Pop Quiz!....Brakes

Gazoo · BADEN, ONT

Pop Quiz!....Brakes

Lightspeed Mike · BELLEVILLE, ONT

First suggestion is get rid of the DOT 5 brake fluid. I causes more problems than it cures (IMHO)
If you use DOT 5 the whole system must be flushed thoroughly, the 2 don't mix.
Crack the lines at the master and press the pedal down. Does it still return slow?
Take the master off the booster and gently press the brake. Does it feel sticky?

Try this and let me know what happens.

wolfman1 · ST GEORGE, ONT

Did you flush the master cylinder out, before you added the dot 5 ?
Maybe still some dot 3 was still in there.
I would think the master should have been pulled and bench bled

fatchuk · ST MARYS, ONTARIO

Gazoo: I might be more suspious of a flex line having deteriated from the inside or have a good look at how they are secured and make sure they are not squeezed to tight or have rust buildup at the bracket where they are secured..You might have somebody pump the pedal while you crack the bleeders to see if your getting a good flow of brake fluid when bleeding..Those caliper piston can you not get them with those Phenelon plastic pistons..they never rust..I do know that I get a lot of siezed calipers in the shop at this time of year ..Every year at time much of my work is electrical problems from road salt migrating into lots of trailer hitch wirng and parking light stuff or wiring that is buried under carpeting with power sliders.. lots-a-good work for me and lots-a-siezed calipers..But I would be checking the flex lines first I see that fairly often..I can't see it being the booster ..but I have seen it in the master ..just not very often..

BARRIE, ONTARIO

pedal linkage binding up ??..77.

v8deuce · OAKVILLE, ONT

Sorry Mike but I'm a firm believer in dot 5, I have used it in all my rods,I started using it in the players challenge seires that gm put on in 88 with the camaro's,I was a crew cheif for my brother and he would get the brakes hot and boil the dot 3 fluid out. Don't hurt the paint and don't absorb moisture so you don't have to change it ever couple years,I only use it on a new system so mixing them is not recommended.But with this problem my money is on a bad booster. Another thing to try is to pull the line off the booster and plug it leaving the booster hole open. My 2 cents worth.

Randy

Gazoo · BADEN, ONT

Chuk; Flex lines are new also, came with the kit.
There is no Dot 3 fluid left in the system, the old steel lines were taken off last fall at the master cylinder, it drained itself dry(ish).
I didn't bench bleed the master, figured I'd trow fluid in the system after I put on the new lines and check for leaks first.
Usually your pedal will simply go to the floor, if the master needs bleeding, right?

Mike; I'll try the pulling the master off the booster when I get back on Sunday. If it feels sticky...what does that mean? (LOL)
Sorry man, couldn't resist.

Gazoo · BADEN, ONT

Randy, I've never had a booster go bad, so what you're saying is if I pull the vacuum line off the booster and plug the line (so the engine doesn't lose vacuum, the brake system should work like a non power assist (so to speak), and if the brake pedal returns somewhat normally...then it's the booster/diaphram.

I also omitted/forgot to mention, I do have a bit of a cam in the engine, would that cause it to loose enough vacuum to make the pedal return slow?

Gazoo · BADEN, ONT

Ok, so I'm back from Stirling, beautiful day, got a couple hours left before diner...so I pop the hood on the old fellow. First I try the pedal without have the car running, it's feels nice and firm, returns to top like it should.

Next I follow Randy's advice, and I pull the vacuum line of the master, and plug the line, fire the engine up, and hit the brakes, the pedal reacts exactly the same as without the engine running, pedal comes right back up.

Next I hook the vacuum line back up, and my issue is back, so I rev the engine up to about 1,200-1,500 rpm, and the pedal returns just a touch faster, but nowhere near what it should.

So next on the list, is Mike's check, and separate the master from the booster, and check for stickiness, but that'll be tomorrow's adventure...

It's simply too nice outside to play in the garage right now!

Unless anyone finds anything odd, about my findings today.

fatstax · COBOURG, ONT

Gazoo wrote:
Ok, so I'm back from Stirling, beautiful day, got a couple hours left before diner...so I pop the hood on the old fellow. First I try the pedal without have the car running, it's feels nice and firm, returns to top like it should.

Next I follow Randy's advice, and I pull the vacuum line of the master, and plug the line, fire the engine up, and hit the brakes, the pedal reacts exactly the same as without the engine running, pedal comes right back up.

Next I hook the vacuum line back up, and my issue is back, so I rev the engine up to about 1,200-1,500 rpm, and the pedal returns just a touch faster, but nowhere near what it should.

So next on the list, is Mike's check, and separate the master from the booster, and check for stickiness, but that'll be tomorrow's adventure...

It's simply too nice outside to play in the garage right now!

Unless anyone finds anything odd, about my findings today.

sometimes those braided flex lines can also restrict fluid releasing from the caliper/wheel cylinders. i use plain ol rubbber flex hoses, you not driving a formula one car

Gazoo · BADEN, ONT

Stax, they are just plain old (brand new) rubber flex lines, it's a restoration kit, aside from the steel lines being stainless.

