MK V Brake Master Cylinder Rebuild

(Melbourne, Australia) #1

I am after some help identifying whether my dismantled MKV Brake Master Cylinder currently has all the correct parts within. I have attached a photo to help.

I wish to purchase a kit to replenish the seals while I have it apart, but am a little confused as different suppliers have slightly different components included within their rebuild kits. These even differ slightly from the workshop manual diagram.

If anyone can confirm if these are the correct parts, or if some are missing, that would be greatly appreciated.

Cheers Frank

(jeffery) #2

Hi Frank. From your photo all the components are there, well they match mine. The work you need to do is have the cylinder re-sleeved, the piston re-metaled and re machined (as the seal that in your photo is immediately in front of the cylinder seals both on the cylinder and the piston), and replace the 2 rubber seals.I neglected to do the piston and continued to not get pressure do to back leaking until I realized the action of the piston/seal. Seal kit is “MCK” Brake parts Kit # K73x (that’s in Australia) but it might give you a lead.
Also note that the system is hard to get a good peddle, but persistence is the Key, after you have rebuilt all the wheel cylinders.

(Rob Reilly) #3

Here’s mine.

And I made a drawing of it.

Sources of repair kits.
Cordell Newby,
The kit number is SP1974.

(Melbourne, Australia) #4

Hi Jeffery

Thanks for your detailed response and suggestions, including the part number. Do you know any suppliers in Australia that sell the kit? I am especially after the metal shim as although mine is still still in its round shape, it has a break.

Thanks Frank

(jeffery) #5

Hi Frank. On checking I do not have a spare metal shim with the holes in it.
My supplier for parts is a local brake and clutch specialist who sourced the kit and had the cylinder and piston reworked. believe the kit came from QLD some where.
Contact is Mark at Clutch & Brake Specialists, Geelong, Australia. Contact 03 52295077. Email
Very Helpful
cheers Jeffery

(Melbourne, Australia) #6

Hi Rob

Thanks for your efforts in supplying photos and your very detailed drawings. When I pulled the master cylinder apart, I found that the rear seal was inserted first into body first, followed by the metal shim and finally the steel spacer. However in your supplied drawings, it suggests that the metal shim be inserted first, followed by the rear seal and then the spacer. Can you confirm this to be correct?

Thanks Frank

(Rob Reilly) #7

Yes, I was very careful to draw all the parts in their assembly order, in fact that was the reason for making the drawing, that I could not find anything published.
Notice in the H1520 piston there are two tiny holes at the forward end. When the brake pedal is fully released, these holes permit the fluid to flow back past the two bumpy rings (H2504 Shims), through the little axial holes in the body, into the larger diameter chamber and finally back into the reservoir pipe. There will be no back flow if the rubber seal is blocking the holes in the piston, thus the brakes would not release.
I see that I should have noted that mine has two shims, where I see only one in your photo.
Also I see you have a pressure brake light switch, which I think is not the usual case in Australia, and it appears to have only one wire connection, where mine has two. I wonder if yours is a later modification, or did some non-USA-delivery cars get the pressure switch in contradiction to the SPC?