Amazon: Rebuilding rear brakes 1966 Amazon

[fishyboy]

Hi all,
A quick update.
Today I finally managed to get the rear brakes back together and also replaced all the brake lines and flexi-hose from the BRV to the brakes drums. Me and my son spent a while bleeding the system I finally got a brake pedal I was happy with. Adjusted the rears to the Green Book specs (just able turn wheel with one arm and then back off 4 clicks). Went out for test drive and the brakes were performing very poorly and could get neither the rears or the fronts to lock on emergency braking.

Back in the garage I decided to take a quick look at the front calipers, disks and pads. Took out the old pads and got my son to gently press the pedal while I observed the piston's movement (using a brake caliper tool to make sure the pistons didn't pop out). And guess what only the large single piston moved, the two smaller pistons appear to be stuck. I assume both should move. I assume that the other caliper will be the same as they car doesn't pull to one side on braking. Maybe the inactive pistons and reduced braking efficiency of the front disks is the cause of all the problems (rears locking up before the fronts - https://www.volvoforums.org.uk/showthread.php?t=307757) that I've been experiencing.

The other thing that was odd was the locking pins provided by Brookhouse were much sorter than the old ones on the car and only just reached the other side of the caliper. This got me wondering whether the newish calipers (fitted 2 years and 200 miles ago, well before my ownership) are correct. I've included a couple of photos to show the calipers (which are stamped B1VOAMR 1485). Do these look correct?

Any easy way to free the pistons or should I just buy two replacement calipers?

Any input welcome as I really want to get the brakes sorted so I can come to Sywell in two weeks.

Phil

[Derek UK]

If you put a pad or piece of wood in the large piston side and get the piston to squeeze that you can then apply more pressure to get the two small ones working. At very low pressure like you're applying now they will all move at different rates. Do the small ones move with a clamp or being levered with a screwdriver? The callipers are fine it's just the pins that are wrong. The new ones are correct. The long ones are wrong. Have a look here.

https://www.youtube.com/watch?v=n7j3VEoRK1A

For the rears I usually adjust up until the wheel locks and then back off the clicks until the wheel turns. It might only be one or two clicks. Do both sides. Pump the brakes a few times and see how each wheel feels. If no sound of continuous rubbing that should be fine. When that happens I usually click them back one to see if it does then rub. Click out again if it does. Not unusual to get a high spot at one or two points and that normally just rubs off on new shoes. You will want to readjust them after a few hundred miles anyway. The handbrake should have been backed right of before you did the shoe change and you may well have done this before taking the drums off. If so you now need to adjust the handbrake. 3-4 clicks to lock the wheel and both sides should lock the same. One side might lock at 3 and the other 4. I would back the side with 3 by one click and that should even things up. If your pedal movement is rather a lot when the handbrake is off rather than when it is on, pump the pedal some more and check the number of clicks to lock the wheels. It may have increased. Reset if it has. Always a bit of juggling while the shoes get themselves centralised and bedded in. Good luck.

[fishyboy]

Thanks Derek,
Great advice as normal.
I'll try and free the pistons when time permits.
I hope that this (i.e. inefficient front brakes) is the cause of the early lock up of the rears under heavy braking.
Phil

[fishyboy]

Hi all
Sorry for not updating earlier.

Rear brake rebuild went fine. New shoes, fixing key and brake cylinders. Ending up putting two new drums on as well. I even managed to get the brakes pipes to fit after a fashion.

With a friend we looked again at the front calipers, which I thought had sticky pistons and found that the pistons were actually moving fine and I was just not pushing the pedal far enough. Installed new pads (and hopefully softer) and bled the system several times.

Took the car for a test run. Warmed up the brakes and tried a few stops and rears were still locking before the fronts and concluded that the BRV must be faulty.

Booked the car into my local classic-friendly garage and asked them to check over my work and change out the Brake Restrictor Valve for the NOS one I had for my '68 1800S (same part number as for the 131 and had "1800 and 121" written on the label). Car came back from the garage and now the rears no longer lock up, the front of the car dips under heavy braking and I can if i really stamp I can get the fronts lock up first.

Drove 200 miles to the Sywell meet two weeks ago and all seemed OK, but I still don't feel that brakes are as efficient as another non-servo 60's car I have with the same set up. I'll see how things are when the brakes are fully bedded in (if they aren't already).

Thanks for all the advice and I will update if there are any changes.

Phil