Bled brakes - now its worse!!?
11-10-2006, 02:34 PM
#1
Addict
Rennlist Member
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Thread Starter
Bled brakes - now its worse!!?
I changed my brake pads and then bled my brakes. They went from great to something wrong. Is there some sort of trick I missed?
Using a turkey baster, I removed as much fluid from the reservior as I could and then replaced it with new. Filled my Motul with the remainer of that can and another liter and then pressurized it to 20 psi.
Bled the rear brakes with no incident. Bled the right front and after the fluid changed color, started getting air bubbles that would not stop. At the risk of running out of fluid, I switched to the inner bleed valve and got air. Then switcehd to the LF and got air. The brakes were working fine until I bled them and now??? Where did all this air come from?
Greg H.
Using a turkey baster, I removed as much fluid from the reservior as I could and then replaced it with new. Filled my Motul with the remainer of that can and another liter and then pressurized it to 20 psi.
Bled the rear brakes with no incident. Bled the right front and after the fluid changed color, started getting air bubbles that would not stop. At the risk of running out of fluid, I switched to the inner bleed valve and got air. Then switcehd to the LF and got air. The brakes were working fine until I bled them and now??? Where did all this air come from?
Greg H.
11-10-2006, 03:05 PM
#2
Nordschleife Master
Greg,
Were you careful to be sure that the reservoir never got low on fluid? It sounds like it got low and allowed air into the system. You will have to refill and start over, and constantly refill the revervoir to make sure it never gets too low.
Were you careful to be sure that the reservoir never got low on fluid? It sounds like it got low and allowed air into the system. You will have to refill and start over, and constantly refill the revervoir to make sure it never gets too low.
11-11-2006, 02:53 AM
#3
Three Wheelin'
On the 993TT there is a special procedure to change the brake fluid. Steve is right you could have ran out of fluid in the reservoir, but if you didn't follow this procedure that may explain the lack of a pedal, and I assume you know how to traditionally bleed a system . . . the 993TT uses an electrohydraulic pump/accumulator system for a brake booster instead of a traditional vacuum booster. The 964 C4/turbo and the 993 C4/TT use this system. This is what many early ABS (late '80s/early '90s) cars like GM used when ABS was first introduced, and they integrated all the components (pump, accumulator, ABS control unit) on the master cylinder in one tidy unit. The rub was, if a lip seal failed inside the master cylinder, you had to replace the entire unit for $1500+!!! And this on some Buick or smoething (another funny thing, I saw one of these integrated units on an '88 Buick, had the same anodized green ATE-manufactured pressure switch on the pump as the Porsches do, for $300+ list!)! The reason I bring this up is, I wonder why Porsche stuck w/ this system thru the late '90s on the AWD 993s after everyone else abandoned it. Expensive stuff to replace. At least they didn't integrate all the components into one unit like other manufacturers did, but they did go back to vacuum boosters for all 996 models which says something (though they kept the clutch hydroboost circuit from the power steering on the 996tt). Anyway I'll copy and paste the procedure I PMed a 993 C4 owner a while back . . . .
What i do is I first use a vacuum pump to suck all the old fluid out of the reservoir, and fill the resevoir with fresh brake fluid. Then, you turn the key on, and you can hear the pump in the front of the luggage compartment running, filling the accumulator. Wait till the pump stops, then pull the bottom electrical connector off the pump(not the one coming off of the green pressure switch, the one below it) to disable the pump. Then, if you look above and to the left of the spare tire, you can see the accumulator, which has kind of a round black plastic sphere on it. There is a bleeder screw on that. Make sure you are wearing safety glasses, and that you hold the bleeder hose tightly on the screw! When you crack this bleeder screw, a good amount of fluid comes out pretty fast, so be careful, but this is cool since it gets a lot of the old fluid out.
