I need help fixing my brakes

by Hs1973 Fri Mar 19, 2021 10:54 am

Hi guys. Im needing some advise. i restored my 75 chevelle years ago but i have never been to happy about my brakes. ( power disc / drum) i used a 9 inch booster from a corvette first time around with a Stock mastercylinder, all other parts are new but Stock items. I worked ok for some years. However my mastercylinder started leaking, so i put a new one in . A 1"1/8 bore and a refurbished 11" booster. And i checked the rest and all seems fine. I bleed them and i Got a really Nice hard pedal.

First time i fired it up the pedal sunk a little and everything seemed ok, but i almost hit the Wall when i put it in gear. The pedal is wery hard and i need to step hard on the brakes to stop. So i rebleed all 4 corners while the little pin on the combo valve was pressed in. I get Nice fluid from all 4. it seemed to get a little better. I can drive it and it stops ok. But i still have a wery hard pedal.

I tryed adjusting the rear drum brakes and change the booster hose, and put it straight to the manifold. But still to hard. I checked the booster check valve and it seems ok. I checked the brake warning light works, but it havent come on like it would if the valve is tripped. It seems worse when idling or moving wery slow to a point where i almost Think the booster is not working right.

Does anyone have any ideas as to what could be Wrong? It almost feels like the booster is not getting enough wacum. Or one circuit is blocked off. Or am i just to used to modern brakes ? Im looking for a a little more bite when just touching the pedal, i feel i have to Press to hard to get a reaktion.

I would be happy for any and all input/ ideas to try as im at the end of my own brain capacity. Also Being in Europe parts are hard to come by and im not to happy trowing money at it all the time.

Regards Henrik.

by ant7377 Fri Mar 19, 2021 5:11 pm

I'm sure you know but usually a hard as hell pedal like that is the booster. I really couldn't think of anything else that would do that.

by Joe73 Fri Mar 19, 2021 8:53 pm

I agree with Ant7377. Whenever I encountered a hard pedal problem, it was the booster.

by Hs1973 Sat Mar 20, 2021 6:32 am

Im also thinking its the booster the more i mess with it. I test drove it today, and i made a panik stop to see how it performs. It stops but did not lock up the wheels. I can feel it brakes when i touch the pedal, but it feels like it has no Real bite to it.

Im going to buy a new booster again. But my problem is i dont know what brand or supplier i can use. I have bought Many parts new that did not work. However Being im in Europe i can not just return them.

So does anybody have any ideas as to where i can find parts im sure will work as intended? Im pretty done buying parts that are restored cause they look ok but seldom work. Thought about upgrading to ccp or wilwood. What are you all running or where do you buy parts from? And have anyone bought parts for other years or models that work. Im thinking camaro or firebird because its easier to find.

by ant7377 Sat Mar 20, 2021 10:15 am

Hs1973 wrote:Im also thinking its the booster the more i mess with it. I test drove it today, and i made a panik stop to see how it performs. It stops but did not lock up the wheels. I can feel it brakes when i touch the pedal, but it feels like it has no Real bite to it.

Im going to buy a new booster again. But my problem is i dont know what brand or supplier i can use. I have bought Many parts new that did not work. However Being im in Europe i can not just return them.

So does anybody have any ideas as to where i can find parts im sure will work as intended? Im pretty done buying parts that are restored cause they look ok but seldom work. Thought about upgrading to ccp or wilwood. What are you all running or where do you buy parts from? And have anyone bought parts for other years or models that work. Im thinking camaro or firebird because its easier to find.

I would check hemmings motor news for a guy that just handles boosters and give him a call. That way you get the right thing the first time and no returns.

by Hs1973 Sat Mar 20, 2021 12:26 pm

Unfortunatly im in Europe ( Copenhagen ) and i can order parts from some parts supplier here or myself from summit or some other vendor. However we have to pay a really High tax on parts imported, so if a part is faulty. I still have to pay tax on a new part i get for a faulty one. We even have to pay tax on the shipping also. That means that i end up playing right around double Price for parts.

So i have to make sure i order quality, cause it can be returned because i will then have to pay tax of the new part again. The refurbished booster i just Got cost me around 600 dollars with taxes and shipping, so it sucks its not working.

Im going to mount my old booster and see how it works before i order something Else. Next time i Might buy a wilwood setup. Or CCP maybe. Have anyone experience with CCP? Parts they look Nice polished and all. I can get a complete setup booster/ master and valve from wilwood. But its like 900 dollars when i get it. So i need to do some researche first.

by 73ss Tue Mar 23, 2021 7:37 pm

What is your vacuum? GM says 14 inches of mercury for the booster to work properly. Mine worked good with 12, The pedal was a tad hard, but didn't affect the way the car stopped. Will your booster hold vacuum? Can you get one good power assisted pump after shutting the engine off?

Try spraying some carb cleaner around the check valve grommet and see if you have a leak. There should also be a rubber seal between the master & the booster where the pushrod comes through. Those can leak as well.

by Hs1973 Wed Mar 24, 2021 11:16 am

I have checked all there is to check. The booster is a new remanufactured unit i Got from a parts vendor i use. However i suspekt it is faulty, even if it test good when i test it. When i empty the booster and start the car the pedal drops as it should. But i have to really stand on it to stop.

So now im doing my own thing. I just ordered a 11" booster with double diaprams and a adjusteble clevis, it is designed for camaro but im going to make my own adjusteble bracket, and put the boosterpin in the upper hole on the pedal. I know its for manual brakes but im going for more ratio on the pedal for more modern feel. If it get to tuchy, i can put it back Down to the power brake hole.

