oily fluid leaking from somewhere

[knightowl77]

The other morning I backed my Av out of the driveway and noticed about 6 different oily spots on the ground where it had been.
I took the truck to a garage and put it on the rack. The oily fluid starts on the left front frame just behind the front tire and runs all the way back. The fuel tank is just covered with the stuff that is continually dripping. Neither I or the mechanic can find the source of the leak. It is kind of a clean light oily substance. By the amount of dripping I'd guess that I have lost almost a pint of fluid from somewhere, but brakes, power steering, engine oil and transmission fluid levels are all fine. The thing is out of warranty or I would take it to the dealer.
I'm not the brightest guy but I am stumped. Anybody got any ideas?

 

[Blueruck]

Knight - sounds similar to a problem I had - we thought it was the power steering put some dye in and it wasn't the problem - discovered the cap on the front diff was loose and leaking - fluid coated the bottom of the AV.

 

[colek]

Could you have hit/run over something (container, garbage, etc) ?
It is still dripping/leaking?
Just noticed that you have 4WD... so, what Blueruck said.

 

[boatnfool]

I agree with the front diff. Mine came from the factory with a faulty vent tube...leaked all over. There was a TSB or recal (I think) on this so I would talk to the service department at Chevy and ask if this is still covered.

 

[knightowl77]

I'm pretty sure I didn't run over something just from the pattern. Its a very small wet stain at the front of the frame getting wider and wider all the way to the back.

I didn't see any fluid around the front diff cover, but I will definitely check it again thanks!

 

[motrctyman]

Very well could be the front axle leaking.....GM still hasn't changed the design....

The vent actualy threads into the axle housing. On the inside is a "hood" that is supposed to shroud the vent tube from direct hits of oil. It does this because it will spin on the tube inlet acting like an umbrella. Problem is that it can actually get spun/stuck upside down.......now it is a funnel!

The PI fix is to take it off, drill a 1/8" hole across both flats at the bottom of the shroud and stick a cotter key in it. This will weight it down so that it won't rotate into the upside down position.

 

[knightowl77]

I agree with the front diff. Mine came from the factory with a faulty vent tube...leaked all over. There was a TSB or recal (I think) on this so I would talk to the service department at Chevy and ask if this is still covered.

I went to the Fed site and couldn't find anything at all on a front differential leak for the Av. DOes anyone know if there is an actual TSB that I could quote to the dealer. Still looken and another question.
If it was this vent tube thing on the front differential, where does it come out? Wouldn't I see oil on the diff itself?

 

[motrctyman]

I agree with the front diff. Mine came from the factory with a faulty vent tube...leaked all over. There was a TSB or recal (I think) on this so I would talk to the service department at Chevy and ask if this is still covered.

I went to the Fed site and couldn't find anything at all on a front differential leak for the Av. DOes anyone know if there is an actual TSB that I could quote to the dealer. Still looken and another question.
If it was this vent tube thing on the front differential, where does it come out? Wouldn't I see oil on the diff itself?

Actually, I don't know if it was an actual TSB or not. I think it was a PI (Preliminary Information). There are thousands of them that basically document problems/solutions but would never be put into print due to "legal" issues. If the Service Manager calls TAC they can read it to him..... Actually, if you can wait until tomorrow, I can pull it up at work and see if I can paste it in here. I'm surprised that the Service Manager or at least the shop foreman isn't aware of it....

One easy way to tell. Trace the hose from th e vent to the end and see if it is wet. Or better yet, pull the hose from the vent itself. It should be bone dry.

 

[draven366]

I discovered I have the same problem with a leak -- it seems to be worse if the Av is parked on an incline (facing upward).

I did a visual inspection underneath the left front, and there's blowback on the shock, and areas around it. I also noticed that there is a point to the left of the front diff where it bolts together, and that seam is wet as well. (Sorry, I'm not mechanically-inclined enough to be more specific!)

Does this sound like the vent tube issue, or something else? I always like to be knowledgeable when I call the service department, especially since this is a known problem.

(By way of comparison, when I brought my Av in a few months ago because the rear was leaking, the service dept. told me it was cracked and I had to put a claim in with my insurance...so I would like to let them know I know it's a known problem.) ; )

-- Draven

 

[kwinsor]

There is a large plastic plug that threads into the front diff on the drivers side. It's 2 or 3 inches in diameter. In the middle of this plug is the breather hose. It goes up into the engine compartment and is held in place right below the fuse box.

Mine had stripped threads and would fall out completely. It looked like a blown axle seal with oil everywhere.

If you have troble finding it first look on the passenger side of the differential. There will be something that looks like a small motor attached to the side of the diff. The plug you are looking for will be on the opposite side of this motor. Looks like its made to mount this motor on either side.

kw

 

[FSUGUY]

I agree with the front diff. Mine came from the factory with a faulty vent tube...leaked all over. There was a TSB or recal (I think) on this so I would talk to the service department at Chevy and ask if this is still covered.

just had this fixed today as well......resealed front vent.

 

[DaveP28]

I'm having a similar issue with a mystery leak. The fluid is oil based and greenish.  Any ideas? It's not trans. or motor oil. Seams to be the middle of the truck. It's the green that's throwing me.

 

[sperry]

His year model wasn't stated, so, unless it's a model-year specific problem, maybe this will help. Is from an 02 look-up.

Not a bulletin, but a repair instruction:

Front Axle Lubricant Leak Diagnosis

Front axle lubricant leaks can occur at the following locations:

    * Axle shaft oil seals
    * Differential carrier assembly mating surface
    * Drain plug
    * Fill plug
    * Inner axle tube assembly to differential carrier assembly mating surface
    * Pinion yoke oil seal
    * Vent tube

Determining the Cause

While most front axle leaks may be easy to find, determining the cause may not be. A thorough inspection of the area around the leak may assist in determining the cause of the leak.

Oil Seals

Lubricant leaks from a oil seal may be caused by any of the following:

    * An improperly installed seal
    * A distorted seal
    * A worn seal
    * A worn shaft
    * A brittle seal lip
    * A hardened seal lip

To determine the actual cause of the leak, clean the area around the leak. Observe the area of the leak and determine the if the seal or another component is causing the leak. A worn seal surface will cause a leak at the sealing lip while a misaligned seal or a seal installed into a housing with an excessive bore will cause the seal to leak at the outside surface of the seal. Hardened or cracked seal lips usually indicate the axle is operating beyond the normal temperature limits for the axle. A seal whose sealing surface has been nicked or cut may indicate that the shaft has a rough, burred, or gouged surface and will need to be inspected before the seal can be replaced.

Sealing Surfaces

Front axles components are assembled using specific sealers. A leak at a surface sealed with sealant is usually caused by a poor fit of the components but can also be caused by the use of the wrong sealant. When correcting a sealant leak, inspect each component for distortion and for nicks or gouges that may prohibit the sealant from sealing properly and when re-assembling the component, use the proper sealant.

Differential Carrier Assembly

Lubricant leaks at the differential carrier assembly can occur at the following locations:

    * Drain Plug
    * Fill Plug
    * Vent tube

Drain and fill plug leaks are usually caused by a loose plug. A vent tube leak can be cause by a loose fitting vent hose or by a vent tube assembly whose interior shield is stuck in the upside down position. Inspect the vent plug's interior shield for unrestricted movement, repair or replace the plug as necessary. Drain or fill plug leaks can be repaired by either tightening the plug or by using an approved sealer on the threads on the plug.

Document ID# 700713​