- Joined
- May 7, 2012
- Messages
- 250
- Reaction score
- 3
- Location
- Near Houston, TX
- My Car
- 1971 Coupe. 302 2V - C4 trans
All,
I'm posting this as a "lessons learned" to a saga that has been tough for me to resolve. I love doing the work on my mustang, but I dislike it when I am my own worst enemy. This is a story one of those days. Sometimes, the most useful purpose of my life is to serve as a warning to others... :-/
It all started when my RR hydraulic cylinder started leaking. I would blow through the front reservoir in only a few brakings.
No prob, I thought, I've got new pads and spring kits on the shelf, anticipating a need to rebuild the rears... "now's the time" so off I go.
I pull the RR wheel and the front side of the RR hydraulic cylinder is bleeding out. "Easy fix" I think. "A rebuild kit is less than $5, and I'll throw the pads and springs in and the brakes will be like new. Hell, I'll do both sides right now"
My local Oreilly's Auto Parts is the best about carrying old car parts. They usually have rebuild kits and parts - many times on the shelf - even for my 71. So I go there and ask for the rebuild kit for a 71 rear drum. I come home with a kit that's supposed to fit. Damn, the seals are for a 1.25in bore hydraulic cylinder. Gotta take them back and get the right rebuild kit. After a revisit, I come home with "the right parts". A 7/8th bore set of seals and springs. Looks right, the 1.25in was way to big, and this is the only other rebuild kit they have.
So I bring them home and begin install. No prob, put it all together, as usual I curse the designer of drum brakes (and his family for 7 generations, because of all the springs, and the requirement for 3 hands everywhere, etc), but I get through it. Typical brake job....
Now I bolt up the wheels and they don't seem to bolt up right, too tight... snug to early, weird, doesn't seem right. Try to drive and it won't move.... after some troubleshooting, PADS are too wide. Crazy. I bought the stock pads for 71.... so time to pull everything again. So I go to Oreilly's, and order them again. They bring me the same thing. SO I go home and get the pads that came off earlier.... they look exactly the same, but they are more narrow. I have the guys double check everything.... computer still calls for 1.25 cylinders and 2in wide pads. Neither of those is right for me. Old pads are 1.75in wide, and I'm still thinking (foreshadow) the cylinders are 7/8in diameter...
So, I have the guys find some pads that are 10in diam, but 1.75. They have some - computer shows for a 69-70... I take them home, that must be right they match what I had before... "Ford must've build this 71 with 70 brake parts" is what I am thinking.
Time to reassemble, the cylinders should be good (already done), redo the brakes, redo the curse on the drum brake designer & fam.... Finally I am getting there...
Replace everything and try to bleed. Bleeding at first works... but I am having trouble with brake adjustment. I had retracted the auto-adjusters all the way to assemble, that unfortunately allows the pad to move to far and the cylinder to bleed out, and ALSO causes them to essentially lock up if drum is on, since the pad can't return to proper position. Somewhere in the learning of auto-adjuster settings, I have problems bleeding the rears. Something happened, and now, no fluid to rears. WTH? Why is this happening?..
Well, months previous to all of this, I had put a new MC on and completely rebuilt the prop valve. Everything seemed to be working prior to RR developing a leak. But now, no fluid to rears. WTH.
so I pull the MC and bench bleed it. Seems fine. I pull the prop valve again and disassemble, seems fine. Why no fluid? I reassemble it all in the car. No fluid to rears. WTH.
I'm lost - I spend hours and hours trying to figure out why the prop valve won't supply fluid to the rears. I rebuilt it previously, but it seemed to be working prior to the problem with the rears.
Now, I'm gonna cut right to the finding that resolved the prop valve issue. I had bought a rebuild kit from musclecarresearch.com (which is an awesome kit & vendor BTW) And, as it turns out, I made a mistake in that rebuild. Apparently, I made a mistake that "kinda worked" for awhile, but during the rear brake fix, it broke hard.
Despite what I would call GREAT instructions about how to rebuild the prop valve (https://www.musclecarresearch.com/valve-rebuild-kh) , I made a mistake that everyone should avoid. There is "some weirdness" about how to assemble the "red piston" - at least to me. Ultimately, I made a mistake by inadvertently swapping the seal on the piston itself, with the seal that goes inside the closeout cap. This piston is between the MC supply for rear-brakes, and the flow to the rear-brakes. In hindsight, it is surprizing that I swapped these seals but i did....
