in each ecylinder which seems good to me, if it was the valve seals or piston rings it would have bad compression right? We might pull the manifold off to see if we can see anything.

 

[77FordTruckMan]

Odometer says 42,000

 

[LEB Ben]

That's really not bad at all...I was hoping you were going to say one was significantly less than the others or that they were all down around 50-60psi. Valve seals, unless totally trashed typically clear up after running a few minutes, but you're saying you're constantly blowing blue smoke???

 

[smokey]

Throw a vacuum gauge on it. You can check a bunch of things with a vacuum gauge just read the directions they comes with the gauge it describe how to read the gauge.

 

[m78]

Is it leaking Into or Onto the manifold. Just asking cause the i&o are right next to each other.

 

[77FordTruckMan]

I think it blows smoke the whole time but I'm not sure. The oil is leaking into the exhuast manifold or at least that's how it looks, it is coming out at the end of the manifold where it goes into the pipe. It is running down the pipe and the whole thing is covored in oil which would explain the smoke. I guess it could be coming from somewhere else and just appear to be coming out the manifold.

 

[midnite]

i personally would check the valve guides and seals 1st off and then go from there. as for milage that could be 142k or 242k or who knows and depending on how its been driven and how badly its been neglected this could be the reason that the previous owner decided to sell it. i have a 79 250 that runs great but was neglected horribly and the previous owners just basically didnt seem to care as long as it ran when they needed it to. just some food for thought as they say.

 

[77FordTruckMan]

We would really like to avoid pulling the head off if possible. The truck had been sitting for 3 years before he bought it.

 

[dustybumpers]

I'm confused here. Is the oil on the outside, or inside of the exhaust manifold?

If outside, replace the valve cover gaskets.

 

[midnite]

since youre trying to avoid head removal if possible and the truck sat for 3 yrs. im going to assume that the oil,and filter have been changed upon purchase of the truck and say try some seafoam easy to use and seems to work great. just simply start the truck and drive or idle until the engine gets good and warm,disconnect your vac line to your brake booster, open the can pull the tab,put the disconnected line into the can but just barely and let the engine suck about 1/3 to 1/2 of the can up and then shut the engine off for about 10 mins or so. while waiting for the 10 mins reconnect your vac line to your booster and after the 10 mins start the truck(it will smoke like crazy) and drive the crap outta the thing. the smoke is all the crud being burned off of the valves and piston tops. drive hard til the huge smoke cloud disappears and then drive home. you can also dump some into the carb and it will help clean that,add to oil and its supposed to clean the rings as well. ive used it quite a few time and have always seen results. a can is about 6-10 bucks at walmart or your local parts store.

 

[LEB Ben]

I'm a little confused as well...there's actual liquid oil leaking on/from the manifold??? I thought we were just talking blue smoke. If there's actual oil run off, retorque you valve cover bolts and/or replace valve cover gasket. The rear of the intake manifold can leak significantly as well, but the leak would only appear on exhaust components if you still have the factory Y pipe or if you routed across to one side.