Chevy disc brake conversion with brake warning light

[Gas Pig]

I did a Chevy front disc conversion on my 74. But I’m getting a brake warning light and my braking is actually very poor. I’m guessing the shuttle inside the proportional valve tripped while bleeding the brakes. Is there a trick on getting the shuttle to go back to neutral position?

Thanks Jeff

 

[Gas Pig]

Reading a little father on some posts apparently there are two ways you can try to rest the proportional valve. First by hitting the brakes hard and keeping constant pressure on them. The other way it to bleed the opposite brake side that it’s tripped too. I’ll try hitting the brakes hard first to see if that reset it.

 

[jamesroney]

Reading a little father on some posts apparently there are two ways you can try to rest the proportional valve. First by hitting the brakes hard and keeping constant pressure on them. The other way it to bleed the opposite brake side that it’s tripped too. I’ll try hitting the brakes hard first to see if that reset it.

You didn't say which prop valve you are using with the new GM disc brakes, and which distribution valve. Also don't know if you are using the original Bronco H-block, and which wire your brake lamp is connected to.

I've never had really good success with the Bronco H-block once it moves. They are usually very sticky, and need to be disassembled and serviced. Once the spool valve moves freely, then the "hit the brakes" technique can work.

Also have had no end of trouble with people adding rear proportioning valves ahead of the brake balance valve, and then wondering why the brake lamp comes on every time they apply the brakes.

Let me know what your configuration looks like, and I can walk you thru the process. Did you change the rear wheel cylinders on your 74 when you added front discs?

 

[1969miller]

He is using the GM style prop valve with the safety shuttle valve inside. I've heard of folks being able to slide the valve back by using a pick inside once the switch itself is removed. Get the bleeding tool, saves a ton of headache!

 

[Gas Pig]

You didn't say which prop valve you are using with the new GM disc brakes, and which distribution valve. Also don't know if you are using the original Bronco H-block, and which wire your brake lamp is connected to.

I've never had really good success with the Bronco H-block once it moves. They are usually very sticky, and need to be disassembled and serviced. Once the spool valve moves freely, then the "hit the brakes" technique can work.

Also have had no end of trouble with people adding rear proportioning valves ahead of the brake balance valve, and then wondering why the brake lamp comes on every time they apply the brakes.

Let me know what your configuration looks like, and I can walk you thru the process. Did you change the rear wheel cylinders on your 74 when you added front discs?

Yep I should have added that into in my description! lol

Anyways I kept the rear drums and I’m running a new front disc and rear drum proportional valve.

I did find a drip of brake fluid from my passenger banjo bolt so that could be my culprit still. I’ll have to address that first.

 

[jamesroney]

Yep I should have added that into in my description! lol

Anyways I kept the rear drums and I’m running a new front disc and rear drum proportional valve.

I did find a drip of brake fluid from my passenger banjo bolt so that could be my culprit still. I’ll have to address that first.

But did you keep your original H-block, or did you remove it completely and replace it with the "new" prop valve?

Most of the disc brake kits end up with BOTH valves.

Which balance valve is turning on the light?

 

[jamesroney]

He is using the GM style prop valve with the safety shuttle valve inside. I've heard of folks being able to slide the valve back by using a pick inside once the switch itself is removed. Get the bleeding tool, saves a ton of headache!

Got it. But is he ALSO using the factory drum brake distribution block? (with the OTHER safety shuttle valve?)

You can just tell me your kit PN, and I'll know what he's got...

 

[Gas Pig]

Got it. But is he ALSO using the factory drum brake distribution block? (with the OTHER safety shuttle valve?)

You can just tell me your kit PN, and I'll know what he's got...

No Just using the GM style proportional valve. I thought I had the tool to hold the shuttle in place but it turned out the one I had was for a different proportion valve.

 

[hyghlndr]

Just fought this on two, a pain. The open one side never worked after a dozen different attempts, Got one centered with a pick and that fixed it. The second I removed and installed a new one for $40 or so from ebay , a shame but easier in the long run.Buy and USE the tool in the future is my best advice to anyone.

 

[ksagis]

Could somebody confirm or correct my version of reality on these two topics?

1. The factory Hblock doesn't do any proportioning or balancing, and is simply intended to detect a pressure differential between front to back brakes circuits for the light?
2. And there is not a tool for the Hblock when bleeding? If there is no tool, is there any special process when bleeding with Hblock in place?

 

[Gas Pig]

Just fought this on two, a pain. The open one side never worked after a dozen different attempts, Got one centered with a pick and that fixed it. The second I removed and installed a new one for $40 or so from ebay , a shame but easier in the long run.Buy and USE the tool in the future is my best advice to anyone.

Was your issues with the new GM style proportional valve? And do you have a link to the tool for it?

 

[hyghlndr]

Was your issues with the new GM style proportional valve? And do you have a link to the tool for it?

Yep the new GM style brake booster.