The seal that goes in the cap is the LARGER seal, and the seal on the piston is the smaller seal:
Repeating.... the seal that goes on the piston itself is the SMALLER seal. It is important to note that both have the same outer diameter, and either will go in the position of the other. The smaller seal fit well in the cap, and the larger one, fit reasonably well on the piston. It offered "some" resistance to piston movement, but I could move it with one finger with the larger seal on, so I figured it was ok.
Through my resolution process, I proved that the piston is difficult move to allow flow to the rear brakes if the larger seal is on the piston. It must be able to move some, as I would swear this thing was working before my rear leak....
So, I'm going to go thru some review of how the "red-piston" is assembled. the GREAT instructions at muscelcarresearch.com are NOT wrong, but for me, they left something critical out. Look at this pic from same site:
But, what's the deal with the "spring cap" washer? It's an odd piece. The OD doesn't fit in the cylinder, so it doesn't go near the piston seal. but it doesn't have ANY good interface to the end cap either. It's OD is exactly the same as the OD (with threads) that goes into the brass valve body. And, there is a sideways u-shaped seal in that cap, and the seal won't fit to or into this spring cap in anyway. Repeating, the seal in the cap basically never touches the spring or the spring cap.
Here are some pics I took of how this red piston cylinder is "closed out". Please note that these were taken with the seals SWAPPED, and these photos show the WRONG placement of seals:
See how the seal fits nicely into the cap? The clue it is NOT in the right position is that the inner diameter doesn't match that in the cap. That larger inner diameter is needed to fit the red piston properly. Now look at the spring cap, see how it fits the spring properly, but to assemble it, the threaded cap is just kinda resting on it? The closeout cap has no accommodation to hold the spring cap inside it. And when properly installed, the spring cap prevents the spring from touching the seal in the cap.
The RIGHT way to assemble this spring cap is to put it on the top of the spring as you would see above, and then balance the threaded cap on top of that... right on the spring cap as you compress the spring to install the threaded cap in the threaded brass valve body. Normally, I would expect some sort of edge to accept and hold this spring cap but there is nothing. It actually felt to me that I was "doing something incorrectly" as I assembled it, but there was nothing technically I could find wrong (in fact nothing was wrong with this assembly).
With this assembly, it is possible to swap the seal on the piston with the seal in the cap. with similar ODs, and similar profiles, the only clue is it a little tougher to insert the piston into the cylinder (also, the ID of the seals are different. The ID on the smaller seal is larger). With the smaller seal on the piston (the correct assembly) the piston moves VERY easily.
Just be sure your prop valve is assembled correctly. If you mess up this portion as I did, you're going to have no fluid at the rear brakes at some point. if you're unlucky like me, it will be in the middle of trying to resolve a completely separate problem.
So I get the MC and the prop valve to finally flow fluid properly to the rear brakes. Whew. I am now days into what should have been a simple RR cylinder rebuild.
Now, as I finally get fluid to flow to rears again, I begin bleeding, and GUESS WHAT? the RR cylinder bleeds out. Both front and rear sides of the RR cylinder are now leaking. At first I think I cleaned the bores to much, but then I realize - these seals really don't seal. They are CLOSE, but don't really fit tight enough. Again... WTH?
Finally I disassemble the RR, trying to find a mistake with the seals I have put in or something... Ultimately, I find out, through trial and error, and 2 or 3 trips to Oreilly's that my 71 has 29/32 rear hydraulic cylinders. They are NOT 7/8ths in diam., and they are for sure not 1.25in diam, but they are REALLY close to 7/8ths.
It turns out that Oreillys DOESN'T sell rebuild kits for 29/32 diameter cylinders. This is why I mistakenly bought the 7/8ths seal kits. they are REALLY close to the 29/32 cylinders I had. My only option was to replace the old cylinders with new ones. SO I do that.
That requires disassembly of both sides brakes, subsequent cursing, and then, after all of that, I had to bleed the entire brake system several times to get the system back to normal, but ultimately, I got everything working.
This whole story is something that NONE of you should ever have to go through. if you've ever found yourself unable to bleed the backs, or if you buy rebuild kits for the rears that aren't right, maybe this will be helpful to someone. Hope so.
