Hitman's Pontiac Trans Am Forum
Trans Am Information => Trans Am Tech => Suspension => Topic started by: L8KRFAN on August 19, 2012, 10:23:43 PM
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Decided to refresh the front end brakes on my 79 T/A. Purchased a new (not reman) M/C from Pep Boys (made in China of course), purchased new rubber hoses from Napa (also made in China, ughhh!), and purchased new hard lines from Classic Industries (Major PITA to install). After all is said and done, I can't get the fronts to bleed. I get fluid to the calipers but now matter how many times my assistant (wife) pushed the pedal then held, when I cracked the bleeder, could not get a fluid stream.
Any ideas? Could I have gotten a bad master? I do seem to see a leak of fluid from between where the m/c seats into the booster. Help!
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If you're getting fluid to the calipers, it would seem the master is working. Try removing a bleeder completely to see if fluid will come out of the caliper hole.
I once had a bleeder that didn't have the hole drilled in the side of it, so it wouldn't bleed. So, that's something else to check.
You may not be leaking behind the master. Maybe it's just some fluid that spilled out the rear chamber, since the master angle is pretty steep.
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Is this a 2 or 4 wheel disc? There is a valve in the center of the prop valve that sometimes can be a pain! Did you bench bleed the master?
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also open the lid on te master, then open both left and right front bleeders and let gravity bleed, as oldschool said, did you bleed the master first? if not then start with that as your new pita hard lines are airated
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If using the pedal to pump up and bleed the system you shouldn't need to touch the proportioning valve, it's for pressure system bleeding.
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If using the pedal to pump up and bleed the system you shouldn't need to touch the proportioning valve, it's for pressure system bleeding.
unless they bottomed out and tripped the valve
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you mean due to operating with low/no fluid or a fault of sorts?
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most depress the brake pedal all the way to th floor when bleeding with a helper and sometimes when depressed all the way will trip the proportioning valve and will have to be reset, when depressing all the way with a worn master cylinder it will flip the seal as well
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To answer a few questions:
Remove bleeders. Yes, did that plus removed the caliper and blew some air into where the banjo bolt/hose mounts as well as the bleeder location just in case there was any crap in there. Didn't seem to help. When I would remove the lines I would get fluid dripping from the lines so fluid is getting there. Just had problem building pressure to the fronts when pedal bleeding.
Bench bleed. Yes, as I alwasys do. It did seem to take forever of plunging the piston and tapping the m/c body to take out I think all the air.
Gravity bleed. Yes, first the rears and they were great, constant drip drip drip of fluid on both sides. Then did a quick pedal bleed a few times and got good squirt and I thought all was good until I moved to the fronts. Fronts too time to get fluid there but again could not get pressure to the fronts. When I would crack open the bleeder (after wife giving four pumps), not much fluid would come out and wife said pedal would not sink.
The situation is the same on both fronts so that tells me it's something above, perhaps the master or prop valve. You guy agree? I think I'm going to take back the master and get another one. They're cheap, only about $40 new. At least start there. Also, how do I reset the prop valve?
It took me most of Saturday and half of Sunday to do all this. I was so tired and frustrated to the laughing point. Lol!
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If using the pedal to pump up and bleed the system you shouldn't need to touch the proportioning valve, it's for pressure system bleeding.
unless they bottomed out and tripped the valve
Thats what I was thinking Joe that it trips when you disassemble or when even just replacing you need that little tool Right?
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should be a nipple on prop valve that you have to push back in, but have to relieve the pressure to do so, if you can get the pedal to depress all the way it will reset itself but assistant has to stop as soon as she feels the click and hold it there whilst you close the bleeeder
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do you have line clamps? if so then clamp off the front hoses and see if you have a pedal, remove the clamps one at a time while assistant holds pressure on the pedal and see if you get a pedal drop, you may have bad hoses. why did you replace calipers? many replace calipers due to seized front brakes when in fact it is a hose
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I'm still having troubles with mine too but have given up until someone else can help out. I've bled the brakes several times after new lines, booster, mc, and rebuilt callipers. There are no air bubbles at all, just fresh fluid coming through. The wheels spin with only slight resistance after bleeding, but pump the pedal once or twice and usually find that one front wheel has locked up and the other very firm. Repeat the process, they free up and think it's sorted, touch pedal after bleeding and they don't release again. I tried driving around the yard while working brake pedal, there's still pressure there. One rear drum felt a little warm after a few laps but it could just need adjusting rather than the same issue.
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aus78, if you press the pedal and the fronts lock up, then crack the bleeder and see if the pressure releases, if so yo have bad front hoses
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An update to my brake problem... The "new" m/c I purchased is definitely leaking. A drop of fluid will build up and eventually drip. I have another m/c on order from Summit, it's Bendix 11944, also a new unit. The first m/c is the Pro Stop brand from Pep Boys. Hopefully the Bendix performs better than the Pro Stop brand.
I found the button on the prop valve but can't seem to get it to depress for the life of me! Tried my finger, screwdriver, etc... I might just buy a new prop valve from inlitetube.com. They cost about $85.
We'll see how it goes this weeknd when I install the new m/c. This is all frustrating as hell! All I want to do is drive my T/A.
