Strange noise when starting

[ny biker]

This started happening a week or so ago. When I first start the car in the morning, I hear an unusual noise, kind of reminds me of someone tapping out morse code. It lasts for a few seconds and then it stops and the engine turns on like normal.

No warning lights, car seems to drive normally.

It only happens on cold startup in the morning. I don't hear it any other time, including when I start the car to go home from work (after it's been sitting all day).

I park outside at home. Temps around here have been in the 40s at night, 50s-60s during the day.

May or may not be relevant: The parking lot at home has a slight slope to it. I back into the space so the front of the car is slightly elevated compared to the rear. I only thought of this while I was driving to work today so I haven't been able to test it to see if the noise happens when I park front-in. (I doubt this is related but I was trying to think of differences between when I hear the noise and when I don't, and since the parking lot at work is flat...)

The car has 9500 miles on it. I'm about to take the car in for an oil change and safety inspection. I want to mention the noise to them but since I won't be able to reproduce it for them I was hoping someone here might have some input as to the cause, or could at least tell me what the car does as soon as you power on so I can sound a bit more intelligent when I'm talking to the service guys about it.

Thanks!

[qbee42]

Is this tapping different than the rattle from the brake accumulator pump? That one sounds like a ratchet down in the driver's footwell, and sometimes it will actuate when you power up.

You also get the coolant transfer pump running when you power up. This should be more of a whirring sound, but it can squeal when it gets cold and old.

Tom

[ny biker]

Originally Posted by qbee42

Is this tapping different than the rattle from the brake accumulator pump? That one sounds like a ratchet down in the driver's footwell, and sometimes it will actuate when you power up.

You also get the coolant transfer pump running when you power up. This should be more of a whirring sound, but it can squeal when it gets cold and old.

Tom

It's definitely not a whirring sound, or a squeal.

Maybe it's the brake accumulator pump. It does seem to be coming from the driver's side front.

[qbee42]

Originally Posted by ny biker

Maybe it's the brake accumulator pump. It does seem to be coming from the driver's side front.

Listen carefully when you press the brake pedal. About every third time or so the pump will activate. If things are quiet in your car, you can hear it.

Tom

[ny biker]

Normally I turn the stereo on just before shifting into Drive, so it's not usually quiet most of the time I'm in the car. I have turned the sound down while driving a couple of times recently since this noise started happening after powering on, and didn't hear anything unusual, but now that I know more about what I'm looking for I'll leave the stereo off and play around with it.

Also now that you've given me a good term to search for, I found the TSB from last February.

Thanks!

[alanh]

When I start up, there's a bunch of clicks from relays engaging.

[icesalmon]

My 14 month old (25k miles) started to make same kind of noise 3 months ago. Have you got yours fixed?

[Jared]

Probably the clicks from the relays. I hear them every time I start, but you may not have noticed them before.

[qbee42]

Relay clicks are quick and then done. The brake accumulator pump runs for about three seconds, and is more of a buzzing or ratcheting sound which comes from the driver's footwell. If it is the brake accumulator pump then it is normal and there is nothing to fix.

Tom

[TSFlyer]

I have around 9,800 miles on my '07 Prius.

I've just recently started experiencing the same ticking noises described in this thread and like the original poster's experience, they only appear at cold startup in the morning. Morse code sounding ticking is a good description.

I never have the stereo on when starting up and have been keenly aware of the normal noises the car makes. This is different.

I've posted a short video of the noises at:
Prius Noise

I'd much appreciate it if someone can take a look and tell me if this is considered "normal"...

Thanks very much.

TS