tcspeer Posted June 7, 2006 Share Posted June 7, 2006 What is the best way to test the master cyclinder, I replaced the front and rear brakes and then bleed them, but it seems like their is not as much pedal on this 98 legacy wagon as most cars. Link to comment Share on other sites More sharing options...
idosubaru Posted June 7, 2006 Share Posted June 7, 2006 when pushing the caliper pistons in did you unscrew the cap to the master cylinder? if not, this can blow the seals in the master cylinder. it's not that uncommon for master cylinders to fail during brake work....why would only be speculation but i guess a master cyilnder close to on it's way out gets subjected to slightly abnormal use during brake work and finally let's loose. who knows, all i know is that i've seen it happen a few times. actually i've never seen a brake master cylinder fail independently...it's always been right after brake work, but i've only seen a couple fail. i like to bleed the brakes with air hose that they use in aquariums (you can get it at any pet store or wal-mart in the pet department. this clear air hose lets you see the fluid as it's coming out (and if you loop it around properly you can bleed yourself). anyway...being clear you can see if there's air bubbles in it. if you're constantly pushing air bubbles through the hose then you have a leak somewhere (look for fluid) or your seals in your master cylinder are bad. if the calipers are installed and you're not loosing fluid, in my experience it's always been the master cylinder that causes soft or no pedal pressure. though other things can go wrong, i've never had to diagnose the brake booster or anything else so i can't help you there. Link to comment Share on other sites More sharing options...
tcspeer Posted June 7, 2006 Author Share Posted June 7, 2006 Thanks for the tips, I will bleed them one more time and check and make sure no wheel cyclinders are leaking, if that dont take care of it I will replace the master cyclinder. when pushing the caliper pistons in did you unscrew the cap to the master cylinder? if not, this can blow the seals in the master cylinder. it's not that uncommon for master cylinders to fail during brake work....why would only be speculation but i guess a master cyilnder close to on it's way out gets subjected to slightly abnormal use during brake work and finally let's loose. who knows, all i know is that i've seen it happen a few times. actually i've never seen a brake master cylinder fail independently...it's always been right after brake work, but i've only seen a couple fail. i like to bleed the brakes with air hose that they use in aquariums (you can get it at any pet store or wal-mart in the pet department. this clear air hose lets you see the fluid as it's coming out (and if you loop it around properly you can bleed yourself). anyway...being clear you can see if there's air bubbles in it. if you're constantly pushing air bubbles through the hose then you have a leak somewhere (look for fluid) or your seals in your master cylinder are bad. if the calipers are installed and you're not loosing fluid, in my experience it's always been the master cylinder that causes soft or no pedal pressure. though other things can go wrong, i've never had to diagnose the brake booster or anything else so i can't help you there. Link to comment Share on other sites More sharing options...
nipper Posted June 7, 2006 Share Posted June 7, 2006 Thanks for the tips, I will bleed them one more time and check and make sure no wheel cyclinders are leaking, if that dont take care of it I will replace the master cyclinder. STOP! (hehe thats right you cant) There is the master cylinder and the power brake booster. both give the same symptons. You also have brake lines that do age internally and you cant really tell. Test the PB. with the car off press the brake pedal untill all boost is exhausted (5-10 times). Put your foot on the brake pedal, then start the car, the pedal should move towards the floor. If it doesnt you have a bad booster. Did you re use the brake fluid from bleeding. you can not do that as the fluid is airated. What do you mean by "their is not as much pedal " exactly. There are claipers on the front, and calipers or wheel cylinders on the rear. How did you bleed the brakes. nipper Link to comment Share on other sites More sharing options...
tcspeer Posted June 7, 2006 Author Share Posted June 7, 2006 Last night I went out and pumped the brakes around five times they held fine, then I started the car and the pedal moved towards the floor. The car has brakes but they are not as good as the ones in my other postal wagon which is a 97, this one is the 98 that I paid 100.00 dollars for back in April. Its now close to 2.000.00 dollars that I have in it,but I would not sell it for that as the right hand drives are getting harder to get. I also noticed when I stepped on the brake pedal the park lights and dash lights came on. STOP! (hehe thats right you cant)There is the master cylinder and the power brake booster. both give the same symptons. You also have brake lines that do age internally and you cant really tell. Test the PB. with the car off press the brake pedal untill all boost is exhausted (5-10 times). Put your foot on the brake pedal, then start the car, the pedal should move towards the floor. If it doesnt you have a bad booster. Did you re use the brake fluid from bleeding. you can not do that as the fluid is airated. What do you mean by "their is not as much pedal " exactly. There are claipers on the front, and calipers or wheel cylinders on the rear. How did you bleed the brakes. nipper Link to comment Share on other sites More sharing options...
