[alanforn]

An odd sound I noticed over the weekend. Sitting still, applied brakes. Noticed an odd high pitch "howl" when applying brake lever. Howl might be an overstatement, but it is easy to hear. Let off it would stop, reapply and the sound would reappear. Cannot tell if noise is present at speed. Obviously something relating to ABS, probably pump? The only difference was that that outside temps fairly cool this weekend, I have only owned the bike since May so have not experienced colder weather with the bike. '03 with 40,000 miles. Normal or not?

 

[Tom_Becker]

ABS Tone

Its hard to tell from your description but I would say its normal. My 2003 certainly makes a whine when using the brakes. The noise comes from the ABS servo. I assume that the brakes work well and you have no warning lights.

Tom

 

[rglassma]

I concur with Tom's response. Almost sounds like a small electric motor everytime you hit the front brake standing still. I don't hear it when moving.

 

[dshealey]

The power brakes use a DC motor to drive the pump, which gives you much higher pressure to the brakes than you can do with mechanics alone. That is where "Servo" comes from, meaning any system which uses an additional power source to multiply a small force to a large one.

What you are hearing is not the motor itself, but the pump it is driving. The pump supplies a high pressure, and the valving in the brake system meters it to the brake cylinders as needed based on how hard you are applying force to the brake levers.

 

[alanforn]

The biggest part that threw me on this is the increased volume of the pump, is it accurate to assume that the noise amplifies during colder weather? I have heard the misc. ABS related noises over the summer, but not this one. If all were not well, I suppose an idiot light would signal trouble?

 

[DavidTaylor]

2002 and later LTs come with power servo assisted brakes. When you pull the brake lever of step on the brake pedal it fires the servos wich provide power assistend braking, similar to a car. The noise is perfectly normal.

 

[mneblett]

The biggest part that threw me on this is the increased volume of the pump, is it accurate to assume that the noise amplifies during colder weather? I have heard the misc. ABS related noises over the summer, but not this one. If all were not well, I suppose an idiot light would signal trouble?

I can't speak to what you did or did not hear this summer, but I suspect you've simply noticed for the first time a sound that was already there. My '05 has a different style pump unit than my '02, and it positively *wails* (to my ears) when sitting at a stoplight -- enough to get looks from other riders!

You are correct in assuming you'd have a light if there were a real problem, as pump operation is one of the *many* things checked and monitored by the electronics. From the experiences shared here, it's pretty clear that it doesn't have to be much out of spec before a fault code is set.

 

[jtalbot]

Your LT is normal. I have an 05' GS and traded my 05' RT in on an 06' LT and they all make the same noise. My wife's 05' F650 GS does not whine as it does not have servo assist. I would be concerned if it did not whine.