Brake servo problem(?) - Audi 100 1985
03-28-2006, 09:04 AM
#11
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Chris G. wrote:
> Hey Steve - thanks for the quick reply
It seems that there's a leak in
> the region of the rear-left caliper - oil mist on the inner-side of the
> tyre, a small drip-pool where the car's been parked up today. Doesn't seem
> like it should be a prob to sort, and cheaper in any case than replacing the
> pressure accumulator; every cloud has it's silver lining
IMO there's a second problem here.
That car should have two separated braking circuits (i.e. left front
operating together with right rear and left rear with right front).
Both systems are actuated via one master cylinder which also separates
the systems.
This should make sure, that even if one braking line blows, the other
should still be working so that you can still - although with higher
foot pressure - bring the car to a stop with only two brakes in operation.
If that car really lost it's brake completely there must be a leak
between circuit 1 and 2, because only in this case the pressure in the
second 'good' circuit could bleed away as well.
Most likely the seal in the master cylinder between the two circuits is
leaking. So you should check that too.
With the loss of one braking line such a car must never lose all its
braking power.
BTDT in a Ford.
Regards
Wolfgang
> Hey Steve - thanks for the quick reply
It seems that there's a leak in> the region of the rear-left caliper - oil mist on the inner-side of the
> tyre, a small drip-pool where the car's been parked up today. Doesn't seem
> like it should be a prob to sort, and cheaper in any case than replacing the
> pressure accumulator; every cloud has it's silver lining
IMO there's a second problem here.
That car should have two separated braking circuits (i.e. left front
operating together with right rear and left rear with right front).
Both systems are actuated via one master cylinder which also separates
the systems.
This should make sure, that even if one braking line blows, the other
should still be working so that you can still - although with higher
foot pressure - bring the car to a stop with only two brakes in operation.
If that car really lost it's brake completely there must be a leak
between circuit 1 and 2, because only in this case the pressure in the
second 'good' circuit could bleed away as well.
Most likely the seal in the master cylinder between the two circuits is
leaking. So you should check that too.
With the loss of one braking line such a car must never lose all its
braking power.
BTDT in a Ford.
Regards
Wolfgang
03-28-2006, 09:04 AM
#12
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Chris G. wrote:
> Hey Steve - thanks for the quick reply It seems that there's a leak in
> the region of the rear-left caliper - oil mist on the inner-side of the
> tyre, a small drip-pool where the car's been parked up today. Doesn't seem
> like it should be a prob to sort, and cheaper in any case than replacing the
> pressure accumulator; every cloud has it's silver lining
IMO there's a second problem here.
That car should have two separated braking circuits (i.e. left front
operating together with right rear and left rear with right front).
Both systems are actuated via one master cylinder which also separates
the systems.
This should make sure, that even if one braking line blows, the other
should still be working so that you can still - although with higher
foot pressure - bring the car to a stop with only two brakes in operation.
If that car really lost it's brake completely there must be a leak
between circuit 1 and 2, because only in this case the pressure in the
second 'good' circuit could bleed away as well.
Most likely the seal in the master cylinder between the two circuits is
leaking. So you should check that too.
With the loss of one braking line such a car must never lose all its
braking power.
BTDT in a Ford.
Regards
Wolfgang
> Hey Steve - thanks for the quick reply
It seems that there's a leak in> the region of the rear-left caliper - oil mist on the inner-side of the
> tyre, a small drip-pool where the car's been parked up today. Doesn't seem
> like it should be a prob to sort, and cheaper in any case than replacing the
> pressure accumulator; every cloud has it's silver lining
IMO there's a second problem here.
That car should have two separated braking circuits (i.e. left front
operating together with right rear and left rear with right front).
Both systems are actuated via one master cylinder which also separates
the systems.
This should make sure, that even if one braking line blows, the other
should still be working so that you can still - although with higher
foot pressure - bring the car to a stop with only two brakes in operation.
