My 93RX7 has a brake problem that I've been trying to solve for last year, and would appreciate some advice.

It's been to dealer three times and cost some real money but not fixed, and they don't have an answer other than replacing expensive parts in a trial and error fashion.

Symptoms. At very slow speed (walking) most often with wheel turned somewhat with very light foot pressure I hear a pinging/warblings sound that lasts for 1-2 seconds that seems to come from immediately in front of the steering wheel, while at the same time the brake peddle drops slightly then recovers over the same 1-2 seconds. This will repeat itself as a apply and release brake.

This happens intermittantly, and even went away for several months.

There does not appear to be any loss of braking, and it never happens above about 10mph.

Break fluid level looks ok and I've had the brakes bled.

I think maybe vacuum assist but dealer didn't think so, since they would expect the problem to be consistant rather than irregular.

Any suggestions would be appreciated.

Bob

 

I'm just guessing, but it sounds like the check valve in the brake vacuum line is sticking (and maybe leaking) somewhat. When you apply the brakes at low speed you use some of the vacuum stored in the brake assist, and the check valve then opens to pull more vacuum. Since the engine is running slowly, what you are hearing might be vacuum pulses in the intake manifold pulsing through the check valve. This would also account for the pedal dropping slightly due to the add'l vacuum as the valve opens.

Therefore, I'd try replacing the check valve.

 

Check to see if Mazda did the brake recall on your car. The early check vavles could fail due to oil contamination.

 

Both DaveW and you are thinking check valve.
The recall was done when it came out but its been a long time.

I'll replace valve unless some better sounding idea comes up.
Thanks guys