Hello,

I have an issue currently with the brakes on my 54' 88 HT. The brakes have been redone by the previous owner. The pedel just started to pulse "bounce" and I believe it to be vacuum related and not the hydraulic system. Any advise as to what it could be? Brakes are working well but this bounce just seemed to have started.

 

I always say "Check the simple stuff first".
And if this were mine I would take the drums off and have them turned, or checked, to make sure they are perfectly round. To me that is the simple thing to do.
If that was a waste then maybe someone else can think of something else to check.
I have seen many people "do" the brakes but not even do a half way job.

 

Redone? Did he install discs?

Is the pulse frequency related to the speed of the car, the speed of the engine, or to something else?

- Eric

 

Warped rotors?
Discs or drums?

 

Sounds like warped rotors or our of round drums.
Hopefully you can find a good shop that can check them and resurface properly if needed. I had a shop warp a set of good original rotors for only 6 bucks apiece. They tried again and was only a little better. I gave up before they were trash.

 

Be careful as Rob stated, take them to someone who will cut just enough to true them.

 

Like everybody else, I'm thinking drums.

The forklifts at work do that when then need brakes. They all have drums

 

If stock a 54 would be a drum car and it could be a out of round drum. You can check for lack of vacuum by pulling the vacuum line off the vacuum tank and listen for the rush of air sucking back in to the tank ( do this with the engine off). If no sucking sound look for a small hole in the tank or bad vacuum lines or a bad one way valve near the tank.If you don't know the tank is located It's on the drivers side along the frame rail You can't miss it it's about 4 inches in diameter and 24 inches long.....Tedd

 

X2 on out of round drums. If rotors, they can be checked with a dial indicator.
I have seen extremely loose wheel bearings do this.

 

Thanks everyone. I guess I was not as clear as I should have been. All stock drums that are true and round. Ted I need to check the vacuum lines as that is the feeling the pedal is sending to me (LOL). Feels like a vacuum issue (pulse/bounce). I will let you guys know what I find this weekend.

 

Your car decided to update itself to ABS, you should be happy A secondary shoe can hang up sometimes if not lubed and seated properly and cause a pulse every time it grabs and releases off the drum. x2 on looking for the simple stuff first that's mostly overlooked. When was the last time it got all the bake fluid flushed out?

 

Entire brake system redone January 10'.

 

Is that January 10, of 2013 or January of 2010? I've seen drums warp that were brand new after driving through a puddle of water when they were hot. Have you checked them? I would assume nothing.

I may be wrong but I don't see this as a vacuum issue unless it does it standing still.

 

That's why I asked about pulsation frequency and whether it varies with road or engine speed.

Still no answer.

- Eric

 

Sorry Eric. The frequency is the same everytime the pedal is depressed. It is not dependant on road conditions or engine speed.

@Oldcutlass. Yes January 2010. This started all at once not over time. One day it was fine and the next time I drove it is when I noticed it pulliing out of the garage. It does it at Idle when the car is not moving.

That's why I'm thinking vacuum and not the drums to start with as Ted suggested. Have not had the change to check it out at all yet. I will keep you all posted.

Terry

 

In that case, I would agree that it's a booster problem.

I'd try checking it while driving uphill and downhill, to see whether the amount of vacuum affects it.

- Eric

 

Is your system like a treadle vac?

 

Yes I have the Treadle vac with a bendix.

 

I know just enough about those systems to get in trouble. There are a few threads on the 2 systems. They are Delco Moraine and Bendix, I believe the master cylinder on a Delco Moraine has 4 attaching bolts on the booster with a square base, on the Bendix has 3 bolts with a triangular base.

Hopefully someone more familiar with these can help you out.

 

I've had my problems with treadle-vacs but never felt a pulsing as you describe. Mine ether worked or I got a hard peddle.If you can get the car up in the air look around the treadle- vac for any kind of brake fluid leak it doesn't take much to be a problem, also around the backing plates there might be a little fluid on on one of the brake linings. Let us know what you find out....Tedd

PS. when I lost a vacuum hose (vacuum hose came off) I just lost all power brakes. maybe if a small hole was in the tank it would pulse or if the valve were to go bad..Don't know...Tedd

 

Well I installed a couple of front wheel cylinders as the front drivers side was leaking. Stop great again. The pedal is solid. Thanks for all the advice!