Big nut master cylinders

**locodriver2007** · 12-09-2012, 11:54 PM

Hi guys, can any one please explain the difference between the BIG Nut master cylinders and the standard master cylinder and why they were used? And did they come out standard on HJ Sandmans?
Cheers Mark

**Taily** · 13-09-2012, 06:21 AM

Originally Posted by locodriver2007

Hi guys, can any one please explain the difference between the BIG Nut master cylinders and the standard master cylinder and why they were used? And did they come out standard on HJ Sandmans?
Cheers Mark

A "Big Nut" ([sic] - it is actually a bolt or a plug) master cylinder is a standard master cylinder. The are a cast iron master cylinder whose design incorporated the nut at the front so as to enable re-kitting. The common one that is seen nowadays is the replacement PBR (aluminium) type whose design does not require access to the front to re-kit (if you could or even wanted to it would be more cost effective to replace the whole master cylinder with a new one, they are now that cheap).

There are different numbers and different types of big nut master cylinders, HK-HG ones were a large, more oval shape to the resovoir, HQ-Z was a smaller, squared-off resovoir. My memory is fading (meaning don't take this as gospel) but remember seeing "DISC" on the odd nut here and there (A9X rings a bell....).

Hope that helps,

Dave.

**ozbox** · 13-09-2012, 12:02 PM

the reason you would replace the pbr master for a large nut master is for authenticity in your restoration...they have disc stamped into them and are date coded as such.

**playwme** · 13-09-2012, 06:59 PM

Good thread topic. I had some issues with this last week. Went to my local brake place for a rebuild kit and got what they had listed for a HZ. Got it home and all sorts of stuff is different so looks like its the PBR kit when my Sandman has a big nut. Anyone know if they do a rebuild kit for the big nuts? And price if you have them [MENTION=119]ozbox[/MENTION]. Local brake joint was a bit clueless about the older cars. Took them long enough to find what they did.

**jennie285** · 13-09-2012, 07:45 PM

Originally Posted by playwme

Good thread topic. I had some issues with this last week. Went to my local brake place for a rebuild kit and got what they had listed for a HZ. Got it home and all sorts of stuff is different so looks like its the PBR kit when my Sandman has a big nut. Anyone know if they do a rebuild kit for the big nuts? And price if you have them [MENTION=119]ozbox[/MENTION]. Local brake joint was a bit clueless about the older cars. Took them long enough to find what they did.

Hey play
My brother in law did up our master cylinder and brake booster he owns hastings brake and exhaust at port Macquarie. We got Ozbox to send him up a big nut brake booster and master cylinder and he re conditioned it all for us. He did the full stainless steel reline. I was going to advertise him through here but didn't get round to it. This was for yellow van he will gladly post it too you and help any way he can.
Cheers j

**playwme** · 14-09-2012, 05:26 PM

My cylinder is pretty good. Nice smooth bore and all. I pulled it apart to clean the gunk that had accumulated in the holes over the past 10 years and just wanted a new set of seals to put in it. Might be worth sending him the whole thing though. Any idea what his "not my sister-in-law" price for a reco is, or should I call him up and do some name dropping?