Brakes Dragging need help with troubleshooting

[Trucknut57]

Setup: 1957, hydro boost and master cylinder under the floorboard remote reservoir on firewall, 4 wheel disk brakes, Camaro front rotors/calipers, S10 rear rotors/calipers. No check valves in the braking system, they are not needed.

Problem: Brakes work normally for the first 10 minutes, after that noticeable drag on all brakes. Hot brake smell also. All brake lines are routed away from heat sources. Now all brake rotors are glazed over and pads are severely used, only about 700 miles on these pads and set up.

My initial thought is, the hydro boost unit is leaking by a little and putting pressure on the master cylinder, hence pushing on the pads.

Anyone have any other ideas?

[1project2many]

Is this something that you've discussed here before? There was a similar thread about a month ago.

Reservoir up high will cause fluid to put pressure on caliper pistons. Depending on size of pistons, might be significant. Pedal adjustment for hydroboost must be correct.

A diagnostic step: Take truck for drive, after 10-15 minutes open reservoir cover carefully. If presure under cover or if fluid comes out then problem may be overfilling of system. Leave more air in reservoir. Also, check temp of all rotors with infra-red gun if possible. If all rotors equally hot then problem is probably fluid presure generated internally from reservoir. If front or rear warmer look for problem on one end of truck.

[4 Wheelin Fudpucker]

Do you have a proportional valve installed?

[_Ogre]

i had a similar problem with truk, my brake drag was caused by the floor pushing the brake pedal down about 1/8''
if you have any pivot bolt on the brake pedal, remove it and see if it can be re-installed easy
without moving the brake pedal down

i had to ''chicago'' the brake pivot bolt, the step down was all it needed
i chucked the bolt up in my drill press and used a cutoff wheel to reduce the bolt shaft



the remote reservoir would need to be 15 to 30 feet above the hydroboost to put any pressure on the mc
my remote reservoir is at least 24'' above my hydroboost

[Coupeguy2001]

I have a hydroboost with a 96 Chevy dually master cyl. and a remote reservoir about 30 inches higher than the master.
I recently changed the master because it was leaking.
The new master comes with a already installed plastic check valve in it.
I removed the guts of the inline check valve and reinstalled it, and the dragging went away.
at first I backed off the proportioning valve, and that didn't fix it.

you can loosen the line on one front or one rear, and if there's pressure, Ogre is right, there is improper pedal adjustment.
Remove the master from the booster a half inch, and make a 1/16" plate to go between the master and the booster. bolt it back together.
If the problem goes away, the rod was not the proper length. If it does not go away, crack the line again to get a feel as to how much pressure is remaining in the line. Be sure to wear eye protection or use one of those clear notebook protectors to shield your eyes in a pinch.
You can make a few plates to go between the booster and master to see if the pressure goes away. 1/16" at a time though.

I have a 1/4" spacer in my truck. but I made a new rod for the hydro boost unit out of a 3/8" diameter rod. I made it to the exact length of the original plus 1/4 inch.
Then I ground a little off the end till I got what I wanted, then left it alone.
Be careful though, there is a plastic rod guide inside the hydroboost, and if you break it, they don't sell those, I can tell you how to fix it.
My email is hillenger512@cox.net

[Trucknut57]

1project2many - as far as I know I didn't post another questions about this problem, but if there was something close to this problem then I will have to search for it, thanks. My reservoir is half way up on the firewall and is only half full.

4 wheelin fudpucker - I have an adjustable proportioning valve on the rear brakes only.

Coupeguy2001 - I used the hydro boost and rod from a 2000 Astro van and since I had to use a remote reservoir also used a micrometer to match the depth of the master cylinders. But I will have to recheck the rod length.



Thanks for all the ideas to look at. Can the hydro boost need to be rebuilt? I kind of looked past the hydro boost since the brakes still work really good.

[tmoble]

IMO the most likely cause is the rod between the hydraboost and the M/C. drive it till the problem occurs, then crack a line at the master. if there's pressure built up it's likely that rod being just a fraction too long.

coupeguy has a good idea. ALso, I've used a few flat washers temporarily on the M/C mount studs to space it away from the booster. if it fixes the problem you need to shorten the rod.

[OrrieG]

Not hydroboost, but had the same issue with my MC, initial set up was with zero clearance and front discs would heat up and seize. Backed it off so MC totally released with about 1/16 clearance and problem solved.

