Brake Trouble

My sons 2009 Tacoma makes an odd humming/hissing noise which I'm told is that the diaphragm in hydraulic brake booster has gone bad. Does anyone have any experience with this or know how easy/difficult of a fix this is? Any assistance is appreciated. I'm by no means a mechanic so please be as descriptive as possible in your response!

 

Can you tell us what trim model you have?

You used the words "hydraulic brake booster" and that is a term that Toyota uses to identify such models that have a sophisticated brake booster controlled by sensors fed to a brake ECU that activates brake boost via solenoids and motors as opposed to the more traditional vacuum booster type. The hydraulic type was necessary for models with the off road feature known as ATRAC.

I am dealing with a hydraulic brake booster issue on mine at the moment. The first thing to do is get a code reader on it and see if there are any codes present. Some codes will not necessarily illuminate the CEL, at least immediately, as I have discovered.

Many of the lower cost readers will not be able to access the codes. You will need to get a hold of Toy's techstream unit or have the dealer read do it who has the techstream. Alternatively, if you have have some other technician do it they will need a good suitable aftermarket reader. If you discover to have a code or two post them up and we can go from there.

Couple of things. The unit is charging up the system's pressure accumulator as it needs to and will also run the internal motors when activating the VSC, the ABS system, and ATRAC. You can often hear a motor run for a couple of seconds when the key is first turned but not started. Thereafter it does so as needed and it does hiss or buzz/hum. So some such noises are normal and occasional but when they becomes frequent this is often a warning of a problem.

 

2009 Tacoma V6 SR5 TRD Off Road

I didn't realize that codes can/will show up without illuminating in the cluster. Good to know information! I will take it to see if any codes show up and post them, if it shows any. It definitely hums louder/more often than it should. Very annoying while driving!! Even the radio can't drown it out!!

 

If it is so annoying the noise has caught your attention while driving, that is a big red flag to me. The motor-like types of noises and the hissing/humming/buzzing should only be occasional.

Try this.
- Park the truck and turn the key off.
- Open the hood.
- Push on the brake pedal some 20-40 times and lit it sit for 99 seconds.
- Have an assistant turn key to on position but do not start while you listen
under the hood near the brake controller.
- Observe for say a minute or two.

What are the noises you hear? A motor running noise at the outset like a small
pump motor that runs for a few second to say 10 seconds or more or does not stop?

 

The pump motor runs intermittently for a few seconds and then stops. The motor runs for about 20 seconds and stops for about 10 seconds...then starts right back...and stops... It even does it a few times after the truck has been turned off.

 

Well, its not designed to run that much otherwise the motor(s) would not last that long. Sounds like it is trying to charge the accumulator and it is loosing pressure to fast. Or the solenoid has issues. The later is the most common.
Me thinks it needs some attention....
If you felt comfortable using a DMM multimeter I could send you the checks at the connectors of the ECU that is attached to the solenoid, otherwise its time to get a code reader (dealer, yikes) to see what shows up.

 

I bought this enhanced OBD2 scanner. It is around a hundred bucks and can pull ABS and Airbag codes. Might be a good investment if you plan on trying to fix this yourself and need to troubleshoot more

https://www.ebay.com/itm/Topdon-TDT...r-1996-Newer-US/402641855179?epid=13038316623

 

Based on what I've shared, what do you feel like needs to be replaced? Solenoid, motor, accumulator? Just asking for best educated guess. I'm planning on taking it to shop this evening and possibly just trade it in if too pricey. I appreciate all your knowledge and help!

 

I don't want to scare you away from trying to fix but be aware that the parts are ghastly expensive.

For example, just the solenoid is around $1100 from a discount dealer place. But that solenoid and MC together as a unit are close to about the same price (go figure, and why would you not?).

The accumulator motor with its reservoir is around $260, again from a dealer discounter.

And the entire hydraulic booster unit with the MC and accumulator tends to be somewhere around $1,700 to 2,100, again discounted, but many dealers are robbing people up to around $3,500 or so for the unit (and install?) so be careful.

See what codes are present. And do not forget to look for leaks at the wheels and around line connections. Leaks would also cause the pumps to run excessively.