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You really don't have to mess with that button on the prop valve if you are using the pedal pump method of bleeding. I've successfully bled the brakes on many cars with the pedal pumping method with a clear jar and clear vinyl hose, and don't touch the prop valve.
If you pressure bleed, and maybe vacuum bleed, then you may have to hold the button down. I tried that once, but then the button starting leaking around it, so I'm not doing that again.
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dont go replacing parts that are not needed, get the new master, bench bleed it and see what happens, i seriously think you have collapsed hoses
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dont go replacing parts that are not needed, get the new master, bench bleed it and see what happens, i seriously think you have collapsed hoses
sory, that was for aus but still do not go changing parts out when we can diagnos the real issue and fix it
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Thanks Guys, no I'm not about to do anything or pull anything, especially until I know I have to. The front callipers are rebuilt, all new lines, new booster and mc, and new hoses. One thing that wasn't rebuilt was the prop valve and I don't want to use those brass block replacements but not sure if rebuild kits available either. It was all in working order, just been unused for maybe 3 years. The problem with checking brakes is that fresh brake fluid is going to end up everywhere, ruining paint where ever it gets and you just know the problem will be elsewhere!
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Hey Aus I just found out that the newer Dot 5 I think it is, is silicone based and not supposed to damage Paint. Not sure if it's true but worth looking into?
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Ok that's interesting, wonder if it's compatible with older systems. You also have to be careful of some of the Japanese 'Dot 4' variants that use the same name but are not suitable. I'm currently out of ideas and patience so just walked away from it, no one else around to lend a hand so the cover is back on for a few more months!
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Wish i was closer bud I would gladly help you out! Your about a continent or two away tho?! ::)
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Haha only a holiday away, let me know when you're due to arrive, I'll get out the good plates!
Nah the thing is doing my head in at present, everytime something gets rebuilt or sent away to be worked on it comes back and seems to be worse.
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If nothing else I can be your hookup over here and ship to you where others won't? I have a step sister and hubby that live there, not sure where cuz they are kinda stuck up and we aren't that close! ;)
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Aus, you can connect some clear tube to the bleeder valves and drain into a container, the brake system on these cars is extremely simple so your issue is quite easy to solve, when you say new lines are you including the actual hoses from lines to caliper
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I need to get some more clear tubing, makes bleeding them easier too by not having to block everything like jar up so high and risk spills!
Yes, new brake hoses to callipers and 1/2 the hard lines throughout system replaced with new, any old lines cleaned and flushed.
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I'm currently out of ideas and patience so just walked away from it,
That's what I did. Two weekend's ago I spent both Sat and Sunday trying to get the brakes right. It was incredibly hot (something like 105 degrees) under my canopy and when things were'nt working I just said F-it... I'm done for now. The car now sits in the garage. Lol!
My batteries feel recharged so I'll try again this weekend.
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Last night (at around 9pm!) UPS delivered the new m/c I ordred from Summit. I joyfully opend the box to see a beautiful blue box that said "Bendix - a Honeywell company" followed by the dreaded three words:
Made in China. Lol! Probably made at the same factory as the leaky Pro Stop m/c I got at Pep Boys.
Well, I was going to exchange the Pro Stop anyways so let's see how this one works.
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Still no luck with mine but believe it could be now the front caliper pistons sticking. These were renewed several years ago but the car has sat for several more years without being operational.
I removed one off the spindle to watch it operate. It applies onto a block of timber fine but releases only half the distance to which it applied. You can then watch it go on and off but not fully release. When cracking the pressure on the bleeder valve to release some fluid it still does not release so must be sticking in the piston and seal rather than from fluid pressure issues.
Next problem is what to do now, remove them for another rebuild kit with pistons and seals and see if it comes good. Or purchase complete rebuilt units and swap over for around the cost of the rebuild kit, still not at all cheap over here though, around $180 per side and our dollar is similar to USD. Otherwise, I'm not sure if there is an aftermarket caliper setup that replaces the stock unit, still works with stock disc rotor and spindle that is actually an improvement and not just because it's powdercoated red!
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did you rebuild them or have the rebuilt, you can probably just freshen them up without rebuild kits, a calipe rebuild kit here is about $10 us dollars and takes about 20 minutes to rebuild a caliper
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Thanks Joe, might be the way to go once I track down who stocks the right parts, check to see if anything else needed. I can't remember pulling the pistons out, but my notes say they were so possibly had them done at time of service or similar. They look fairly clean inside the pistons, not terribly old or used. Either way, hopefully will rule out that area if it doesn't actually fix the problem!
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Looks like my problem is solved. I rebuilt the front calipers (again) with new seals and bushes, the pistons cleaned up as new. They were awfully gummed up inside though, surprising they applied or released at all. It also seems that one of the jobs I thought was done years ago was in fact not, must have just slipped past and forgot to tell me. The other problem was that even though the casting numbers on the calipers matches those used on 77-78 models, the bleeder screws and banjo bolts were metric. So some were either introduced before 79 or the same casting numbers were used over the different versions, makes ordering parts fun, wait weeks only to find they are wrong and you are stuck with them!
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glad you resolved it