After the fluid is done coming out of the accumulator, close that bleeder, and now you can bleed the brakes in a conventional manner. I would highly recommend using a pressure bleeder, but I have manually bled a 993tt with a helper since the guy wanted ATE blue fluid and we didnt want to contaminate our pressure bleeder with it. Bleed the brakes in the traditional sequence: RR, LR RF, LF. There are 2 bleeder screws on each caliper, open the inner one first, after you bleed the first one and you see clean new fluid coming out, you only have to bleed the outer one for a couple of seconds, since you are now only flushing out only that small area of the caliper.
Once you are done, make sure there's fluid in the reservoir, then reconnect the connector for the pump, and turn on the key again and again wait until the pump stops. Then, and only then can you accurately check the brake fluid level. Correct it as necessary and then make sure you brake pedal is there. As I mentioned in my post on the hydroboost cars, the pedal feel is kinda weird compared to the vacuum boosted cars, but thats normal. Well, hope this helps, and good luck!
BTW I grew up in Orinda, cool to see someone on here from there!
---
Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA
What i do is I first use a vacuum pump to suck all the old fluid out of the reservoir, and fill the resevoir with fresh brake fluid. Then, you turn the key on, and you can hear the pump in the front of the luggage compartment running, filling the accumulator. Wait till the pump stops, then pull the bottom electrical connector off the pump(not the one coming off of the green pressure switch, the one below it) to disable the pump. Then, if you look above and to the left of the spare tire, you can see the accumulator, which has kind of a round black plastic sphere on it. There is a bleeder screw on that. Make sure you are wearing safety glasses, and that you hold the bleeder hose tightly on the screw! When you crack this bleeder screw, a good amount of fluid comes out pretty fast, so be careful, but this is cool since it gets a lot of the old fluid out.
After the fluid is done coming out of the accumulator, close that bleeder, and now you can bleed the brakes in a conventional manner. I would highly recommend using a pressure bleeder, but I have manually bled a 993tt with a helper since the guy wanted ATE blue fluid and we didnt want to contaminate our pressure bleeder with it. Bleed the brakes in the traditional sequence: RR, LR RF, LF. There are 2 bleeder screws on each caliper, open the inner one first, after you bleed the first one and you see clean new fluid coming out, you only have to bleed the outer one for a couple of seconds, since you are now only flushing out only that small area of the caliper.
Once you are done, make sure there's fluid in the reservoir, then reconnect the connector for the pump, and turn on the key again and again wait until the pump stops. Then, and only then can you accurately check the brake fluid level. Correct it as necessary and then make sure you brake pedal is there. As I mentioned in my post on the hydroboost cars, the pedal feel is kinda weird compared to the vacuum boosted cars, but thats normal. Well, hope this helps, and good luck!
BTW I grew up in Orinda, cool to see someone on here from there!
---
Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA
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jac911 (12-23-2023)
12-22-2023, 04:40 PM
#4
Rennlist Member
On the 993TT there is a special procedure to change the brake fluid. Steve is right you could have ran out of fluid in the reservoir, but if you didn't follow this procedure that may explain the lack of a pedal, and I assume you know how to traditionally bleed a system . . . the 993TT uses an electrohydraulic pump/accumulator system for a brake booster instead of a traditional vacuum booster. The 964 C4/turbo and the 993 C4/TT use this system. This is what many early ABS (late '80s/early '90s) cars like GM used when ABS was first introduced, and they integrated all the components (pump, accumulator, ABS control unit) on the master cylinder in one tidy unit. The rub was, if a lip seal failed inside the master cylinder, you had to replace the entire unit for $1500+!!! And this on some Buick or smoething (another funny thing, I saw one of these integrated units on an '88 Buick, had the same anodized green ATE-manufactured pressure switch on the pump as the Porsches do, for $300+ list!)! The reason I bring this up is, I wonder why Porsche stuck w/ this system thru the late '90s on the AWD 993s after everyone else abandoned it. Expensive stuff to replace. At least they didn't integrate all the components into one unit like other manufacturers did, but they did go back to vacuum boosters for all 996 models which says something (though they kept the clutch hydroboost circuit from the power steering on the 996tt). Anyway I'll copy and paste the procedure I PMed a 993 C4 owner a while back . . . .
