Ford F250 suddenly eats oil

[Run]

1993 F250 I6 4.9L 170000 KMS This truck has had a hard life. It was always pulling heavy loads and constantly idling. Recently it developed an insatiable appetite for oil to the tune of 1/2 quart in 2 days. Its driven about 200~ KM in that time. There are no obvious leaks. Gaskets were changed a year ago and nothing drips to the ground.

I must confess I'm not too familiar with the inline 6 engines. Do these things have a PCV system? I know there is a breather hose that goes from the valve cover to the air box. The air filter with less than 20,000 KM looks awful. Something is very wrong here.
Old filter with the darker oily residue which lines up with breather hose.

Old and new side by side.

Holding up the old filter against a lamp.

 

[DoubleWasp]

PCV valve is on top of the valve cover toward the rear. It's a real pain to see because of the intake manifold.

Your engine might be drinking oil through its PCV system being clogged. Replace the PCV first.

Once that is done, carefully remove the oil cap while the engine is running and leave it set right in its hole. If the cap dances around from air coming up, you probably have a lot of blow-by.

 

[KD0AXS]

I had one that did that. Worn out rings were causing excessive blowby, sending oil out the breather tube. I put in new pistons and rings, honed the cylinders, new main and rod bearings, and a complete gasket set. Maybe spent $150 on everything. Still ran great 5 years later when I decided to get rid of it for my 2005 F-350.

Probably one of the easiest and cheapest engines there is to work on.

 

[demarpaint]

Originally Posted By: DoubleWasp
PCV valve is on top of the valve cover toward the rear. It's a real pain to see because of the intake manifold.

Your engine might be drinking oil through its PCV system being clogged. Replace the PCV first.

Once that is done, carefully remove the oil cap while the engine is running and leave it set right in its hole. If the cap dances around from air coming up, you probably have a lot of blow-by.



Good idea! A little under 106K miles, typically those engines go way longer than that. After checking for blow by I would also consider doing a compression check, if you pass the blow by test.

You could also have bad valve stem seals, but you're using a lot of oil for that.

 

[Run]

I took some time to check the truck carefully. I'm afraid the engine is a write off. The PCV valve was operating fine and the problem lies elsewhere. There is simply too much blow by happening. I didn't even bother with a compression test as that would only state the obvious. The truck is now in the shop.

 

[artificialist]

See if you can free stuck rings by putting seafoam or MMO down the spark plug holes.

However, if the rings are in extremely bad condition, no chemical can save your engine. Lucas oil additive might make it run a little bit better.

 

[Panzerman]

What kind and weight oil are you using? I would change oil and go with a heavier oil. Even a 15w40 oil and see what happens. I certainly would go dumping Sea Foam down plug holes-yet? Diesel oil is very robust and I think will really stop or greatly reduce your oil usage. It's cheap and easy.

 

[Run]

The trucks are all feed bulk 5w-30 from a local repair shop. I tested 20w-50 in this truck and nothing changed. I'm just waiting for the expert opinion before trying any chemical treatments.

 

[vssjim]

Make sure the PCV system is drawing in gases from crankcase 100% for sure first. If it is then working you can figure Piston/ring problem as the only way to get oil fumes in air filter is if PCV air intake hose you speak of is being over loaded and engine is pumping crankcase pressure out of air intake hose in air box.

 

[ironman_gq]

I'm going to suggest that stuck rings might be part of the problem. Warm up the engine, pull the spark plugs and dump a few ounces of seafoam or B12 into each of the cylinders. I like to let it sit for an hour or two, crank the engine for a few seconds before installing the plugs, then install the plugs and start it up. Expect a bunch of smoke, let it run and take it down the road running it hard. Repeat a couple of times and change the oil and see if it's better.

I've done this on lots of vehicles from a 78 Jeep, an old skidsteer that sat for 10 years and countless other small engines and vehicle engines. I've got a pretty good success rate as long as nothing else was wrong.