Heat related brake problem

[stevenelle]

You may remember seeing this posted before, but still no satisfactory resolution to this problem so will try again. In hot weather, pressure seems to build up in the M/C and brake lines. As a result, very little freeplay in the pedal when braking. In cold weather, there is very much freeplay in the pedal and sometimes wonder if I will get any braking at all. Seems sort of dangerous, but if pedal is pumped a few times, I get adequate pressure, but only with pedal near the floor.

There must be an explanation and a fix for this since I know it is not normal. The hotter the system gets or the hotter the temperature, the less pedal freeplay. The colder it is, the more freeplay. The M/C filler cap has good open vents. The brake lines are old but hold pressure. The two ports between the M/C reservoir and pressure chamber are not clogged. Is there an adjustment I need to make in the length of the pushrod? If so, why would it vary so much with outside temperature? Thanks for any insight or ideas.

[Norm's Coupe]

Actually, it sounds like you may have air in the lines. Sounds more like they were not bleed fully. I know some years ago GTK mentioned he had a problem with air getting in the system and couldn't find where. Finally, he found a small leak at the T where the brake switch fits into it. So, I'd look for something like that, then bleed the brakes again.

[greg g]

Check the relief hole in the bottom of the reservoir in the MC. There are two holes there, one to provide fluid to the piston and one to allow it to return after the pedal is released. If it is plugged or partially blocked it could cause these symptoms. Plus by not letting the shoes retract completely this puts more heat into the system through drag. Remove the cap of the MC and shine a flash light beam into the reservoir, you should clearly see the two hole in the bottom of the casting. If you only see one probe around with a piece of wire to find and or unblock the second one.