Hydraulic Brake Booster, Gen 3

[bhanganek]

I really hope someone can assist

I got the cruel report back from our local dealership, that they are of the opinion that the HBB unit needs to be replaced, and as some of the dealerships do, they prefer to replace the complete unit, current quote, R58 000 incl labour

With my limited knowledge of this, I am of the opinion that it is only the pump and accumulator that needs to be replaced, seeing that you can get these separate, quoted around R11 500 and R3500

The pump would "kick=in" around 2 times every 15 seconds or so, even if the vehicle is switched off, with only the ignition on, and during normal driving, without touching the brakes

The accumulator on the side, would vibrate quite a bit during this time, and as the pump gets hotter, or more "tired", i presume, you would here a slight "squeaking" noise coming from it

I have had it tested by two places now, both the dealership and other place had it on their "pc's", and no fault codes given. The one shop even manipulated the brake sequence between all four wheels, and in each case, the unit seemed to react as normal, yet, the pump keeps going. On one forum I read that they have experienced that the bag inside the accumulator, that is holding nitrogen, as I understood, have torn, and this caused lower pressure

What worries me, is what is giving the pump the signal to keep pumping? Is it that the pump and accumulator is actually one unit, and this means that the pump, through the pipe that connects it with the accumulator, receives or reads the pressure through this pipe, and that is why it is initiating the whole time?

Is there anyone with some advise for me please

Thank you

Andries

[4ePikanini]

There was a recall on them. Check if yours applies.

Mine was done close to 300'000km, no questions asked.

Sent from my S55 using Tapatalk

[bhanganek]

Thank you for the advise

How do I do such a check?

[kermit]

It's your accumulator that is going out. This is causing the chirping noise and the cycling of the pump. Replace the accumulator and all should be well.

[bhanganek]

Thank you Kermit

You're spot-on. I took my vehicle to another dealership, and here the senior technician had previous experience with similar cases, and after about 30 seconds of doing a scan with a "MUT 2" device, it showed -accumulator low pressure-

The part was ordered and replaced the next day, and so far, 4 days later, everything seems back to normal

I experienced the following;

1. Not all dealerships have the experience to deal with the Pajero
2. Not all dealerships have the correct tools to do thorough scans, in this case the first dealer was using a "laptop" to scan the Pajero. I presume, this laptop is for later models, or rather for Mercedes vehicles
3. Be careful when the dealership wants to just replace the whole unit
4. First quote, R59 250. Accumulator replaced, actual cost, R5250

[kermit]

You're welcome. I'm glad it worked out. It was a pretty easy diagnosis to anyone with experience with these vehicles. That was quite a difference in cost!