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BT7 brales poor stopping power - any advice?

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fishyboy

Jedi Hopeful
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Hi all,
I've owned my 1961 BT7 for 25 years. Currently the brakes do not appear to works as well as they have in the past. The peddle has some travel and then has a firmish response. Pumping the brakes does not produce a higher or firmer peddle. When applied the brakes don't exactly bring the car to a shuddering halt, but are slow and progressive. In the past I am sure that the brakes had more stopping power.

The Master Cylinder is newish and the reservoir is only a year old. I have replaced the pads and shoes this week. I have bled and adjusted the rear brakes, but not bled the from calipers.

My thoughts are:-

1) Is there still air in the system? Could air be trapped at the highest point in the system where the pipe enters the MC? I have tried pumping the peddle and loosening the brake pipe nut but only fluid comes out.

2) Could there be a problem with the MC? How can I test the system to try and isolate where the problem might be?

3) Have the brakes always been inefficient and I am somehow remembering them being better than they were?

Any advice welcome.

Phil
 
How old are the brake hoses ?
 
Front brakes do the majority of the stopping so you should certainly bleed them as well, but if there were air I doubt you would have the firm pedal you describe.

Perhaps there is some problem with reassembly that is preventing either the fronts or rears or both from fully activating?

You may also have a collapsed hydraulic hose somewhere in the system.
 
Thanks for the replies.
All three hoses have been replaced with steel braided ones in the last 12 months.
I shall try to bleed the fronts today.
Phil
 
If you have a firm pedal and it doesn't pump up much, you probably don't have air in the system. Did the change in brake efficiency coincide with the arrival of new pads and are the rears working properly? There's quite a bias to the rears on a Healey, so if they have stuck pistons (common fault) or whatever, it might account for what you're experiencing.

Pistons can can also stick in the calipers so try locking the wheels to see if wheels are locking prematurely.
 
Hi all
The brakes were poor before I changed the pads and shoes.
EV2239
What do you mean by "locking the wheels to see if wheels are locking prematurely"? If I hit the brakes as hard as I can I cannot lock the wheels when out driving (I certainly could in the past). I don't think the pistons are sticking (the front of the car dips on breaking which suggests the fronts calipers are working). I'll try to check the check the rears by removing the wheels and hubs and applying the brakes.
Phil
 
Phil--

In your first post you said that the brakes do not seem to work as well as they did in the past but in your last you said they did not work well before you changed pads and shoes. Without getting into symantics perhaps this indicates that the problem lies elsewhere in the system such as cylinder sizes, type of fluid, etc. Have you changed any of the components and inadvertently gone to different diameter cylinders? Are you using a different type of fluid? Is it possible there is some problem with the pedal itself?
 
Hi all,

The brakes have been poor for the last couple of years. They are good enough to pass the UK MOT, but do not feel as good as they could be to me. Since the decline I have been slowly working my way through the system, replacing elements until I have reached today where I am at a loss where to go next (I shall bleed the front caliper when time permits). This is what I have done so far.

August 2015
Fitted new Brake MC, new Dual reservoir and three steel brake hoses with no noticeable improvement

June 2016
Fitted new rear brake shoes and front Pads, followed by bleeding and adjusting the rear brakes - again with no noticeable improvement

Phil
 
Phil,
You should definitely be able to lock the wheels up when driving. I believe in renewing the entire hydraulic system at one time - you haven't said how long it has been since the entire system was rebuilt. You have done the master and flex lines so if you rebuild/replace the front calipers and rear wheel cylinders you will have a fresh hydraulic system to go with the new pads and shoes. At the very least it will give you more confidence knowing all is renewed.
From your description I'd bet on sticky front caliper pistons (the fronts do 60% or more of the braking) but it's just speculation until you open them up and see what condition they are in.
 
