54olds

Well, I finally got my brakes to work after months of frustration and a lot of colorful swear words

Turns out it was a bad master cylinder brake hose. Special ordered one from Fusick and brakes work now! (btw, I highly recommend Fusick - they were very helpful and my part got here very quickly.)

What's weird is, when the car is running and you press on the brake, the idle drops somewhat. I also noticed that when slowing down to stop, everytime the transmission shifts the idle dipped.

Is this normal, or do I have another problem?

59-59-59

I dont know if this is yor exact problem, but this has happened to me in both '57 and '59's that I own - There was a HUGE rot hole in the bottom of the vacuum canister. This will cause an odd rough idle with the brake applied since you basically have a huge vacuum leak. Hook up an external vacuum hand pump directly to the canister and pump and see if it will hold any vacuum.

joe_padavano

I agree. The only thing related between the idle speed and the brakes is the vacuum booster for the power brakes and the associated vac lines. There's a leak in the booster someplace that only opens up when you step on the pedal.

54olds

I took the canister off a few months ago to inspect it. It was a bit rusty, but I found no holes or cracks. I did use a small pump to check vacuum, and it seemed to hold OK.

There is an electrical solenoid that controls vacuum to the canister - could that be a possible cause?

54olds

Oh, one more thing - I sent the master cylinder/booster away to be rebuilt a few months back. I've noticed sometimes the brake pedal doesn't always return fully once it's been pressed and released, even though the brakes seem to be working fine. Any ideas on that one?

59-59-59

One more possibility - check the line from the back of the carb with the vacuum pump. You may also have a bad check valve in this assembly or just a couple holes in the steel line ( I've seen it before ) I am still betting on the vacuum canister - all you need is a couple pinholes that will drive you nuts as far as idle goes

54olds

I did a little more detective work on Monday and found that the previous owner had cut the wire supplying 12v to the vacuum line solenoid. Repaired the connection, and that seemed to cure my idle drop. Yay!

I still have the issue where the brake pedal doesn't fully return, though.
I'm not quite sure why that's happening.

59-59-59

For stock, there should be no external vacuum pump with a +12 volt wire going to it. This is telling me that there is a leak somewhere else in the system and whoever did this didnt try to find the exact cause of the leak! I would love to see a picture

tarps3

My '53 power brakes have all of a sudden become very hard to depress.
When i stand on them, it slows the car down, but not very quickly.

A month ago, they were hair-trigger and would stop the car with the slightest pressure.

could my hard pedal also be caused by a vacuum leak?

54olds

Check first to make sure you don't have a vacuum line that might have come off somewhere. Check your vacuum line going to the power booster and make sure you have vacuum at the booster. If the '53 has a reserve vacuum canister like my '54 does, check the lines going to it and the canister itself for leaks. You may also have a leak in the power booster itself.

tarps3

thanks for the reply 54olds.
I have checked the lines and all seem fine.

I think it's at the booster since I can hear a loud hissing when I press the brake pedal.
I bought a rebuild kit that should be here by the weekend.

Is this a hard project?

Texascarnut

The whole job ranks right up there with a wresting match with a Grizzly Bear! Good luck.

88 coupe

Yes. It gets worse, when the idle speed is set too high.

Should be 400 RPM, in drive.

Norm