Interesting noise from the caravan

Hi everyone. My 94 grand caravan is making a strange noise. 120k
miles. This is a new noise for me. It's a groaning noise, like a hum
or vibration. When it happens, it hums for maybe 3 seconds, then
stops. It's related to braking, although the brakes feel great. ABS
is working fine, no warning lights. When I stop at a light, there's a
50/50 chance that this noise will happen. I can feel the vibration in
the brake pedal, but the vibration doesn't affect braking. It seems
to happen more often at low speeds, but doesn't seem speed or rpm
related. It has happened for no apparent reason while sitting at a
light before, not moving. I can't find anything else wrong with the
car. I suspect that it's vacuum related, maybe with the power brake
booster, but there's no change in braking effort, so I'm at a loss.
Any ideas?

brian

 

It's likely an ABS malfunction, you need to get it in and have it checked
out.

--Geoff

 

You finally described what I'd been hearing in my 96 Voyager LE.

Recently I had a master cylinder failure and had it replaced and asked
them to look at this noise. Shop said it was the ABS pump that was
going, causing the noise but it was not compromising the performace of
the ABS system. They said pump was $700 so unless I didn't want to pay
for the pump until it goes, I should leave it.

Don't know it this is right or not, but the brakes seem to work ok.

 

It's the pump on the Abs brakes.
Mine, on a 93 Voyager le did that for 5 years and 90,000 miles before it
finally quit but even then I wasn't sure that was what caused it to quit at
175000 miles.

 

And what did it cost to replace?

 

So how did it die? Did you just get no abs and an abs light, but
braking still worked, or did the brakes fail?

brian

 

That pump has been running all along, and you are just now hearing it. It's
an electrically driven hydraulic brake booster, not vacuum. You should
particularly hear it when you first start the car up.

Now, why are you just noticing it after 120k miles? That's the question.

 

Um, nope. You don't hear it running when you start up.

I don't have 120K miles. only 88K and it's only done this for the past
few months.