I've been working on getting my 69 1800 up and running after it sat for seven years. It runs fine now but the brakes don't work very well, to say the least. I replaced the master cylinder, had the brake booster rebuilt, bled the brakes and it still has the same problem. The pedal is firm but it takes a long time to stop. Any ideas? Could the brake booster be out of adjustment? Is there a special way to adjust it?

The reversed check valve is the item to check first, just because it is easy to do.

Frozen calipers is always a possibility. The test suggested by C. Mullet may detect the problem; but, may not. The earlier 1800 is different than my 142; but, I believe still has live pistons on both sides of the caliper. If only one side of the caliper is frozen then you will still get enough drag from the other side of the caliper to fool a hand rotation test. If the calipers were seriously frozen on one wheel the car should pull to that side on hard braking. If the car stops straight, then I would look elsewhere.

Did you replace the brake pads? If so, what type of pad? By my own error I installed some performance front pads on my 142 when I rebuilt the system. Braking was poor during normal driving - performance pads need to be hot. Some replacement semi metallic pads from Beck Arnley were much better for normal driving. Make sure that that your pads or disk surfaces are not contaminated with oil, grease or brake fluid. You can clean the disks. I would probably be inclined to throw away seriously contaminated pads.

I had a rebuilt brake booster on my car. It never worked. The solution was a new replacement from VP Auto. If everything else checks out fine, time to scrutinize the booster.

If they brake hoses are more than a few years old I would replace them.degraded hoses can collapse inward & that would prevent proper brake action

I bled the master cylinder (duh) and rebled the brakes and they work a lot better but still not like they should. The pads weren't changed. The hose from the BB goes to the manifold with the one way valve arrow pointing toward the manifold. The hose "T"s off to the PCV valve.
You can't download photos here?

Pads not changed but have you had them out? If you haven't you won't have properly checked to see if all of the pistons move smoothly and at the same time. Some pieces of hardwood about the same thickness as worn pads can be used. the pistons should all lever in and out with minimal resistance. When you first revived the car what was the state of the discs? They can corrode quite badly, especially if they were worn and bit groovy. If rusty and now "clean", the rust is possibly now imbedded in the pads. This doesn't make them very efficient. If the pistons are good a new set of pads plus a fitting kit is a no brainer. Not expensive. Clean up all of the sliding surfaces on the calliper with a file and put it all together using a smudge of copper grease on these points plus the backs of the pads where the pistons push on.
I've just had to replace a calliper on my '67 Wagon. Although I could get the pistons to move under pedal pressure they were reluctant to return. After hard braking it caused the calliper to jam the pads onto the disc and overheat. This would boil the fluid and you would lose the brakes, pedal to the floor. You only have to have this happen once. Luckily without a mishap in my case.

If all of the bleeders flowed well during the bleeding process then likely the hoses are not collapsed..... yet. Maybe some of the caliper pistons are frozen. Have you spun each wheel while it's in the air and had someone hit the brakes? Also, are you sure the check valve on the vacuum line is pointing in the right direction?

Frozen calipers is what I'm thinking. Where is the check valve and where should it be pointing?

1969-1973 Volvo 1800S, 1800E and 1800ES use inline brake booster check valves installed in the vacuum supply hose and they can be installed backwards which would block the vacuum supply from the intake manifold which means the brake booster wouldn't work.

I would inspect your check valve installation 1st because if you did install the check valve incorrectly, it is way cheaper to fix than rebuilt calipers.





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