Symptoms of a bad ABS pump?

[cshields]

Hi there! This is my first time posting to this forum, but I have relied on it in the past to trouble shoot problems with my X5, so many thanks to those of you who unknowingly helped me in the past.

I have a 2004 3.0L X5 and am having a problem with the brakes. When I brake firmly I'm getting a momentary dull grinding noise that I can feel in the pedal. It happens at speeds as low as 25mph. If I brake gently all is well. This problem appeared yesterday for the first time, but is the latest problem in a week of problems.

Here's the background: last week I was in southern california. The car was due for new front pads and rotors. Took it to our beloved, trusted mechanic who has serviced it for years. He replaced the pads and rotors. After he took it off the lift the auto leveling suspension was misbehaving but not giving a fault code. He recalibrated it, but it still wouldn't level. After the car sat for 1.5 hours it leveled itself and seemed to be fine.

I drove to northern california the next morning. On the drive we noticed the ABS kicked in a couple of times when it ordinarily wouldn't. The suspension started to act up again, and was sitting low on the passenger front corner.

I took it to a mechanic in northern california. They found a loose bolt in the front passenger side lower control arm and tightened it. This seems to have fixed the suspension leveling issue, but the following day the grinding noise while braking popped up. I took it back to the mechanic, who test drove it and said it was the ABS going off. Mind you, this is not the rhythmic pulsing you typically feel when the ABS kicks in. This is the sort of dull grinding that makes you wince when you hear it because it sounds like a lot of money draining out of your bank account. The mechanic thinks it may be the ABS pump but wants to do some more testing before replacing that part.

There are no warning lights on the dash, and no codes in the computer to indicate a problem.

So...what are the symptoms of a bad ABS pump? These problems are driving me crazy...I welcome any and all input!

[upallnight]

If you have warning lights on the dash you have trouble codes. A simple OBD II scanner will not be able to scan for the codes, you need a BMW scanner to get these codes.

[TerminatorX5]

i don't think yo got a pump issue... the problem is directly related to the brake job you got done, as you did not have issues prior to the brake job... as you have noticed a loose bolt affected the suspension...

there is a possibility that the either the rotors or the pads are not seated correctly and backfeeding into the pump which in turn "activates" the ABS module which tries to "dry" the rotors/pads by applying quick braking... another possibility, is a pinched hose...


lift the car up, pull the wheels off, pull the brakes off and reinstall them... well... before that, do a visual on the something obvious, like a kinked hose, or a screw stuck between the rotor and a pad...


welcome to the forum... how about some pictures?

[cshields]

Thanks for your suggestions! They make perfect sense to me. I passed them along to the mechanic, but he still seems convinced the problem has something to do with the pump. The car still isn't giving any fault codes or warning lights. He says the onboard diagnostic they use on test drives is showing everything is normal, even when the grinding sound is occurring.

At this point I think I need to find another mechanic to do a second opinion.

I'll post back once I have more info.

EDIT 3/16/15: What a long, strange trip it's been! After I wrote the above post I took the X5 to several shops and a dealer as the ABS and air suspension problems worsened and no one was able to figure out the problem. Fortunately I live near a Dinan service center, and left the car with them for several weeks last summer...yes, the problem was so deep down the electronics rabbit hole that even Dinan had a hard time diagnosing it. Eventually they decided it was "likely" to be the air suspension control module causing the problems with both the ABS and suspension. I was hesitant to spend the $$$ to replace the control module without being certain it was the problem, so I asked them to recode the module, which they did. This fixed the problem for about six weeks, after which all the problems returned.

Dinan then installed a new control module, coded it to the car and said it was fixed- the suspension was leveling properly and there were no ABS issues. When I went to pick the car up after hours the left rear was sagging. I left it there and went back in the morning to talk to the master technician and service manager. They scanned the car and didn't get any fault codes. Ultimately we decided to recode the whole car, not just the suspension module. SUCCESS!

I'm happy to report that it's been a little over six months now and there haven't been any suspension or ABS issues. The problem was this: the suspension control unit is part of a computer area network. When the suspension control was flaking out it was sending out bad information to other control units on the network, primarily the ABS control unit. Clearing fault codes wasn't enough to entirely clear out the bad information, but completely recoding the car did clear it.