Hydro-boost with Disk/Disk Prop Valve

[Orange Crate]

My disk/disk hydro-boost conversion proportioning valve turns the "brake" light on when applying the brake. This is a new first installation/test in the garage. I had selected a disk/disk proportioning valve when putting it together but it is obviously not the correct combo. So anyone with hydro-boost have a part number for a proportioning valve that works? I used the search function above with lots of info but non with a hydro-boost added in. The system has been bled numerous times and the light can easily be reset. I'm not looking for trouble shooting info unless you have hydro-boost.

[Rust_never_sleeps]

I don't speak hydroboost, but the type of assist should have nothing to do with the combo valve, which only interacts with the MC. Boost only changes the amount of pedal pressure it takes

[HO455]

I'm in the same camp as Rust_never_sleeps. The valve is shifting off center due to a pressure difference on the piston, inside the valve. Whichever side the piston is moving to is the low pressure side. Whether the low pressure is from a leak, or trapped air in a caliper, or possibly low pressure from the master cylinder is what you need to figure out. A brake pressure guage should help locate the problem.

Some rear disc brake calipers can be notoriously hard to completely purge of air. Sometimes the caliper has to be removed from the mounting and a plate inserted to mimic the rotor and then while the caliper is held so the bleeder is in the absolute upper position the caliper is then bled.

Good luck.

[Orange Crate]

So I thought I would start with a known good part number for the prop valve from someone whose hydro system already works, and go from there. Like I said in the first post, I searched on here a lot and the nightmare stories of bleeding gallons of fluid set me on the part number first.

[KQQL IT]

Caddy park brake calipers? A friend has been fighting a similar issue.
Was told the re pop caddy calipers are not the best.
He's switching to a later model mustang caliper kit.

[Orange Crate]

OK so I need two new rear calipers because a friend was told they were the problem? Is the "friend" on this board? If so maybe you could convince that person to log in and give everyone the real scoop (with pictures please, because everybody likes the pics...) I'm asking for a friend....I'm going to go broke if you guys keep spending my money like that, oh wait I need a brake pressure gauge too! I wonder how much a known good part number will cost me....

[KQQL IT]

It's on a oldsmobile.
Was relaying his experience with repop cad style rear calipers.

Pv4 is the standard name for disc disc, as far as a oem pn sorry.

[KQQL IT]

3667810 gm

Try this..

[Orange Crate]

Originally Posted by KQQL IT

It's on a oldsmobile.
Was relaying his experience with repop cad style rear calipers.

Pv4 is the standard name for disc disc, as far as a oem pn sorry.

An Oldsmobile with hydro-boost? I guess I'm not too sure how re-mfg calipers are the cause of a brake light AND he decided to get rid of them for another style? Were they leaking? I get that some calipers are hard to bleed but to give up on a set, they must have been really messed up. What was wrong with them specifically?

[Orange Crate]

Originally Posted by KQQL IT

3667810 gm

Try this..

So that is the one your friend has on his disk/disk hydro-boost system that works?

[fun in dirt]

I just used a universal, manual adjust, valve in the rear brake line. Don't remember exact brand without looking at it, but similar to this https://www.summitracing.com/parts/leb-apv02 . But I did pair it also with a new master cylinder off '01 Chevy with disc front & back.
Been working for 10yrs now with zero problems.

[Orange Crate]

Originally Posted by fun in dirt

I just used a universal, manual adjust, valve in the rear brake line. Don't remember exact brand without looking at it, but similar to this https://www.summitracing.com/parts/leb-apv02 . But I did pair it also with a new master cylinder off '01 Chevy with disc front & back.
Been working for 10yrs now with zero problems.

Congratulations on being the first with hydro-boost to reply. I would have thought more people would have already converted seeing how easy it is. Ya, looking at manual adjust valves the last couple of days. I have the stock disks/ calipers on the front D60 so they are close to the stock D44 rotors. D60 at 12.7 diameter and D44 at 12.4. not a big change there, but could need pressure adjusted because of that. The major difference is the width, D60 at 1.625" and D44 at 1.25". Some nerd info, the rear disks are actually the front disks from the old D44. I'll put a cab over camper on this Camper Special so I think I'll like the extra heat dissipation, although the original set up seemed to work just fine for over 40 years. Here is the old camper and the old "guard" dog.

[KQQL IT]

After his brakes wouldn't bleed, he took to a shop.
They told him the re pop calipers are a pita to bleed/adjust.
And still won't be good.
So swap to a more modern system is his solution.


You ever think a metric non park brake caliper to see if it's a proportioning valve or caliper issue ?

[Orange Crate]

Originally Posted by KQQL IT

After his brakes wouldn't bleed, he took to a shop.
They told him the re pop calipers are a pita to bleed/adjust.
And still won't be good.
So swap to a more modern system is his solution.

Non of that makes any sense....

So now I need MORE calipers? Maybe it because they would be metric....ya, that's it.

[LS short box]

On my 66 Mustang project with a hydro boost unit I used a Wilwood adjustable prop valve in the rear brake line. I used C5 Corvette disc brakes all around so not apples to oranges but the Wilwood prop valve once adjusted worked perfect.
Not a great pic but hard to see underneath the master.
One thing I had to add after installing the hydro boost was add a fluid resisvoir with a filter to eliminate micro bubbles. This per the folks at Hydra-Tech.

[Orange Crate]

Originally Posted by LS short box

One thing I had to add after installing the hydro boost was add a fluid resisvoir with a filter to eliminate micro bubbles. This per the folks at Hydra-Tech.

Super excellent info, much appreciated. So where exactly did the extra reservoir go? Which system was it plumbed in to, the master cylinder sys, or the hydro sys? Gold star for the nice Stang!

[67 twins]

Originally Posted by Orange Crate

Congratulations on being the first with hydro-boost to reply. I would have thought more people would have already converted seeing how easy it is. Ya, looking at manual adjust valves the last couple of days. I have the stock disks/ calipers on the front D60 so they are close to the stock D44 rotors. D60 at 12.7 diameter and D44 at 12.4. not a big change there, but could need pressure adjusted because of that. The major difference is the width, D60 at 1.625" and D44 at 1.25". Some nerd info, the rear disks are actually the front disks from the old D44. I'll put a cab over camper on this Camper Special so I think I'll like the extra heat dissipation, although the original set up seemed to work just fine for over 40 years. Here is the old camper and the old "guard" dog.

Yeah tell me how easy the Hydroboost is again. You can't seem to get it to work. Then you seem to have an attitude towards those that have replied. Good luck. As said already the type of booster dhould have nothintg to do with what proportioning valve ypu would need.