Total brake failure....without WARNING!!!!
08-22-2002, 02:23 PM
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Total brake failure....without WARNING!!!!
Well, this just happened to me yesterday. I jumped in the car, waited for all the warning lights to go off and started driving. On my very 1st stop I realized my brake pedal was rock hard and I could barely get it to stop. I drove right back to my house and I noticed a puddle of brake fluid on the ground. This scared me because the brake just died without any warning at all!
The last time I drove th car was 3 days earlier and it ran great.
The brake fluid is leaking from around the ABS pump area, but not sure exactly where.
In my search of the earlier posts I have found another C4 with similar faith. However, it is not clear to me if it is my pump that has failed or just the pressure sensor switch and the pump relay.
When the car is ideling I do hear this constant buzz that sounds like an electric pump from the front, but it never goes away. The buzz also sounds different from what I remembered.....
So where do I start to trouble shoot this?
Thanks,
Mike
The last time I drove th car was 3 days earlier and it ran great.
The brake fluid is leaking from around the ABS pump area, but not sure exactly where.
In my search of the earlier posts I have found another C4 with similar faith. However, it is not clear to me if it is my pump that has failed or just the pressure sensor switch and the pump relay.
When the car is ideling I do hear this constant buzz that sounds like an electric pump from the front, but it never goes away. The buzz also sounds different from what I remembered.....
So where do I start to trouble shoot this?
Thanks,
Mike
08-22-2002, 04:32 PM
#2
Hi,
I imagine someone (probably Adrian) can tell you this exactly, but in the meantime :
I have had brake problems myself and one thing I was told is that it's fairly common for part of the pump to begin leaking. I was told that there's a part of it (can't remember what they called it - blow off valve or something) that can fail and then start leaking. My guess would be that this is what has happened to you. Not sure if this means you need to replace the whole pump since this wasn't my problem.
I'm fairly surprised you didn't get warning lights though.
Dave
90 C4
I imagine someone (probably Adrian) can tell you this exactly, but in the meantime :
I have had brake problems myself and one thing I was told is that it's fairly common for part of the pump to begin leaking. I was told that there's a part of it (can't remember what they called it - blow off valve or something) that can fail and then start leaking. My guess would be that this is what has happened to you. Not sure if this means you need to replace the whole pump since this wasn't my problem.
I'm fairly surprised you didn't get warning lights though.
Dave
90 C4
08-22-2002, 05:44 PM
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Perhaps it is the pressure switch which sit on top of the pump. With a "puddle" I imagine it is time to have it flat-bedded to a dealer and replace the switch, flush and bleed the system (pump= approx $200.00, BTW. Been there done that)
08-22-2002, 06:28 PM
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Horst,
So how many miles did you have on the car when the pressure switch failed? Is the pump really $200 or just the switch?
Even now there is still no warning on the dash after the initial start sequence.
Mike
So how many miles did you have on the car when the pressure switch failed? Is the pump really $200 or just the switch?
Even now there is still no warning on the dash after the initial start sequence.
Mike
08-23-2002, 12:50 AM
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Michael,
this exact thing happened to me...what had happened in my case was that there was insufficient pressure in the abs system, and this caused the pump to constantly work. This translated to one very hot pump, which in turn melted the connecting point of one of the hoses to the pump- end result was the brake fluid leak...and complete failure of my brake system...boy was that fun...
ended up getting my mechanic to make a new connector rather than replace the entire hose (which is how porsche apparently sells the part)...touch wood the brakes haven't failed in the last year.
Harold
<a href="http://members.rennlist.com/complete964" target="_blank">Complete 964</a>
this exact thing happened to me...what had happened in my case was that there was insufficient pressure in the abs system, and this caused the pump to constantly work. This translated to one very hot pump, which in turn melted the connecting point of one of the hoses to the pump- end result was the brake fluid leak...and complete failure of my brake system...boy was that fun...
ended up getting my mechanic to make a new connector rather than replace the entire hose (which is how porsche apparently sells the part)...touch wood the brakes haven't failed in the last year.
Harold
<a href="http://members.rennlist.com/complete964" target="_blank">Complete 964</a>
08-23-2002, 03:34 AM
#6
Michael:
You might want to get your owners manual out and make sure ALL your warning lights really are working.
I'm guessing on this, but I think the noise you're hearing is because your system can't pressurize properly due to the lack of fluid and the fact that the system may not even be able to hold it's pressure because of the leak.