Long story short this took me DAYS to resolve when a simple brake job could have been completed MUCH quicker if I had been more careful in my replacement and rebuilding of stock parts.
Jay
I'm posting this as a "lessons learned" to a saga that has been tough for me to resolve. I love doing the work on my mustang, but I dislike it when I am my own worst enemy. This is a story one of those days. Sometimes, the most useful purpose of my life is to serve as a warning to others... :-/
It all started when my RR hydraulic cylinder started leaking. I would blow through the front reservoir in only a few brakings.
No prob, I thought, I've got new pads and spring kits on the shelf, anticipating a need to rebuild the rears... "now's the time" so off I go.
I pull the RR wheel and the front side of the RR hydraulic cylinder is bleeding out. "Easy fix" I think. "A rebuild kit is less than $5, and I'll throw the pads and springs in and the brakes will be like new. Hell, I'll do both sides right now"
My local Oreilly's Auto Parts is the best about carrying old car parts. They usually have rebuild kits and parts - many times on the shelf - even for my 71. So I go there and ask for the rebuild kit for a 71 rear drum. I come home with a kit that's supposed to fit. Damn, the seals are for a 1.25in bore hydraulic cylinder. Gotta take them back and get the right rebuild kit. After a revisit, I come home with "the right parts". A 7/8th bore set of seals and springs. Looks right, the 1.25in was way to big, and this is the only other rebuild kit they have.
So I bring them home and begin install. No prob, put it all together, as usual I curse the designer of drum brakes (and his family for 7 generations, because of all the springs, and the requirement for 3 hands everywhere, etc), but I get through it. Typical brake job....
Now I bolt up the wheels and they don't seem to bolt up right, too tight... snug to early, weird, doesn't seem right. Try to drive and it won't move.... after some troubleshooting, PADS are too wide. Crazy. I bought the stock pads for 71.... so time to pull everything again. So I go to Oreilly's, and order them again. They bring me the same thing. SO I go home and get the pads that came off earlier.... they look exactly the same, but they are more narrow. I have the guys double check everything.... computer still calls for 1.25 cylinders and 2in wide pads. Neither of those is right for me. Old pads are 1.75in wide, and I'm still thinking (foreshadow) the cylinders are 7/8in diameter...
So, I have the guys find some pads that are 10in diam, but 1.75. They have some - computer shows for a 69-70... I take them home, that must be right they match what I had before... "Ford must've build this 71 with 70 brake parts" is what I am thinking.
Time to reassemble, the cylinders should be good (already done), redo the brakes, redo the curse on the drum brake designer & fam.... Finally I am getting there...
Replace everything and try to bleed. Bleeding at first works... but I am having trouble with brake adjustment. I had retracted the auto-adjusters all the way to assemble, that unfortunately allows the pad to move to far and the cylinder to bleed out, and ALSO causes them to essentially lock up if drum is on, since the pad can't return to proper position. Somewhere in the learning of auto-adjuster settings, I have problems bleeding the rears. Something happened, and now, no fluid to rears. WTH? Why is this happening?..
Well, months previous to all of this, I had put a new MC on and completely rebuilt the prop valve. Everything seemed to be working prior to RR developing a leak. But now, no fluid to rears. WTH.
so I pull the MC and bench bleed it. Seems fine. I pull the prop valve again and disassemble, seems fine. Why no fluid? I reassemble it all in the car. No fluid to rears. WTH.
I'm lost - I spend hours and hours trying to figure out why the prop valve won't supply fluid to the rears. I rebuilt it previously, but it seemed to be working prior to the problem with the rears.
Now, I'm gonna cut right to the finding that resolved the prop valve issue. I had bought a rebuild kit from musclecarresearch.com (which is an awesome kit & vendor BTW) And, as it turns out, I made a mistake in that rebuild. Apparently, I made a mistake that "kinda worked" for awhile, but during the rear brake fix, it broke hard.
Despite what I would call GREAT instructions about how to rebuild the prop valve (https://www.musclecarresearch.com/valve-rebuild-kh) , I made a mistake that everyone should avoid. There is "some weirdness" about how to assemble the "red piston" - at least to me. Ultimately, I made a mistake by inadvertently swapping the seal on the piston itself, with the seal that goes inside the closeout cap. This piston is between the MC supply for rear-brakes, and the flow to the rear-brakes. In hindsight, it is surprizing that I swapped these seals but i did....
