Proportioning Valve

[kowalzekc]

So here is the question, I just did a 4th gen rear swap and now I have 4 wheel disk. I havn't done the Proportioning Valve yet but I know I need too. What is the best option to compleate this?

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[JamesC]

Originally Posted by kowalzekc

So here is the question, I just did a 4th gen rear swap and now I have 4 wheel disk. I havn't done the Proportioning Valve yet but I know I need too. What is the best option to compleate this?

Listing your model, make, and year is always helpful. You should find the info you require in the following FAQ:

http://www.thirdgen.org/techboard/tr...-10-bolts.html (FAQ About 10-Bolts)

JamesC

[kowalzekc]

My bad. 1992 firebird 5.0L 5 speed. Used to have drum rear. Now it had disk from an LT1 car.

[radical82]

I'm sure there's some stuck item that would work, my personal choice is a properly sized master cylinder, a 2lb. residual valve in the front and rear line as close to the M/C as reasonable, and an adjustable proportioning valve in the rear line.... After you get the system bled, then use a brake pressure gauge to get close on your front and rear pressures, then a final tune up of the pressures at a track or big old deserted parking lot..... Yup, lots more expensive!!! but I don't like to cut ANY corners on the brakes, lots of other less important areas on a car to try to save a few bucks......

[JamesC]

Originally Posted by kowalzekc

My bad. 1992 firebird 5.0L 5 speed. Used to have drum rear. Now it had disk from an LT1 car.

The 2nd design 1LE valve will do the trick. Try the classifieds or the mod that Ed Miller offers:

http://www.flynbye.com/catalog/i160.html

JamesC

[kens86]

i put an adjustable wilwood to the rear brakes, but i also have manual brakes and it turned out i did not need it at all.

[Harvey1113]

Hi guys,

I'm working with an '83 Trans Am with the 305 V8 Cross Fire and 4-wheel disc brakes. My dad and I just went threw the process of replacing the fuel pump. First time we've ever done this (many thanks to the thread on this forum - great help! ) Anyhow, my dad inadvertantly cracked the brake line that runs from the master cylinder to the driver's side rear axle.

So, we've replaced the faulty line with a new one and bled the brakes. However, even after bleeding the four calipers the brake pedal still hisses. When I checked the service manual, it mentions bleeding the master cylinder but doesn't detail what a person is to do. Also, my dad is wondering the combination (proportioning) valve may be bad. Does anyone know how a person would going about checking/testing the proportioning valve, and what its settings is to be?

My apologies if I'm asking stupid questions here, I'm still learning about these cars. Many thanks in advance for any help!

[radical82]

Actually it's called a combination valve...no real adjustments to it. The only accurate way to check brake pressures is with a brake pressure gauge, check the pressure at each wheel. The pressure on the front should always be greater...60% front, 40% rear...

[Harvey1113]

Originally Posted by radical82

Actually it's called a combination valve...no real adjustments to it. The only accurate way to check brake pressures is with a brake pressure gauge, check the pressure at each wheel. The pressure on the front should always be greater...60% front, 40% rear...

Thanks for the correction. So, if the pressure at the front brakes are not greater, where does a person go from there?

[radical82]

On a stock system, would mean you have either a master cylinder problem or your combination valve is malfunctioning.... More pressure to the rear will lock up the rear wheels and make stopping a long distance operation!!!! Not a good deal at all!

[JamesC]

Originally Posted by Harvey1113

So, we've replaced the faulty line with a new one and bled the brakes. However, even after bleeding the four calipers the brake pedal still hisses. When I checked the service manual, it mentions bleeding the master cylinder but doesn't detail what a person is to do.

If the master has been bled dry for some reason, you'll need to bench bleed it. Most auto stores sells kits for it.

JamesC

[Harvey1113]

Originally Posted by JamesC

If the master has been bled dry for some reason, you'll need to bench bleed it. Most auto stores sells kits for it.

JamesC

Okay, I'm just not certain as to how one bleeds the master cylinder while it's still on the car. Do you just loosen each connection like one bleeds the valves on the calipers?

[radical82]

Originally Posted by Harvey1113

Okay, I'm just not certain as to how one bleeds the master cylinder while it's still on the car. Do you just loosen each connection like one bleeds the valves on the calipers?

To bench bleed the master cylinder, take if off the car and clamp it (gently) in a vise... Fab up a line to go from each port back into the master cylinder reservoirs making sure that the tubes are low enough in the reservoir to stay covered with brake fluid.... Fill the master cylinder with brake fluid and slowly push the piston in on the master cylinder, then release it. Continue doing this until there are no bubbles showing in the reservoir as you push the piston in.... Remove the tubes, put the cover on the master cylinder and reinstall it in the car.... This will get all the air out of the ports inside the master cylinder.

[//<86TA>\\]

the master has to be level to bench bleed properly. You have to plug the 2 outlets of the master, or bend up some new lines to route from the outlets back into the reservoir. Then pump the piston in the master, or if its in the car, push the brake pedal until the bubbles stop. You may have to do this with the car running, you may run out of vacuum before the master is completely bled.

[Harvey1113]

Thanks guys, I'm wondering if I'll need to replace the combination valve as well as rebuild the master cylinder....