If that car really lost it's brake completely there must be a leak
between circuit 1 and 2, because only in this case the pressure in the
second 'good' circuit could bleed away as well.
Most likely the seal in the master cylinder between the two circuits is
leaking. So you should check that too.
With the loss of one braking line such a car must never lose all its
braking power.
BTDT in a Ford.
Regards
Wolfgang
03-28-2006, 09:04 AM
#13
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Chris G. wrote:
> Hey Steve - thanks for the quick reply It seems that there's a leak in
> the region of the rear-left caliper - oil mist on the inner-side of the
> tyre, a small drip-pool where the car's been parked up today. Doesn't seem
> like it should be a prob to sort, and cheaper in any case than replacing the
> pressure accumulator; every cloud has it's silver lining
IMO there's a second problem here.
That car should have two separated braking circuits (i.e. left front
operating together with right rear and left rear with right front).
Both systems are actuated via one master cylinder which also separates
the systems.
This should make sure, that even if one braking line blows, the other
should still be working so that you can still - although with higher
foot pressure - bring the car to a stop with only two brakes in operation.
If that car really lost it's brake completely there must be a leak
between circuit 1 and 2, because only in this case the pressure in the
second 'good' circuit could bleed away as well.
Most likely the seal in the master cylinder between the two circuits is
leaking. So you should check that too.
With the loss of one braking line such a car must never lose all its
braking power.
BTDT in a Ford.
Regards
Wolfgang
> Hey Steve - thanks for the quick reply
It seems that there's a leak in> the region of the rear-left caliper - oil mist on the inner-side of the
> tyre, a small drip-pool where the car's been parked up today. Doesn't seem
> like it should be a prob to sort, and cheaper in any case than replacing the
> pressure accumulator; every cloud has it's silver lining
IMO there's a second problem here.
That car should have two separated braking circuits (i.e. left front
operating together with right rear and left rear with right front).
Both systems are actuated via one master cylinder which also separates
the systems.
This should make sure, that even if one braking line blows, the other
should still be working so that you can still - although with higher
foot pressure - bring the car to a stop with only two brakes in operation.
If that car really lost it's brake completely there must be a leak
between circuit 1 and 2, because only in this case the pressure in the
second 'good' circuit could bleed away as well.
Most likely the seal in the master cylinder between the two circuits is
leaking. So you should check that too.
With the loss of one braking line such a car must never lose all its
braking power.
BTDT in a Ford.
Regards
Wolfgang
03-28-2006, 09:23 AM
#14
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Wolfgang,
If the loss of fluid was enough that the master was sucking air, then it may
have felt like a total failure of the brakes....maybe? I agree that there
may be problems with the master cylinder - both from what you note about the
dual diagonal brake circuits - and if the brake fluid was not changed
regularly (~ every 2 years or so), the portion of the cylinder bore that
never saw the piston seals may have developed some corrosion that could
damage the seals when the brake pedal was pressed to the floor. I would
make sure the brakes are really well bled after hose replacement, and then
hold the car on the brakes to see if the pedal creeps down. As brakes are
nothing to be trifled with...<insert standard disclaimers here>
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)
"Wolfgang Pawlinetz" <w.pawlinetz@a1.net> wrote in message
news:1143558183.457287@news...
> IMO there's a second problem here.
>
> That car should have two separated braking circuits (i.e. left front
> operating together with right rear and left rear with right front).
>
> Both systems are actuated via one master cylinder which also separates the
> systems.
>
> This should make sure, that even if one braking line blows, the other
> should still be working so that you can still - although with higher foot
> pressure - bring the car to a stop with only two brakes in operation.
>
> If that car really lost it's brake completely there must be a leak between
> circuit 1 and 2, because only in this case the pressure in the second
> 'good' circuit could bleed away as well.
>
> Most likely the seal in the master cylinder between the two circuits is
> leaking. So you should check that too.
