2005 Suburban ABS pump seems to run while driving, not when stopped

[bhcbman]

I've got a 2005 Suburban (160,000+ miles) and I'm hearing a running pump noise that I think is the ABS pump, but I'm not sure? I have a Service Stability message in the DIC that comes on when I put the truck in drive and hit about 5mph. The noise is present whether the ABS fuse is pulled or not. I have no dash lights unless the fuse is pulled. I've also replaced my front hubs (Timken 515036) in the past 2000 miles or so and this behavior hasn't changed. As my speed increases I hear a PPPHHTTT (blow air out of your mouth between your lips so they vibrate against each other fast) noise that seems to be coming from under my drivers seat. As I slow down the noise changes to something slower like ticka-ticka-ticka, and stops completely as the truck stops. I pull away and the cycle repeats. If it's the ABS pump shouldn't that not happen if the fuse is pulled? This truck also has Autoride but I've replaced the shocks with Bilstein 5100's, kept the height sensors connected and wired in resistors to simulate the electrical signals from the original shocks. The compressor pump by the rear axle looks like it's half corroded away so I don't think it can run, but maybe it is? The sound seems to be coming more from right under me though, but maybe that's an illusion. Any thoughts? Could pulling the EBCM and having it re-soldered be a cure? Thanks!

 

[Scottydoggs]

bad front axle? any vibration when on the gas?

 

[Doubeleive]

bad u-joint/s, bad differential, pinion bearing or something of that nature, jack up the rear end put it in drive and inspect or get under there and take a close look at everything. seems to me if for some really strange reason the abs pump was making noise it wouldn't matter if you were actually moving or not it would just matter if the key was on or not.

 

[bhcbman]

bad front axle? any vibration when on the gas?

No vibrations. Truck drives smooth and straight up to the fastest I've had it, about 75-80mph. The noise does not speed up or slow down with the truck's speed, its either the fast speed or switches to the slower ticka-ticka speed as I come to a stop. Sometimes while driving the fast speed noise will stop for awhile, but it will start back up in time.

Would it be safe to pull the power connector from the ABS pump (or is it connected to the EBCM?) under the truck and drive it like that to see if the sound goes away? Is that different than pulling the ABS fuse?

 

[bhcbman]

bad u-joint/s, bad differential, pinion bearing or something of that nature, jack up the rear end put it in drive and inspect or get under there and take a close look at everything. seems to me if for some really strange reason the abs pump was making noise it wouldn't matter if you were actually moving or not it would just matter if the key was on or not.

The sound does not go up and down in sync with speed; it really sounds like a pump running, and it can run at two different speeds. It isn't running when the truck is stopped. I've inspected everything underneath real well recently since I had to replace the fuel pump and dropped the tank, and I've also installed Z71 springs on the rear axle. The sound existed before the fuel pump was replaced, so that's not it.

 

[Doubeleive]

I would either have it put on a rack and inspected or jack it up and put it in gear and see if the noise source can be pinpointed these trucks can be real tricky with noises might sound like it is coming from under you but could be actually coming from somewhere completely different.

 

[Scottydoggs]

can you get a vid of the sound? might help some.

 

[bhcbman]

I would either have it put on a rack and inspected or jack it up and put it in gear and see if the noise source can be pinpointed these trucks can be real tricky with noises might sound like it is coming from under you but could be actually coming from somewhere completely different.

I could try to duplicate it that way if I could convince myself it's safe. I have plenty of jack stands. I'll only have myself to blame if it falls on me! I also should just get rid of the Autoride compressor since it's not needed, and eliminate that as a possibility. I've left it connected so it doesn't throw codes or light up dash lights. I hate dash lights and have worked hard to rid this truck of them with correct fixes. I think you have to pull some sort of fuse if you remove the compressor, need to search on that again...

 

[bhcbman]

can you get a vid of the sound? might help some.

Maybe take a chance with my cell phone, dunno. I used to listen to Pat "Motorweek" Goss' radio show and he talked about a tool he used called a "chassis ear" to figure out where sounds came from. It had multiple microphones and I think to pinpoint it I may need one in the front by the ABS pump and one out back by the compressor.

 

[Doubeleive]

I could try to duplicate it that way if I could convince myself it's safe. I have plenty of jack stands. I'll only have myself to blame if it falls on me! I also should just get rid of the Autoride compressor since it's not needed, and eliminate that as a possibility. I've left it connected so it doesn't throw codes or light up dash lights. I hate dash lights and have worked hard to rid this truck of them with correct fixes. I think you have to pull some sort of fuse if you remove the compressor, need to search on that again...

I've done it, if it is just in gear and idling it's not as scary as it seems, I did all that and got under the truck and listened and I was still wrong about the source of the noise though I was sure it was the transmission but it was actually the rear differential, but in your case it may be easier to find a pump type noise