[joedoh]

Originally Posted by OrrieG

Not hydroboost, but had the same issue with my MC, initial set up was with zero clearance and front discs would heat up and seize. Backed it off so MC totally released with about 1/16 clearance and problem solved.

same here, my truck needed a slightly shorter rod, I couldnt bleed the rear brakes because the master wouldnt release all the way.

tmoble is exactly right, crack a line when pressurized/dragging and if the wheel releases, it is the rod length on the pedal.

[dsraven]

have a buddy help you, when you have things warmed up and the brakes are dragging, take the lid off the master cylinder and have a buddy tap the brakes while you watch inside the reservoir. there should be a little "fountain" of fluid come up in the master cylinder when the brakes are first touched. that is fluid coming back into the reservoir through the hole in the master cylinder bore that is supposed to be uncovered when the brakes are released. as the pedal is pushed it starts to pressurize the bore and the fluid comes back through the hole until the piston covers the hole, then pressure starts to build inside the system and the brakes are applied accordingly. that little hole is what allows the pressure in the system lines to be released back into the res when the pedal is released.if the pedal is not adjusted properly, is hanging up on something or whatever, then the hole never gets uncovered and system pressure can build when things start heating up and expanding, applying the brakes. if there is a small "fountain" effect of "rush back" fluid then at least you know that part is working. now, try to push the vehicle a bit to see if the brakes are still grabbing. if they are suddenly good then maybe the lid of the reservoir is not venting like it should. if the brakes are still tight, start checking at each bleeder to see if there is pressure in the system or the problem lies somewhere else- possibly mechanically. things to check:
-brake caliper mounts are freely moving. this may require that the pistons are pushed back into the calipers a bit to make sure the calipers have some room to slide back and forth on their mounts. I have found the S10 calipers are bad for getting tight on their mounts.
-brake pads are freely moving in their mounts. some have abutment plates on the caliper wear areas and these can get rust behind them so they swell, causing the pads to bind in their mount/slide areas.
-brake hoses are all in good shape. check for cracks etc by bending them slightly. I have seen hoses look good on the outside but have deteriorated on the inside which can cause a "flap" on the inside which works like a one way valve.fluid gets out to the brake calipers but can't get back when the pedal is released. this will cause pressure in that caliper which would be picked up when you crack the bleeder screws (with the brakes released) and only one has pressure.
-check the steel brake lines for kinks or flat spots from line clamps or road debris that may have come up and hit a line.
-check the park brake adjustment and cables for hanging up. especially if it is just the rear wheels that seem to be hot or hanging up.
-check the mechanics of the brake pedal and all linkages to make sure there is nothing with excessive play or no play. make sure the pedal is free moving against all sheet metal etc. check to be sure the pedal push rod has some clearance against the master cylinder.
if you think it may be the hydro boost giving you issues, is there a way for you to take the belt off without affecting something else? maybe bypass the booster and try it without the boost. if it is good that way then it would point to a booster issue.

anyway, good luck and keep us posted

[Layedoutsonoma91]

I had this same thing on my truck, i spaced my master cylinder and booster apart some and it made it a ton better. I think i may have some trash in my prop valve causing me some of it tho. Check that too.

[mr48chev]

Do you have a return spring on the brake pedal? I'd think that either the pedal isn't returning like it should and leaving pressure on the piston in the master cylinder or the push rod is too long as was previously suggested. The height of the remote reservoir should have no effect on the brakes and put no pressure on the brakes. That's just more fluid as would be in a larger master cylinder reservoir and puts no pressure on the brakes.

I'd believe that at times the piston is pushed just enough in so that the bleed back hole (s)in the master cylinder is/are covered or partially covered not allowing the fluid to return to the reservoir as it should.

If that isn't the case there may be a check valve behind the brass seat in the fitting the brake line screws in. Those are put in for drum brakes but not needed for disk brakes.

[1project2many]

the remote reservoir would need to be 15 to 30 feet above the hydroboost to put any pressure on the mc
my remote reservoir is at least 24'' above my hydroboost

I'm thinking of pressure at the calipers. 24" of rise and 3.5" of caliper piston surface is about 4 psi pressure on the pads. Thanks to a huge volume rebuilder and unknown country of origin for parts sourcing, calipers and seals today seem to be mix and match and it's very possible the seals aren't returning the pistons enough. Static pressure of fluid can aggravate condition. This problem is not reserved to remote reservoir system. It can happen with typical master-on-firewall configuration as well.