>
> With the loss of one braking line such a car must never lose all its
> braking power.
>
> BTDT in a Ford.
>
> Regards
>
> Wolfgang
If the loss of fluid was enough that the master was sucking air, then it may
have felt like a total failure of the brakes....maybe? I agree that there
may be problems with the master cylinder - both from what you note about the
dual diagonal brake circuits - and if the brake fluid was not changed
regularly (~ every 2 years or so), the portion of the cylinder bore that
never saw the piston seals may have developed some corrosion that could
damage the seals when the brake pedal was pressed to the floor. I would
make sure the brakes are really well bled after hose replacement, and then
hold the car on the brakes to see if the pedal creeps down. As brakes are
nothing to be trifled with...<insert standard disclaimers here>
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)
"Wolfgang Pawlinetz" <w.pawlinetz@a1.net> wrote in message
news:1143558183.457287@news...
> IMO there's a second problem here.
>
> That car should have two separated braking circuits (i.e. left front
> operating together with right rear and left rear with right front).
>
> Both systems are actuated via one master cylinder which also separates the
> systems.
>
> This should make sure, that even if one braking line blows, the other
> should still be working so that you can still - although with higher foot
> pressure - bring the car to a stop with only two brakes in operation.
>
> If that car really lost it's brake completely there must be a leak between
> circuit 1 and 2, because only in this case the pressure in the second
> 'good' circuit could bleed away as well.
>
> Most likely the seal in the master cylinder between the two circuits is
> leaking. So you should check that too.
>
> With the loss of one braking line such a car must never lose all its
> braking power.
>
> BTDT in a Ford.
>
> Regards
>
> Wolfgang
03-28-2006, 09:23 AM
#15
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Wolfgang,
If the loss of fluid was enough that the master was sucking air, then it may
have felt like a total failure of the brakes....maybe? I agree that there
may be problems with the master cylinder - both from what you note about the
dual diagonal brake circuits - and if the brake fluid was not changed
regularly (~ every 2 years or so), the portion of the cylinder bore that
never saw the piston seals may have developed some corrosion that could
damage the seals when the brake pedal was pressed to the floor. I would
make sure the brakes are really well bled after hose replacement, and then
hold the car on the brakes to see if the pedal creeps down. As brakes are
nothing to be trifled with...<insert standard disclaimers here>
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)
"Wolfgang Pawlinetz" <w.pawlinetz@a1.net> wrote in message
news:1143558183.457287@news...
> IMO there's a second problem here.
>
> That car should have two separated braking circuits (i.e. left front
> operating together with right rear and left rear with right front).
>
> Both systems are actuated via one master cylinder which also separates the
> systems.
>
> This should make sure, that even if one braking line blows, the other
> should still be working so that you can still - although with higher foot
> pressure - bring the car to a stop with only two brakes in operation.
>
> If that car really lost it's brake completely there must be a leak between
> circuit 1 and 2, because only in this case the pressure in the second
> 'good' circuit could bleed away as well.
>
> Most likely the seal in the master cylinder between the two circuits is
> leaking. So you should check that too.
>
> With the loss of one braking line such a car must never lose all its
> braking power.
>
> BTDT in a Ford.
>
> Regards
>
> Wolfgang
If the loss of fluid was enough that the master was sucking air, then it may
have felt like a total failure of the brakes....maybe? I agree that there
may be problems with the master cylinder - both from what you note about the
dual diagonal brake circuits - and if the brake fluid was not changed
regularly (~ every 2 years or so), the portion of the cylinder bore that
never saw the piston seals may have developed some corrosion that could
damage the seals when the brake pedal was pressed to the floor. I would
make sure the brakes are really well bled after hose replacement, and then
hold the car on the brakes to see if the pedal creeps down. As brakes are
nothing to be trifled with...<insert standard disclaimers here>
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)
"Wolfgang Pawlinetz" <w.pawlinetz@a1.net> wrote in message
news:1143558183.457287@news...
