Guys , got back late Sunday night froma trip to michigan and back...roughly 1900 miles round trip, pulling a 8800lb traile rthe return leg.

truck ran great all the way up, no real issues at all.......checked all fluilds and filled them before leaving.

however, on teh way home( with the trailer) she began to have issues!

Bottom of the truck is covered with oil from frame rail to frame rail and from teh rear of the bell housing back to the rear axle... tranny is still full, PS fluid all accounted for... engine oil low by about half a quart. No sign as of a leak on teh rear of the block, or on the bell housing. While looking for a leak, I noticed alot of exhaust smoke coming from the blow-by tube while idleing...
could this be where the oil is coming from? its a light coating all over the bottom of the truck, like some one sprayed it with a palnt-mister filled with oil...

The rear wheel seal I replaced a few months ago went out again... gonna have to redo it and the rear brakes.....

Speedo and Odometer both quite a few hundred miles from home, but I think the wires being covered in oil may have soemthign to do with that.

The oil pressure gauge started dropping off to nothing while under load, btu if I took my foot off the throttle, it came back up..idiot light never came on, and cracking the ol line at the filter while runnign showed it definitly had pressure!!!!!

It started leaking a little bit of coolant to the rear of where the thermostat housing is located, I thought it was the head gasket , but it quit on its own afte ra few hours.. hasnt started again and no cross contamination in the oil or loss of coolant...gonna watch that closely...

But over all I have to say the old truck did GREAT!!!! fueled in Atchinson KS and not again untill Springfield Mo,23 gal , then again near the gary Indiana exit, etc etc. Figuring very roughly that we got an average of somewhere aroudn 17-19mpg.....

 

Yes the blow-by tube will cause a mist all over the underneath of your truck. At first I was thinking that you may have blown the seal in your vacuum pump, that will cause massive blow-by as well. But with the oil preassure dropping off I am not so sure of this. I would plumb in a preassure guage to the top of the oil filter housing and get an accurate reading from there. It may somehow be a head gasket also. I just hope it's nothing major.

 

I am not sure I actually WAS loosign oil pressure is the thing.. idiot light never came on, engine never acted different,
and why would it come back up at lower rpm?

 

I think what he is saying is put a mechanical gauge in there because the stock one sucks.

-Steve

 

Yes get a mechanical. The Suburban that we have has a electronic oil pressure gauge. It shows no pressure at idle but give it a little gas and it perks up. Nothing wrong with anything except the sending unit. Your trucks sounds like the same thing except opposite. Hopefully this helps you out!

Jon

 

I am not as concerned about the oil pressure( I am sure it is just the gauge ) as I am about the oil all over the underside of the truck.
Need to figure that out and repair it asap.
Any other ideas? I am thinking timb is on the right track with the vacuum pump and blow-by unless someone has another thought.

 

Also check to make sure your vacuum system is tight. A leak in the system will make the vacuum pump pump a bunch of air into the timing cover.

It's normal to see blowby from the breather tube after a hard pull.

 

I am getting ready to pull my vacuum pump possibly this week because of the blow-by issue. I have a lot of blow-by but without the oil residue. Cummins northwest tells me that they do not have a rebuild kit for the 1st gens, but I am sure that I can pick up the parts from the local bearing supply. I will take pics and let you know what it takes to rebuild.

 

on the rear wheel seal, be sure the breather tube isnt plugged up. i just figured out from this board why i kept ruining the wheel seals i had on my old chevy i got rid of 2 years ago. i wish i had joined this back then. it would have saved me alot of money

brett

 

This place can save you a lot of money yes. But, it can cost you a lot of money as well.

 

Timb, that would be great...THANKS!!!