Just did the brakes on my Brat. Definitely better! Completely bled the system and I'm sure there is no air in it. Not mushy or anything. Now here's the problem. When the car is not running the brakes are great, I barely have to press the pedal, minimal travel, and they grab great. When the car is running I get about half way down on pedal travel before brakes apply and it seems I have to apply more pressure than necessary. I don't have to stand on the pedal but I does seem like I have to apply more pressure than should be necessary.

 

Ideas? I'm suspecting the Master Vac.

 

P.S When I apply the brakes at idle I get a slight drop in rpm's.

Edited May 5, 201312 yr by jonas

Ok, did the master vac check according to HTKYSA manual and it is working properly.

Bump for the evening crowd.

So far all my research is pointing to a bad master cylinder. It's not leaking fluid but I don't have the pressure I should. I'll change that and see what happens.

Have you checked the shoe clearance on the rear brakes? That will cause excessive travel + throw off the proportioning valve. In case you don't know how to do it:

 

Jack up the rear of the car until the rear wheels are just free of the gound. (Be smart, block the wheels and use jack stands, don't need to be losing any board members from the car falling off the jack)

 

Crawl under the rear, and at the bottom of each backing plate is a small screw. You may have to use some penetrating oil on the threads if the rubber cap is missing. They are a square drive, but I've always just used a small adjustable wrench or an 8mm open end. 

 

Crank it in one side at a time until you can no longer move the wheel by hand. (You will feel it "click" as you turn, make sure it's between clicks when you check the wheel. You'll feel it when you actually do it, it will be hard to turn at first and then it will "click" and will get easy again. If it won't turn, you may need to replace it, they will rust up and strip out. Once the wheel won't move, back it off two clicks. You might hear the brakes dragging very slightly (I usually pump the brakes a couple of times to center the shoes and then spin again) but you shouldn't feel any resistance. Back it off another click or two if you feel there is too much resistance. 

 

If it won't adjust all the free play out, pull the drums and check the linings and the drums, if they are worn excessively you won't be able to adjust all the free play out of it.

Yup, rear brakes have been replaced and adjusted. Master cylinder is all i have left. Bled the system several times. not a terribly expensive part so we'll see what happens.