Hello,

I recently replaced the brake calipers on my 94 Accord LX MT Sedan, and I noticed something very peculiar when the car was jacked up:

With the engine on and gear in neutral, the front tires would spin at a constant rate (rear tires were on the ground). Also, as I was bleeding the brakes with the engine running, the engine would rev slightly as I released the brake pedal.

Is this normal or should I be concerned? Here's a list of work that has been done on the car in recent months:

- replaced timing belt, serpentine belt and water pump
- replaced sway bar bushings
- replaced front driver-side CV axle
- replaced front driver-side control arm



Thanks!!

 

Why have the engine running while bleeding brakes? Anyway, it's all normal.

The synchro-hubs are like little clutches, one for each gear. When the transmission is in neutral, all the gears are actually meshing. For each gearset (like 1st, 2nd, etc) the gear is free to spin on it's shaft. But that bearing still has some friction, which gently pushes the output-shaft to spin.

The vacuum booster for the brake uses engine manifold vacuum. So it's already "charged" with vacuum before you step on the brake. When you release the brake it has to "recharge" with vacuum, which really means that the air inside the booster gets sucked into the intake manifold. Same as a vacuum leak, it causes the engine RPM to rise for a moment.

 

The gear oil alone (esp when cold) to allow the wheels to turn a bit when off the ground.

All is well...

BTW, no need to have the engine running when bleeding brakes. Doesn't "hurt", but isn't needed.