I have a 460 that began burning 1 qt to 300 miles. Problem started suddenly on road trip. Leak down test show good compression. Still runs great, no leaks. Anyone know where the oil is going or how to fix it. Engine has 90,000. 91 f-350. Can this be bad valve seals ? Could it be a whole in the intake manifold gasket ? Local ford shop doesn't seem to know where to look.

 

Greg, I am fighting the same battle as you are. I have an 82 F-250 4x4 with the 400M engine which I bought this summer. It had 85,000 original miles on it, it now has 90,000 on it. The miles are documented with paper work. Plus I got it from the original owner. Any way it uses 2 quarts to 300 miles, with no signs of where its going. Does your truck smoke any? My truck smoked on start up only which seemed like valve stem seals or guides. I have done a compression check it had 150 to 160 lbs. in all cylinders. I used the vacuum gauge test to check the guides, which also showed good steady vacuum.I replaced the stem seals and it did nothing to help. It only stopped the smoking on start up. I have no serious leaks, no smoke at the tailpipe,We have followed in another vehicle to verify this, no fouled plugs, this is driving me nuts. I have also wondered if the intake gasket is bad and letting it draw oil from the lifter valley, or the vacuum test is not a reliable way to check the guides. I thought it may have some stuck oil rings as it had sat mostly for the last 8 years. Did 2 Rislone treatments maybe helped some. Thats why I'm thinking about the intake gasket, the 400M uses a big metal pan type intake gasket which could be rusted some from where it sat so long with the moisture that could have collected in the motor while setting. The motor runs fine also. No problems what so ever. Hunting season is over so my Son and I are going to get after it again. We have just been feeding it oil as needed. Keep us posted as to what you find. I'll post what I find. Good luck! I know this doesn't help you any, but just sharing my experience with the same problem you have.

 

Thanks Dave,
Can't seem to get the mechanics to believe that it could bea hole in the intake manifold gasket
Did you replace the valve seals ??
I hear that is another possibility.

Greg

 

Greg, Yes I changed the valve stem seals, I guess I just called them the stem seals in my post. All it solved was my smoking on a cold start, which it just puffed smoke for a second and quit. I would think at the rate I'm using oil my truck should be bellowing smoke, but it doesn't smoke at all. Does your truck smoke any? We have followed it down the road ,had my Son stomp it front a dead stop and hold it down till he hit about 70 mph, no smoke. Then tried him driving a steady speed about 40 mph then stomp it up to about 60 mph, nothing. A little black smoke from the carb.The valve guides will let the engine smoke also, but the only way I know to check them without taking the engine down is with a vacuum guage, A steady needle and good vacuum is supposed to mean the valve guides are good. If the needle bounces around a lot the guides are supposed to bad. I have a feeling my Son and I are going to have to tear into the motor. I want to try and save this motor because it runs perfect and its quiet and has very decent miles for its age.

 

Thanks Dave,
Mine does not smoke. Possibly a tiny bit on cold start but not to obvious.

Any thoughts on the intake manifold gasket possibility ??

Good luck with yours...........Greg

 

You might try looking for the smoke at night with another vehicle. It is much easier to see. Have you let the truck idle for awhile and then rev it? Sometimes it will blow a good cloud after idling a few minutes. I am as curiouse as you are as to the cause...

 

Greg, Sorry I have not been on here for a while. Do you know if the 460 uses the type of intake gasket I mentioned the 400M uses? I'm still wondering about it. On mine there is no fiber material at all, just a stamped metal pan, even where the intake and heads meet. Thats why I think it could possibly be rusted a little right where the gasket go from the lifter valley to the ports in the heads. The way this truck sat it could have had a lot of moisture build up in this area. Tearing it apart will reveal this I guess. Of course its been like fall all winter so far here in Southern Indiana, now its cold as all get out, that just makes you want to feed it oil for now !!

 

Oil can get out of an any engine in only 2 ways- 1) leak to exterior which is usualy obvious by virtue of oil on the ground &/or onthe underside of the vehicle. 2)leak internaly, in which case oil laeks passed the valve seals & guides &/or passed the rings & out the tailpipe thus giving the inside of the tailpipe a black coating. There is one exception to these rules, that being the PCV valve. If it hangs open, intake vacuum will cause a negative press. in the crankcase. Because oil is partially vapor & also tiny droplets it will get sucked thru the PCV system & into the cylinders & burned, altho inefficiently. Cylinder leak down testing,"when done correctly is the most effective way to check the rings. GOOD LUCK

 

vanman, .I have established without a doubt that my PCV system is working properly. I have no leaks that amount to anything. The only smoking I had was on cold start up and on deceleration, which I cured with new valve stem seals. The only way that I know how to check the valve guides without disassembly is with a vacuum guage which read 18 lbs with a steady needle. I do have a sooty looking tailpipe. I have no fouled plugs. I don't have a leak down testing apparatus. I only have a compression gauge, which showed good compression. Why couldn't an internal intake leak draw oil from the lifter valley? I would think the intake pulse would be plenty strong enough to pull oil from around the intake gasket if the seal is broken between the head and intake, in my case possible rusted metal gasket. How much better would the leak down test diagnose possible ring problems compared to the compression test? I am the first to admit I'm grabbing at straws now. Thanks.