I have a 52 f1 that someone put a Fatman M2 ft suspension under with 78-85 GM calipers,I bought this truck 18 years ago from a friend, the brakes have always been soft but it would stop, the master cyl went bad so I replaced with a new 85 mustang thats what it had ,the master cyl and booster are mounted under floor, I have tried two different new master cyl and a new distribution valve and can not get a pedal, tried the pump up and hold bleeding and also air vac bleeding letting the calipers hang down lower than M C and also above, has anyone else had this problem? I have also checked booster to make sure the plunger is coming out far enough
Which ‘85 mustang master did you get, there are at least 3 different ones. SVO/SVT is for 4wheel disk brakes and won’t work with front disk/rear drum. There are also multiple bore sizes later foxbodies had 3 outlets. Do you have residual valves? ‘85 mustang master would not have them because the master sits above the calipers.
My self I have never used the residual, All mine are under floor master with dic. When comes to bleeding , There been a few Dic & drums been a pain , I have used different techniques I have found when using a vac bleeder Its best to have a****ortment of bleeders with the nose cut off or dill hole in end So when you screw in it seats & does not***** air @ thread & make sure tight fit On rubber boot , & sometimes do not pull full Vacum , when bleed add original bleeder in. Then with no help & vac bleeder A liter bottle 1/4 full brake fluid Same with bleeder with hole in Rubber hose Clear more desirable Pump brakes Slow & steady , Taken 5-10 to push to floor full puddle stroke , & 5-10 sec back to rest . Also I have installed tire rim steam In master cylinder top & pressure the master cylinder with 5 psi with slightly cracked bleeder .
Holding the calipers down lower than the master didn't help bleed the system, it only complicated matters. The air in the system wants to rise, so calipers need to be higher than the master to eliminate air, not lower. And as others said, did you bench bleed the master first? Also, you should have someone gently push the pedal down as you break the fittings loose at the new master to get any air trapped at the outlets out first.
Are they the low drag calipers? Much has been written about the issues they cause unless you use a master cylinder designed for them. The other solution is to switch out the stock low drag GM calipers to an aftermarket version without the low drag (Speedway sells them for example).
Distribution valve you say? Isn't there something that needs to be done with those when bleeding? Some kind of reset, or is it a replacement part installed during the bleeding process? I've never done it, never had such a valve but am aware there's a peculiarity with them, just can't recall exactly what! Chris
If you have a safety valve in line, there is a plug with a Pin in it to keep from moving the barrel valve and blocking one port. Very Few home mechanics think about that till it's too late.
Thanks to all Yes I bench bleed master cyl master cyl is for a v8 fox body not a svo I've did everything like 19eddy30 except modifying bleeder but I had give it a thought so thats my next try the cover is really close to floor , I have to take a mirror to see fluid level, going to do like 19eddy30 and install a tire valve in cover if I have room Also have the distribution block pined so spool can't move Don't know if caliper is low drag the part number is 18007150 and 18007151
I definitely recommend a vacuum bleeder for difficult to bleed systems. My Toyota pickup is extremely difficult to bleed because it has a load sensing proportioning valve. The vacuum bleeder makes it simple, quick and no mess. https://www.princessauto.com/en/pne...0z2azOr1kqJvobzkQyQz7ukTeDzAHYhoCyH4QAvD_BwE#
@Randall Strickland All so , did you install any new Inverted fitting or pre made hard lines? Just asking I have encounter many new OFF BRAND , ( Autozone ect) inverted fittings & premade lines the cone / taper shape is not correct and will ***** air and sometimes not leak Fluid , my fixes to have multiple old brass fittings and OEM to reshape the cone /taper correctly and I even have a $200 Master cool die kit & typical bench vice style also
Based on what I've seen, those are the metric low drag calipers...check out the following thread. You need to change the calipers as I said before, Speedway sells a version of this caliper that is not low drag (I have them on my '32...they work) as does Afco (part numbers in the thread below). or if you want to keep those calipers you need a stepped bore quick uptake master cylinder designed for use with low drag calipers. It's been discussed nany times on the HAMB...see the following. https://www.jalopyjournal.com/forum/threads/gm-metric-low-drag-calipers-fixed.1202460/
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