ABS HELP
Can anyone Help with the ABS problems I'M having.
Basically the Brake pedal vibrates and goes very stiff and doesn't stop the car and you have to stamp on the brakes - at which point the brakes lock up causing a skid. Now I may be wrong but it only seems to happen within the first few minutes of Starting the car or on another occasion after using then switching off the diff locks( using the diff locks switches of ABS by default). I have a Steep driveway and It tends to happen as you try to brake before entering main road. It seems to work normally after this first initial Press of the brake pedal, but does happen almost every time after you start the Car.! Though the first part of my lane at home I reverse down and it never happens when I use the brake in reverse, only when I go forward down the Lane.
Unfortunately today it happened to the Mechanic at our Local Garage as he took it out for a initial test run. They too have a steep driveway onto a main road and same thing happened, he nearly skidded into wall and he crapped his pants. He/they then refused to look at the car until the ABS fault was attended to by a Mercedes Garage. No amount of explanation would convince him to look at the car further.
Can't blame him as it is scary when it happens first couple of times. It' happens on level roads also after starting.
Apparently the Previous owner had problems with ABS due to water ingress. This was apparently fixed and a new ABS sensor.
They neglected to tell me this until after I had bought the car and asked. which was a bit disappointing.
Can anybody throw some light on this or suggest what to do next.
Hello Lego,
Any competent garage or mechanic should be able to tackle this job for you. The attitude of your local garage mechanic surprises me; I would look for a new garage.
In most cases, it is the ABS speed sensor at fault but here the ABS light usually illuminates . Check for cracks in the ring gear as these can contribute towards your type of condition. Check the rear drums, leaking wheel cylinder and a lightly contaminated drum can give similar faults without showing ABS fault light.
In extreme cases old brake fluid may also cause such faults. The ABS relay could be a cause.
To be sure of a competent garage my suggestion would be to go to a Bosch agented garage.
Cheers,
What happens if you turn ABS off manually on dash?
Do you get ok brakes?
What Model/age of G?
Turning Off, of the ABS on the dash will disable ABS function but you do retain conventional braking.
Regards,
Haven't properly tested under normal driving with ABS switched off permanently.
Did once switch it off and then back immediately - as I wasn't sure if it had come back on after using Diff Locks- and the next time I braked hard I skidded with no ABS trying to kick in. It was wet and I braked hard but definitely no attempt to kick-in by ABS.
Seemed to delay coming back on once switched off, which sort of ties in with having the problem the mentioned above. - ABS coming on improperly when brakes first used after starting engine. Actually just thought! ABS may not be working at all after intial attemp after start-up -as I have tried braking hard(when safe) in wet and on uneven surfaces and it has neither skidded nor had any assistance from ABS!
Puzzled
Will find some loose stuff tomorrow to test on.
REPLY TO THREAD No: 2
Hi Lego,
Cracked ring gear and, or dirt collected in the ring gear throws off the magnetic pattern which the system is designed not to reckognise.
Under such conditions the ABS, because of a partial reckognised pattern coming on, tries to engage ABS braking but then, comes a pattern not reckognised; this happens so quickly, that the system comes on and then decides to cut out, hence the brake judder (ABS activated) followed by wheel lock up, (ABS disengages reverting to convential braking resulting in brake lock up).
What Postal area are you in?
Cheers,
OK Update.
Tested on some loose gravel this morning.
ABS does not work. After Initial Judder first time pedal is pressed after starting car - ABS switches off. After this, braking hard on the loose stuff, just causes skid with no attempt by ABS to operate and prevent skid. Switching ABS off has no effect as it is already off. No light on switch and no ABS light on Dash.
Judder does not happen happen while braking and reversing down my drive. Only when I move forward.
After rain yesterday passenger footwell V wet and I'm V depressd :(
Model is 1993 300GES Auto Swb
I'm in Edinburgh postal area
Hi Lego
Rakesh if referring to the ring gear not as the engine ring gear used to start the car but as the ABS exited ring that is attached to the wheel hub that the ABS sensor runs near and picks up its signal from. A damaged or clogged up exiter ring could cause the problems you describe just like a damaged or poorly located sensor could
Gav
Thank you Gav,
For clearing the point.