> IMO there's a second problem here.
>
> That car should have two separated braking circuits (i.e. left front
> operating together with right rear and left rear with right front).
>
> Both systems are actuated via one master cylinder which also separates the
> systems.
>
> This should make sure, that even if one braking line blows, the other
> should still be working so that you can still - although with higher foot
> pressure - bring the car to a stop with only two brakes in operation.
>
> If that car really lost it's brake completely there must be a leak between
> circuit 1 and 2, because only in this case the pressure in the second
> 'good' circuit could bleed away as well.
>
> Most likely the seal in the master cylinder between the two circuits is
> leaking. So you should check that too.
>
> With the loss of one braking line such a car must never lose all its
> braking power.
>
> BTDT in a Ford.
>
> Regards
>
> Wolfgang
03-28-2006, 09:23 AM
#16
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Wolfgang,
If the loss of fluid was enough that the master was sucking air, then it may
have felt like a total failure of the brakes....maybe? I agree that there
may be problems with the master cylinder - both from what you note about the
dual diagonal brake circuits - and if the brake fluid was not changed
regularly (~ every 2 years or so), the portion of the cylinder bore that
never saw the piston seals may have developed some corrosion that could
damage the seals when the brake pedal was pressed to the floor. I would
make sure the brakes are really well bled after hose replacement, and then
hold the car on the brakes to see if the pedal creeps down. As brakes are
nothing to be trifled with...<insert standard disclaimers here>
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)
"Wolfgang Pawlinetz" <w.pawlinetz@a1.net> wrote in message
news:1143558183.457287@news...
> IMO there's a second problem here.
>
> That car should have two separated braking circuits (i.e. left front
> operating together with right rear and left rear with right front).
>
> Both systems are actuated via one master cylinder which also separates the
> systems.
>
> This should make sure, that even if one braking line blows, the other
> should still be working so that you can still - although with higher foot
> pressure - bring the car to a stop with only two brakes in operation.
>
> If that car really lost it's brake completely there must be a leak between
> circuit 1 and 2, because only in this case the pressure in the second
> 'good' circuit could bleed away as well.
>
> Most likely the seal in the master cylinder between the two circuits is
> leaking. So you should check that too.
>
> With the loss of one braking line such a car must never lose all its
> braking power.
>
> BTDT in a Ford.
>
> Regards
>
> Wolfgang
If the loss of fluid was enough that the master was sucking air, then it may
have felt like a total failure of the brakes....maybe? I agree that there
may be problems with the master cylinder - both from what you note about the
dual diagonal brake circuits - and if the brake fluid was not changed
regularly (~ every 2 years or so), the portion of the cylinder bore that
never saw the piston seals may have developed some corrosion that could
damage the seals when the brake pedal was pressed to the floor. I would
make sure the brakes are really well bled after hose replacement, and then
hold the car on the brakes to see if the pedal creeps down. As brakes are
nothing to be trifled with...<insert standard disclaimers here>
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)
"Wolfgang Pawlinetz" <w.pawlinetz@a1.net> wrote in message
news:1143558183.457287@news...
> IMO there's a second problem here.
>
> That car should have two separated braking circuits (i.e. left front
> operating together with right rear and left rear with right front).
>
> Both systems are actuated via one master cylinder which also separates the
> systems.
>
> This should make sure, that even if one braking line blows, the other
> should still be working so that you can still - although with higher foot
> pressure - bring the car to a stop with only two brakes in operation.
>
> If that car really lost it's brake completely there must be a leak between
> circuit 1 and 2, because only in this case the pressure in the second
> 'good' circuit could bleed away as well.
>
> Most likely the seal in the master cylinder between the two circuits is
> leaking. So you should check that too.
>
> With the loss of one braking line such a car must never lose all its
> braking power.
>
> BTDT in a Ford.
