Brake Vaccum Booster weirdness...
10-22-2007, 04:12 AM
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Brake Vaccum Booster weirdness...
I think I have found the source of a brake problem I have been having but I thought I would ask around...here are the symptoms:
1 - Brakes are normal during the first 1-2 seconds of activation. You can modulate them fine and braking increases with pressure.
2 - After the 1-2 seconds the pedal remains firm but requires much more pressure to get the same braking. It feels like it just gets much harder.
3 - If you stand on the brakes they work just as well as usual but it requires lots of foot pressure. The pedal remains hard and does not sink to the floor.
4 - If you take your foot off the pedal and then reapply a few seconds later you have the same characteristic as (1).
5 - If the brake is pumped and pressured before startup and the car is started the brakes will "sink" a bit as the brake booster cuts in (which is normal)
6 - I have gotten a few CELs lately that indicated loading problems with the engine. This code usually means the engine is getting too much air for the fuel/load; i.e. there is a vacuum leak. The problem is not active now even with the braking problem.
I suspect its the vacuum brake booster. I have tested the vacuum line from the booster to the engine and its does not appear to leak. The car has not CELs (at the moment) I am not sure how to test the booster. The engine appears to have normal vacuum (with my crude guage).
This part is not common. I can get it from Sunset but its like 8 weeks out unless I pay the extra extortion money to Porsche to get it within 10 days. I have looked around on the net and there are various sources but Sunset is the cheapest. I am not sure if I should get a used unit ; I do not like to fool around with brakes.
So, does this sound like a failing vacuum booster and where can I source one cheaply?
All help is appreciated!
Cheers,
Mike
1 - Brakes are normal during the first 1-2 seconds of activation. You can modulate them fine and braking increases with pressure.
2 - After the 1-2 seconds the pedal remains firm but requires much more pressure to get the same braking. It feels like it just gets much harder.
3 - If you stand on the brakes they work just as well as usual but it requires lots of foot pressure. The pedal remains hard and does not sink to the floor.
4 - If you take your foot off the pedal and then reapply a few seconds later you have the same characteristic as (1).
5 - If the brake is pumped and pressured before startup and the car is started the brakes will "sink" a bit as the brake booster cuts in (which is normal)
6 - I have gotten a few CELs lately that indicated loading problems with the engine. This code usually means the engine is getting too much air for the fuel/load; i.e. there is a vacuum leak. The problem is not active now even with the braking problem.
I suspect its the vacuum brake booster. I have tested the vacuum line from the booster to the engine and its does not appear to leak. The car has not CELs (at the moment) I am not sure how to test the booster. The engine appears to have normal vacuum (with my crude guage).
This part is not common. I can get it from Sunset but its like 8 weeks out unless I pay the extra extortion money to Porsche to get it within 10 days. I have looked around on the net and there are various sources but Sunset is the cheapest. I am not sure if I should get a used unit ; I do not like to fool around with brakes.
So, does this sound like a failing vacuum booster and where can I source one cheaply?
All help is appreciated!
Cheers,
Mike
10-22-2007, 10:11 AM
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Mike, I have a used brake booster that came with a complete 993 front end I bought a few months ago. You are welcomed to it -- just cover the shipping.
The owner of the car this front end came from said everything worked fine before the crash
The owner of the car this front end came from said everything worked fine before the crash
