Engine/Transmission (1994 - 1998) I think I found my blowby problem

[Lonestar]

I have been trying to diagose a blowby problem since I owned the truck (98 12valve) The truck had a full blowby test right before I bought it, and it passed with flying colors. I still have lots of steam coming out of the breather tube on the bottom of the truck.



Yesterday, I was thinking about that, and I killed the truck and immediately looked under at the tube. As the turbo was spinning with the truck off, the steam gradually decreased at the same rate as the turbo quit spinning. So I'm guessing the problem is coming from the turbo seals? Several times before, I have revved the motor while in park to see if there was a change in the level of steam, and there appeared to be none. Today, I put the truck in drive, and had a buddy load up the boost while the truck was sitting in the driveway. As the boost built, the steam built as well.



SOOO, How do I fix this? Is this a bad problem? Do I have to buy a new turbo, or is it a simple fix?



Corey

 

[MMeier]

Are you sure it is "steam", and not just regular vapor/ smoke? If so, sounds more like a head gasket problem to me.

 

[Lonestar]

sorry about that, it isn't steam, it is regular vapor. I can understand how that could be a little misleading

 

[Lonestar]

TTT any ideas????

 

[QWaller]

Doesn't everyone's have more blowby on a loaded engine as cylinder pressures go up?

 

[CumminsPower98]

Blowby and oil consumption both go up as the boost goes up because of increased cylinder pressure. If you have bad turbo seals this would be directly related to more crankcase pressure as your boost pressure will leak past the compressor side and into the oil drain tube and then into the crankcase. It's normal to see a little smoke/vapor coming out so I wouldn't get too excited about it. Maybe have it tested again. I have gone through my turbo twice. First time I had a slight oil leak from the exhaust side at low mileage. The next time my shaft just seemed to have a little more play then I liked so did it again. I have 392k.

 

[Lonestar]

Ok, I understand a small amount of blowby is a normal thing on these trucks, My question is, AFTER the engine is killed, not turning, no cylinder pressure, only thing still moving is the turbo, I STILL have blowby. I have this blowby until the EXACT second the turbo stops spinning. 30 or so seconds after the motor quit. The amount of vapor I get, is enough to see from the cab when sitting at an intersection, a little excessive from any of the other 4 12valves I have owned.



Back to my original question, is there a way to fix this, or does it require a new turbo?



Sorry for the confusing original post.



Corey

 

[Signal73]

probably just coincidence. no way the turbo has enough pressure after shutdown to push vapor out the tube.

If that were the case you would be making 0 boost going down the road and you would have blown out every seal in your engine.

 

[DCreed]

try relieving the cooling system pressure(remove cap when cold) and see if that stops it. sounds like your first impression of "steam" may be accurate, if so the HG is probably shot.

 

[TyThompson]

If there is a problem with the turbo, this is a whole lot cheaper than a new turbo: eBay Motors: Dodge Cummins HX35 Turbo Rebuild Kit Holset (item 220167482300 end time Nov-09-07 08:36:00 PST)

 

[MCummings]

It's not going to be the turbo. If you really want to make sure it isn't, then pull off teh intake bvoot drivers side closest to the motor, then start your truck and see what the blowby does.



Unless you have ALOT of modifications a Cummins motor will not make boost at idle. (Just don't tell my truck, the ECM thinks it has 9Lbs at idle, LOL)



Do that and se what you find.



My guess is the time it takes for the blowby to stop coming out of the tube is a coincidence with how long the turbo takes to whine down.



Blowvby increases with more RPM, more boost, and more timing...



A motor that has lost tension on the piston rings will have considerable amount of blowby as well. This usually happens when the motor is overheated.



Also if the motor gets "dusted" (dirt in teh intake), it will have alot of blowby from rings and cylinder walls who aren't "buddy/buddy" anymore







Merrick

 

[RDyson]

Also, these engines put up 45-80# of oil pressure, from what i've read. I know there is a restrictor in the oil feed line to the turbo, but I would think that if you had bad turbo seals the oil would be getting into the compressor side of your intake piping. Plus at idle, you really don't have any boost to push air into the turbo drain line to cause the vent that you are seeing.

I've had my air inlet piping off and my turbo only spins for about 5-10 seconds after shutdown.



Randy

 

[Lonestar]

Well, off to the drawing boards... ... AGAIN



I will try the couple of things mentioned above to see if that makes any difference. I know I will have to live with some blowby, but choking on the vapor at an intersection with the window down is getting old.



Thanks again for the help, and I'll post back what I find this afternoon.



Corey

 

[MCummings]

Also, Rotella oil gives off teh most vapors, and the first 500 miles or so after an oil change, it's normal to have an excess of vapors...



Merrick

 

[CumminsDoofus]

This might be a long shot but go out and plug your vacuum inlet with a short hose and bolt or finger and see if it slows the "Appearance" of blow by.



The vac pump discharges the air into the crankcase,... . Here's a vid of the pump turning slower then the truck idles the only reason the glove doesn't blow off is because it fill's up and then blows out the end that the drill is stuck in. (normally blocked by the P/S pump drive

 

[Mactruck]

Do you have an Exhaust Brake???



I have a friend that went through the same thing only to find out it was some sort of valve having to do with his Pac-brake.



Just an idea... .

 

[Vaughn MacKenzie]

Lonestar, an idea to rule out the turbo seals is to remove the rubber section of the oil return hose from the turbo and put a long piece of heater hose on it. Run into a bucket or back into the oil fill then run the engine to see how much vapor comes out of it. I don't know how much oil volume runs through the turbo but using a bucket might be better so the end of the hose is lower than the turbo, otherwise it might get occluded with a slug of oil.

 

[Lonestar]

I will try to remove the turbo oil drain line and run it into a bucket. No Exhaust brake. Today, I pulled the coolant cap off, to relieve pressure, no change in vapor. I'll keep pecking away till I find it