Is there any way for me to test my brake booster to make sure it's working property? The car is a 1981 308 I sent it off for a rebuild. My mechanic says it's still not working right. The rebuilder says there's no way it's not right because they test every unit before shipping it. I can send it to another rebuilder if necessary, but I had to take it off again without knowing for sure, so is there any way I can check it myself? Thanks
Find a way to pressurize the booster. At the suction port of the booster you would have to fabricate a tire valve and maybe install an air gauge to see if air is leaking out. Remember there is a rubber bladder inside the booster. If air is leaking around the rubber diaphram then the brake booster will not work. Did you check the hose and valve going to the brake booster? If you have a vacuum leak, then the booster will not work. Was your master cylinder leaking inside the brake booster? When brake fluid leaks inside the booster the brake fluid will destroy the rubber diaphram. Charles
What is the car doing to make your mechanic think its not right? Running rough? Hard brake pedal? I have rebuilt them many times. Not a job that you can really mess up. Just a rubber diaphragm basically. Unless it was pinched going back together? If the booster is working correctly, it should have no noticable effect on the engine, but if it is leaking because of a torn diaphragm, it will cause problems. Do the checks ckracing has mentioned. Im sure that it will be fine. You may want to check the hose in particular and the 1-way valve.
Have you ever shut your engine off before coming to a stop and then stepped on the break? That's what the breaks feel like. You have to put a lot of pressure on the break to stop, and it still takes a while to come to a complete stop. The mechanic said he could hear a vacumm leak coming from the booster, which is why I originally sent it in for a rebuild. I would appreciate any other suggestions as to what may be the problem. Right now I seem to have a mechanic and a break booster rebuilder who disagree.
Ok, yes, that sounds like the brake booster is not working. If the rubber diaphragm is torn, then this can happen, but it will make the engine run rough when the brake pedal is depressed. Also, I have seen the vacuum hose going to the booster internally block up/perish from old age. That means, the brake booster is not getting engine vacuum and will not work. The one-way valve going into the booster could also be faulty? It can only be 3 things mate, its not rocket science.The booster(which is apparently rebuilt) vacuum hose or one way valve. Surely your mechanic can diagnose this. Uncle paps booster testing procedure- Hook up the vac guage. Start the engine. Note the reading. This is your "base" reading. Stop the engine, disconnect the booster vacuum line and cap the port on the manifold. Start the engine, look at the guage. If this reading is substantally higher than the base, you have a leak in the system, probably in the lines leading to the booster. Stop the engine, remove and test the one-way valve (should be able to blow into it one way but not the other). Air should only pass in the direction indicated by the arrow printed on the top of the valve (make sure to reinstall it in the correct direction). Reconnect the one way valve and vacuum line to the manifold and start the engine. Watch the vac guage as a friend depresses the brake pedal. It should dip as the pedal is depressed and return to the base reading. If it drops slowly, but returns, you have a blockage/collapse in the vac line. If it falls and does not return, you have a torn diaphram in the booster. Especially indicative of a torn diaphram is a hissing when the pedal is depressed.
i think the 308 like the mondial have a vacuum tank to supply vacumm to the booster. the vacuum line has a one way check valve just off the manifold. that line then runs to the tank from the tank a line runs to the booster but goes thru another check valve first. if you don't a have a tank, then nevermind. on my mondi i was getting the same problem until i noticed a leak at the tank, after taking apart the footwell for another problem. the vacuums so low on these cars that the manual advises against coasting to a stop as there won't be enough vacuum to run the booster.
