strange noise

[Zephod]

Odd motors: http://youtu.be/SgnaWZoTs68

I put the key in the ignition on my 1995 carpenter international 3800 dt466 and turn one click and get an electrical motor noise. Its not the starter - I haven't turned the key that far. No air brakes either. What's the noise and why do the gauges all max out?

[luvrbus]

Does that have the Hydro-Brake system or air

[Purplewillie]

I believe Cliford is on it...again!
Brake booster.
Mark

[baker4106]

I thought you said air brakes.   Noise is brake booster when engine is not running.   Have three of them at my church.   Brakes should work without engine running.

[Zephod]

A brake booster? What is its purpose? Why is it running when the handbrake is on?

[TomC]

Hydraulic brakes on a truck/bus work with the power steering. No engine running, no brake boost. So they have an additional electric motor to power the brake booster when the engine if off. It is only supposed to work if you have your foot on the brake. If it is running all the time, the pressure switch in the unit is bad. Good Luck, TomC

[Zephod]

Highly likely for a neglected bus. I know it had some bad neglect before I bought it. The back tyres were horrific. Now they're merely terrible after I made the previous owner change them before I bought the bus. I suspect I'd have been better off trying to find somewhere in Augusta to change the tyres and get $1,000 off the price.

I'm going to have to make a list of things that need attention. How does one change a pressure switch or check one? Where do I find it and what does it look like? On that theme, the bus has a governor that just restricts fuel flow. How do I adjust that so that I can keep up with the traffic?

[chessie4905]

   Remember that most buses of that type have rear axle ratios of 5:29 to 7:20 to one. The governor is controlling excess engine rpms. If you want more road speed, you'll most likely need to do a rear end ratio change. Block the bus from rolling, jack up the duals on one side, and with trans in neutral and driveshaft brake released, have someone rotate free duals EXACTLY two revolutions while you count the revolutions of the driveshaft after marking it so you can accurately count. Repeat to verify your result and then report the result to us.

[baker4106]

Booster noise should always be there when engine is not running but not when engine is running.   If you step on the brakes when engine is not running the noise will get louder.   The video matches all our buses on start up.   Our buses with 444E's will run 65 against the governor.

[Zephod]

Ah... I stomped on the brake and the noise did indeed change. It IS a brake booster. Problem solved.