Lego, I have prepared a list for Bosch agents you could possibly try.
Bosch Garages - Edinburgh
http://www.boschcarservice.co.uk/
www.chathams.boschauto.co.uk - EH8 8EL
Keith Elgin Motor Engineers, EH10 4SU - Tel: 0131 446 0755
www.jackwalker.boschauto.co.uk - EH12 8NR
East Coast Garage, EH21 8NE - Tel: 0131 665 1343
www.eastcoast-car.com -EH32 9SB
www.bradburygroup.co.uk - EH32 9SF
www.markwallacecars.co.uk - EH52 5NN
www.cbautoservice.co.uk - KY2 5QW
www.randysautorepair.co.uk - EH41 3PE
Cheers,
Yes was I puzzled at first Gav, but worked out must be different Ring Gear.
Thanks for list Rakesh. I actually had contacted 2 of them by email last night from Bosch website.
One has got back saying cant do job. Will go through others next week.
Apart from switch on dash( which gives no indication) Is there anyway I can disable ABS permanently. So I can feel sure the problem wont occur again.?
Hi
The dash switch should do it.
I guess if you pull the fuse controlling the circuit then you would have to same effect.
Not sure that there is any easy way to disable it mechanically that would be reversable
You will also need it working for the MOT anyway
Hope this helps
Gavb
To know if the ABS has been disabled, trigger the switch on the dash; this will immediately illuminate a warning triangle on your instrument panel with ABS! marked on it. This alarms you that ABS is disengaged and you have only conventional brakes.
Perhaps, I am over estimating Bosch agents; given that garages are expected to have the right equipment as part of Bosch's contractual agreement and have the full training resources from Bosch to the most up-to-date technology, I am amazed under these conditions garages claim they can't tackle this type of job. This is becoming a JOKE!.
Cheers,
Rakesh, it seems that you have been out of the trade too long!!!
Most (but thankfully not all) just want the simple service and repair jobs that they can make a killing from and are not really bothered about customer service and getting involved in that tricky diagnostic work.
You need to come out of "retirement" and provide a service to us all!!
Gav
Hi Rakesh,
The light on the ABS switch does not illuminate at any position and the light on the instrument panel does not work at any time including ignition/start-up. Bulb may be gone on instrument panel?
So I have no idea if it is actually switched Off or not. If I can be sure it is Off , then I can at least drive it in the mean time -with a bit more confidence knowing the ABS/brake pedal problem is not going to happen. If it happened at speed it could be disastrous.
Is there a fuse for ABS?
No ABS light sounds suspicious, could indicate that the previous owner has removed the bulb.
Yes there is a fuse, suggest you start there. Sorry I don't have the number but it's in the manual.
If that's OK check out the bulb and get that working. It's relatively easy to remove the instrument cluster.
Then move onto the wiring connectors at each wheel. If these have been opened and not re connected properly you'll have corrosion problems. Clean and seal with silicon grease.
I'd also check out the rear drums. You could have some nasty's in there, friction material parted company with the shoes?
Good luck!
BTW mine in the last few weeks:
Engine stop........stopped Working
Front brakes
Rear brakes
Rear springs
Centre diff lock
Front tension pulley.......
Oh and the battery, which eveyone knows is about the size of a small bungalow and costs about as much for a decent make.
LR D3 / 4's make these look silly :-)
Sounds like the previous owner / garage has removed the display bulb to hide the problem either for resale or to sneak it through the MOT?
When you switch on, ABS light should be on, and then go out if working ok.When you lock any diff the light should be on.Like wise if you press dash switch.
It sounds like someone has removed the bulb, probably to get around mot.
There is no separate fuse,, a big relay that probably is ok.
All the ring gear is internal in the axles, so failure unlikely.
Most likely a dodgy sensor, I think front two are the same, but back are sided and pricey.
How do I know?, I replaced two sensors and mine stopped working again, Sort of put up with it.
If you really lucky you might be able to see damaged wiring, but hard to spot, especially if been off road..Try to look at back sensors for cracking of wire?
Someone else had the switch fail which caused no ABS.
