[Davy]

Bill,

Be careful about mixing apples and oranges.

Oil pressure is that which insures the oil circulated through your engine is being delivered to the surfaces that need a constant supply of lubrication from your crankcase oil.

Bearings such as your crankshaft bearings, cam bearings, etc. have oil pushed to them via your engine’s oil pump. You can read that pressure directly from your dash. At normal highway cruise speeds you are likely to see 50 PSI on a warm engine, higher if the engine is cold. That oil pressure will not blow the cap from your oil fill tube.

You also have crankcase pressure. Your engine crankcase gets pressure from the oil heating up and from the slight blowby of the piston rings. But in order for the crankcase to build enough pressure to blow off the oil fill tube it has to be pretty high something under normal circumstances is not possible. The crankcase is vented. The excess pressure exits the crankcase via a breather tube which is about 3/4 to 1″ in diameter. That allows the crankcase to breathe freely.

If my coach exhibited the problem you describe I would start looking for an obstruction in the breather tube. The only other thing I could imagine blowing the cap off the filler tube is a set of broken rings such that on the compression stroke the compressed air in the cylinder is getting past the piston and is of such volume the breather cannot keep up with the compressed air produced and eventually the crankcase gets pressurized enough to blow off the cap.

All speculation so I would be very interested in what is found out. I really question a professional attributing the problem to excessive oil pressure or bad seals.

[Archived]

A leaky Tu-Flo air compressor can also cause excessive crankcase blow-by.

[Archived]

But then wouldn’t the pneumatic system be unable to build required pressure?

[Archived]

The air compressor,a valve,turbo,the breather on top of the valve cover,broke head bolt or a cracked liner will all cause it hoping for it is a minor problem.I seen a lot of the 12L series 60 crack a liner at around 130,000 miles

good luck

[Bob]

I don’t know Jon.

The only places where excessive crankcase pressure can come from are the S-60 cylinders, turbo, and Tu-Flo compressor. Each should be ruled out before spending on repairs. The Tu-Flo is an often overlooked point of failure. Detroit Diesel Allison Service Centers have tools and methods to check each of these items. The turbo needs to be checked at full load, the Tu-Flo requires full rpm and a disconnected outlet, and the cylinders can be leak down tested. I’m anxious to hear what the true cause is. Please keep us informed! 🙂

[Archived]

I can understand valve guides, engine cylinders, and air compressor cylinders being the source of high crankcase pressure or pressure being restricted due to a blockage of their vent tube in non EGR engines. I can’t understand how the turbo can be the cause. Can someone explain how the problem can be turbo related?

[Jim]

I’m not buying it, very curious to hear the results. Reason being it was just just serviced. I’m not a Detroit fan but I won’t go there.

I could be comparing apples to oranges but I blew the cap off my fill tube climbing the North side of Baker with a C13 Cat. Got to the pull out on top and lost 2 gallons of oil and I was able to tape and wire the cap back on and nurse it into Vegas Cat.

They replaced the tube and put a new cap on it and ran the engine 60k miles and the guy I sold it to has put another 40k on it with no problems,

There is pressure in the fill tube, how much I don’t know but after his service the mechanic could of stripped the plug when tightening. If so the lost oil could of greased the belts enough to come off while driving.

Wouldn’t that be wonderfull if that’s it.

Good luck.

Later

bv

[Archived]

I got a suggestion fron one of the top engine guys at Prevost. He said it sounds like a problem with the Crankcase Ventilation System separator. He didn’t have a diagram for the Detroit engine but he sent me one from the Volvo and indicated where to find it on the Detroit. Thanks for suggestions I will post the results.

[Archived]

I sent suggestion to Atlantic, hope to hear tomorrow.

From Admin – Here’s the link about Crankcase Ventilation they sent Bill to make sure Atlantic checks it out:

CVV

[Davy]

Bill, I don’t think the pre-egr engines had a separater.

The turbo can pressurize the crankcase thru a faulty Tu-Flo air compressor, which could be an explanation for the OP’s loss of power, and possibly thru the turbo’s return oil line.

[Greg]

I can understand valve guides, engine cylinders, and
air compressor cylinders being the source of high crankcase pressure or
pressure being restricted due to a blockage of their vent tube in non
EGR engines. I can’t understand how the turbo can be the cause. Can
someone explain how the problem can be turbo related?

If the seal on the compressor side of the turbo leaks it allows the boost pressure that leaks pass the seal to enter the crankcase through the the turbo oil drain back tube. That results in excess blow by.

Ken

[Archived]

Bill initially stated he lost all power.

That is consistent with a blown seal on the turbo with pressure from the turbo directed into the crankcase. Sounds like Ken is on the right track.

I still cannot get my head wrapped around how the compressor can pressurize the crankcase without losing the ability to pressurize the pneumatic system.

[Ronald]

I can’t see a turbo seal being the problem. It is as high volume, low pressure (30 psi max) source. If it has a seal leaking so bad to significantly increase crankcase pressure the engine performance would suffer. A seal leaking that bad would also likely leak into the turbo from pressurized oil line. That would result in visible smoke from the exhaust.

[Dale]

They need to remove the turbo fresh air outlet tube to check for oil. The compressor may be pumping air but allowing pressurized intake manifold air into the crankcase. S60 techs often recommend removing the compressor’s intake manifold line, plugging it at the manifold, and permanently connecting the compressor input to the air cleaner.

[Archived]

David, my CAT powered coach was plumbed as you describe; into the air filter supply line. Why would the compressor supply line even be connected to the pressure side of the turbo? That air is hot and there’s no since in taking boost pressure, even if it’s only a little bit.

The air compressor, like the engine, can increase crankcase pressure if it has leaking cyclinders. How much it can increase the pressure I don’t know. It can leak and supply air to the coach, although it will supply the air slower than a new or newer compressor. Only thing for sure. If the compressor has excessively worn cyclinders or leaking rings there will be excessive oil being supplied to the dryer.