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Discussion Starter #1
A friend is working on a 67 Camaro, it had drum brakes and they converted to four wheel, manual disc brakes.
He is now having issues with no rear brake pressure.
He has the correct master cylinder but it looks like he bought the wrong proportioning block.
It's for front disc only.
The brake rod is on the top hole of the pedal assembly.
Can he use the same brake lines?
I was thinking the front lines are different between drum and disc, but the rear are the same?
Thanks
 

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When he buys the new prop valve (disc/disc), it should state what the connection sizes are for it. Worse case, he will have to buy an adapter or two. I recommend he check the rear flexible hose that connects the main front to rear brake line, to the T-connector on the diff lines. On my '68, it was severely broken down, to the point fluid wouldn't pass through it. At that point, I replaced it and all my lines with stainless steel lines. I even replaced the T-connector. It's inexpensive enough and in my opinion one of my best investments into make my Camaro safe for the street.

BH
 

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I forgot to mention, if he needs adapters, they are only a few dollars each. Be sure to screw the adapters into the prop valve first. Then install the brake line into the adapter. It's probably common sense, but I thought I mention it anyway. ;)

BH
 

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Discussion Starter #5
Thanks again.
I just talked to him and he's going to check the rear rubber line and "T" as well.
He did say, no matter what he did, the brake pedal wouldn't pump up or get any pressure.
I asked him if he brake bleed the master cylinder and he said he did.
He's replacing the master cylinder tonight, but I still think it has to do with the proportioning valve.
I told him just to get an adjustable one.
Thanks
 

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The symptoms he describes, is what led me to that flex line being badly deteriorated. You couldn't tell from just looking at it, you need to take it off. The outside looked fine. Disconnect it at the T-connector and try pumping brakes, to see what/if any fluid comes through it. If the MC and prop valve are disc/disc, then odds are they are fine. There is always the possibility that it came defective. I am no mechanic or expert like most of the guys on here. However, I just finished doing my brakes and this is what I learned from my experience. My setup was manual all wheel drum. I converted the front to disc brakes. The rear conversion is next. I am currently running a disc/drum prop valve, but I already purchased a disc/disc prop valve for that job. As it stands now, I just installed new shoes, drums and springs to the rear. I did replace the MC as well. She brakes fine, but I have decided at some point in the future I will convert to power brakes. that will probably ne either next year, or the year after. It's not a priority and like I said, she brakes fine as is.

BH
 

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I reread this a couple of times. My pedal was so stiff, it wouldn't move, which led to me find that hose was shot. It sounds like his pedal has no pressure at all and goes to the floor. Did he inspect for leaks? Hopefully he bled the MC, correctly. How is his calipers setup, is the bleed valve facing up? Did he bleed the calipers correctly, because that could cause his problems as well. I'm sure the experts will chime in soon.
 

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There is some controversy on pumping the brakes the bleeding, verses pushing it down one time and bleeding. I see both sides.are the rear brakes adjusted? If not you will get no pedal. As a rule of thumb for me, I replace all rubber lines. Like said before, they may look good from the outside, but its like rust, it usually works from the inside out. It could also be a air lock. I have had that problem before. Just mash the he'll out of the pedal one good time and then bleed. This should dislodge the air if it is in the master cylinder. Too much pumping and at a fast rate will cause cavitation and making it almost impossible to bleed. Take time in doing this, and as mentioned make sure the calipers are not upside down.
 

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Discussion Starter #9
Here's an update and it's not good.
He replaced the master cylinder twice, he put on a proportioning valve for 4 wheel disc, he installed a new rear brake hose and he still has issues.
He said the pedal will pump up but after you take your foot off the pedal, within a few seconds, the master cylinder doesn't have any pressure but still there are no leaks.
He did mention that the owner of this car bought this brake setup off of eBay and it was dirt cheap. He was wondering if this could now be a caliper issue. He said he found out that a replacement caliper for this system would be off of a Cadillac El Dorado. I don't know if that means anything?
Instead of using a master cylinder for a disc brake system, would it be possible that he would need one for a drum system? The owner can't find the information for the brake system he bought, so that's no help.
He also told me that all the brake lines have been replaced with new lines.
Thoughts??
 

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Unless one of the experts has a better idea, I would disconnect the brake line at the furthest wheel and cap it and test. Work my way around and plug at each connection point from front to back. I would think that would help determine where the air/leak is in the system. If I recall that's the system with an 80's Cadillac caliper. He just needs to know that in case he has to rebuild or replace, but they should be more than fine.

I did a little digging thinking what would I do, and this might be perfect for plugging the lines and testing.

https://www.ebay.com/itm/Brake-Line-Plug-Qty-1/132108077237?hash=item1ec24148b5:g:tkQAAOSw3mpXKAoA


BH
 

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Discussion Starter #11
Funny you should mention that, we talked about that last night.
Where we work, we use 1/4" ball valves, he was going to install them on all four corners and close one off at a time but I'll pass what you found, might be easier.

Thanks

Bruce
 

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With the set/up he has installed you have to adjust the e/brake before you bleed the brakes.

My bet is this was not done. The MC does does displace enough fluid to fill the rear calipers with the pads too far from the rotors when the e-brake is not adjusted to place the pads close to the rotor.

You pump up until firm however the pads will return to their original position when you let off the pedal for a few seconds.
 

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Discussion Starter #13
Thanks John,
Didn't even think about that.
I just talked to the guy doing the work and he said the calipers do have provision for e-brake but they are not hooked up.
Hopefully that is the problem?
 

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Thanks John,
Didn't even think about that.
I just talked to the guy doing the work and he said the calipers do have provision for e-brake but they are not hooked up.
Hopefully that is the problem?
I’ll dig up the ebrake adjustment procedure
 

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The cady calipers have a screw in \out piston, that's what I was talking about on the adjustment. Sorry I was not more clear on that.
On a side note though... Those calipers were not very reliable, and the Cady mechanics replaced them often. Good luck.
 

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The cady calipers have a screw in \out piston, that's what I was talking about on the adjustment. Sorry I was not more clear on that.
On a side note though... Those calipers were not very reliable, and the Cady mechanics replaced them often. Good luck.
I’ve installed a couple sets for guys and no problems once adjusted properly.

I don’t follow the instructions the 1st time. So I learned the hard way lol
 

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Yes, I have used them too, but I would not use them on my car. I would use the second gen Trans Am instead.
 
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