Size of reservoir is unknown but if there's insufficient unfilled volume then heated fluid will have no room for expansion and can apply additional pressure at all calipers. Same problem happens to our buses when the shop kid overfills the reservoir. Combination of dragging pads heating fluid and nowhere for fluid to go will create self-activating brakes.

you can loosen the line on one front or one rear, and if there's pressure, Ogre is right, there is improper pedal adjustment.

I would not make that assumption without further testing. Brake flex hose problems were mentioned and I've dealt with that more than once. Clamping flexible hose with hose clamp pliers or Vice Grips can break the inner liner in the hose and cause the one way valve effect mentioned earlier. Although YouTube seems to think it's a great idea, I've got a Tee-shirt from my early days as a tech that says otherwise.

Pedal may not be adjusted correctly, but that typically shows up right away. First application of brakes causes dragging or hanging brakes in most applications. I suppose heating of m/cyl from exhaust and engine could aggravate issue? But that might not be my first hunch without more questions. How long does truck have to sit before dragging goes away? Is dragging ever present right away if truck is started when warm and driven immediately?

dsraven provides great advice for comfirming pedal is coming to rest on the stop and m/cyl piston fully returning. If you can see into the reservoir the fountain is a good visual confirmation. Be sure to check while brakes are dragging.

[Trucknut57]

mr48chevy - I do have a return spring but for some reason lately I have had to use my foot to pull the pedal all the way back up, guess I better check to see what is keeping it from returning before I tear into anything. Good catch, I didn't even think about that.

1proiject2many - I only keep the reservoir about half full. All the brake components are pretty low mileage and were new when installed. When I do use the brakes, I barely touch them and they work, I've never had to slam on them and that is probably a good thing, it would probably send me thru the front window.

[Coupeguy2001]

Oh by the way, there is a company called Pirate Jack.
They have hydroboost overhaul kits for about $50-$65. They also have online instructions so you know what you are getting into ahead of time.

[Trucknut57]

Coupeguy2001 - Thanks, that's where I purchased the booster bracket and master cylinder. I'll go there and look for the rebuild kit.

Unfortunately I have been moving all the boxes out of my shop lately and into the house so I have not had the time try any of the great remedies from everyone. I'm going to get out there this weekend and see what I can get done.

[dsraven]

make sure the mechanical stuff is all free moving, not worn out or siezed up and there is clearance on the pedal pushrod and also the pushrod that moves the master cylinder.

-disconnect the pushrod at the pedal end of things and ensure the pedal swings easily and doesn't have a bunch of bushing/shaft wear.
-check the pushrod pivot to look for the same things, wear and excessive play or too stiff to move freely
-assemble the pushrod again and check to be sure the adjustment for free play is correct.
-check the pushrod on the master cylinder to ensure there is correct endplay/gap.
-make sure the hydroboost is fully bled so no bubbles in the system.

- THEN start looking to see if the booster is at fault or the master is toast or whatever.
when the brakes are hot and TIGHT, is there pressure in the system when you crack a bleeder screw? is it only the rear brakes? do you have the rear brakes connected to the correct ports on the master?
-don't overthink it before doing some good old hands on. internet is great for ideas but doesn't troubleshoot like a good set of eyes and hands doing actual tests.

[1-ton of fun]

had a similar problem on a mustang, turned out to be that the rod between the booster and MC needed adjustment, it was too long. loosen the nuts a little that hold the mc to the booster and see if it goes away. if so, the rod needs to be shorter or you need a spacer. shorter rod is the correct way to fix, but a spacer can work.

[Trucknut57]

Update on the problem,

I FINALLY got time to try the washer in between the booster and the master cylinder suggestion and I'm happy to report it worked great, the brakes no longer drag. Now I can go get my rotors resurfaced and throw on some new pads on all four corners.

Thank you to all who chimed in on my problem.

[_Ogre]

thanks for the feedback.
always nice to know we fixed something

[dsraven]

So, is the pushrod adjustable or are you planning on fabbing a proper spacer?

[Trucknut57]

I will have to make a proper spacer, the pushrod coming from the hydro-boost unit is non-adjustable and I really don't want to grind or drill into the master cylinder. So making the spacer is the best option.