I have a 1965 122s with the stock single line braking system. I would like to switch over to the newer dual line system. Any suggestions as far as where i can get the necessary parts: master cylinder, power cylinder? Is this pretty involved as I'm new to all this? Thanks

Yeah, it's not trivial.

But you CAN use an early Mazda RX-7 master to do a front- back split.
You'd need to replumb a bit of the rears, and a bit more of the front,
and ovalize the holes of the master to bolt it on. But it WILL give you a separate
front and rear circuit. And maybe best, the reservoir on it has a float
which trips a 'low fluid' light.

I agree, it's not the same as the fabulous 70's and 80's
dual front calipers- but then, those are gone now too...

But if you're not comfortable getting this involved, I agree,
brakes are NOT the place to hone your plumbing skills!

What you CAN do is change the fluid anually. That does a lot to preserve
a brake system...

fwiw,
t
--
122t

Well, thanks to all, I'm going to go with the stock system but go thru all of it.
Overhaul and replace everything necessary. This is actually my 16 year old daughters car she bought for $50. We are slow to start on this project, but are having a good time so far. New battery, coil, wires and hoses, cleaned out the fuel system and it now runs. Thanks again.

If the peon driving it will not be looking under the hood regularly I would really recommend a float in the brake fluid reservoir. No fluide = no brakes, and in a single line system one leak = no fuid.
--
Patrick, '68 220, '92 Eurovan , '53 PD4104 (highway coach conversion).

Hello,

To begin with, the stock brake system is just fine as long as everything is in good condition including the parking brake cables.

The 1968 122/1800 dual circuit arrangement is pretty much standard in the automotive industry for cars without ABS, except for the fact that the "hydroboost" type of brake booster that was used at the time only boosts the front circuit.

There are many ways to convert, some are more involved and some are simpler.

For the simplest dual circuit conversion that can I suggest, use the following parts and techniques.

If necessary, get the calipers rebuilt and rebuild or replace the rear wheel cylinders.

If necessary, get an original style "hydroboost" brake booster rebuilt. If you do not have one, you should get one.

Check and if necessary replace all 3 brake flex hoses.

For a brake master, use either the bolt on dual circuit brake master for a 1968 122/1800 from CVI which will need a reservoir, or use the replacement brake master kit for the 1968 brake master, which might also need a reservoir.

For the warning valve/splitter, find an original warning valve/splitter or use a Volvo 240 warning valve/splitter.

If you use the Volvo 240 version which are available new, you will have to plug some of the extra ports.

Install a very simple brake imbalance warning light system.

You will have to re-route the rear brake line from the junction at the firewall to the warning valve/splitter and plug the open port at the firewall junction.

You will need to make a few brake lines or connections from the master to the warning valve/splitter, from the warning valve/splitter to the booster and from the booster to the firewall junction.

The result will be as near to a modern dual circuit system as you can get without going to a modern booster/master setup where the booster pushes on the back of the brake master and therefore boosts both circuits.


--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502

Unless you switch the front calipers as well it will not be a true dual line system, stock ones only have one brake line in. Unlike the dual lines that IIRC the 69 122's had as well as the 1800's etc on up. What you'll probably end up having to do, which is what I did on my 66 122 wagon was to split the front and back into 2 circuits. As well as adding a brake booster and dual master cylinder, you'll end up having to get some hard brake lines made up if you don't have a donor car for all the plumbing and parts.

sounds like it's beyond my expertise at this point, thanks for the info.

it's involved and the later '68 front back split system is only a little safer than a single line system. The fastest and cheapest way to a safer single line system is
1: a well adjusted fully functioning handbrake with good condtion cables.
2. A warning system that tell you if you have low brake fluid.
As soon as you get a chance, replace any suspect hard and flex lines in the braking system, with that all done a single line is safe enough.
--
Patrick, '68 220, '92 Eurovan , '53 PD4104 (highway coach conversion).