Brake accumulator noise, cycling

[eng208]

Hey guys. I have always found this site very informative and have tried to contribute to the knowledge base as much as possible over the last 6 years. This issue has me somewhat stumped. My wife came home today saying the truck had a slight whistle type whine noise. The A/C has cycled audibly and she is aware of that noise. This accumulator made a diaphragm squeak one time, but I could capture it. Is it supposed to cycle this frequently in Park? I know what it costs to replace and the thought of this thing going out makes me sick. Any help on whether or not this is normal would be much appreciated.
Forgot to add, this is an 07 4Runner with 116,000 miles.


07 4Runner accumulator - YouTube

 

[eng208]

Can anybody just confirm their 4Runner cycles the brake accumulator while in park like this one is doing? Thanks

 

[M1911]

I think that is cycling too often.

 

[nevada]

I just barely notice mine cycle every once in while. usually right after I start it. and even then I have to really be paying attention to notice it.

 

[eng208]

Thanks. I was afraid of that. This is one of the few things I don't think I should tackle in my shop. Should I take it to a shop now or wait?

 

[Kmvreter]

Not sure if anyone on here has had their unit serviced rather than replaced.
Rather than take it to a stealership, who are going to hose you on replacing the entire M/C, can you find a shop that would be willing to service the unit and replace the accumulator? I'm thinking the M/C is still good because you can stop and don't have a brake warning light. The pump is OK because it is obviously still working unless you wait and it burns itself out.

Don't do any of the steps involving the M/C internals. You want to get at the sensor in step 21 or the accumulator as in step 29 in the following (this is from '04 but should still work).