1971 MGB Roadster Brake Problems
Discussion
Looking for some help/advice please.
The braking system on the car is acting strange. When driving the car on suburban roads when you need to use the brakes frequently the feel of the brake pedal changes. It becomes hard with no movement available on the pedal. The car also becomes sluggish as the brakes are actually on. On a motorway the same thing happens but after braking if I do not touch the brake pedal the sluggish performance gradually abates and pedal free play returns. Then when I have to use the brakes again the problem returns, gradually abating until I have to touch the pedal again.
I think that it is a brake servo problem as also if I have to brake hard after hitting the pedal quickly and firmly the pedal actually pushes back at my foot noticeably.
I'm going to have a look at the Servo etc tomorrow. I know that a Brake Servo is not necessary part as early cars did not have them fitted, so if I disconnect the vacuum hose and put a sealing bolt in the manifold take off should the brake pedal behave normally? Or should I blank off the servo vacuum entry pipe too?
Thanks
The braking system on the car is acting strange. When driving the car on suburban roads when you need to use the brakes frequently the feel of the brake pedal changes. It becomes hard with no movement available on the pedal. The car also becomes sluggish as the brakes are actually on. On a motorway the same thing happens but after braking if I do not touch the brake pedal the sluggish performance gradually abates and pedal free play returns. Then when I have to use the brakes again the problem returns, gradually abating until I have to touch the pedal again.
I think that it is a brake servo problem as also if I have to brake hard after hitting the pedal quickly and firmly the pedal actually pushes back at my foot noticeably.
I'm going to have a look at the Servo etc tomorrow. I know that a Brake Servo is not necessary part as early cars did not have them fitted, so if I disconnect the vacuum hose and put a sealing bolt in the manifold take off should the brake pedal behave normally? Or should I blank off the servo vacuum entry pipe too?
Thanks
Yes, this sounds like it's time for a new servo. But, when was the last time your brake system was completely overhauled, including a new brake master cylinder, lines, fluid et al. May be now is the time to do this. Replace the steel brake lines with cupronickel [copper-nickel] brake lines and your flexibles with braided lines.
Straight after stopping the engine, press the brake pedal and count how many presses it takes for the pedal to become firm.
If it is firm already or needs only one then the servo is faulty, any experienced mechanic could check this in seconds if you are not sure.
You could disconnect the vacuum pipe and plug it and see if the engine runs better, if it does then that's also a sign the servo is faulty.
If it is firm already or needs only one then the servo is faulty, any experienced mechanic could check this in seconds if you are not sure.
You could disconnect the vacuum pipe and plug it and see if the engine runs better, if it does then that's also a sign the servo is faulty.
All the Braking System (Except the Servo) were updated in 2012. New Master Cylinder. Copper/Nickel brake lines, new Calipers, Discs and Pads, new Rear Wheel Cylinders, and of course new Fluid. In fact all of it except the Servo. Should had done that too at the time!
If there is confusion on my Handle (User Name) I changed it this morning to Packman65.
If there is confusion on my Handle (User Name) I changed it this morning to Packman65.
Edited by Packman65 on Thursday 28th May 08:25
kev b said:
Straight after stopping the engine, press the brake pedal and count how many presses it takes for the pedal to become firm.
If it is firm already or needs only one then the servo is faulty, any experienced mechanic could check this in seconds if you are not sure.
You could disconnect the vacuum pipe and plug it and see if the engine runs better, if it does then that's also a sign the servo is faulty.
The way to test the servo is to do as you say and pump the pedal until hard then with your foot held hard on the pedal you should start the engine and the pedal should sink slightly as the vacuum builds up. A faulty servo or collapsed vacuum pipe would show itself as a very hard pedal when driving.If it is firm already or needs only one then the servo is faulty, any experienced mechanic could check this in seconds if you are not sure.
You could disconnect the vacuum pipe and plug it and see if the engine runs better, if it does then that's also a sign the servo is faulty.
You could try jacking the car up and applying the brakes, let them off again and see if the wheels rotate easily. I'd go with a sticking piston in one or more callipers or maybe a warped disc due to the feedback in the pedal.
OP, if you want to eliminate the servo then clamp the vacuum pipe and test drive it like that, if you still have the same problem the servo is fine, as I suspect it will be.
Edited, if you disconnect the vacuum pipe make sure the engine side is plugged, no need to worry about the servo side, on re-reading your post the vacuum pipe may be collapsing inside.
Edited by jagracer on Monday 1st June 18:45
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