Painted front hubs a no-no?
11-26-2012, 02:49 PM
#31
Rennlist Member
Thread Starter
Dr. Bob, IMo000, thank you for this info. I had not been aware that the colors had to match on the connector barrels, thought the connectors were one way only. I will put my attention more to the rear this evening.
Thomas
Thomas
11-26-2012, 02:51 PM
#32
Rennlist Member
Thread Starter
The symptoms you describe point to problems at the rear sensors. They aren't seeing the rear wheels moving on the lift, so no warning. When you drive, the controller sees the front wheels turning, and since it can't see the rears turning it sets the light.
In the barrel connectors there are three places to plug things in. One for pad sensor, one for wheel sensor, one no pins. Double check that you aren't connected to the no-pins hole, and verify with wire colors that you have the pad and wheel sensors in the correct spots. Trace wire colors to be sure. It's easy to make a mistake here. The wheel sensor impedance may be low enough to satisfy the pad sensor circuitry. But the pad sensors are too far from the toothed ring to read it...
Thoughts on terminology: hub has wheel studs pressed in. Carrier or upright has a wheel bearing pressed in. Stub axle holds them together.
In the barrel connectors there are three places to plug things in. One for pad sensor, one for wheel sensor, one no pins. Double check that you aren't connected to the no-pins hole, and verify with wire colors that you have the pad and wheel sensors in the correct spots. Trace wire colors to be sure. It's easy to make a mistake here. The wheel sensor impedance may be low enough to satisfy the pad sensor circuitry. But the pad sensors are too far from the toothed ring to read it...
Thoughts on terminology: hub has wheel studs pressed in. Carrier or upright has a wheel bearing pressed in. Stub axle holds them together.
Thomas
11-26-2012, 03:51 PM
#33
Team Owner
check the wire connections first,
then inspect the rear sensors.
then inspect the rear sensors.
11-26-2012, 11:24 PM
#34
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The sensors are magnetic, therefore tend to grab on to iron filings and other ferrous bits that ultimately interfere with their ability to read the flux change effected by the rotating gear. So cleaning the sensor tips is high on the list. They can be damaged if they are banged or bent during the pressing of the stub axle and bearing. They also have the wire dangling while they are off the car, so damage to that wire is always a possibility.
I previously mentioned the potential to get the plugs in the wrong holes only since I managed to do that myself. Pad wear sensor plug ended up in the blank no-pins hole in a barrel connector on one wheel last time I replaced pads. Traced back through all my original steps until I found the step that I did wrong.
I previously mentioned the potential to get the plugs in the wrong holes only since I managed to do that myself. Pad wear sensor plug ended up in the blank no-pins hole in a barrel connector on one wheel last time I replaced pads. Traced back through all my original steps until I found the step that I did wrong.
11-26-2012, 11:56 PM
#35
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John made a comment re the light coming on when the car moves (vs stationary??). My 87 S4 will have the light off for a while when moving but, after hitting a bump the light will come on. If I stop and switch the key off and then again on the light will be out until the next bump. Anybody got ideas regarding that?
11-27-2012, 11:28 AM
#36
Team Owner
BJBPE you issue sounds like a bad wire connection problem spots are under the hood on each fenderwell the barrel vonnectors may be damaged or crumbling,
Check for bad connections at the rear barrels by each rear wheel
What was the last thing you fixed
Check for bad connections at the rear barrels by each rear wheel
What was the last thing you fixed
11-27-2012, 11:05 PM
#37
Rennlist Member
Thread Starter
So now I am getting a little pissed at this. I have R&R the wheels at least 6 times today. Connectors, sensors all check out good. I am noticing spongy pedal though. When I drive it I hear a rear brake pad clicking sometimes. I also notice the rear pads are easy to remove each time I have had to during this troubleshooting. I would think I should have to retract them to remove them. The car stops good with what feels like the fronts doing it all. No fluid leaks but a slight rough spot which is felt in the pedal when pressing it. I just installed new rotors and pads on the rear. The drilled rotors came with pads that looked different from stock, they have been ground down on front and rear edges. I am starting to think I might have the wrong rotors as I type. I do not recall the pistons sticking out like they are either.
Any help is welcomed.
Thomas
Any help is welcomed.
Thomas
11-27-2012, 11:14 PM
#38
Team Owner
have you swapped out the rear bias valve?
its possible this valve is blocking the fluid as they do fail internally
IIRC there are rotor specs in the WSM for the year of your car ,
If your rear brakes are not working or you suspect this ,
then get the IR gun and go for a short ride with a few brake applications ,
then stop and check the rotors to see how hot they are getting,
if the rears are cool then you may have a plugged bias valve and or the MC may have damaged seals from going full stroke.
its possible this valve is blocking the fluid as they do fail internally
IIRC there are rotor specs in the WSM for the year of your car ,
If your rear brakes are not working or you suspect this ,
then get the IR gun and go for a short ride with a few brake applications ,
then stop and check the rotors to see how hot they are getting,
if the rears are cool then you may have a plugged bias valve and or the MC may have damaged seals from going full stroke.
11-27-2012, 11:33 PM
#39
Rennlist Member
Thread Starter
have you swapped out the rear bias valve?
its possible this valve is blocking the fluid as they do fail internally
IIRC there are rotor specs in the WSM for the year of your car ,
If your rear brakes are not working or you suspect this ,
then get the IR gun and go for a short ride with a few brake applications ,
then stop and check the rotors to see how hot they are getting,
if the rears are cool then you may have a plugged bias valve and or the MC may have damaged seals from going full stroke.
its possible this valve is blocking the fluid as they do fail internally
IIRC there are rotor specs in the WSM for the year of your car ,
If your rear brakes are not working or you suspect this ,
then get the IR gun and go for a short ride with a few brake applications ,
then stop and check the rotors to see how hot they are getting,
if the rears are cool then you may have a plugged bias valve and or the MC may have damaged seals from going full stroke.
Thomas
11-28-2012, 01:01 AM
#40
Team Owner
the bias valve shouldnt have anything to do with the ABS but it will effect the rear brakes working properly.
Lets get the brake system working properly first ,
NOTE you may also need to install a new MC
then move on to the ABS
Lets get the brake system working properly first ,
NOTE you may also need to install a new MC
then move on to the ABS
12-10-2012, 12:02 AM
#41
Rennlist Member
Thread Starter
Fixed the ABS, it was a bad connection inside the barrel connector in the wheel well on passenger front. The wire would loose connection when wiggled. HB4 was the reason we got it nailed down after several hours tracing wires. Thanks Bill and a big thank you to Stan and others for your input. ABS light stays OFF now.
Replaced rear bias valve and master cylinder also.
The end
Thomas
Replaced rear bias valve and master cylinder also.
The end
Thomas
12-10-2012, 02:15 AM
#42
Shades of troubleshooting steel mill controls in the 60's. These days it's the John Deere 318 up in Guemes and your sensors. That sure is one well maintained 928.
And the treat of getting to play in your shop. How 'bout them Seahawks!
And the treat of getting to play in your shop. How 'bout them Seahawks!
