Weird brake issues - The sage continues. HELP!
07-23-2010, 01:26 AM
#16
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Firstly, mine is a C2.
Secondly, I know pumping the foot on a used master is bad news but it shouldn't be an issue on a new master unless you are an idiot and push it through the firewall and root the seals. (no seal rooting jokes please!)
I would hae thought that disconecting and disabling the ABS unit would be enough but if not, I guess we try to bypass it.
This problem was not there prior to master being changed however it did do the same thing with two second hand master cylinders that i tried so to me I am assuming it is not the master.
We were wondering about the booster.
How do we check that?
Thanks all....
Secondly, I know pumping the foot on a used master is bad news but it shouldn't be an issue on a new master unless you are an idiot and push it through the firewall and root the seals. (no seal rooting jokes please!)
I would hae thought that disconecting and disabling the ABS unit would be enough but if not, I guess we try to bypass it.
This problem was not there prior to master being changed however it did do the same thing with two second hand master cylinders that i tried so to me I am assuming it is not the master.
We were wondering about the booster.
How do we check that?
Thanks all....
07-23-2010, 01:36 AM
#17
Nordschleife Master
Its not an issue on a new cylinder .
If the abs unit is messed up internally , unplugging the electronics from it will not fix it .
"We were wondering about the booster."
I guess you have boost because the brakes grab at some point .
A bad booster causes a "heavy" pedal . You step down and the pedal takes more leg to do the same work . The pedal does not go floppy with a dead vacuum assist .
A test for a vacuum booster is , does it leak ?
Will it hold a vacuum ?
If the abs unit is messed up internally , unplugging the electronics from it will not fix it .
"We were wondering about the booster."
I guess you have boost because the brakes grab at some point .
A bad booster causes a "heavy" pedal . You step down and the pedal takes more leg to do the same work . The pedal does not go floppy with a dead vacuum assist .
A test for a vacuum booster is , does it leak ?
Will it hold a vacuum ?
07-23-2010, 03:55 AM
#18
Nordschleife Master
What's the pedal like with engine and all electrics off? If it's normal but then goes bad when the engine is on, that would indicate to me that the problem is an electronic issue.
07-28-2010, 02:16 AM
#20
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Pedal sux **** al the time. Ignition on or off.
The guys are still regoing through it all methodically as such.
Rebleed several times with Motive Power Bleeder, cycling with hammer,pst. (Still not sure what that is but was recommended previously in the post and the mechanics knew what they were talking about. Assume it's some diagnostics test)
If still no good (where we are at currently) block master outlet to test master again.
Then if pedal goes rock hard, bypass ABS pump to see if that fixes it. If it comes good, I buy an ABS unit, if not, we're screwed as i have no idea what else it could be!
The guys are still regoing through it all methodically as such.
Rebleed several times with Motive Power Bleeder, cycling with hammer,pst. (Still not sure what that is but was recommended previously in the post and the mechanics knew what they were talking about. Assume it's some diagnostics test)
If still no good (where we are at currently) block master outlet to test master again.
Then if pedal goes rock hard, bypass ABS pump to see if that fixes it. If it comes good, I buy an ABS unit, if not, we're screwed as i have no idea what else it could be!
08-02-2010, 06:33 AM
#22
Nordschleife Master
Since the pedal is bad all the time my guess is that the piston in the master cylinder is stuck part way. I would put the pressure bleeder on and see what happens without opening any bleed valves. If the piston is stuck, hopefully it will force it back to its normal resting position and you'll see the fluid level in the reservoir drop.