>
> Regards
>
> Wolfgang
03-28-2006, 09:51 AM
#17
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Steve Sears wrote:
> Wolfgang,
> If the loss of fluid was enough that the master was sucking air, then it may
> have felt like a total failure of the brakes....maybe?
Agreed
> I agree that there
> may be problems with the master cylinder - both from what you note about the
> dual diagonal brake circuits - and if the brake fluid was not changed
> regularly (~ every 2 years or so), the portion of the cylinder bore that
> never saw the piston seals may have developed some corrosion that could
> damage the seals when the brake pedal was pressed to the floor.
Yes both options are possible.
> I would
> make sure the brakes are really well bled after hose replacement, and then
> hold the car on the brakes to see if the pedal creeps down. As brakes are
> nothing to be trifled with...<insert standard disclaimers here>
Yep. I would just try to check if the circuits are still separated. That
would make Me nervous.
A simple check would be to bleed off the air in one circuit, leaving the
other one open. Then apply foot pressure. The pedal still shouldn't
creep to the floor, right?
Regards
W.
> Wolfgang,
> If the loss of fluid was enough that the master was sucking air, then it may
> have felt like a total failure of the brakes....maybe?
Agreed
> I agree that there
> may be problems with the master cylinder - both from what you note about the
> dual diagonal brake circuits - and if the brake fluid was not changed
> regularly (~ every 2 years or so), the portion of the cylinder bore that
> never saw the piston seals may have developed some corrosion that could
> damage the seals when the brake pedal was pressed to the floor.
Yes both options are possible.
> I would
> make sure the brakes are really well bled after hose replacement, and then
> hold the car on the brakes to see if the pedal creeps down. As brakes are
> nothing to be trifled with...<insert standard disclaimers here>
Yep. I would just try to check if the circuits are still separated. That
would make Me nervous.
A simple check would be to bleed off the air in one circuit, leaving the
other one open. Then apply foot pressure. The pedal still shouldn't
creep to the floor, right?
Regards
W.
03-28-2006, 09:51 AM
#18
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Steve Sears wrote:
> Wolfgang,
> If the loss of fluid was enough that the master was sucking air, then it may
> have felt like a total failure of the brakes....maybe?
Agreed
> I agree that there
> may be problems with the master cylinder - both from what you note about the
> dual diagonal brake circuits - and if the brake fluid was not changed
> regularly (~ every 2 years or so), the portion of the cylinder bore that
> never saw the piston seals may have developed some corrosion that could
> damage the seals when the brake pedal was pressed to the floor.
Yes both options are possible.
> I would
> make sure the brakes are really well bled after hose replacement, and then
> hold the car on the brakes to see if the pedal creeps down. As brakes are
> nothing to be trifled with...<insert standard disclaimers here>
Yep. I would just try to check if the circuits are still separated. That
would make Me nervous.
A simple check would be to bleed off the air in one circuit, leaving the
other one open. Then apply foot pressure. The pedal still shouldn't
creep to the floor, right?
Regards
W.
> Wolfgang,
> If the loss of fluid was enough that the master was sucking air, then it may
> have felt like a total failure of the brakes....maybe?
Agreed
> I agree that there
> may be problems with the master cylinder - both from what you note about the
> dual diagonal brake circuits - and if the brake fluid was not changed
> regularly (~ every 2 years or so), the portion of the cylinder bore that
> never saw the piston seals may have developed some corrosion that could
> damage the seals when the brake pedal was pressed to the floor.
Yes both options are possible.
> I would
> make sure the brakes are really well bled after hose replacement, and then
> hold the car on the brakes to see if the pedal creeps down. As brakes are
> nothing to be trifled with...<insert standard disclaimers here>
Yep. I would just try to check if the circuits are still separated. That
would make Me nervous.
A simple check would be to bleed off the air in one circuit, leaving the
other one open. Then apply foot pressure. The pedal still shouldn't
creep to the floor, right?
