Engine/Transmission (1994 - 1998) Very Strange Blow By situation...Rings??

[pwerwagn]

Here is the deal:

My truck uses no oil driving around town normally. I dont do a whole lot of freeway driving. I had never really made this connection but here are the symptoms:



Anything over 75 mph, empty, it uses about a gallon or so every 100 miles. It makes a royal mess of the tailgate, everything. Just a mess.

Right at 70mph, it will use about 2 quarts in 500 miles (found this out after a recent empty road trip).



Under 70mph empty, it uses none. Ive tried driving in 4th at like 60 (same rpm as 5th at 75+) and it doesnt do it then either. Only 70-75+mph, empty, in 5th.



The weird part: If I put anything behind it and load it, it goes away. I tried driving 90mph with the camper and boat for about 10 miles, expecting to have to clean the boat thouroghly, and none. Maybe a few specks on the trailer but thats it.

Even with just the boat (3500lbs or so), It pretty much goes away.

Yet empty, its horrible.



I had a vaccuum leak once, but found it after a lot of searching. There is a slight haze of smoke out the breather at idle, but you can only see it in sunlight.



With the increased load, the egts go up about 150* or so (even more with the camper on). Im curious if that is just enough heat to allow the pistons to expand enough seal better than when cooler?

I have not yet done a compression test, just making sure there isnt something im missing here.

FWIW, the motor has been pretty hot (EGT wise) quite a few times. 1800* or so, if not more.

It has around 180,000 miles on it.



Thanks for any insight,

-Jeff

 

[ALehman]

My buddy has the same truck with about the same miles on it and it uses oil like that. Start the truck and take the fill cap off and sit it on and see how much pressure is comming out. Then rev the truck slowly and constantly and see if the pressure increases. Thats a good sign of rings. After rebuilding my engine and knowing that my rings were seated, mine did not change in rpm and I had not white gas come from my fill tube like my buddy.

 

[pwerwagn]

I'll go out and try that. I have seen another truck that had bad rings and it had a problem of blowing the dipstick out.

I once tried to leave the dipstick out a little to try to relive pressure, but that just made a royal mess under the hood!!!



I'll let you know what it does with the fill cap.



-Jeff

 

[pwerwagn]

Ok, tried it. If I pull the cap off, it doesnt seem to have any noticeable pressure there. I held my hand over it and rev'd it, and didnt notice any difference.

If I set the cap on it there isnt enough pressure to lift it even at 3,000 rpm.



There is some white smoke that emmits from it though. Not drastic, but some.



Have any of you noticed when you pull the oil cap off there is a lot of noise coming from it??? Almost like a pinging noise...



--Jeff

 

[dpuckett]

I think that pinging noise is just gear noise that gets muffled with the cap on.



Daniel

 

[pwerwagn]

Yeah, thats what I figured the noise was. Just seemed louder than I remember it. Maybe becuase I was being paranoid...

 

[Graphic man]

do a leak down test on it, and see what you get.



a leakage test is not a compression test, 2 different things



a leakage test will tell you a % of leakage you have in the motor.



either it is leaking down pass the rings or up through the valve seats.











Scott

 

[pwerwagn]

Im familiar with a leakdown test. Thats what we do with outboard motors to determine whether or not they are in need of a rebuild.



I dont have the equipment to do a leakdown or a comp test on a cummins though.

How large of guage would I need for a comp test on my truck?

 

[Graphic man]

Im familiar with a leakdown test. Thats what we do with outboard motors to determine whether or not they are in need of a rebuild.



I dont have the equipment to do a leakdown or a comp test on a cummins though.

How large of guage would I need for a comp test on my truck?

you can get the kits on E-bay. for around $20-30. 00..... search "cummins" and you will find them, you may need the right fitting to fit your truck but it is a cheap start



480-500psi

i think most of the kits will read up to 800psi



Scott

 

[Vaughn MacKenzie]

There's been a few times where TDR members have had blowby & oil usage problems, and it ended up being the turbo. If the seal is degrading boost pressure blows past it and into the crankcase via the oil return tube. But that would make more sense if oil usage occurred when working the engine hard.

 

[pwerwagn]

Not the turbo, Its had 3 or 4 turbos on it with this same situation. The turbo on it right now has about 3,000 miles on it.



So why do you guys figure it goes away under load? Is it also possible that my factory breather is slightly plugged and creating just enough crankcase pressure that the rings aren't sealing good, and then causing more blowby?



--Jeff

 

[Schlickenmeyer]

I believe it is not working it. My mechanic was very pleased to see the paint burned off the manifold when she was newer, said they have to be worked hard to break in properly, and most never do. When I run empty, which I do a lot, I wind it out, especially 5th getting on the freeway when she's up to temp. If I have not done this recently, the cloud of crap is amazing. then there is just rings seating and such, again, has to be worked. I pull 10k 5-6 times a year, and it loves that. 110k and uses NO oil.

 

[Moparsean]

Have you experimented with a different oil. . like a synthetic? Its possible if it hasn't been worked hard at times in its life, that the rings are stuck in the groove on the piston. Possibly not,but its something to try before you pull apart the motor. You can try a couple of quarts of ATF or marvels oil in the crankcase ot free them up (don't leave it in too long it will lower oil psi some). Also make sure the engine is not running cold (open thermostat). I've found that to cause some excessive oil consuption. BTW I have 433,000 on mine (never apart) and it uses no oil,I use amsoil 15w-40. I am a diesel mechanic by trade and am a firm believer in synthetic oil. If you have to go in for surgery use a synthetic after the break-in.

 

[pwerwagn]

I dunno about its life before I owned it, but I've worked the crap out of it. I didnt notice this oil situation right when I got it though. It seemed to get bad about the beginning of June (this year). Before that, there was some oil (under same circumstances) but I think it may be worsening.

For about a year, I was hauling tires a few times a week. Usually 50 miles or so and rarely below 20,000lbs. I also tow the enclosed trailer (~7,000lbs) usually once a week or so. So it does get worked some. Even empty I run it pretty hard. I drive about 60-70 miles per day, and usually put my foot in it a few times a week.



I was actually contemplating adding a quart or two of marvel to the oil when it gets low next time, and then run the crap out of it. I think I will do that if the leakdown and comp test come back bad. I may hook on to the gooseneck and load up a truck or soemthing and haul it around for a few days.



Thanks for all the suggestions guys. At least I got a bunch of things to try!!!



--Jeff

 

[pwerwagn]

Im also wondering if I have a cracked head or head gasket problem? could that pressurize the crankcase without having a problem with water/oil mixing?? Im not loosing any water at all...



--Jeff

 

[ALehman]

There's been a few times where TDR members have had blowby & oil usage problems, and it ended up being the turbo. If the seal is degrading boost pressure blows past it and into the crankcase via the oil return tube. But that would make more sense if oil usage occurred when working the engine hard.

What do you do to check if the seals are bad in the turbo?

 

[Bob V]

I would also check the vent tube, is it pinched? Did it start after you R&R'ed the starter?

 

[pwerwagn]

You know, you bring up a good point. It wasnt all that long ago that I did starter contacts. I'll have to check on that one...



--Jeff

 

[LOtero]

im jumping on board this one wagn. . im pretty interested to see what you find out. hey gimme a call when you get a chance

 

[Champane Flight]

Leaning towards turbo bearing seals

Check exhaust for oil residue. . If it is, sooner or later it will come into the light, it wil throttle up by itself...