Soft brakes after idling for 5 minutes

[mferris]

Nice day yesterday - so I took the SV/1725 out for a 10 mile run, then let it sit idling for 10 minutes in the driveway while I swept the winter out of the garage.

I got it in it and backed it up into the garage, stopped (gently) no problem, then pulled forward and had no brakes at all (completely to the floor). One pump and it was fine.

I have noticed a soft pedal sometimes while driving, but never that severe.

The brake fluid reservoir is completely full (overfilled without any air space - is that the problem?), with fresh oil, and I've never seen any leaks or lost any fluid level in the reservoir. Apparently fresh rubber brake lines at least in the front, I need to look at the rear. The brake booster was also removed, and as far as I can tell the stock cylinder remains.

My guess: The thermostat was higher than normal (since I don't usually idle) so the oil was boiling somewhere along the lines, and once I pumped the brakes it compressed the gas in the line.

Thoughts?

 

[pcmenten]

I wonder if one of your slave cylinders needs adjusting. When I adjust the rear cylinders on my MGB, I adjust them until the drum locks up then back it off until it is just barely scraping.

But my first thought was the brake line is too close to the exhaust and the brake fluid is heating up. Also, some brake fluids absorb water and if the water vaporizes, it will create gas pockets in the brake line, which, as you already know, will cause soft pedal or no pedal.

I started a thread in the Chit-chat forum about my pulsing brakes. One of the replies has an amazingly informative link from a brakes expert. He mentions brake fluid issues.

I'd suggest checking the adjustment of the rear cylinders then flushing the brake fluid.