Master cylinder?????

[jbake]

Last month I picked up an 82 regal for my 15 year old son first car. Last weekend we got it running and took it for a test drive on gravel roads near house. All was good till we pulled back into drive way when I lost all brakes! Foot went to floor and almost hit house. Lol. Do we got it back on jack stands n checked all the lines,well cylinders,and calipers. No leaks or busted parts. If you pump brakes you keep brakes but if it sits over night there's no brakes again. Little looking I found that 81 impala has same size fittings as gbody but with 1 1/8 bore. Swapped it out bleed brakes now car has hard pedal but braking distance has doubled. HELP please. It's my kids car so I'm not going to cut any corners. Need the best a broke b*st*rd can afford.

 

[1983regal]

Did the impala have manual or power brakes? Master has to match power/power and manual/manual you can't interchange them.

 

[78MC-BBC]

it seems that you may have blown the brake booster, i'm pretty sure you have vacuum assist brakes, cause i have never seen a stock 78-88 g-body with manual from the factory

 

[jbake]

Suppose to be power vacuum booster. But got it at orileys so never know with them. Part number is 10-1870. Thought maybe had lines backward but they r diff sizes so can't hook up wrong.

 

[78MC-BBC]

so you already replaced the brake booster? double check the vacuum line from the booster to the manifold, look for cracks etc.. and make sure the check valve is on the right way. http://www.aa1car.com/library/bfixes.htm

Lack of power assist may be due to low engine vacuum, a leaky vacuum hose to the brake booster, or a defective brake booster. The booster is located between the master brake cylinder and firewall in the engine compartment. Sometimes a faulty check valve will allow vacuum to bleed out of the booster causing a hard pedal when the brakes are applied. This condition can be diagnosed by starting the engine (to build vacuum), shutting it off, waiting four or five minutes, then trying the brakes to see if there is power assist. No assist means a new check valve is needed.

A quick way to check the vacuum booster is to pump the brake pedal several times with the engine off to bleed off any vacuum that may still be in the unit. Then hold your foot on the pedal and start the engine. If the booster is working, the amount of effort required to hold the pedal should drop and the pedal itself may depress slightly. If nothing happens and the vacuum connections to the booster unit are okay, a new booster is needed (the vacuum hose should be replaced, too).

 

[jbake]

Nope same booster. I'll double check vacuum line when I get home. Didn't hear leak or see any bad spots in line. Maybe I didnt get all the air out of line. This car sat in mother-in-law garage for 13 years so who knows whats all wrong with it.

 

[jbake]

Ok so I checked vacuum line and booster. Nothing. Pedal still hard as a rock and no brakes to speak of. So.......... anyone got any ideas? I'm lost never had this problem before and I've been turning a wrench almost 15 years now.

 

[rustyroger]

If you have a rock hard pedal the problem almost certainly is with the booster, could be it isn't compatible with the new M/C.

Are you sure it is all assembled correctly?, vacuum leaks would make it idle like a pig, sounds to me like you might not be getting vacuum to the booster, could be a collapsed hose or frozen non return valve, or simply a plugged vacuum outlet in the manifold.

If the brakes are worse than before double check your work, could be you just had a senior moment. 🙂

Roger.

 

[78MC-BBC]

if you havent replaced the booster, than you should now. booster can go bad just by sitting there. seals can rot away

 

[Bonnewagon]

I vote booster too. If the Impala MC was good, the bigger bore is a plus. You would get less pedal travel with slightly more pedal effort, and I recommend that as an easy brake upgrade. A rock hard pedal is not seeing any power assist, and that should be addressed first.