At least the dash bulb cheap and easy!
Hi
Jason is correct that the front exciter rings are within the hub unit so the chance of it being clogged up is remote but i guess damage is still possible either through something wrong within the axle or if it has beem removed and damaged say during bearing replacement. I guess there is a chance that this could happen although small.
If there is not a seperate fuse for the ABS? Then the one in the top of the OVP (Overload Protection Relay) has some control over the ABS although removal is not possible as other circuits run through it, checking it is OK is a start. The OVP is near the fuse board and is usually 3" long x 1" square silver relay with a flip top plastic cover with the fuse underneat, 10amp from memory.
There are also 2 relays (A003 545 27 05) that control the ABS in the fuse board area as well as the ABS Control Unit (A008 545 44 32 4-channel or A017 545 42 32 3-channel)
The front sensors are all the same and not handed where as the rear sensors are handed like Jason states and also the are chassis serial number cut offs for early and late production. The later type rears also have a cage that they push into the can get damaged if re used and make the sensor not sit right. The front all just have o ring seals i believe.
Again if you let me have an email address i can send you a simply schematic of the system, although as these systems go it is really simple technology that any garage should be able to fix.
You should be able to check a lot of these yourself to see any obvious faults.First stop is the dash warning bulb i guess and go from there to check the switch operation, any fuses, check for damaged / missing cables etc. The bulb is probably going to be a small 12v 1.2w capless not sure if its built in a holder or seperate but there should be other behind there to use for testing as they are all similar.
The switch is part number A003 545 26 07 and is the same switch as the Rear Window Dimister, Rear Interior Lamp and others is you want to swop it to check the functions OK.
Gav
REPLY TO THREAD No: 13
Hi Gav,
I think you are right - I have been out of the trade too, too long.
Will have to change that some how.
Cheers,
I am no expert on ABS but the symptoms you describe suggest that the high pressure pump is not charging the accumulator on start up. When you turn on the ignition you should hear the pump run briefly and then cut off when the accumulator is charged and the ABS light will then go out.
In your case it would appear that the ABS light may have been disconnected to hide the fact that the ABS system is not working. If the accumulator is not charged there will be no initial brake boost hence the hard pedal and the ABS system will fail to operate as you have discovered.
A few presses of the brake pedal after start up while stationery should soften the pedal and increase feel but you will still not have decent brake boost unless the ABS system is disconnected. I would reccommend a visit to your Bosch dealer to get the problem properly diagnosed. I think they might be able to get a fault code from the system which would identify your problem.
Hello Bigblock,
I feel you are describing a hydraulically boosted braking system employed in some Audi and BMW models; that system is not employed in this model, may be the newer G's,the 500's and the like might. Any how, you are correct in saying that our member needs to go to a Bosch dealer, but that's just the problem, he already has.
Cheers
Hello Lego, this sounds sadly like all the bosch agents so far are scared of the fault as it is possibly life threatening and fear being sued if they touch it . someone needs to grow some b@£$s and get it bloody sorted , i bet an agent in germany could, and i hope somebody here can too. it sounds like the vehicle has had its wiring 'frigged' to fool the m.o.t. or new purchaser as they will observe the operation of the lights and the fact that they extinguish showing system check 'ok' chances are the wiring needs to be corrected before the fault can be repaired as it may actually prevent the fault being fixed. oldest trick in the book i am afraid ,i have heard of the oil pressure light being wired to the alternator light so it goes 'out' when the engine starts despite the engine having virtually no oil pressure , two words 'motor trade'.
this will take a good and knowing tech to sort out ,this may not be cheap as they will be trying to diagnose around someones bodge .. best of luck.-mike
Yes with 2 Bosch agents so far not wanting to touch it, it may just be that they are scared as you say.
I don't think there was anything dodgy attempted by the seller as they have been understanding of the faults and have offered me some money back, which hopefully will go some way to sorting the problems. It looks like I may have to take it to a Mercedes dealership to get it sorted, as nobody else seems to have the knowledge or B@!!$ as you say. I dont expect it to be cheap at Mercedes.
I've have heard that the John Weir dealership in Perth has good knowledge of G Wagens so have provisionally booked it in there.