If I was going to troubleshoot it myself, I would do the following:
1. Check the brake fluid level. It will (I assume) be low.
2. Fill up the brake fluid resevoir just to see how much fluid you really lost.
3. With the fluid filled, you might want to see if the noise stops or at least reduces when starting the car. I don't know how good a test this would be since you now likely have air in the system. If it does reduce or eliminate the pump noise, then you can likely expect it to start up again once the fluid leaks out again. I would guess that as the fluid leaks out you're losing pressure in the system and you may damage the pump too. I don't really know.
4. Trace the source of the leak while stuff is running if you decide to try that.
I would certainly NOT drive the car anywhere at all. It's amazing to me that you were even able to stop the car at all after losing fluid. If it was my car I'd have it flat bedded and taken to a shop to get it fixed. The system is complicated and you'll need a bleed or even a complete fluid change anyway once the system is fixed.
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You might want to get your owners manual out and make sure ALL your warning lights really are working.
I'm guessing on this, but I think the noise you're hearing is because your system can't pressurize properly due to the lack of fluid and the fact that the system may not even be able to hold it's pressure because of the leak.
If I was going to troubleshoot it myself, I would do the following:
1. Check the brake fluid level. It will (I assume) be low.
2. Fill up the brake fluid resevoir just to see how much fluid you really lost.
3. With the fluid filled, you might want to see if the noise stops or at least reduces when starting the car. I don't know how good a test this would be since you now likely have air in the system. If it does reduce or eliminate the pump noise, then you can likely expect it to start up again once the fluid leaks out again. I would guess that as the fluid leaks out you're losing pressure in the system and you may damage the pump too. I don't really know.
4. Trace the source of the leak while stuff is running if you decide to try that.
I would certainly NOT drive the car anywhere at all. It's amazing to me that you were even able to stop the car at all after losing fluid. If it was my car I'd have it flat bedded and taken to a shop to get it fixed. The system is complicated and you'll need a bleed or even a complete fluid change anyway once the system is fixed.
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08-23-2002, 05:04 AM
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Dear Michael,
The leak I am sure is coming from the pump seal or the pressure switch seal. You have to take the carpet out of the luggage compartment, remove the black cover over the ABS hydraulic unit, remove the spare tyre, get in there with a torch and a mirror and you will see the leak I am sure.
This C4 must not be driven. You must also clean up the leak before it damages your paint work.
Leave a rag or fifteen in the area to soak up any residue. Do not turn the ignition on because as Bill says you cannot make pressure which means you will eventually burn the pump out but the extra heat will actually damage the seals more increasing the leak. The pump is an intermittant pump not a continuous running pump. No fluid in the pump will also destroy it. It will cavitate then disintergrate,
Ciao,
Adrian
911C4
PS: I think you will have to replace the pump anyway. However get it to your mechanic or strip it down at home. No more driving.
The leak I am sure is coming from the pump seal or the pressure switch seal. You have to take the carpet out of the luggage compartment, remove the black cover over the ABS hydraulic unit, remove the spare tyre, get in there with a torch and a mirror and you will see the leak I am sure.
This C4 must not be driven. You must also clean up the leak before it damages your paint work.
Leave a rag or fifteen in the area to soak up any residue. Do not turn the ignition on because as Bill says you cannot make pressure which means you will eventually burn the pump out but the extra heat will actually damage the seals more increasing the leak. The pump is an intermittant pump not a continuous running pump. No fluid in the pump will also destroy it. It will cavitate then disintergrate,
Ciao,
Adrian
911C4
PS: I think you will have to replace the pump anyway. However get it to your mechanic or strip it down at home. No more driving.
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08-23-2002, 10:24 AM
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Michael: sorry not to be more clear. The $200.00, as I recall was for the pressure switch only, and the flush. I provided the dealer w/ the ATE 400 fluid. BTW, GET SOME SIMPLE GREEN! Spritz that anywhere, everywhere the brake fluid may be!. By this time may be too late. Simple Green (no I don't sell the stuff) is simply the best stuff for instantly neutrilizing the brake fluid. As I have mentioned, have the car flat-bedded to the deal. Don't try to drive it.
08-23-2002, 02:26 PM
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Thanks for all the reply,
Don't worry about me driving it. In fact, I only went about 300 meters from my house before I realized I had a problem. I have already made an appointment with my mechanic to flatbed the car in early next week. However in the meantime I will need to clean up and neutralize the brake fluid before it does any further damage to the paint.
So where is the electric pump located?
Would I need to replace the hydarulic unit or just the prsssure sensor switch and seal?
