[Westy]

So I took my 1993 968 in for some service, including a complete brake check.  Well, this morning I was advised the module/valve on the right front is stuck in the closed position, which means they cant bleed it 'cause the brake doesn't work.  He advised the part is no longer available, and as of right now he can't find anyone who rebuilds them.  Anyone else have this problem and came up with a fix?  TIA
 
Brian

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[MCL968]

When I replaced my rotors and pads a year or so ago, I just bled everything using a pressure bleeder, and I think it flushed the ABS unit in the process. I was not aware there was a bleeder on the ABS unit. Brakes are solid as a rock, so I wonder if it really needs to be done.

 

Anyone out there want to weigh in on this?

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[unknown4u]

I've read a long time ago that parts from a mercedes will fit. Try perhaps a search for that
I've read a long time ago that parts from a mercedes will fit. Try perhaps a search for that

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[Westy]

When I replaced my rotors and pads a year or so ago, I just bled everything using a pressure bleeder, and I think it flushed the ABS unit in the process. I was not aware there was a bleeder on the ABS unit. Brakes are solid as a rock, so I wonder if it really needs to be done.

 

Anyone out there want to weigh in on this?

I don't think I was very descriptive here.  I don't know anything about this specific design, but I think he was saying the ABS valve on the right front wasn't working (frozen) so he couldn't get fluid thru the caliper to bleed the system.  Funny thing is, when I hit the brakes at any speed, the car does not pull one way or another.

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[Waylander]

He must be doing something wrong, even with a totally seized ABS pump you can still bleed the brakes, I know I have had that on my car


You are correct about the Mercedes pump, you need one out of a 190e, they live in the engine bay on a 190 so they are always in good condition


The main valve block is different but the issue with the 968 pump is the motor and pistons, these can be swapped with the merc ones

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[Westy]

OK, talked to the guy this morning.The broken part is the hydraulic unit.  It's stuck closed, and there is no fluid going to the left front brake.  Here's the diagram.

 

Hydraulic Unit Anti-lock Brake System (autoatlanta.com)

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[Waylander]

You can buy a new one but I still dont think thats the issue


A new pump from Porsche is about $2000, there are no parts of the brake system that is NLA, the ABS unit is available as exchange


And also if that was the case that the valve seized does not allow the brake to be bled, you would have noticed the car shooting sideways as only one front brake was working


It would have been a nightmare to drive........


I think you need a second opinion


Also I dont think any car manufacturer would have a braking system where if there was a fault with ABS it would leave you with no brakes

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[ds968]

+ 1  on what Waylander  posted . 

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[MCL968]

Agreed, if you have ever driven a car with a seized caliper, you will not mistake any other part failure for that experience. The cool thing is you can steer (in one direction) with the brakes.

 

A simple check would be to just jack up the wheel and spin it and hit the brakes. I am willing to bet that it will stop and that you are getting bamboozled. The ABS pump cycles every time you start the car, so the possibility of it rusting up is pretty minimal.

 

One of my friends had a Land Rover, and when her ABS system was failing, upon braking the brake pedal would just go randomly to the floor. 99% of the time it would be fine, but once in a while she would just have no brakes. It was an exciting vehicle to drive for so many reasons.

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[dlearl476]

If these modules are similar to Mercedes, you might want to give ModuleMaster a call. They rebuilt my ML 500 pump and module for ~$300.


(208) 892-0764

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[Westy]

Thanx for all the input.  Module masters doesn't do Porsche ABS systems, but it was worth a shot.  Thanx again.

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[Waylander]

They are Bosch systems, no idea why they cant do it


Its used in a lot of early 1990s cars

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