How to repair a Faulty ABS / HBB Motor Pump on a Pajero / Montero / Shogun

[kiwi horan]

.
Turned out to be the 40 amp fusible link and the relays.
I got the Toyota relays for $57 each. Mitsubishi quoted $148 each!
Worked a treat. Thanks for the info.

Same part number ???
where from ???

Cheers Grant

[outbackogre]

Many thanks to everyone who has contributed to this thread. On several occasions with my NW, I've noted the four dash ABS lights coming on along with an alarm, but only for a few seconds then it all turns off. The brakes have never been affected until today, when the brake pedal went hard and I had no brake boost. I crept back home (about 4kms) with handbrake at the ready and in manual mode to drop it down a few gears if necessary. After a couple of kms, the brakes started working again and I made it home ok. I found this thread and after a couple of hours of reading am starting to feel sick in the wallet. I've pumped the brake pedal to empty the accumulator, then started the engine. I can hear the pump re-filling the accumulator for a few seconds and then stopping. The pump sounds ok (ie, not overly noisy). I've noted that some people have fixed their problem by replacing the accumulator. Does this seem likely in my case? I have no reader, so cannot easily check codes. Thanks.

[benckj]

May be accumulator but my guess would be the pump motor. The brushes become sticky and catch on the commutator segments that are worn through. I determined the problem by tapping on the motor housing when brake pressure was low and then it would start spinning until it reached stop pressure. It always stopped on the broken part and wouldn’t start again unless I tapped casing.

Not sure how to test accumulator but believe there was a method on how to do in this thread. It’s actually the easier part to replace and much less expensive than motor.

Good luck and keep us posted on your progress.

[outbackogre]

Thanks benckj, that's exactly what is happening with mine, so I guess it's the motor. Today, when I started the car (just to check the brakes), I noticed the brake pedal was hard and sure enough there was no boost. I tapped the pump motor and it started immediately, running for a few seconds until the accumulator was full. Today, I bought a code reader from Jaycar, but it says there are no codes. I'm not sure why there are no codes. There's a guy (advertising on ebay) in Rye (Mornington Peninsula in Victoria) who reconditions the whole brake booster unit for $1500. Another option is a wrecker, but then there's a chance the problem will reoccur. What to do ...

[benckj]

....I would try and remove motor without pulling whole brake unit out. Several others have done this and there are some tips in this thread. If it is the motor it will be quite obvious when you pull apart as there will be a heap of carbon dust and very worn brushes & commutator. I believe there was attached some pics to my post for reference. It can be re-built but truck will be off the road for a few weeks. Another option is buying new motor off Parqual or even getting from ebay (rebuilt) as I did. I wouldn't risk buying a 2nd hand used unit as there is no way to tell how long it will last. The refurbished unit may be tempting if indeed it is completely rebuilt. It will still take some work to swap out and then bleed out as really need to use MUT to do. Maybe you can check some references?? .

[outbackogre]

Thanks again benckj, I pulled the motor (many thanks to those who've described this). It looked ok (see pics), but I took it to Paul at Stewart Auto Elec anyway. He said it was the best one he's seen, and there's nothing wrong with it. I'm not sure what to do now. I was sure this was the culprit because it starts as soon as I give it a tap (like so many others with this problem). Ideas?

[outbackogre]

I also bench tested the motor (holding it in a vice) and it sounds fine. I took a video and tried to upload it but received a message that MP4's are not accepted.

I guess my question now is - if the motor is ok, why did it seem to seize up with the accumulator empty and then start running only after I gave the ABS body a bit of a tap?

[benckj]

That does look in decent shape from your provided pics. Not perfect but unlikely to be your problem if this is the condition you found them in. Did you find & remove a large quantity of carbon dust? If so, this could have been an issue effecting the brushes to stick and not making contact with commentator.

Provided you do not have any problems with motor I'd reassemble and test your system again. If you still have a problem it could either be the pump, accumulator or electronic (relay or pressure sensor). Only guessing at this point as really need to determine through process of elimination.

[outbackogre]

Thanks benckj. The inside of the motor was pretty clean. I've screwed it to the accumulator, but the screws to secure the bracket are a real pain to get started on the thread. I'm using a shortened allen key that was fine removing the screws but I think I'll have to shorten it further to get room for them to go in straight. Working with a mirror is a real challenge.

[outbackogre]

Finally got the screws into the bracket. After fiddling around with the front one for ages, it was actually easier to get the rear one in on the end of a long allen key. Getting that one in and leaving it a little loose allowed me to screw in the front one by hand. Started the engine and the ABS pump motor sounds fine, but then it sounded fine before I removed it. I guess I'll just wait to see if the dash lights and alarm return, or the dreaded brake fade and pedal hardness.

[Scooby]

What do you tap to get it going and how hard?

Have you checked the connectors going to the HBB unit and relays?
Have you checked the relays, the contacts could be dirty.

Put a test light on the power terminals to the motor, if you have power and it’s not spinning it’s the motor.
Put a test light on the relay and check the same, no power out it’s the relay.

If all these test good, but hitting the HBB control box gets it going, it could be an unserviceable pressure sensor in the control box.

Hopefully it’s just a dirty contact.

Have a read of the manual, about how it all works and test that can be done.

http://faq.out-club.ru/download/pajero_iv/maintenance/Service_Manual_2008_2013/2012/index_M1.htm

[outbackogre]

Thanks Scott. Just a light tap with a socket extension bar on the front of the ABS unit. I've removed and silicon sprayed the connectors. I haven't yet checked the relays, so that's another possibility. I sure hope it's not a pressure sensor, but the tap test does suggest some issue in the ABS unit (rather than a relay mounted elsewhere). Thanks for the manual excerpt. I give it a read.

[4ePikanini]

Mine made this noise last week and I immediately ordered a new accumulator. I hope there isn't more to my issue than just the accumulator

https://www.youtube.com/shorts/Rw-n64KUjz4

[outbackogre]

That sounds like the chirping noise that earlier contributors on this thread have suggested is caused by a failing accumulator. The good news is that access to these is easy (unlike the pump motor) but they still can be difficult to remove (I think using an oil filter removal tool). Make sure you pump the brake pedal 40 times to completely empty the accumulator before removal.

[outbackogre]

I'm running out of (cheaper) ideas with my issue. After reinstalling the pump motor a couple of days ago I finally had time to take it for a longer drive and the brakes failed (went hard with no boost) after about 30kms of suburban driving. Fortunately I was able to drive slowly home, with brake boost coming and going a couple of times. Once home I removed the two relays and did the test described at the beginning this thread. They tested fine, so I re-installed them. I also did the test described in Scooby's manual excerpt and it passed that. I'm stumped. I guess it could be a pressure sensor issue, as Scooby suggested. I suppose that means a new (or second hand) ABS/HBB unit. At least if I go second hand I could swap my good pump motor onto it.