318 Burning Oil

[Stone]

Hello all, I have a 318 CID motor in my W150 off-road truck. The motor runs great but it is eating up a ton of oil. There is blue smoke/black smoke coming from the tail pipe when the truck is cold and first started; however after the engine has been run and warmed up the smoke and cloud are no longer present.
The motor is old and had been sitting for a while before i owned it so i'm not shocked by this development. However I am wondering what is causing the leak and burning of the oil. I have narrowed it down to the Valve system or the rings, how can i tell the difference between the two problems, if at all? The spark plugs are clean and are not fouled or oily at all, there is no lope of miss while the motor is running, and aside from eating fuel (and now oil) the motor has been great.
I would like to be pretty sure what the problem is before i go tearing around in my motor and cause more headache, and cost.
Any other clues or insights would be very helpful

[Al]

How about an engine compression test. It will tell you something about the condition of the rings. Try it dry first and then wet and you'll know.

[Stone]

Wont the compression test also be affected by a possible vacuum leak though? Meaning that if there is a leak the test might come back low when there isn't a fault in the rings. And thank you for the idea, I never thought of running a compression check to test the rings for leaks, ill try that in the morning.

[tan top]

could  check that oil is not being sucked into the intake ports , ( can sometimes  be a problem on B & RB motors with valley pan seal
 not sure on the set up on 318

compression test will check the sealing ability of the combustion chamber ! ,   ie  bore . ring ware !!  valve seal , head gasket seal !   ,    more time consuming but a better idea would be a leak down test !! fill each cylinder inturn with compressed air while at TDC  ,  not how much pressure escapes over a given amount of seconds /minute  in each cylinder !! listen for air escaping at
exhaust = ex valve
top of carb = intake valve

oil filler cap or dipstick = rings /bore ** this is where you would be looking **  if checks out ok !!  worn guides /stem seals 


bubbles in coolent =  headgasket  ,  could be a crack or warped head , but you would know all about this !!

[Stone]

Thanks for the second test idea. I know the head gaskets are in good shape cause the oil and coolant aren't mixing, and there motor isn't knocking or smacking while running. Idk about the valley pan effect on my engine, it is a 1987 318 so im not sure that would be an issue, but it is an idea to look into. What is a decent time for the air to escape during a leak down test?

[tan top]

http://en.wikipedia.org/wiki/Leak-down_tester

you don't have to buy the tester , i made my own  well , just gutted an old spark plug & welded an air line fitting to it & then used an old air pressure regulator off one of my old satas (paint gun) , i only leave each cylinder under pressure for a minute or 2

[Stone]

Ok I can do that to make a new tester. And the compression test came back clean: #1 Cylinder- 120+, #3- 120+, #5-120 dead-on, #7-119 for the left bank. The right back was #2-115, #4-115, #6-113, #8-125+. All of the heads were within 15psi of one another so i figure its not the rings or valves. So possibly the intake manifold pan....?

[flyinlow]

I would suspect the valve seals are bad. The smoking on start up is a classic sign. You may get a puff of light blue smoke as you pull away from a traffic light after you have idled for awhile. The umbrella seals get hard after time and letting the engine sit for along time then putting it back into service can finish off whats left of them. Worn rings will show up more as blue smoke under along hard acceleration.
The compression is OK. for an older engine. You can burn a quart of oil in 500 miles with bad seals and with todays clean burning oil not foul the plugs. Combine this with an external leak and you will use alot of oil.
Seals are not hard to replace on a 318. An afternoons work and about $100 in parts and tools. They can be replaced with the engine in the truck.

You would need an aircompressor. hose with the fitting to pump air into the cyclinders and a screw type valve spring compressor.
Parts: valve stem seals, valve cover gaskets.

Remove valve covers
Remove the rocker shafts
Remove the sparkplugs

[flyinlow]

pump air into the cylinder and keep it preasurised. this will keep the valves in place
Use the valve spring compressor to take the load off the keepers and remove the keepers/retainer /spring
You should see the seal now ,replace with the new ones.
install the spring/retainer/keepers and lossen the spring compressor, watch your fingers and wear safety glasses.  Repeat the last four steps 15 more times.
moving the air line to each cylinder and pair of valves

Replace rockershafts/valve covers and sparkplugs

[Stone]

Replacing the valve umbrella seals isn't hard but wouldn't the compression test show that they were the problem? I will prolly replace the seals anyways i just wanted to hopefully pin exactly where the leak was. And should i replace all the valve seals or just the intake seals? I figure i should do them all since i am in the motor.

[flyinlow]

Make sure you have stoped all the external leaks first.

No compression test wet or dry will pin point bad valve seals. The wet vs dry gives an indication of piston ring condition. A big improvement in the wet readings over the dry readings indicate worn rings. If the rings are ok that leaves valve guide wear/worn seals. The valves are sealing the combustion chamber preasure ok from your test results. The seals are loose on the valve stems or laying in pieces inside the valve springs. Valve seal condition does not effect the compression readings.

Did lots of these at a Plymouth dealership in the late 70's . Common problem. I am not saying that your valve guides are not worn also. Never did just the intake valves, so I dont know how much doing just them will help. 

[Stone]

Cool thanks for the info. The wet compression test values were comparable to the dry ones so I'm ok in that department until i rebuild the motor next summer. And i suppose doing the valve guides at the same time as the umbrella seals wont be too much to budget for, especially since i have access to almost all the tools i need to do the job. As for the external leaks they are all sealed, so there is no oil leaking out of the bottom or sides of the motor, it is all leaking for the inside being burnt. Just a question of curiosity what is a good compression for a stock 318; higher than 125...130?

[firefighter3931]

From what you're describing the valve seals are the problem. 

Those can be replaced in the engine bay with the heads on the motor. 



Ron

[Stone]

so new development the breather is kicking a large amount of oil into the air filter unit. I have no doubt that the valves are a problem but what besides over filling causes the breather unit to kick large amounts of oil into the air cleaner element?

[flyinlow]

Check for proper PCV valve operation. Clean or replace the breather.

Some oil on the air filter near the breather pipe as the filter nears the end of its life is normal for an older engine.  Not dripping wet however.

[Stone]

there is a slight pool building up and on the air filter there is a black cloud that is oil. There is a great deal of oil building up within the air intake.