Either way, I am sure it is going to be expensive...
thanks all,
Mike
At least now I know what kind of damage to expect.
Don't worry about me driving it. In fact, I only went about 300 meters from my house before I realized I had a problem. I have already made an appointment with my mechanic to flatbed the car in early next week. However in the meantime I will need to clean up and neutralize the brake fluid before it does any further damage to the paint.
So where is the electric pump located?
Would I need to replace the hydarulic unit or just the prsssure sensor switch and seal?
Either way, I am sure it is going to be expensive...
thanks all,
Mike
At least now I know what kind of damage to expect.
08-23-2002, 11:19 PM
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I have spent some time taking everything out of the front and taking some pics for you to see:
This is shows the ABS hydraulic unit and what I believe to be the ABS pump towards the front.
This following pics is where the brake fluid is leaked out of the system.
The interesting thing is that the brake fluid resevor is still full. Also when I start the enginer the warning lights would go off right away instead of the usual 30 sec. routine.
ALso the constant electric buzz is coming from behind the dashboard. Not the leaky pump.
Is what I have shown in the pics the pressure sensor unit and the ABS pump?
The connection between the pump and what I believe is the switch (shown in pic 3)looks just like this. As if it had bursted open.
Either way, looks like mucho dinero to get my baby running again....
thanks,
This is shows the ABS hydraulic unit and what I believe to be the ABS pump towards the front.
This following pics is where the brake fluid is leaked out of the system.
The interesting thing is that the brake fluid resevor is still full. Also when I start the enginer the warning lights would go off right away instead of the usual 30 sec. routine.
ALso the constant electric buzz is coming from behind the dashboard. Not the leaky pump.
Is what I have shown in the pics the pressure sensor unit and the ABS pump?
The connection between the pump and what I believe is the switch (shown in pic 3)looks just like this. As if it had bursted open.
Either way, looks like mucho dinero to get my baby running again....
thanks,
08-26-2002, 06:52 AM
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Dear Mike,
You should be able to get away with just replacing the pump. However a lot is going to depend upon what is available. I believe and I say I believe because I have never seen this myself, that the post model year 1995 993 units which are sold as replacements may not fit the old 964 ABS hydraulic unit.
I would certainly contact Bosch in the USA and ask if they have an exchange or rebuild service.
Hopefully you will be able to find a replacement pump which fits properly. Do not give up if you have problems in the USA. The UK is a great source of components as well.
Ciao,
Adrian
911C4
You should be able to get away with just replacing the pump. However a lot is going to depend upon what is available. I believe and I say I believe because I have never seen this myself, that the post model year 1995 993 units which are sold as replacements may not fit the old 964 ABS hydraulic unit.
I would certainly contact Bosch in the USA and ask if they have an exchange or rebuild service.
Hopefully you will be able to find a replacement pump which fits properly. Do not give up if you have problems in the USA. The UK is a great source of components as well.
Ciao,
Adrian
911C4
08-26-2002, 11:45 AM
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I had a similar situation but no sign of brake fluid anywhere...
Problem - After hard braking ABS comes into action. Next time I was in need to brake, the brake pedal feel hard and I could barely stop.
Solution: Pressure Sensor replaced(US$247.55 - Part # 964-606-904-00), Relay replaced (US$33.81 Part # 964-615-135-00), Rubber O-Ring replaced(US$4.99 Part # 999-707-094-40). Labor US$147.90 Minus 10% Porsche club discount.
Problem - After hard braking ABS comes into action. Next time I was in need to brake, the brake pedal feel hard and I could barely stop.
Solution: Pressure Sensor replaced(US$247.55 - Part # 964-606-904-00), Relay replaced (US$33.81 Part # 964-615-135-00), Rubber O-Ring replaced(US$4.99 Part # 999-707-094-40). Labor US$147.90 Minus 10% Porsche club discount.
08-29-2002, 10:07 PM
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Thanks all,
The culprit was the pressure sensor switch. The brake fluid had actually leaked out of the switch and stopped the pump from a complete meltdown. I consider myself lucky not having to replace the pump, just the switch. My mechanic replaced the switch, flushed the whole system and I am back on the road again. The switch was $185 and overall labor was 4 hours.
thanks,
Mike
The culprit was the pressure sensor switch. The brake fluid had actually leaked out of the switch and stopped the pump from a complete meltdown. I consider myself lucky not having to replace the pump, just the switch. My mechanic replaced the switch, flushed the whole system and I am back on the road again. The switch was $185 and overall labor was 4 hours.
thanks,
Mike
