Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

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toofless
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Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by toofless » Fri Mar 29, 2019 9:53 pm

Hi everyone,

I just got SRL10160 back on the road after a ton of work inside the engine bay. One of the only things that remains untouched/un-replaced in there is the master brake cylinder.

I have mushy brakes. There's clearly a leaking master brake cylinder plus the rear brake reservoir went completely dry in the last 5-10 miles. There are no other leaking parts that I can find after careful inspection. I've researched this topic quite a bit today on this site (thanks for all of your contributions!) and I have narrowed my options to the ones listed below.

In trying to balance price vs. likelihood of doing this right the first time, I am wondering if anyone has: 1) used a Datsun 510 master cylinder in their roadster?, or 2) tried a rebuild kit or a re-manufactured part, only to have to bite the bullet and buy an entire new, OEM part?

I'm leaning toward the rebuild kit but that's not free and there's a huge price range for these options. If you have any insight I would love the advice!
SRLBrakeMasterCylinder.jpg
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- '69 SRL
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- '10 Panamera

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Phred58
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by Phred58 » Sat Mar 30, 2019 2:53 am

Some things to think about / confirm before buying a non-roadster master cylinder:

mounting bolt spacing of replacement cylinder
reservoir height - hood needs to be able to close however you can usually use your old reservoirs if the new ones are too tall
pushrod ball socket design is same as the roadster (there are a couple of different designs I've seen out there)
pushrod length matches or it should be adjustable
brake line fitting - is it the original 3/8-24 or M10?

I usually recommend trying a rebuild kit first but if the bore is damaged, to get it resleeved at Karps in SoCal as this is, in my opinion, the best bang for the buck if you want to stay original. If you don't mind going non-stock, there are a couple of other brake master cylinders that do work once modified; I think they may be listed in the Wiki. If neither of those work for you, the OEM one is available but very pricey.
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bobd
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by bobd » Sat Mar 30, 2019 5:30 am

I had my original one sent out for a rebuild by NAPA a few years ago, not sure if that is still a viable alternative.

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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by spl310 » Sat Mar 30, 2019 5:58 am

Bobd, how much did they charge?
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by toofless » Sat Mar 30, 2019 10:19 am

I second that question - do you remember how much NAPA charged for the rebuild?

And thanks so much for the detailed response - this is exactly what I was looking for @Phred68. I will probably start by disassembling the current part to inspect the bore which I figure is the main reason you'd need a completely replacement (or re-sleeve). If it's bad and I can't get it re-sleeved then I might go backwards in trying to fit a part from a different platform to save the money.
- '69 SRL
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- '10 Panamera

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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by Gregs672000 » Sat Mar 30, 2019 1:05 pm

Ive had a 510 master for 30+ years as when I redid the brake lines I didn't realize the Roadster had a different pitch. Nevertheless, there are easy to use adaptors that will allow you to use the 510 master, with the only differences being the bleed screws are on the opposite side and you'll likely have to swap out the pedal arm... easy. The last 510 master I got off rockauto was $15 bucks on clearance... doubt they're that cheap now, but gee that's a bargain.
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bobd
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by bobd » Mon Apr 01, 2019 5:38 am

Sorry apparently that is one of the receipts I did not save. My receipt file for the roadster is about one inch thick, but I don't have them all. I kept a running tab on the last project car. Seeing the total at the end made me stop doing that!

But wait! I just checked my old posts and found this:

I just picked up my '69 1600 master cylinder from NAPA. They sent it to Cardone to be remanufactured - $73.99 plus $18.00 shipping both ways. It took almost two weeks over the New Year's holiday.

Dated Jan 11, 2010.

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theunz
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by theunz » Mon Apr 01, 2019 8:33 am

I'm using the 510 cylinder on mine with the adapters and my reservoirs . It fits and works well.
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toofless
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by toofless » Mon Apr 01, 2019 5:45 pm

Thanks again everyone. The Cardone 11-1538 master cylinder noted in the wiki is out of stock everywhere right now, with the best hopeful date at restocking I found to be in early May. I found the Centric 130.42107 that looks to be an identical part that's in stock at several suppliers - $70 new from CarID.com. It doesn't look like it comes with a pushrod so I suspect I will have to figure that out but hopefully those are pretty standard and available locally. I also found plenty of local options for the 3/16"/24-to-M10x1.00mm adapters.

