I had a similar problem with not being able to get a pedal and air in system. Turns out corvette caliper was faulty. ****ing air but no leaks. How I found my problem was like this. I crimped all 4 flexible lines at the wheels. Checked my pedal and was hard. This told me my master was good. I let loose one crimp at a time checking for hard pedal. Pedal went to the floor when I hit the bad one. Changed calipers did normal bleed and no more problems since. It is important to mention as Groucho did DO NOT pump the pedal as it aerates the fluid. Push and hold stroke by stroke or you will just be chasing your ***.
Pop the cap off and look closely at the casting.there's somewhat of a bulge at the front, and it narrows at the rear. You're right, typically a true drum or disc/drum m/c will have the residual built into the drum circuit. Yours won't. Easiest way to tell? unfold a paper clip, and GENTLY poke it into the brake line port. DO NOT PUSH IT IN, just "drop" it in. If it hits something a quarter inch in, THAT'S the residual. If it drops in further than that, 3/4 inch or so, there's no residual. Drum brakes NEED the 10 psi residual pressure to overcome the return springs. Otherwise, just like "quick take up" calipers, the shoes will retract too far away from the drum, and it'll take two "hits" to get brakes.
Damn, sorry about that. Maybe it was 76? Definitely some late 70s GM that worked for me. I think it mentioned the right ones to use on the MPbrakes website (that's were I got the idea). I will try to find it again. Ok....I just went through the entire stack of receipts I have kept from building the car and I think I found the right one for the calipers, which is from Kragen. Of course it doesn't show what the car make/year is for the parts, but shows "PA 6821953 LOADED CALIPER RC4126 AND PA6821946 LOADED CALIPER RC4125" as their numbers for them. Hopefully they are still the same #s - this was in 2003. These ones looked exactly the same as the Monte ones I took off - not larger and no plastic. I knew I should have written it down - my memory ****s. If you do go and get these, let me know what they say they fit so I can re-charge my memory for when I have to replace them in the future. Thanks and sorry again to send you on a wild chase. (One thing's for sure - I don't want to add up all these receipts to find out what I spent on building the car - Damn, there is a LOT of them).
Learn something new everyday, We have metric calipers on our coupe & the brakes always felt a little ...squishy. they worked good, would lock up all 4 wheels if you wanted it too but the pedal wan never what I would call firm. if anybody nails down exactly what the non quick take up calipers came off of please post it up.
If the pedal/mc combo is new-check your pedal adjustment-if it is set without a little free play it will cause the MC compensating ports to not close which means you will never bleed the air out.The MC piston needs to be able to return and seat-it don't take much to give you big problems. Jim
According to RockAuto.... This part No. fits a whole slew of vehicles, including the '82 monte. (But NOT the '78 firebird, lol)
Ok...did a little comparitive shopping... According to rockauto that caliper fits, for example, 1978 to 1988 monte carlo. The pictures rockauto has are very helpful. The master cylinder for the 1988 has the obvious bulge indicating the quick takeup. The master cylinder for hte 1978 has no bulge, same body size the whole way. So, how will the same caliper work for both masters? And, on a side note, why did the caliper I bought locally have a 3/8-16 thread inlet and bleeder, rather than the M10x1.5 that all these other calipers show. Just when I think I'm making headway, no dice.
Ok, that sorta makes sense for my feeble brain - I sometimes believe I have dyslexia - I now believe that I originally requested the 78 Firebird calipers (to replace the low-drag ones that were already in place and causing me problems according to MPbrakes info) - got them home and, like you, found they were too big (and I just found the receipt for returning those), went back & requested 78 Monte Carlo calipers instead, and I am positive those are the ones on my car now and according to the MPbrakes info those should be prior to the low drag feature which came about in 1980. However, it is interesting that Rock Auto shows that part # as being good for 1978 - 88 which spans past the time that GM went to the low drag 'metric' caliper (1980), So I believe that they are showing that it is possible to use this NON-low drag caliper on a (1980-up) 'quick take up' MC and they would still work but just wouldn't have the low drag feature. In other words... they are just showing them as being interchangeable, which is what you want - a normal caliper that bolts on in place of the low-drag one. So...I really believe that if you were to buy the calipers using those part numbers I supplied that they are the right calipers and not the low-drag 'metric' & it would solve your problem. I just initially complicated things by forgetting that they are 78 Monte Carlo & not the Firebird (I do now remember returning the Firebird calipers). Sorry to confuse, but I think those part numbers are good for what you need.