Regards
W.
03-28-2006, 09:51 AM
#19
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Steve Sears wrote:
> Wolfgang,
> If the loss of fluid was enough that the master was sucking air, then it may
> have felt like a total failure of the brakes....maybe?
Agreed
> I agree that there
> may be problems with the master cylinder - both from what you note about the
> dual diagonal brake circuits - and if the brake fluid was not changed
> regularly (~ every 2 years or so), the portion of the cylinder bore that
> never saw the piston seals may have developed some corrosion that could
> damage the seals when the brake pedal was pressed to the floor.
Yes both options are possible.
> I would
> make sure the brakes are really well bled after hose replacement, and then
> hold the car on the brakes to see if the pedal creeps down. As brakes are
> nothing to be trifled with...<insert standard disclaimers here>
Yep. I would just try to check if the circuits are still separated. That
would make Me nervous.
A simple check would be to bleed off the air in one circuit, leaving the
other one open. Then apply foot pressure. The pedal still shouldn't
creep to the floor, right?
Regards
W.
> Wolfgang,
> If the loss of fluid was enough that the master was sucking air, then it may
> have felt like a total failure of the brakes....maybe?
Agreed
> I agree that there
> may be problems with the master cylinder - both from what you note about the
> dual diagonal brake circuits - and if the brake fluid was not changed
> regularly (~ every 2 years or so), the portion of the cylinder bore that
> never saw the piston seals may have developed some corrosion that could
> damage the seals when the brake pedal was pressed to the floor.
Yes both options are possible.
> I would
> make sure the brakes are really well bled after hose replacement, and then
> hold the car on the brakes to see if the pedal creeps down. As brakes are
> nothing to be trifled with...<insert standard disclaimers here>
Yep. I would just try to check if the circuits are still separated. That
would make Me nervous.
A simple check would be to bleed off the air in one circuit, leaving the
other one open. Then apply foot pressure. The pedal still shouldn't
creep to the floor, right?
Regards
W.
03-28-2006, 10:34 AM
#20
Guest
Posts: n/a
Re: Brake servo problem(?) - Audi 100 1985
Wolfgang,
I'm almost positive that when I last bled the dual-diagonal circuit brakes
on both my 5ktq and 5k manually (I use a home-made pressure bleeder now), I
could push the pedal to the floor when I had my friend crack the bleed screw
on one corner only. I checked on the net and there are warnings about not
pressing the pedal all the way to the floor:
http://forums.probetalk.com/showthre...1029134&page=1
(third post)
Maybe Chris' master cylinder is not malfunctioning......maybe?
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)
"Wolfgang Pawlinetz" <w.pawlinetz@a1.net> wrote in message
news:1143560984.347220@news...
>
> Yep. I would just try to check if the circuits are still separated. That
> would make Me nervous.
>
> A simple check would be to bleed off the air in one circuit, leaving the
> other one open. Then apply foot pressure. The pedal still shouldn't creep
> to the floor, right?
>
> Regards
>
> W.
I'm almost positive that when I last bled the dual-diagonal circuit brakes
on both my 5ktq and 5k manually (I use a home-made pressure bleeder now), I
could push the pedal to the floor when I had my friend crack the bleed screw
on one corner only. I checked on the net and there are warnings about not
pressing the pedal all the way to the floor:
http://forums.probetalk.com/showthre...1029134&page=1
(third post)
Maybe Chris' master cylinder is not malfunctioning......maybe?
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)
"Wolfgang Pawlinetz" <w.pawlinetz@a1.net> wrote in message
news:1143560984.347220@news...
>
> Yep. I would just try to check if the circuits are still separated. That
> would make Me nervous.
>
> A simple check would be to bleed off the air in one circuit, leaving the
> other one open. Then apply foot pressure. The pedal still shouldn't creep
> to the floor, right?
>
> Regards
>
> W.