Thanks red57,
I like the idea of rebuilding the front calipers, but is probably beyond my capabilities. What is the best way to find out if there is a problem with the calipers before booking it into a garage/shop. Is there something I can check with the wheels off?
Phil
 
Phil,
You can look for any signs of brake fluid leakage. You can also look to see if the rubber dust excluders (outer seals around the pistons) are cracked/torn or damaged in any way - if these seals are damaged, it can allow grit to enter the bores and cause the pistons to not move freely. But it is also possible that there is corrosion inside the bores that will not be visible until disassembly, but would also result in grit possibly impeding the free movement of the pistons. You haven't mentioned, but if the brakes pull to either side, that is also a possible indication of a sticky piston - eg, if it pulls to the right, look to a possibly sticky piston on the left side. Upshot is more than likely you will need to disassemble to know for sure.
Side note - the original pistons are steel with chrome plating and this plating can fail and allow the steel pistons to rust (most brake fluid is hydroscopic and attracts moisture). I recommend when rebuilding that you replace the pistons with stainless steel ones. Two advantages to SS pistons are, no more rust possible in future and less heat transfer to the brake fluid, extending the life of the fluid (this last part is just my opinion).
Dave
 
Red57 said:

I believe in renewing the entire hydraulic system at one time - you haven't said how long it has been since the entire system was rebuilt.

This might not be the most economical way to solve the problem but I wish I had a dollar for every time I have thought I solved a problem by replacing one component of a system only to find that another piece was also part of the issue. All of the moisture, dirt, rust, rubber bits and other detritus that has lived within your brake and clutch systems (remember, they share a common reservoir) have--potentially--contaminated and compromised every component, fitting and connecting hose.
 
fishyboy said:
Hi all,

The brakes have been poor for the last couple of years. They are good enough to pass the UK MOT, but do not feel as good as they could be to me. Since the decline I have been slowly working my way through the system, replacing elements until I have reached today where I am at a loss where to go next (I shall bleed the front caliper when time permits). This is what I have done so far.

August 2015
Fitted new Brake MC, new Dual reservoir and three steel brake hoses with no noticeable improvement

June 2016
Fitted new rear brake shoes and front Pads, followed by bleeding and adjusting the rear brakes - again with no noticeable improvement

Phil
Click to expand...

Assuming you meant braided stainless flex hoses.
So the only things remaining are: rebuild calipers with new pistons and seals; rebuild rear slave cylinders; bleed all 4 wheels in this order: LR, RR, LF, RF.

I like sealing the bleeder screw threads with teflon tape & using a syringe to pull out the fluid through each bleeder.

One of the posters here suggested tightening the rear brake shoes as tight as you can get them for bleeding, then loosening for operation.
 
Phil,

Since you just replaced pads and shoes, I would suspect the pads/shoes aren't bedded in just yet. Did you follow the instructions for bedding the pads? Usually it includes several hard stops from 30mph, and then 60mph until the pads are very hot, then allow to cool and you're good to go. On the rear shoes, since no one arcs the shoes anymore due to asbestos dust fears (which no one uses that anymore), the rear shoes probably have a small contact patch and need time to bed in. You can check the rear shoes to see exactly how much is in contact to verify this theory.

On a side note, the stock pads often offered by the usual suspects don't have a great friction factor. If you dig down into the detail of the pad, via the manufacturers website, you can usually find a friction factor to compare with other manufacturers. I've had good luck with EBC green pads on street vehicles if you decide to lesson pedal pressure at a minimal cost.

This all assumes that the car isn't pulling to any one side, no one wheel is locking up, etc. which implies mechanical malfunctions.

Also, is the MC you replaced the same bore size as specified in the manual??
 
Hi all,
Thanks for all the advice. I think the calipers might be the root of the problem and will check them out.

The new pads and shoes were bedded in. The new ones were the "Couinty" brand. Ill take a look at the EBC ones next time.

Phil
 
More than likely if the calipers need rebuilding so do the rear wheel cylinders as has been said. The calipers will usually not release well if they are bad but the rear wheel cylinders will cause the brake pedal to be hard when they are frozen.
 
Hi all,
Ive ordered a pair of restored exchange calipers and new rear wheel cylinders which will be fitted at the end of this week. I shall let you know what happens!
Phil
 
Hi all,
Got my local garage to install rebuilt exchange front calipers on my BT7. As the rear brake cylinders were fine they were left.
Big improvement in the brakes. firm peddle with no sponginess, but with a lot of travel. Front wheels now lock under Hard braking.

However, only leaves skid marks on the road from the right-hand front tyres.

Any ideas as to why this may be? Also why is there so much travel on the brake peddle before it firms up?

Phil
 
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