nipper Posted June 7, 2006 Share Posted June 7, 2006 Last night I went out and pumped the brakes around five times they held fine, then I started the car and the pedal moved towards the floor. The car has brakes but they are not as good as the ones in my other postal wagon which is a 97, this one is the 98 that I paid 100.00 dollars for back in April. Its now close to 2.000.00 dollars that I have in it,but I would not sell it for that as the right hand drives are getting harder to get. I also noticed when I stepped on the brake pedal the park lights and dash lights came on. Your the second with that light issue. Remove the bulbs one at a time in the brake lights til the problem goes away, then inspect that socket or replace it. Also make sure thy are working and the fliamint isnt shorting out the lights. its quite possible that it is the master cylinder then. You may want to replavce the flex brake lines. People seem to over look those. I would replace those first (since they are old enough to warrent it anyway). nipper Link to comment Share on other sites More sharing options...
tcspeer Posted June 8, 2006 Author Share Posted June 8, 2006 Thanks Nipper for the tip on the lights, I had no idea how to go about trouble shooting that issue. Your the second with that light issue. Remove the bulbs one at a time in the brake lights til the problem goes away, then inspect that socket or replace it. Also make sure thy are working and the fliamint isnt shorting out the lights.its quite possible that it is the master cylinder then. You may want to replavce the flex brake lines. People seem to over look those. I would replace those first (since they are old enough to warrent it anyway). nipper Link to comment Share on other sites More sharing options...
nipper Posted June 8, 2006 Share Posted June 8, 2006 Thanks Nipper for the tip on the lights, I had no idea how to go about trouble shooting that issue. not a problem im begining to think thats a commone (but rare) failure mode. And since its a postal vehical, the mastercylinder may be worn out. Your MC sees almost 10x's more stops then a normal master cylinder. nipper Link to comment Share on other sites More sharing options...
lmdew Posted June 8, 2006 Share Posted June 8, 2006 When you pump the brakes to bleed, put a 2x4 under the pedal so you stay in the same stroke range as when the MC is in normal use. If you go full stroke, you are putting the seals into the junk that may have built up in the MC. I have one off a 96 with booster that is good if you need it. $35+shipping. Lmdew@hotmail.com Link to comment Share on other sites More sharing options...
tcspeer Posted June 8, 2006 Author Share Posted June 8, 2006 I dont know if I need one yet, but I think it must be a right hand drive, so that means I will probably have to buy a new one. I remember someone on here trying to put one from a right hand drive to a left hand drive and saying the line connectors are on the wrong side. I think it is one of the few things that wont swap from one to the other. When you pump the brakes to bleed, put a 2x4 under the pedal so you stay in the same stroke range as when the MC is in normal use. If you go full stroke, you are putting the seals into the junk that may have built up in the MC. I have one off a 96 with booster that is good if you need it. $35+shipping. Lmdew@hotmail.com Link to comment Share on other sites More sharing options...
Log1call Posted June 9, 2006 Share Posted June 9, 2006 Put your foot on the pedal once and take note of the height of the pedal. If you give the pedal three or four quick pumps the pedal should only pump up about one-half inch, if it pumps up much more than that then you have either air in the system or the pads arent sitting close enough to the discs for some reason... perhaps the plates behind the pads are warped, misplaced etc. Next test is to take your foot off the pedal and then slowly, very slowly, push the pedal down, if it keeps going down with a slow push but builds up pressure with a slightly quicker press then your master cylinder has worn seals inside it. If it passes these two tests, and it's already passed the booster test, then the problem is a mechanical one not a hydraulic one. Perhaps the pads need bedding in, perhaps the pads are a hard material. The light problem is a bad earth in the rear lights. The power goes down to the brake filiment, can't get to earth so goes back through the taillight filiment, out through some other park/driving/dash light's filiment and so to earth. Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now