This is important to check out before jumping on the different caliper. If that isn't the issue, then I am betting you currently have the low drag caliper.
The metric calipers are referred to as metric because they came about in '78 when GM briefly made a big push to convert America to the metric system. The pins that hold them in and fittings are metric, hence the name. The quick take up deal could definitely be the problem so I would chase that a bit. The proportioning valve should make no difference at all to the bleeding of the rear brakes. A residual check valve how ever would. Technically, a firewall mounted master cylinder shouldn't need resdual checks, but sometimes they do. What they do is keep a small amount of pressure on the wheel cylinders or calipers to keep them full of fluid and ready to do they're job when you step on the brakes. The other thing they do is to restrict the flow of fluid backwards into the master cylinder, which becomes necessary when the cylinder is mounted below the actual wheel cylinders or calipers. In my experience, the need for these is more sensitive with wheel cylinders in drum brakes than with calipers. Without, the return springs in the brakes tend to evacuate more fluid back to the master cylinder than necessary, requiring more of a stroke to fill the cylinders and do the braking on the next stroke. This usually manifests itself in a spongy pedal, or the need to do a full stroke before stopping action begins. Go for the calipers first, if stuff is still too spongy, try a 10 lb residual in the rear line.
Ok! So this discussion started getting me a bit paranoid as I have lateish 82-92 metric camaro calipers on my 51 ford and I can't get the pressure I want. I called uop eci hotrod brakes and they said the quick takeup deal is a nonissue if you go with a lot of line pressure. I guess the flared MC gives you a hundred or so extra pounds at the beginning of pedal application so you don't have as much pedal travel, fwiw. He said they recommend a 7/8th" bore mc with a single diaphram 9" booster. I'm running a huge mc and hugest booster and I'm not getting enuf line pressure, so I'm gonna take the MC down 1/8" to see if I can get the fronts to enough pressure to lock up. I shoulda called the kit manuf. sooner! Edit: you have a single 7" and 1 1/8" master? Hell! You need a smaller mc sir! And the elephant in the living room that nobody has mentioned is your booster is tiny tiny. If its offshore aftermarker junk its even worse. You need 1000#+ at that wheel for discs and you aren't getting it with that combo. I'd loan you my pressure gauge and adaptors for the calipers to measure but I need it right now. You can get them for $50 kit made by ssbc, from jegs or the like.
Haven't double checked the master bore size yet...went with a small booster because i have a higher ratio pedal and actually mounted the booster on the other side of the firewall, so for clearance. I'm getting full stroke though. Booster is a TuffStuff product. Not sure who did the reman. master. Got it from the Rod Shop in calgary...but starting to think he sent me the wrong master...my fault for not doing a little more checking before install.
Ok...no real news...but I gotta get this out...called MP Brakes to try and get some extra, 'professional' advice. All the guy wanted to do was sell me bigger brakes, under the guise that those small calipers won't stop my truck. I don't appreciate a sales pitch when it's not accompanied by an answer to my question. Am I looking for something that doesn't exist? Is there an identical caliper, except for the low-drag annoyance? Or were all the small calipers 'metric'? How easy is it to upgrade to the larger caliper? (The one that's 7" bolt to bolt...not the 5.5" that the little metric one is...) I know I'd need a new bracket...and I'm pretty sure I've got 11" rotors...
Dude, I gave you the part numbers for exactly that. I'm sorry I confused the issue by referring to them as Firebird when they really weren't, but those numbers should net you a caliper that will bolt right on in place of the low drag ones.
Any '78 - '80 gm midsized car should be non quick take up, and what is referred to as "metric". They should work just fine for normal use on most hot rod type applications. The only time I worry with mine are when I push to some extremes. I jave done some racing and super fast long distance touring with my Plymouth in years past.
Sorry Cleatus, got myself on another train of thought there...took the weekend off from this problem...will update when I have news! Thinking about changing the bracket to go with the larger caliper...no decision yet...already have 11" rotors.
.....After all that...the brand new master was bad. Put a different one in and now I'm driving the truck. Ended up using the same calipers, well, new replacements. I'd still like a little better pedal but it's coming along. Thanks so much to all who had input! I learned more than I thought I would! Later... Mike
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