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Jim Grant Tech Tips Jim Grant Tech Tips
A collection of helpful articles based on reader submissions
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  Jim Grant's Tech TipsJim Grant's Tech Tips
Below is a collection of Jim Grant's Tech Tips sorted by Vehicle Make. These Tech Tips were answers to questions submitted to Jim by ALLDATAdiy.com users over the course of many years.
If you have any questions, please feel free to email us.
 
 

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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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