Also i have bought an adjusteble valve, for better rear brake action. So all in all i have hope for better brakes soon. However i know there are limited to what the original calipers can do. But im limited by rulles here in my country. I cant just put 4 disc brakes on it and buy a wilwood setup with giant discs. If i do, i have to pay a large sum off money and re register the car as a modified car, wich in turn cost alot more in Road taxes and so on. I live in a bad place if you are a gearhead. But im going to make the most of what i can with the original parts availeble.

I will Update when the project is done and post my experience. Thank you for all your help and time

by Joe73 Wed Mar 24, 2021 11:28 am

There is the option of installing a MANUAL master cylinder. Doing away with the booster all together. Ive driven two 73 chevelles with manual brakes and its no big deal. And no need to worry about too large of a cam not producing enough vacuum for the brakes.

by impalamonte Wed Mar 24, 2021 11:54 am

Could also go to Hydro-Boost braking system that GM has used for years.

by Hs1973 Fri Mar 26, 2021 12:27 pm

I thought about manual, and i Think it sounds actually ok when i researchede the options. I cant use hydroboost. Its a modification that is not alowed, unless you pay for exstensive testing and pay alot of fees. So im sad to say im Living in a place that limits a gearhead from Being creative. I cannot modify any major components, that means no Big brake kit or blowers or 4 link unless another year of the same model Came with it from the factory. If i do my chevelle is considered not a classic car anymore, and han it will cost an arm and a leg i Road tax and insurence. And also it will have to undergo exstensive and expensive testing like i mentioned before. Its not fun but a true hotrodder findes a solution.

So im limited to use whatever i can find that can go for original equipment. However i will take it as far as i can with what i can get hold of that can be mistanken for original equipment.

by Iggy Sun Mar 28, 2021 2:40 pm

I "robbed" a set of backing plates from a 1977 Monte Carlo - they are for 11" drums vs the 9" drums that came on my 1975. Is this a modification you would be allowed?

by Zed06 Tue Mar 30, 2021 11:16 pm

You didn't answer 73ss. What is your manifold vacuum at idle?? Are you running a stock cam?
It's sounding like this a problem that may be corrected with an aux vacuum booster pump but without knowing what available vacuum is, who knows.

by g3chevy / Mr Pontiac Tue Mar 30, 2021 11:41 pm

I recently restored a 77 El Camino and had issues with the brakes. The pedal felt very hard and didn't have any stopping power. I was thinking the booster was bad at first. Then I pulled out the check valve at the brake booster and bench tested it. It was stuck closed. Replaced with with new one for about $12 and it fixed it. Hope this helps.

by Limey SE Tue Mar 30, 2021 11:51 pm

Iggy wrote:I "robbed" a set of backing plates from a 1977 Monte Carlo - they are for 11" drums vs the 9" drums that came on my 1975. Is this a modification you would be allowed?

I think it would be Because both my 1977 SE's have 11" brake drums

by Hs1973 Sat Apr 03, 2021 11:12 am

Hi guys im back. So it Got the problem solved. Turned out that my new rebuild booster did not work.even if it felt like it worked. Go figure why? So I bougt a 11" double diafram booster for a 77 camaro. I made i fit by opening the hole for the pushrod up. Then i Found that 3 of the bolts ligned up. And i Found a hole already in the firewall for the 4th bolt. It fit ,but would have a to step angel so my hood could not close. But i made a bracket that would alow it to sit at an lower angel, not much just a quarter inch or so.
But still be abel to use stainless nuts and have enough tread to bolt securely to the firewall. Luckely the bracket on the new booster is made from steel, so its thinner then the original alu.
Now it sits like the old one but high enough to use the upper hole in the brakepedal. However the underhood light had to be relocated as Well.

I know of course that the upper hole is for manual applications, but i chose to use it anyway out of ease. And what a difference it made. Now it has almost modern Feeling brakes and stops on a dime. They are not to sensitive but just right. And give a feel of having brakes that work like a modern car has. Alittle touch slows you Down, but Press a little harder and you feel the bite. No dragging or noise just a god bite, easy to dose.
The pushrod is adjusteble wich made it easy to adjust it to perfektion. And everything sits and looks original. So im happy now.

I must just once again conclude that refurbished parts are not good. It seems that every time i get something restored, i dosent work or dies fast. So no more rebuild parts. Thank you for all your help. I love this site because of all of you. If any of you are interested in the mod, i can take a picture and supply the partnr. All is bought from summit. Henrik.

by Hs1973 Sat Apr 03, 2021 11:28 am

Oh and to iggy. Mine already has 11" drums on the rear. But yes i can use anything original if a 73-77 was original fitted with it. Or as long as no one can tell the difference. But i cant by a wilwood Big brake setup or a hydroboost from astrovan or similar. However there is plenty of parts out there that can go for Being original, if you are not an expert. So us guys here are getting good at working around the rules without obviasly braking them.

They dont care to much about wheels or paint. But any mods to brakes or suspension or any parts in the chassis or driveline means Big bills and Lots of Trouble. Also i cant use a bigger engine than original, and i am only alowed to increase horsepower by 20 procent over original too. Luckely most officials dont know how much hp a mid 70s chevelle had. And they have no Way of measuring it. So as long as you keep it mild its ok. But no blowers or turbo or 500 hp 454, unless it was original a bigblock. However again most officials would not now the difference between a Big and smallblock, nor do the Cops. So if you dont brag and keep low profile you can get away with alot.

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