The seal that goes in the cap is the LARGER seal, and the seal on the piston is the smaller seal:
Repeating.... the seal that goes on the piston itself is the SMALLER seal. It is important to note that both have the same outer diameter, and either will go in the position of the other. The smaller seal fit well in the cap, and the larger one, fit reasonably well on the piston. It offered "some" resistance to piston movement, but I could move it with one finger with the larger seal on, so I figured it was ok.
Through my resolution process, I proved that the piston is difficult move to allow flow to the rear brakes if the larger seal is on the piston. It must be able to move some, as I would swear this thing was working before my rear leak....
So, I'm going to go thru some review of how the "red-piston" is assembled. the GREAT instructions at muscelcarresearch.com are NOT wrong, but for me, they left something critical out. Look at this pic from same site:
But, what's the deal with the "spring cap" washer? It's an odd piece. The OD doesn't fit in the cylinder, so it doesn't go near the piston seal. but it doesn't have ANY good interface to the end cap either. It's OD is exactly the same as the OD (with threads) that goes into the brass valve body. And, there is a sideways u-shaped seal in that cap, and the seal won't fit to or into this spring cap in anyway. Repeating, the seal in the cap basically never touches the spring or the spring cap.
Here are some pics I took of how this red piston cylinder is "closed out". Please note that these were taken with the seals SWAPPED, and these photos show the WRONG placement of seals:
See how the seal fits nicely into the cap? The clue it is NOT in the right position is that the inner diameter doesn't match that in the cap. That larger inner diameter is needed to fit the red piston properly. Now look at the spring cap, see how it fits the spring properly, but to assemble it, the threaded cap is just kinda resting on it? The closeout cap has no accommodation to hold the spring cap inside it. And when properly installed, the spring cap prevents the spring from touching the seal in the cap.
The RIGHT way to assemble this spring cap is to put it on the top of the spring as you would see above, and then balance the threaded cap on top of that... right on the spring cap as you compress the spring to install the threaded cap in the threaded brass valve body. Normally, I would expect some sort of edge to accept and hold this spring cap but there is nothing. It actually felt to me that I was "doing something incorrectly" as I assembled it, but there was nothing technically I could find wrong (in fact nothing was wrong with this assembly).
With this assembly, it is possible to swap the seal on the piston with the seal in the cap. with similar ODs, and similar profiles, the only clue is it a little tougher to insert the piston into the cylinder (also, the ID of the seals are different. The ID on the smaller seal is larger). With the smaller seal on the piston (the correct assembly) the piston moves VERY easily.
Just be sure your prop valve is assembled correctly. If you mess up this portion as I did, you're going to have no fluid at the rear brakes at some point. if you're unlucky like me, it will be in the middle of trying to resolve a completely separate problem.
So I get the MC and the prop valve to finally flow fluid properly to the rear brakes. Whew. I am now days into what should have been a simple RR cylinder rebuild.
Now, as I finally get fluid to flow to rears again, I begin bleeding, and GUESS WHAT? the RR cylinder bleeds out. Both front and rear sides of the RR cylinder are now leaking. At first I think I cleaned the bores to much, but then I realize - these seals really don't seal. They are CLOSE, but don't really fit tight enough. Again... WTH?
Finally I disassemble the RR, trying to find a mistake with the seals I have put in or something... Ultimately, I find out, through trial and error, and 2 or 3 trips to Oreilly's that my 71 has 29/32 rear hydraulic cylinders. They are NOT 7/8ths in diam., and they are for sure not 1.25in diam, but they are REALLY close to 7/8ths.
It turns out that Oreillys DOESN'T sell rebuild kits for 29/32 diameter cylinders. This is why I mistakenly bought the 7/8ths seal kits. they are REALLY close to the 29/32 cylinders I had. My only option was to replace the old cylinders with new ones. SO I do that.
That requires disassembly of both sides brakes, subsequent cursing, and then, after all of that, I had to bleed the entire brake system several times to get the system back to normal, but ultimately, I got everything working.
This whole story is something that NONE of you should ever have to go through. if you've ever found yourself unable to bleed the backs, or if you buy rebuild kits for the rears that aren't right, maybe this will be helpful to someone. Hope so.
Long story short this took me DAYS to resolve when a simple brake job could have been completed MUCH quicker if I had been more careful in my replacement and rebuilding of stock parts.
Jay
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