HBoost - "No Brakes" - Resolved

[Jerryl]

Fwiw. Here is a pic of the current setup.

 

[No disintegrations]

What is the donor car for these kits? Buick Roadmaster?

 

[Jerryl]

What is the donor car for these kits? Buick Roadmaster?

I used the pn for the 84 GN.

 

[1952ray]

Fwiw. Here is a pic of the current setup.View attachment 283972

Nice and clean looking, please let us know when you solve this issue, and you will solve this!!

 

[No disintegrations]

I used the pn for the 84 GN.

ok. I had a silverado with hydro boost. With no air in the system the pedal was soft, but the braking power was very, very good despite that. Other cars with it I test drove always seemed to have a different pedal than vacuum or powermaster.

My gut feeling is you need more fiction at the drums and rotors. simply because the parts list is so long it's hard to believe you missed the mark there. Hard to say without seeing the car in person.

 

[RmvBfrFlght]

You have a real head scratcher with this one. I have an idea that should narrow it down to either the brake hydraulics or the HB unit.

Remove the two lines from the MC and plug the MC ports. Now try the brake pedal, it should be high and firm. If it is then the brake hydraulics are the cause. In this case unplug one port and reconnect that line. Try the pedal again to find out if it is the rear circuit or the front circuit that is the cause.

If the pedal is still soft with both ports plugged then the HB unit is bad.

RemoveBeforeFlight

 

[Jerryl]

You have a real head scratcher with this one. I have an idea that should narrow it down to either the brake hydraulics or the HB unit.

Remove the two lines from the MC and plug the MC ports. Now try the brake pedal, it should be high and firm. If it is then the brake hydraulics are the cause. In this case unplug one port and reconnect that line. Try the pedal again to find out if it is the rear circuit or the front circuit that is the cause.

If the pedal is still soft with both ports plugged then the HB unit is bad.

RemoveBeforeFlight

I tried the plugs a while back on the old MCs, which is how I determined they were leaking internally.

During my converstaion with Butch @ Talon hydraulics, he stated that the HB unit is a 1:1 connection, IOW: It is a mechanical connection that should move the master cyl piston regarless of power assist pressure. THAT was the "nugget" to my brain.
I made sure I understood what that meant and asked the same question 3 times. Lol
Cutaway diagram of the HB confirmed it.

Keeping the 1:1 in mind + soft pedal = air. Just stumped with a MC that holds pressure, no leaks and 5.5 quarts.

Head scratcher, yes.
There are not an infinite number of parts in a brake system so feel I am getting close. Lol

Sometimes you need to type stuff out and explain in detail to get a fresh perspective, or confirm. It sure makes one think deeper . . . . Thanks fellas.

 

[1KWIKSIX]

Jerryl,

Here's a suggestion:
How about trying to bleed the air out of the brake fluid via the master cylinder by using vacuum?
Kinda reverse bleeding, but might get the air out your set up. Will just need to make up some sort of master cylinder cover that will accept a small vacuum hose & will enable you to pull vacuum . Maybe these are already available commercially ? Dunno...just a thought!

 

[RmvBfrFlght]

OK, so with both ports plugged the pedal is good. I would connect one line leaving the other plugged and see what that does to the pedal. To see if it is either the fronts or the backs or both.

A while back with a manual brake setup I had a hella' of a time getting a good pedal. The system had been open and the lines and such were empty. What it took was a pressure bleeder. I used a small garden sprayer for the bottle and charged it to 15 psi from the air compressor.

I didn't connect it to the MC, I connected it to each line from the MC (one at a time). As I opened the bleeders used a soft hammer to bang on the combo valve and the various lines. It took quite a bit of fluid to get all of the air out. Was also recycling the fluid as it was new & clean.

Eventually I got a good pedal. Right before that the air exiting the system was the smallest train of tiny bubbles.

RemoveBeforeFlight

 

[Jerryl]

Jerry,

Here's a suggestion:
How about trying to bleed the air out of the brake fluid via the master cylinder by using vacuum?
Kinda reverse bleeding, but might get the air out your set up. Will just need to make up some sort of master cylinder cover that will accept a small vacuum hose & will enable you to pull vacuum . Maybe these are already available commercially ? Dunno...just a thought!

Great suggestion.

I tried that a few months back and saw a lot of constant air comming up but fluid level did not drop. I determined it was leaking through the back seal of the mc. (??)

I may need to try it again though.

