jar sound from ABS unit

[jeyare]

Pajero 3.2.DiD (NS) 2008, 118kW

Got a strange short jar-noise coming from my ABS unit. Duration of the sound is just 0.5sec. First time 2 months ago, randomly 1x/day. Now 5x/hour, increasing frequency. No matter if the brake pedal is depressed (but mostly, when the pedal is released).
It is pump? Thx.

[nnikbg]

Can be from electrical motor bearings.

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[jeyare]

Can be from electrical motor bearings.

Thx for the answer, but I don’t think so. The sound is like when you fast pull a fork at thin iron plate. Just for a half of second. Then “no such sound” is listening 10-60 minutes (randomly).
Bearings you will listen continuously.

[4ndy]

Sounds like HBB motor might be dying - if you have the ignition turned on (but not start the engine) and pump the brake 20 times do you hear the noise?

[nnikbg]

The strange thing is that jar-noise last only half second. HBB motor is running for 30 sec and more.

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[jeyare]

Sounds like HBB motor might be dying - if you have the ignition turned on (but not start the engine) and pump the brake 20 times do you hear the noise?

First try:
ignition ON (not started) .... 20x pumped .... no noise

1minute rest

Second try: ... no noise, but after 7th time car starts warning me with 10sec beeep sound + light control of ESC, ESC OFF, ABS, Brakes (during the warning beep sound)

Same for third try.

[benckj]

Having had a recent HBB motor rail it doesn’t sound like you describe. I’d look at the accumulator or possibly pump issue.

[jeyare]

Changed rear brake pads, this morning. Then checked rear and front brake fluid pressure by diagnostic tool. Evaluation:
1. Rear brakes (both) with proper fluid pressure. Pretty fine, in normal condition.
2. Front brakes (both) with different situation than Rear brakes. There is less fluid pressure (also visually).

The jar noise comes from brake pedal and it can be feel by foot (vibration during the noise), when the pedal is depressed.
But as I wrote. The noise is randomly occurred, not just when brake pedal is depressed = often when car is driven w/o braking situation.

Questions:
1. When the brake fluid is in different pressure distributed to rear and to front is it still reason of the pump (motor)?
2. What about a main part of the HBB - the master cylinder/pressure switch? Then jar sound can be produced here?

Now my technician tried disassembly whole unit to find an issue. Keep in touch.

PS: when you try purchase just new motor for the pump - here is an answer:
How to repair it:

https://youtu.be/vrsXN6hy-JM

Where to purchase it (you can choose specific model of your car - not just for Mitsu):

https://www.ebay.co.uk/itm/Engine-Electric-ABS-PAJERO-MR407202-MR569728-FAREWELL/382359719523?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

[jeyare]

Here I found complete HBB detailed description.

http://faq.out-club.ru/download/pajero_iv/maintenance/Service_Manual_2008_2013/2011/35/html/M235000130004900ENG.HTM

seems to be they have tons of such documents

[jeyare]

Having had a recent HBB motor rail it doesn’t sound like you describe. I’d look at the accumulator or possibly pump issue.

That was my idea, that this is not the motor sound.

Needs to wait for disassembly findings.

[RUGGA]

That was my idea, that this is not the motor sound.

Needs to wait for disassembly findings.

Have you seen this detailed thread at all? https://www2.pajeroclub.com.au/forum...ad.php?t=46516

[jeyare]

yesterday, but thanks for the hint
I found similar and together with motor parts repair kit here:

https://youtu.be/vrsXN6hy-JM

but all the described issues in the mentioned thread are about - brake death or nearly death clear symptoms:
- if you lost the HBB pump motor or whole pump (monitored by ECU)= you will lose breaks = no brake fluid pressure
- if you lost the HBB accumulator pressure (monitored by ECU) = you will lose breaks = no brake fluid pressure
Every time you will obtain the engine light/brake light as warning, include Fault codes

Diagnosis code No........ Item.............................................. .....Reason
16................................Abnormal power-supply voltage........... Low voltage/High voltage
31...............................Abnormal IG2B power-supply voltage drop
53...............................Pump motor system problem...........Pump motor lock/Current detection circuit problem
54...............................Motor relay system problem...........Relay open/Relay short/Coil problem
55...............................Pomp motor long-term operation
56...............................Pressure switch problem...........PH open/PL open or short
57...............................Accumulator low pressure...........Pomp problem/Accumulator problem
58...............................ASTC-ECU problem




But my problem is about:
- no Fault codes
- no engine/ABS/Brake lights
- just strange frequently jar noise and brake pedal vibrations (during the 0.5sec noise)
- the noise is discovered randomly no mater, if the brake is used or no
- from Today - normal brake fluid pressure in Rear, less than normal in Front brakes

Waiting for a result from today's HBB disassembly.
The master cylinder is a single-piston type which generates hydraulic pressure which is transmitted to the front brakes.

[jeyare]

Today’s brake test evaluation:
- Rear (both) in perfect condition 3.07kN max, reached in 2seconds
- Front (both) 3.86kN max, reached in 9 seconds!!

My point:
- the power (brake fluid pressure) is distributed to Rear brakes in normal condition
- The time of the max power in Front brakes is really out of expected range
- Front brakes must be more intense (better power for same time than Rear)

Then insufficient fluid pressure for the Front brakes could be considered by:
- insufficient power from HBB pump (but why just for the Front only)
- insufficient power of the pump motor, which provide power for the pump (no Fault code)
- insufficient pressure from the main pressure switch for the Front (reasonable)
The brake pedal is little bit soft.
Main problem is, that no way to find/purchase just the main pressure switch. Only chance is to find second hand from crashed car.

[jeyare]

Definitely I foud attached video on YT with my noise. This guy has the sound few times per minute and more frequently (2times in row). Mine is 1-3 per hour. But this is the sound.
From this perspective (never happened with open engine) it seems to be the pump motor or pump accumulator.

https://youtu.be/Wt8oIwUKK6U