After today's checks, what I'm leaning towards is the power brake booster, as this issue is not there when then engine is running or the booster is disconnected.

If that's the case, anyone know where I can get parts to rebuild the booster?

fatchuk · ST MARYS, ONTARIO

Hi Gazoo:

Lots and Lots of yard work all week-end..just got back to this post..Say I have both the phone number and e-mail for John Stewart Power brake Company..These are really good guys to deal with and they are out of Stoney Creek ..they can help you Here is the phone number..1-800-309-1995 ..or local 905-662-7274..or e-mail jstuart@netrover.com 349 Millen Road North Stoney Creek Ont..

Gazoo says

I'm leaning towards is the power brake booster, "as this issue is not there when then engine is running" or the booster is disconnected.

If there is no issue when the engine is running... It does sound like you may have contaminated that booster with change of brake fluid or the booster is just old and failing sounds like the vaccum valve inside the boooster can is leaky or sticky. It has to completely close to vacuum and expose the lower side of the diaphragm to atmospheric pressure when pressure is removed from the brake pedal. Otherwise, lower pressure on the booost side of the diaphragm will be fighting the internal return spring pressure...probably be a good ides to do the homework before removing the booster..I would talk to the guys at John Stewart and see if they have a suggestion or confirm that may be the cause..I have not had any business with them as of late but back a few years I dealt them and they were great to deal with...

-- Edited by fatchuk on Monday 6th of May 2013 02:54:51 PM

34guy · MISSISSAUGA, ONT

Did you change your rear flexhose to the rear end brakes ? mostly overlooked as well.

Gazoo · BADEN, ONT

34guy wrote:
Did you change your rear flexhose to the rear end brakes ? mostly overlooked as well.

Every line in the system are new, even the front proportioning block, the rear proportioning block is the only thing that is used. Wheel cylinders are new and the front calipers are rebuilt also.

So the only things not changed in the whole system, are the booster, master cylinder and rear proportioning block.

The pedal has great feel, it just won't come back like it should.

Chuk; I had John Stewart rebuild the front calipers, as he would not sell me the rebuild kit. I called him today also, about rebuilding the booster, as he won't sell you the kit. He's way up there in price. I can get a rebuilt booster, and master cylinder, and fresh plated yellow zinc dichromate in the US, for less than what he wants to rebuid the booster alone, and it won't be plated.

Although I may have to go that route, I'd like to find a better alternative.

I also re-read my post Chuck, and the issue is there when the engine is running and the vacuum plugged in. I'll go back and edit that, it's misleading.

Gazoo · BADEN, ONT

I'd like to add, thanks for all the replies, keep them coming, you always seem to overlook the simple stuff.
In the meantime, I'm looking for platers and rebuild kits, or places to rebuild it in Canada.

oldkoot · BROCKVILLE, ONT

You mentioned you're running a bit of a cam, what sort of vacuum are you running-15-18 inches or lower. Did you check the rubber boot/filter on the back of the booster?

slim · DUNDAS, ONT

Is there a booster check valve where the vacume line enters .It is supposed to regulate pressure inside the booster . I'm not to shure how to go about testing it but it would suck to fork out the cash for a new booster if the check is screwing up

Gazoo · BADEN, ONT

Oldkoot/Slim, both excellent points, and that is something I overlooked. I found the check valve as i was surfing for booster rebuild parts or...I'm for sure getting one as soon as I can get it. It's been on the car since 1971, and it's a very inexpensive part.

That's something I had overlooked. I hope that's it.

Thank you!

hemi43 · ONTARIO

This is the best I could find. I circled the area where the valve is located in red. I would take the booster appart and make sure this area looks clean and has no damage. Another area I thought of that may give you problems, is the area I circled in blue. This is a vent, and if clogged might cause issues. If I remember, there's a filter in this area. Make sure it's clean also.

Edit; I just read Grump's reply, and here's a way you can figure out if the problem is the booster or something else. Disconnect the 2 nuts that hold the master cylinder on the booster, and pull it away so that it's not hooked up to the booster anymore . Start the car and push down on the pedal. If your problem persists, then you know it's the booster. If the pedal returns the way it should then Grump might be right. It's a process of elimination.

-- Edited by hemi43 on Tuesday 7th of May 2013 03:04:14 PM

Gazoo · BADEN, ONT

oldkoot wrote:
You mentioned you're running a bit of a cam, what sort of vacuum are you running-15-18 inches or lower. Did you check the rubber boot/filter on the back of the booster?

My vacuum gauge is pooched, but the cam was in there with the old fluid etc... and it worked OK, not perfect.

The cam's specs are not overly agressive, I wanted it streetable , the specs on the cam are : Crane Cam, 284 H12, the lift @cam is .320" both intake and exhaust, with a 1.5 rocker arm ratio, the lift at valve is .480". The duration on both lobes is 284*.

