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MG MGB Technical - Brake pedal travel:2 pumps=perfect!!
|I just completed a full brake system overhaul on my 1967 B Roadster. I have bled the brakes 3 times and am not happy with the fact that on the first stab, the pedal is a bit low (however, it's very solid). If I lift off and press two more times, the pedal travel comes up to the very top and feels even better. The new master cylinder is a TRW with plastic resevior. I have noticed that the fluid level drops upon the second and third pump, then the level returns to the same level as if I just pushed the pedal, without the extra pump-up's. The rear brakes are adjusted with just a bit of drag, front pads are new, as are calipers, rear cylinders and steel flex lines. Is there any cure for this annoying (at least for me)condition? After running 3 quarts of DOT4 fluid through it, I see no air bubbles. I just want the pedal to be "Right There". Too much to hope for? Thanks in advance for any input...Ken R.|
|You need the 'second stage' bleeding process. I've found this on the several MGBs I have done over the years. When no more air comes out with 'normal' bleeding i.e. low-pressure a gunsons EeziBleed, get someone to press down hard on the brake pedal while you rapidly open and close each caliper nipple in turn. This *always* ejects another lump of air, and after that they are fine. Whether the high pressure is needed to dislodge small air bubbles from the walls, or whether the very high flow just knocks them off or out of any crevices I don't know, but it makes all the difference.|
Had the same problem after replacing Brake hoses & remote servo.on my '73bgt Follow Paul's advice (as I did)it worked for me, brakes are now are spot on. Bill
|or too much play in the front wheel bearings,|
|For the pads to be knocked back the car must be moving. If the lost motion is still there when the car is stationary we can kick that theory into touch. Its quite ok for an MGB front wheel to have discenable movement at the rim The wheel bearings do have end float.|
|One of the problems bleeding the B was air in the remote servo piston and pipe. The brakes were vacuum bled at the factory which sorted this, but cranking the servo up at the piston end and rotating the valve to 4 O'Clock (or 8 O'Clock)helps bleeding.|
I also remember reading a Lockheed or Girling article, many moons ago, describing the "pattern" of pedal pumping. One steady long push followed by 2 or 3 quick short pushes, hold it on the floor and close nipple. I also have an Eezybleed AND a vacuum pump!!!
Belt and braces, eh.
|A timely post for me, this, having done a low pressure bleed (twice!) and not had the required firmness at the brake pedal.|
Maybe Eezibleed should include a helper person in the box?!
I'll have a go with a helper pressing down hard...
This thread was discussed between 14/02/2011 and 09/03/2011
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