Dual Circuit Brake System conversion?

Hi,

The master cylinder for my '65's brake system pretty much died yesterday. And, before I spend money on a replacement, I have a few questions.

I have heard of some people coverting their 66 and older bugs' single circuit brake system to the later dual circuit brake system. Has anyone on this site done this before? Is it even worth it? And if so, is it simply replacing the current master cylinder with a '67 dual circuit master cylinder with the matching reservoir?

Thanks for any help.
-Jon

I've done it multiple times. Personally I used a dual circuit with a Volvo reservoir. But the theory is the same as long as you use a reservoir for a dual circuit. It's pretty straight forward although you will have to bend your metal lines a bit. As far as being worth it, it is a good safety upgrade in my opinion. Also, you will have to have two brake light switches.

yes, I've done it as well. much safer

Ok, that's what I thought.

So to be clear, all I would need to do is replace my single circuit cylinder with a '67 dual circuit cylinder, bend the metal brake lines to the fittings, find a dual reservoir, and get two brake light switches?


Last thing, is there any specific wiring that needs to be done with the switches? And can I get the reservoir at a place like Autozone or Advanced Auto?

Jon65 wrote:
So to be clear, all I would need to do is replace my single circuit cylinder with a '67 dual circuit cylinder, bend the metal brake lines to the fittings, find a dual reservoir, and get two brake light switches?

Yes.  I did this on my beetle a long time ago.  The volvo reservoirs fit the brazilian varga master cylinders.  If you were to fork over the bigger money and get a german master cylinder, you would need to find a rabbit reservoir.  The difference is the spacing between the inlets or something like that.  I went the varga/volvo route with mine.  

There is a little more that you may need/want to do depending on how you want to fill the volvo reservoir.  Some people modify the cap of the volvo reservoir by adding a nipple inlet and still use stock reservoir, adding a line from the stock unit to the cap on the dual circuit unit.  Hope that makes sense.

I completely ditched the stock reservoir and just get under the car on occasion and tap on the reservoir to make sure the fluid level is still ok.  As long as you have no leaks, you shouldn't really ever have to fill or top it off.  Just check it on occasion.  And even if you do have to fill it, your car is high enough that it really shouldn't be to hard to wiggle under there and add a little fluid.  You could always remove the drivers side wheel if needed.

Jon65 wrote:Last thing, is there any specific wiring that needs to be done with the switches? And can I get the reservoir at a place like Autozone or Advanced Auto?

Wiring is pretty simple, you'll just need a couple of those 3-way connectors.  Power goes to tab A on one switch, and then jumps to tab A on the other switch.  The output goes from tab B on one switch to tab B on the other switch, and then is jumpered to the output wire going back to the taillights.  


Not sure if new reservoirs are available from parts stores.  They are available aftermarket for pretty cheap from vw sites
http://www.socalautoparts.com/product_info.php/industries-brake-fluid-reservoir-fits-all-dual-circuit-master-cylinders-top-mount-p-13497

Better yet, if you don't need it right away, let me know the next show (or airheads meet) you are coming to, and I have a clean original I snagged from a volvo at PAP you can have for free.

If you need new brake line you can get it at advance auto or wherever. I don't think you really need to wire up both, you only have one now. Here is mine

I did this conversion on my bus and the 63 beetle. My bus has the ATE master cylinder with a rabbit reservoir, but the beetle is a Varga with the Volvo reservoir. On the beetle I had to tweak the hard lines a little to make the connections but was not difficult. Also I wired the senders in tandem. Not really required, but I figured if I had a sender go bad this way I would still have brake lights.

Thanks everyone. This has really helped, especially the pictures.

Eric, thanks for explaining it so thoroughly, and the offer on the reservoir. Unfortunately, I wouldn't be able to wait that long because this car is how I get around to work, school, and everywhere else, so I wouldn't be able to wait until the next get-together. Thank you though, I really appreciate it.  


I was already going to take time today to install the heater boxes I got early this week, so I might as well go ahead and get the master cylinder taken out, that way all I have to do is run over to Herrel's tomorrow and get the parts.

Thanks again everyone! 

Cool man, good luck with it.  Be careful when taking the old master cylinder out.  You may already know this, but there are spacers/sleeves inside the firewall that the mounting bolts go through.  If you pull the bolts all the way out, those sleeves will fall to the bottom of the firewall.  You'll need to fish them out and put them back on the bolts before you install the new master.  Those sleeves keep the firewall from caving in as you tighten the master cylinder down.

Ok, thanks.

I got everything installed and it works properly now. The brakes are even stronger than they have been in a while. So, I'm really happy about that.

Thanks to everyone for the help.  

Jon65 wrote:I got everything installed and it works properly now. The brakes are even stronger than they have been in a while. So, I'm really happy about that.

Thanks to everyone for the help.  

Plus, if one circuit goes out, the other one will stop you   

Grifspop wrote:

Jon65 wrote:I got everything installed and it works properly now. The brakes are even stronger than they have been in a while. So, I'm really happy about that.

Thanks to everyone for the help.  

Plus, if one circuit goes out, the other one will stop you   

Exactly.