The stock cam had .444/.453" lift @ valve and duration was 276/284*, so not an extreme difference.

I will try to find a vacuum gauge just the same, to check that.

hemi43 · ONTARIO

Inside the booster, there's a valve that regulates how much vacuum is applied to the diaphragm. If you push the plunger in 1", the valve will regulate vacuum so that the plunger will not travel any further. When you remove your foot off of the pedal, this valve is supposed equalize the vacuum so that the pedal returns back to normal position.It works much the same way as an air regulator you find on your air compressor. It sounds like your valve is sticking !! Disassemble the unit and check this. It's easy to do !!
The valve that slim mentioned, is just a one way valve that retains vacuum in the booster so that the brakes will always have some vacuum reserve. This valve is the reason your power brakes will still work once even after the engine is shut off.This valve will not cause the symptoms you've described.Also, the cam you have will give you more enough vacuum

Cat in the Hat · BRANTFORD, ONT

Gazoo,

Its because for these issues that I don't run Boosters on my rods...

I use a Wilwood dual master brake system.. (Stock car stuff) about $200 for complete set up.

If its good enough for stock cars....beating the crap out of brakes lap after lap....

It's good enough for me....BTW .... locks the brakes at will

my 2 cents on your problem......flex lines...front and back....even new ones have been known to colapse

Flush full system......Dot 5.....New flex lines.....just sayin ;)

Gazoo · BADEN, ONT

hemi43 wrote:
Inside the booster, there's a valve that regulates how much vacuum is applied to the diaphragm. If you push the plunger in 1", the valve will regulate vacuum so that the plunger will not travel any further. When you remove your foot off of the pedal, this valve is supposed equalize the vacuum so that the pedal returns back to normal position.It works much the same way as an air regulator you find on your air compressor. It sounds like your valve is sticking !! Disassemble the unit and check this. It's easy to do !!
The valve that slim mentioned, is just a one way valve that retains vacuum in the booster so that the brakes will always have some vacuum reserve. This valve is the reason your power brakes will still work once even after the engine is shut off.This valve will not cause the symptoms you've described.Also, the cam you have will give you more enough vacuum

I went out and got me a check valve and some new hose, believe it or not, the check valve i got from NAPA won't fit, LOL. So I put the old check valve back on with the new hose, and new cap for the port not being used. I increased my idle speed from 650rpm to 850rpm and the pedal does return faster, but still not what it should be.

If the valve inside the booster is sticking, can I just clean it up, does it have adjustment?

I did a test before deciding to change the check valve, basically with the engine running I pinched the vacuum line, and then pressed on the brake pedal, and the pedalfelt like a power brake pedal should, but the second time I pressed the pedal with the line still pinched, it had no power assist. This told me that the old check valve is still good, and the booster retained vacuum for at least one activation.

So I've got to think it's inside like you've said.

Grumps: I think if I had bloated flex lines...the brakes themselves would stay somewhat locked up, like a seized caliper for instance, as there is no pressure pushing the fluid to return up the system, or pulling the fluid back up. The fluid flows great, it's was obvious when I blead the system, I use a clear plastic line on the bleeders to my bottle, lots coming out, and you see it pull back when the pedal is released.

This is an original car, unmolested, and I would like to keep it that way, believe me I've considered going to aftermarket SSBC brake conversion, but they come with their own new issues, like I would need to change my rims to 15" which would mean I'd have to get axles made up for the rear etc...

hemi43 · ONTARIO

Gazoo wrote:

If the valve inside the booster is sticking, can I just clean it up, does it have adjustment?

It's been a long time since I rebuilt my booster (25+ yrs) so I can't recall what the valving looked like. I do recall it was an easy thing to do and could be done quickly. I'm 95% sure that's what the problem is. I'll try and find an exploded view of the guts. As far as adjustments, there's none!!

Cat in the Hat · BRANTFORD, ONT

wilwood dual master.jpg

This is the master unit i have used on Many cars.....works like a champ

Colapsed line will not show.....

Gazoo · BADEN, ONT

Well, I'm this far into it now, the car is quite drivable the way it is, and since no one will sell me a rebuild kit for the booster, I think I'm just going to get it rebuilt. I found a place in London, they'll rebuild it and replace check valve and filter, seals etc...for $160. I can go get it replated at Plating Master for another $70.
That'll put me at a stand still for another 2 weeks, but that ain't so bad. This way I can concentrate working on the '38 in the meantime.

Thanks a lot for the replies, you fellows helped me out, pointing me in the right direction.
But I figure for a couple hundred bucks more, I may as well get a completely new brake system from end to end.

hemi43 · ONTARIO

Gazoo wrote:

That'll put me at a stand still for another 2 weeks, but that ain't so bad.

On my B-body (Roadrunner), I was able to remove the booster from the car, and bolt the master back onto the firewall, This made for a harder pedal effort, but I was able to drive the car. I had just enough movement in my brake lines to allow me to do that.

Cat in the Hat · BRANTFORD, ONT

Check .... www.speedway.com they might have what you need in stock...cheaper