If anybody knows otherwise or can recommend a dealer in Scotland then let me know.
thanks again everyone
i expect that the bosch agents will give a sigh of relief not to have to diagnose this one! mercedes will have the backup of liability to do this, however lets hope their techs have the g knowledge to find and cure the fault .
you may well find that they start changing large expensive abs units to diagnose by replacement of valve blocks /modules this could be a bit scary money wise just make sure they keep you in the picture labour and parts wise or it could cost thousands.
a friend of mine runs a business taking all the nightmare jobs that local garages and dealerships give up on ,nasty intermittent faults you name it. hope they find it and its not something really obscure like an internally broken wire..
Hi Lego - I get my G serviced by Weirs (Inverness branch). Have always found them to be pretty good not least because the previous owner of my G was the wife of the franchise holder ...... her son also owns a current model G as well .....
Good luck with getting your G sorted!
Thanks MG7, Hopefully then their Perth branch will be just as good.
Cant afford the petrol to Inverness ;)
Very angry to find out yesterday that the ABS warning light bulb was missing from it's socket.
Seems very likely it was removed by someone to hide ABS fault.
Reading this with interest.
Since the bulb is missing, you don't have the issue of it being maliciously wired. Just that ABS detection is busted. suggestions have been those ABS sensors. So it might not be so difficult to find the fault.
Anyway, just putting a new bulb in will enable you to see when you have 'turned off' ABS and avoid the potentially drastic issue of it cutting in when you least need it!
Hi Marko,
I have a 300 G D cabrio 1990 and i have the exact same problem with my G. When the ABS is switched of i can brake normal, without ABS. If i put the ABS switch on, the pedal gets hard and pulsates(that sounds kinda dirty, lol) and braking is almost impossible unless you take your foot off and brake again.
Mercedes checked the whole system and they said, after paid 300 euro for a simple job, that i had to change ALL the sensors. Costs around 2000 euro. I cant believe that because of a faulty sensor the car gets so dangerous that you can not brake. It has to be something else. Did you ever find out what the problem is? I want to find it out because i restored the cabrio to almost new and want to keep it till they can bury me in it.
Thanks,
Jantie
Hi
I understand that Marko has swopped his ABS ECU for a known good one and the fault goes away.
He is just trying to source a reasonably priced Used ECU
Gav
Hi Jantie
Instead of resurrecting three old threads on this subject you would be better served by creating a new topic so that any assistance from members can be concentrated in the one thread.
I have a 1990 300GD as well with the same problem. I have replaced every part of the ABS system. Main computer, all 4 sensors, all fuses and relays, even the main pump. Still the same issue. In my research I have found that when the ABS light comes on look at the light closely while driving. If it flickers the problem is with some component of the ABS system, if it does not flicker them something electrical in the Diff lock system is at fault. Triggering the ABS to shut off.
[quote=Lego] . Apparently the Previous owner had problems with ABS due to water ingress.quote]
You also mentioned water ingress at the passenger side, which also coincides withe the fuse and relay boxes location. I would say that checking all the relevant electrics in this location may be a good start???
Hi Folks,
Not been on here for a while so only just noticed this.
As Gav said I sourced another good used ECU from Germany via Ebay. (£500) over a year ago now.
Nobody could repair mine despite being sent away to ABS repair specialists.
Before buying it I swapped known good ECU from another G to confirm it was indeed the ECU.
My ECU failed in the other G.
Best bet is to meet up with another G owner who is willing to swap the ECU to confirm faulty or not.
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Hi Rakesh,
Yes attitude of garage was very disappointing and I have written a complaint to them which I will pass onto Bosch.
Yes! believe it or not! they are Bosch accredited and weren't willing to sort my HID lights problem or my "dangerous " brakes problem. They gave me number of an auto electrician for lights and expected me to collect and drive my "dangerous" car elsewhere, to have brake problem fixed, but I could bring it back for them to look at other stuff once the brake issue was fixed.
Thanks for thePointers I'll pass these on to another Bosch appointed garage who is willing to sort them.
Excuse my Ignorance Rakesh but, why could Ring Gear contribute to problem.
cheers
Marko