 

[Jerryl]

OK, so with both ports plugged the pedal is good. I would connect one line leaving the other plugged and see what that does to the pedal. To see if it is either the fronts or the backs or both.

A while back with a manual brake setup I had a hella' of a time getting a good pedal. The system had been open and the lines and such were empty. What it took was a pressure bleeder. I used a small garden sprayer for the bottle and charged it to 15 psi from the air compressor.

I didn't connect it to the MC, I connected it to each line from the MC (one at a time). As I opened the bleeders used a soft hammer to bang on the combo valve and the various lines. It took quite a bit of fluid to get all of the air out. Was also recycling the fluid as it was new & clean.

Eventually I got a good pedal. Right before that the air exiting the system was the smallest train of tiny bubbles.

RemoveBeforeFlight

I have a pressure bleeder and this is exactly what I am thinking about doing next. Thanks for the reply.

 

[Toby_Goodmk]

you will find something silly as the culprit. Call Jim at hydratech and ask him which line you remove and press down on the brake to see if a bunch of fluid voids. I believe it was the return. I cannot remember. That is how I figured I had lines reversed. I believe I removed the return, put it into the reservoir and had someone pump brakes during operating. You will have a little fluid, but if a bunch something is wrong in valving inside the unit or a seal is blown. Or in my case I had things reversed.

 

[Toby_Goodmk]

you will find something silly as the culprit. Call Jim at hydratech and ask him which line you remove and press down on the brake to see if a bunch of fluid voids. I believe it was the return. I cannot remember. That is how I figured I had lines reversed. I believe I removed the return, put it into the reservoir and had someone pump brakes during operating. You will have a little fluid, but if a bunch something is wrong in valving inside the unit or a seal is blown. Or in my case I had things reversed.

 

[haywire4130]

+1 on the pressure bleeder, i bought one from "motive products" after borrowing one from a friend- it is just like a pump sprayer as mentioned above... it was the ONLY way i was able to get a good pedal in my car. Only change i made was to ditch the hokey chains they give you to hold the adapter to the master and use a pair of quick grip clamps to keep it tight and avoid a big mess. Ive used it a bunch of times since, the thing really earned its keep! With the hb setup correctly bled you should go through the windshield with a hard brake application. I tried the pump and hold method till i was blue in the face, pressure is the only way to go

 

[Jerryl]

Update:
-Raised the back end of the car.
-Verified MC level and re-bled in car
-Verified proportioning valve level (8 deg) so the bubble would move towards the line.
Pressure bled all brakes while "tapping" the proportioning valve with a hammer to dislodge air.
-With the back end up, the angle/location of the front bleeder screws change - Removed calipers and rotated the so the screw would be in top while pressure bleeding.
-AFTER all that, foot pedal pumped the system in sequence about 1 qrt total.
-Results; Same brake pedal.

Placed a call to Tallon.
Much appreciate the time spend on the phone and wanted to share.
-Was suggested (this time) the HB unit is defective.
-Also stated that the visible valve stem in the proportioning valve (pv) for the front circuit should not move out when applying pressure, and, the pv may be incompatible with the hb.

-Went to storage to verify this on the 84 with good working HB. The valve stem does move out of the proportioning valve when applying the brakes.

-Ordered a replacement unit. Installing possibly next weekend.

 

[No disintegrations]

To clarify,. The hboost unit is suspect? Sounds like you might wrap things up soon! Here's hoping!

 

[KentuckyV6]

Without looking to see if they can be mounted on the wrong side of the vehicle, are your calipers reversed? When you mentioned you had to remove calipers to get the bleeder on the top made me think maybe they were reversed. Normally the bleeder should be on the top.

 

[Jerryl]

To clarify,. The hboost unit is suspect? Sounds like you might wrap things up soon! Here's hoping!

Sure hope so. Lol.
What a saga for something soo simple.

 

[Jerryl]

Without looking to see if they can be mounted on the wrong side of the vehicle, are your calipers reversed? When you mentioned you had to remove calipers to get the bleeder on the top made me think maybe they were reversed. Normally the bleeder should be on the top.

Mounting is correct.
Envision the bleeder at the top.
Jack the back of the car up high. The bleeder rotates fwd and down. To get it to the top, the caliper has to he rotated towards the back.
Just the detail I am forced to go through. . .

 

[turbocamino1]

the only thing i didnt see you mention......are the front calipers/pads in goodshape? my stockers where half froze....is the rear wheel cyl's / hardware items good?