I had a plastic tool but ended up buying a much nicer aluminum one. Link here https://www.amazon.com/gp/product/B096JZNXJZ/?tag=classicbroncos-20

 

[Oldtimer]

There are two different size tools.
Drum - Drum brakes typically have a pressure diferential valve and use a 3/8-24 threaded tool.

Drum - Disc brakes typically have a combination valve and the GM version that everyone sells use a 1/2-20 threaded tool.
Note: The GM PV2 valve that all the Bronco vendors sell are not plumbed to use 3/16 brake lines in SOME of the ports, and tend to leak.

 

[MThalfcab]

Hey GasPig, when you get it figured out can you come to house and help me do mine, these parts coming out of these kits(mine didn't even have instructions) and parts just to replace old parts are junk now a days, everything I get either breaks, or just doesn't last long. When buying new parts for our Broncos, where does one go for good parts, my brakes on my 74 are so spongy, I live in the mountains, might as well be at a wild park! I'm learning off your pain and hope you get it figured out! There has been Great feedback on here!

 

[ksagis]

There are two different size tools.
Drum - Drum brakes typically have a pressure diferential valve and use a 3/8-24 threaded tool.

Drum - Disc brakes typically have a combination valve and the GM version that everyone sells use a 1/2-20 threaded tool.
Note: The GM PV2 valve that all the Bronco vendors sell are not plumbed to use 3/16 brake lines in SOME of the ports, and tend to leak.

View attachment 906275

View attachment 906276

Interesting on the tool for the OEM Hblock (first pic), haven't seen that before Do you have a part number or source for it by chance?

Here's a source, there's a lot more of the 1/2" versions....

https://www.musclecarresearch.com/brake-valve-tool?v=53

 

[Oldtimer]

Interesting on the tool for the OEM Hblock (first pic), haven't seen that before Do you have a part number or source for it by chance?

NPD

TOOL, BRAKE PRESSURE DIFFERENTIAL SWITCH, STEEL - #914-7 - National Parts Depot

Buy part #914-7 TOOL, BRAKE PRESSURE DIFFERENTIAL SWITCH, STEEL for your classic vehicle from National Parts Depot. Free shipping on orders over $300, fast delivery & everyday low pricing! Order now!

www.npdlink.com

 

[Gas Pig]

Hey GasPig, when you get it figured out can you come to house and help me do mine, these parts coming out of these kits(mine didn't even have instructions) and parts just to replace old parts are junk now a days, everything I get either breaks, or just doesn't last long. When buying new parts for our Broncos, where does one go for good parts, my brakes on my 74 are so spongy, I live in the mountains, might as well be at a wild park! I'm learning off your pain and hope you get it figured out! There has been Great feedback on here!

Yeah that’s great thing about this community is wealth of knowledge and willingness to help! If I ever figure it out I’ll be glad to assist!

It’s frustrating when my single master cylinder with drum brakes breaks on ‘66 brakes better then vacuum assisted front disc ‘74. Go figure!

 

[hyghlndr]

Hey GasPig, when you get it figured out can you come to house and help me do mine, these parts coming out of these kits(mine didn't even have instructions) and parts just to replace old parts are junk now a days, everything I get either breaks, or just doesn't last long. When buying new parts for our Broncos, where does one go for good parts, my brakes on my 74 are so spongy, I live in the mountains, might as well be at a wild park! I'm learning off your pain and hope you get it figured out! There has been Great feedback on here!

There is something wrong with your setup. How are the lines, fully bled, calipers, master cylinder?? I just completed two 77s with hydroboost even with 35s they will lock up all tires and if not care make you hit the steering wheel...as good as a new car or better minus ABS. Stock 77 discs and rear drum, everything new. Have the GM disc setup on other and still great braking.

 

[MThalfcab]

There is something wrong with your setup. How are the lines, fully bled, calipers, master cylinder?? I just completed two 77s with hydroboost even with 35s they will lock up all tires and if not care make you hit the steering wheel...as good as a new car or better minus ABS. Stock 77 discs and rear drum, everything new. Have the GM disc setup on other and still great braking.

This is my kit, I'm by myself, I'm sure I'm missing something, I wished it was like when I was young, I just bolded over everything but parts stores and businesses were a lot closer, I've watched many videos and they all look pretty much the same as far as assemble, where I live there's not much summer so might have to wait till next year!! Don't see much improvement! If you were down the street I'd hire you

 

[MThalfcab]

Yeah that’s great thing about this community is wealth of knowledge and willingness to help! If I ever figure it out I’ll be glad to assist!

It’s frustrating when my single master cylinder with drum brakes breaks on ‘66 brakes better then vacuum assisted front disc ‘74. Go figure!

I'm starting to wonder being so far out of civilization, I contacted a few Off Road Shops that were 8 hrs one way, they act like you can just drop by, $$ ruins all! In my part of the woods there's maybe half dozen Broncos and most have no mechanical skills. I had a guy 4 hrs but I think he was just trying to sell me his stuff, fell on a deaf ear so to speak. Hunting is around the corner and might have to continue this next year. Good before brakes,