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Q: Cannot flush the brake system

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I have a 1985 Ford Mustang, 2.3l with only 29,000 miles. I am trying to flush the brake lines.

I have a small vacuum pump as can be found in any auto store. With great effort I was able to flush the right rear (drum) brake. However, although all the other bleeders are free, I cannot get any brake fluid out of the other three wheels (front disc) although the pump shows about 15" of vacuum. The pedal is firm, with no signs of air in the system, nor does the car pull to either side.

I removed the bleeder on the left rear wheel and it is not clogged.

For what it's worth, I drove the car after filling the master cylinder with new fluid and flushing the right rear. Now the front brakes (large) reservoir shows some old fluid, but the small rear brake reservoir still appears clear to me. I don't know if that means something is amiss with the rear brakes, but in any event that wouldn't explain why I can't flush the front brakes.

I'd appreciate any advice you can offer.

My car has 29000 miles.
My car has an automatic transmission.

A: Hi there. From the description you have pro...

Hi there. From the description you have provided for flushing your vehicle’s brake fluid, something is amiss. Assuming, your vehicle is not equipped with ABS (anti-lock braking system) it could be a problem with combination/proportioning valve not allowing fluid to flow, with a vacuum pump.

It could also be the master cylinder not allowing the fluid to flow. Considering your vehicle has a good, firm brake pedal and no pulling issues. I would not recommend replacing either component.

You could try flushing the system with an assistant. Open the bleeder, have an assistant depress the brake pedal and hold while you tighten the bleeder. Have your assistant release the brake pedal and then repeat the procedure until fresh fluid is seen. A clear vacuum tube would help direct the dirty fluid into a container. If you would like to have this done, a qualified professional from YourMechanic can perform this brake fluid service at your home or office.

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