I Need Some Brake Help ASAP

[64nailhead]

Did you read the other post ? Whats your opinion of the info the guy from Master Power gave me about the bore on the master ?

Everyone is entitled to an opinion.

The master cylinder has to be completely released (moved to the rear of the car) inorder for the master cylinder to achieve full volume per stroke. If this doesn't occur, then the size(diameter) of the master cylinder x the length of the stroke are erroneous. Why increase the diameter of the cylinder by 12.5% if you're going to limit the stroke by 5-10%. The net effect of a larger bore cylinder when that occurs is minimal or negative.

Also, disassemble a master cylinder and see how the fluid is pulled back into the bore. If you do this then you'll see why the cylinder not returning fully rearward will cause a loss of brake performance.

 

[mikester]

I appreciate all this info. What would be the right/easiest fix ? Get the right booster from a place like rockauto ? New booster should have the correct rod ?

 

[mikester]

Personally I woulds listen to 64nailhead before some employee at a parts reseller...I have read many of 64naihead's posts which shows his expertise and knowledge while I have no idea who the guy from Master Brakes is.....

I called Moser first since I bought the 12 bolt from them and it came with the Torino brake setup. The guy there told me to try a brake company. Master Power sells the same Torino brake setup that they use.
Im hoping 64nailhead reads my last post. It sounds like hes up on this stuff. This is way beyond my skills.

 

[fleming442]

Good luck.

 

[pontiacgp]

Something I just realized I didnt mention in any of the posts.
This soft pedal is on a car thats not running. Now before anyone says thats the issue, the wagon isnt running either but the pedal in the wagon is higher and firmer. My thinking is when its running its going to feel different because of the booster.
The 81 feels like crap now. What happens when the booster kicks in ? Will the pedal pressure feel better or worse ? And if better, why the difference in the wagon ? I would think they would/should feel close to the same.

if you havn't got the car running I would take a break on the brakes til you have the car running.

 

[mikester]

if you havn't got the car running I would take a break on the brakes til you have the car running.

Not that easy. I had to pull the left header to get the one brake line out and to have enough room to get the new proportioning valve in. That also involved taking the valve cover off so it was easier to get out the back bolt.
I want the brakes done first.
Since I dont know if the generic booster had the right length rod I'll just get the correct part number booster for the year and try that. Hopefully 64nailhead and mc96 are right about the rod length. I'll let you folks know.

 

[pontiacgp]

Not that easy. I had to pull the left header to get the one brake line out and to have enough room to get the new proportioning valve in. That also involved taking the valve cover off so it was easier to get out the back bolt.
I want the brakes done first.
Since I dont know if the generic booster had the right length rod I'll just get the correct part number booster for the year and try that. Hopefully 64nailhead and mc96 are right about the rod length. I'll let you folks know.

without the engine running if you do not have a source of vacuum I don't know how your getting the brake pedal feel. When you say rod do mean the pin that compresses the piston in the master cylinder?

 

[mikester]

So far Im not having much luck today. LOL
Im a fan of AC Delco parts. Been using them for many years. Just went on rockauto again and it said there was a 1 day delay for a dual diaphragm booster for an 81 Malibu. Put it in the cart to get a delivery date. As soon as I did that it came up as unavailable. Went off rockauto to see if I could get it anywhere else and the same deal. Unavailable. So I go back on rockauto and the part is gone. Not even listed. Geez, theyre fast !!! LMAO

 

[mikester]

without the engine running if you do not have a source of vacuum I don't know how your getting the brake pedal feel. When you say rod do mean the pin that compresses the piston in the master cylinder?

Yup, the rod in the booster that goes into the master. It was a generic dual diaphragm booster. Im assuming (I may be wrong) that if theres multiple part numbers for the boosters there must be different size rods ? Like I said, this is way beyond my skill level.
I considered running out to the local yard and getting a rod out of a booster from a Cutlass to see if the length is the same but how do I know if even thats the correct length ?

As far as pedal feel, Im comparing how the coupe pedal feels compared to the wagon. Pedal in the wagon feels firm and doesnt go down to the floor. The coupe feels very soft and drops way down. Almost to the floor. Pump it up and theres not much difference. Im thinking they should both feel similar. The wagon is also not running yet.

 

[pontiacgp]

when you say rod I think of this