Vlocity

Hi:

I noticed what I thought was brake fluid under the center section of my
89 C-4 yesterday and decided to investigate today. After removing the engine pan and the pan just ahead of the torque tube, it was obvious that the leak was in this general area. I used brake cleaner and dried the area and let the car sit for about an hour. After returning I noticed a small drop starting to form at at what I believe is the differntial slave cylinder. For reference this is at the head of the torque tube and situated just above one of the lower torque tube bolts on the drivers side of the car.

It appear that this slave is held in place by one cap headed allen bolt.

I was surprised that the slave appears to rotate slightly with the rotation limited by the steel line. I loosened and then retightened the allen head cap bolt, but this had no effect on the slave.

I have read the threads and it appears that I need the BOSCH hammer in order to bleed a replacement.

I just wanted to post to see if anyone else has had this problem and what I should expect to run into beyond this for repair.

I assume as long as the leak doesn't progress and I keep the brake fluid reservoir topped off I can continue to drive tis until repaired.


Regards,

Ken Bigham
Vlocity 89 C-4 37,000 miles.
Uproar 85 928 S

Adrian

Dear Ken,
I have to change one of mine as well. You are talking about the centre diff lock which is the one I have to change.
However I recommend until you get it fixed if it is leaking is to pull the connector off the PDAS/ABS control unit. The fluid used is from the brake booster circuit and if this runs out of fluid you in deep pooh pooh. By disconnecting the control unit you ensure the system does not get fluid. The centre diff lock activates very often especially in the wet.
Yes you do need a Bosch hammer to bleed the system and another reason to keep the system isolated to ensure air does not get back into the boost circuit. By the way mine is not leaking I just wore it out again.
Ciao,
Adrian
964C4

Vlocity

Adrian:

Thanks for the reply.

A few follow up questions if you don't mind.

The leak is pretty minimal at this point and I think if finally puddled enough in the pan to finally creep out and I noticed it right away.

If I disconnect the system are you indicating I should unplug it at the PDAS/ABS unit or would I be better to disconnect it at the Differential lock dual solenoid valve.

In either will an idiot light appear that will need to be reset?

I have some freinds in the 928 community and I might be able to find a loaner hammer. How difficult is the bled process?

Is there a rebuild kit available?

Best regards,

Ken Bigham
PS: Love your book
Vlocity 89 C-4 37,000 miles
Uproar 85 928 S

garrett376

Adrian, how is it you wear out the differential locks so frequently??

Adrian

I live in the moutains and do not go up hill slowly. So quickly by the way is 4 years.

Dear Ken,
It is best to disconnect the control unit. You are going to get the warn lights whatever you do. By disconnecting the control unit you are removing all power sources. You can disconnect the solenoid but then the control unit will still be partially powered and with nothing to do.
Ciao,
Adrian
964C4