Brake help needed

[BadAssChevy502]

Brake help needed

I have a problem with my brakes every time when I first press the brakes I press them almost to the floor, if I then release it and press it again them I have full pressure this happens all the time and especially at low rpm’s when parking for instance.
Is this a booster problem or a master cylinder, proportioning valve or????

PLEASE help because these brakes are scaring the **** out off me, and I don’t know if ill be fast enough on a emergency situation where I don’t have time enough to press it twice

INFO; 1972 Chevy ¾ ton pickup power brakes, front disc rear drum

[GMCPaul]

2 things I would consider first is there is air in the brake line and they need bled,or your steel brake lines are corroded or rubber lines are deteriorated and when you first step on the brake they swell to maximum size then second step on brake allows more fluid to moveto move brake cylinders & calipers. If its the last scenario your about to blow some brake lines.
GMCPaul

[BadAssChevy502]

i have bled all the brakes and have no bad brake hoses as far as i can see,the steel brake lines i have to check again but i'm not loosing any fluid out off the master cylinder

[GMCPaul]

If its corroded lines swelling when pressure is applied you will not lose fluid until a line bursts or developes a small leak. In order to check the hoses for swelling have someone step on the brake while watching the hose to see if it enlarges.
GMCPaul

[68 Suburban]

The same thing was happening with my burb. It turned out to be the master cylinder. A trip to autozone and $11 later, it was as good as new.

[BadAssChevy502]

New or repair kit ?????

[BadAssChevy502]

Ok so the steel brake lines are good , the rubber hoses are also good (not swelling up) and it’s not leaking any brake fluid…………. What else can this be……….. !@#$%#$@!*&%$#@$ I’m going NUCKING FUTS here (thanks to another board member for this translation LOL)

[palallin]

Replace the MC. Yours will eventually fail (and it sounds like that isn't far off). The result? Well, my pics are at home, so I'll have to post them later. . . . Trust me: it's unpleasant.

[sneakysnake]

Back shoes are not adjusting takes two pumps to reach the drum? Check to see how much play you have. Pull a drum check your shoes and run the adjuster out as far as you can,then after you put the drum on take a flat screw driver and run it out till you just start to hear or feel slight contact while spinning the wheel.

[71GMC_3/4T]

Sounds like the MC has a bad cup. There are two seal cups, one for front and one for rear.
If the front one is bad, you will have problems like you are describing. If the other is bad, you will lose brake fluid out the back end of the MC.
I'd go with new. Any I've rebuilt were rust pitted real bad and didn't last very long.

[A.P.]

I had the same the problem with my truck and it turn out to be the MC.

[ckhd]

There are several things that could cause that, most have been mentioned. I've been having the same problem with my '68 K20 for about two years now - tried a new M.C., checked balooning lines, bled like a crazed monkey, etc... I just fixed it yesterday.

Turns out that there was too much slack in the rear drums. I crawled under there and used a couple of screwdrivers and turned the auto adjusters like mad until there was a little bit of drag on the drum, then backed them off a little.

Amazing difference. I used to have to pump at LEAST once (usually twice) before I could get any braking action. Now, my pedal is firm and I can stop when I want.

Something to try before you start spending cash. Even though the master cylinder is very cheap (under $20 for a lifetime warranty one).

[krue]

I used to have a Mazda B2200 that I would adjust the brakes on and they would be tight as a drum, but the more I drove the more I would have to pump....turned out the back adjusters where on backwards!!! They were loosening everytime I stopped.

[lukecp]

I also think the master cylinder is the problem....only takes 1/2 an hour to install, and costs $20.

[greasemonkey]

lol krue, the dude before me put two short shoes on the left rear and two long shoes on the right rear.

[BadAssChevy502]

Thanks all, I’ll go and check the rear brakes, and if that doesn’t work I’ll replace the MC

This board has been so helpful to me there should be an AWARD for best board or something , I would definitely vote for this board, two thumbs up

[BadAssChevy502]

...

[JimKshortstep4x4]

Does the thumbs up mean your brakes are fixed?

Your 72 is a well optioned truck.

Jim

[BadAssChevy502]

Thanks, JimKshortstep4x4 it sure is a well optioned Truck and I’m real happy with it ,but I still haven't located the brake problem so I'm going order A brand new MC ,but I was wondering about something, I can buy a repro non brand name MC for $49 and I can buy a original GM one for $110 what do you guys and gals think is there a difference between these two, my gut feeling tells me to get the GM one because I don’t want to play ”Russian roulette” with my brakes

Please Advice

[BadAssChevy502]

any one

[A.P.]

I bought my from Chief Autoparts, now known as Autozone. That was a few years ago and I have not had any problems.

[JimKshortstep4x4]

I have had very good luck with rebuilds from Autozone and other parts stores.

Jim

[Adam12]

I just bought one 2 weeks ago from Pep boys for $15.99, I wouldnt spend $110 on one.

[lukecp]

I've got a $15 O'Reilly's MC in mine....been in there about a year and works great

[Longhorn Man]

I just noticed you are not in the states, that explains the huge frikken prices there.
You will be fine with the cheap parts. I see no reason to go with the GM one, I think it is just a chap part with there box wrapped around it.
If you know someone here in the states, you could probably get it cheaper by having him buy it and ship it to you. Seems people jack up the price exsesivly when dealing with over seas shipments.