What i do is I first use a vacuum pump to suck all the old fluid out of the reservoir, and fill the resevoir with fresh brake fluid. Then, you turn the key on, and you can hear the pump in the front of the luggage compartment running, filling the accumulator. Wait till the pump stops, then pull the bottom electrical connector off the pump(not the one coming off of the green pressure switch, the one below it) to disable the pump. Then, if you look above and to the left of the spare tire, you can see the accumulator, which has kind of a round black plastic sphere on it. There is a bleeder screw on that. Make sure you are wearing safety glasses, and that you hold the bleeder hose tightly on the screw! When you crack this bleeder screw, a good amount of fluid comes out pretty fast, so be careful, but this is cool since it gets a lot of the old fluid out.
After the fluid is done coming out of the accumulator, close that bleeder, and now you can bleed the brakes in a conventional manner. I would highly recommend using a pressure bleeder, but I have manually bled a 993tt with a helper since the guy wanted ATE blue fluid and we didnt want to contaminate our pressure bleeder with it. Bleed the brakes in the traditional sequence: RR, LR RF, LF. There are 2 bleeder screws on each caliper, open the inner one first, after you bleed the first one and you see clean new fluid coming out, you only have to bleed the outer one for a couple of seconds, since you are now only flushing out only that small area of the caliper.
Once you are done, make sure there's fluid in the reservoir, then reconnect the connector for the pump, and turn on the key again and again wait until the pump stops. Then, and only then can you accurately check the brake fluid level. Correct it as necessary and then make sure you brake pedal is there. As I mentioned in my post on the hydroboost cars, the pedal feel is kinda weird compared to the vacuum boosted cars, but thats normal. Well, hope this helps, and good luck!
BTW I grew up in Orinda, cool to see someone on here from there!
---
Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA
What i do is I first use a vacuum pump to suck all the old fluid out of the reservoir, and fill the resevoir with fresh brake fluid. Then, you turn the key on, and you can hear the pump in the front of the luggage compartment running, filling the accumulator. Wait till the pump stops, then pull the bottom electrical connector off the pump(not the one coming off of the green pressure switch, the one below it) to disable the pump. Then, if you look above and to the left of the spare tire, you can see the accumulator, which has kind of a round black plastic sphere on it. There is a bleeder screw on that. Make sure you are wearing safety glasses, and that you hold the bleeder hose tightly on the screw! When you crack this bleeder screw, a good amount of fluid comes out pretty fast, so be careful, but this is cool since it gets a lot of the old fluid out.
After the fluid is done coming out of the accumulator, close that bleeder, and now you can bleed the brakes in a conventional manner. I would highly recommend using a pressure bleeder, but I have manually bled a 993tt with a helper since the guy wanted ATE blue fluid and we didnt want to contaminate our pressure bleeder with it. Bleed the brakes in the traditional sequence: RR, LR RF, LF. There are 2 bleeder screws on each caliper, open the inner one first, after you bleed the first one and you see clean new fluid coming out, you only have to bleed the outer one for a couple of seconds, since you are now only flushing out only that small area of the caliper.
Once you are done, make sure there's fluid in the reservoir, then reconnect the connector for the pump, and turn on the key again and again wait until the pump stops. Then, and only then can you accurately check the brake fluid level. Correct it as necessary and then make sure you brake pedal is there. As I mentioned in my post on the hydroboost cars, the pedal feel is kinda weird compared to the vacuum boosted cars, but thats normal. Well, hope this helps, and good luck!
BTW I grew up in Orinda, cool to see someone on here from there!
---
Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA
Thank you so much Chris for this post that I found deep deep in the archives. I had my front calipers refinished and after reinstalling and going through the regular bleeding procedure, the ABS light was on and the brakes were spongy, and the pedal felt like soft poo. Your instructions on bleeding the accumulator separately resolved this issue! Merry Christmas!