If everything goes well I hope to have an update to provide after this weekend. Thanks again for all of the insight!
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by Linda » Mon Apr 01, 2019 9:09 pm

Did you research resleeving with Karp's?
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by toofless » Fri Apr 05, 2019 10:51 pm

I didn't, Linda. I chose the Datsun 510 master cylinder. I got the old master out last night and didn't even attempt to break it down - I just need to get at the pushrod which is definitely incompatible with the new master. I figure if I want to go back to original I can still try the rebuild route at which point I'll inspect it for the need to re-sleeve.

I got the adapters for the pipes at NAPA; part info per the Wiki. I will bench bleed the new master tonight. A friend to made a custom pushrod for me this evening and I pick it up tomorrow...should be back in business before Monday!
- '69 SRL
- '08 Triumph Tiger 1050
- '10 Panamera

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Linda
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by Linda » Sat Apr 06, 2019 8:13 am

The push rod usually swaps over. Or you can usually cut the adjustable push rod to work so it doesn't hit and adjusts correctly.
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toofless
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by toofless » Sat Apr 06, 2019 9:59 am

In this case the push rod had two incompatibilities. First and most importantly, the groove for the retaining clip in the end of the cylinder - the clip that holds in the semi-hemispherical washer, and therefore the push rod end ball itself - was too deep in the cylinder...the washer is just thick enough that you can't hold it in, and I suspect that if you could it might have been engaging the pistons a little too much any. So that was just a plain no-go.

Second, while the new cylinder is the exact same length as the old one so has the same amount of piston travel, etc., the old one sticks further into the firewall; the net of that situation is that the new MC sticks into the engine bay about 3/8" more than the old one. There's nothing you can do with shims because adding them on the other side of the firewall only makes the situation worse. So even if the original push rod's ball would have fit nicely into the socket using the standard washer, the push rod needed to be 3/8" longer. That's a pretty easy job for even a novice welder but the retaining clip made the attempt fruitless.

Luckily, unlike the old MC that only had a dished ball socket, the new one has the dish but also a cylindrical extension (a hole recessing deeper into the piston plunger). That enables the use of either a ball-end push rod, or a more-common option that's just a straight bar. My custom solution uses the latter approach that will require probably a total of ~3/4" longer rod than the original but won't require reuse of the original washer and still won't fall out.

Below are pictures of the original vs. new differences I've tried my best to explain in English! :) I will follow up later with the custom push rod which I'm using to get the length correct before ordering manufactured parts for the ultimate solution. The new push rod's end will need to be milled down to something like 7mm to accommodate for lateral play, but that's a simple job I can do on the bench.

End of old MC piston - only ball end is possible:

oldMCend.jpg


End of new MC piston - ball end or straight rod end possible (see "hole" inside ball socket):

newMCend.jpg


New MC requires longer push rod because old MC is recessed further into the cabin than new now:

MCDifferences.jpg
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- '69 SRL
- '08 Triumph Tiger 1050
- '10 Panamera

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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by Gregs672000 » Sat Apr 06, 2019 1:09 pm

Interesting... I noted no such differences, but then realized I have not been dealing with a stock Roadster master for all these years! However, as an FYI I have not had any location or pedal problems with the 510 master. I did note differences in the push rod, with one that did not adjust enough to work, but they were easily swapped. Sorry for the misinformation.
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Re: Tandem Brake Cylinder Leak: Rebuild, Re-Man, or OEM?

Post by dads311 » Sat Apr 06, 2019 3:32 pm

I also used a 510 MC and the stock rod. My new cyl did not have the option for a straight rod, which is a nice option. It fit exactly the same as the old. The problem I had was that the retaining washer was not allowing the rod to come all the way off the piston, so it was keeping the piston partially engaged and keeping an increasing amount of pressure in the front brakes eventually causing them to lock up before I could get home. That did not impress the wife on her first test ride with me. :oops: I ended up having to grind the ball end of the stock rod down enough to engage the piston properly and allow it to travel all the way back releasing all the pressure. I ended up with about 1/16 to 1/8 inch of free space between the rod and the piston. No problems since.

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