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Jim Grant's Tech Tips
Mazda
626, Morning Brake Sickness
Q:
I
have a Mazda 626 and am having trouble with the brakes. When I first start
the car in the morning the brakes won’t work. The brake pedal is
hard, but if the car runs a few minutes it’s ok, (and this is a
stiff, stiff pedal). It usually doesn’t do it again during the day
if car is driven. The car does not have ABS braking. I have taken it to
several garages and they don’t seem to know why this happens. Do
you have any experience with this problem? Eugene Williams
A:
Your vehicle has a vacuum assisted power brake system. The engine creates
the vacuum. Knowing this, it becomes easier to understand where the problem
may lay. In Vacuum Brake 101 the first diagnostic step is to step on the
brake pedal several times before starting the engine. With your foot still
on the brake pedal, start the engine. The brake pedal should drop as engine
vacuum creates power assist, we’re talking 3 to 5 seconds here.
If the pedal does not drop then it is possible that the engine vacuum
supply to the power brake unit is restricted. If that is the case then
the vacuum supply from the engine must be checked. Vacuum should be checked
at the engine and then compared to the vacuum supplied to the vacuum booster.
There should be no difference. If there is, the vacuum hose is restricted
or there is a check valve problem. The next test requires using a vacuum
pump to check the brake booster itself. A failing brake booster can leak
vacuum and get better in the early stages of failure. Diagnosis is not
that high tech for this system. You just need someone that understands
the system. It is a little on the old school of training which is often
overlooked in the new world.
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