Rav4 Brake Problem

[taff_rav]

Hi All

Having problem with brakes on 98 rav.Getting juddering on brake pedal when braking almost all the time.

On advice from others(warped discs) have changed front discs and pads to no avail.

Have perfectly good 2nd hand discs if anyone interested ;)

I now feel that the problem lies with abs system and may be a sensor.

Can these sensors be tested? and has anyone had any experience changing or repairing these?

Any advice about the braking system and its faults would be appreciated

Cheers

Taff

[NMaria]

Taff

This may be wide of the mark in your case, but I had the same problem with my old Mitsubishi Galant - drove me mad. I got steering wheel judder as well. Eventually found that the tyres (Avons) were not round. Bought new tyres - problems fixed. I achieved diagnosis by jacking up the whole front of the car, starting the engine and putting it (very gingerly!) into first gear. Soon saw that the wheels moved like a random orbital sander, if you see what I mean.

Hope of use

Maria

[matfrost]

I doubt it would be an ABS sensor issue, unless you can feel the abs malfunctioning.

Could it need a 4 wheel alignment ?

[anchorman]

Welcome to the club Taff

ABS modulation feels more like a high frequency vibration than a judder which is normolly one pulse per rev of the wheels. You may also hear the ABS pump whirring away in the background. If it is modulating during normal braking it thinks for some reason that a wheel is locking up. Don't forget that you can get pedal judder/flutter from wharped rear brakes. If it has drum brakes just ease on the handbrake while you are moving at low speed and you will feel any run out on your hand. Rear discs are harder to detect but if it is bad enough that it is effecting the pedal then you should be able to see it by turning the disc and watching the clearance between the pad and the disc.

An OBD11 reader is no use for ABS as you need something to read the suppliers software so you need to go to Toyota or a ABS specialist if you want to cut out a lot of work. However, that will be expensive so you could start by making sure there is nothing obvious like rust or shale built up around the sensor tips and that the teeth are relatively clean on the exciter rings (but don't go crazy about these because they do not have to gleam). You can also make sure all the leads appear to be in one piece. If you have digital volt meter you can disconnect each sensor and set the volt meter on millivolts with the meter connected accross the wires. jack up and spin the wheel and it should generate a small but noticeable voltage.

Failing all that you will have to cough up at the specialists!

Good luck!

[bothwell_buyer]

Hi Taff

2 simple solutions -

1. Do the brakes actually work - ie stop the car? If so buy a pair of Doc Martins shoes with the air cushioned soles

2. If the brakes don't work, visit the chandler (a shop that sells boaty type things) and buy 2 steel anchors. When stopping, chuck an anchor out and hope it catches a nearby pedestrian. In an emergency, throw both anchors out. remember to connect a bungee rope to them!

I don't have ABS on my RAV as the Japs hadn't thought of that in '94

[Uncle Bob]

Hi All

Having problem with brakes on 98 rav.Getting juddering on brake pedal when braking almost all the time.

On advice from others(warped discs) have changed front discs and pads to no avail.

Have perfectly good 2nd hand discs if anyone interested ;)

I now feel that the problem lies with abs system and may be a sensor.

Can these sensors be tested? and has anyone had any experience changing or repairing these?

Any advice about the braking system and its faults would be appreciated

Cheers

Taff

As a general rule of thumb.....

Brake judder through the pedal and steering wheel is front discs distorted ,

Brake jubber on the pedal only is distorted brakes at the rear,

As the early RAV4's had drum brakes on the back ,( if it was me ) i would get the drums skimmed at an engineering shop, if its a high spec early RAV4 ( VX ) it will have discs on the back, if so and there is plenty of thickness left on the discs ,get them skimmed and fit new pads......good luck.

[taff_rav]

Ho Ho Ho my sides are splitting here!

You will no doubt be living in the roll over cage, throw in a strait jacket you'll be sorted

[taff_rav]

Thanks Bob

real advice,yes they are drums on back will check tomorrow,let you know how i get on

[dave.m]

Taff, welcome to TOC and the craziest forum on it B)

Maria, long time no hear how are you doing up there in the frozen north ??

[bothwell_buyer]

Jeeez

Ahm jist amazed at the amount of information that crawls oot the woodwork here.

In 1994, I bought the top spec RAV4 3 door GX wi all the acrutriments and accesssories. The rear brakes could only be drum brakes and after 167,000 miles the original drums are still oan and have never been skimmed.

Hooever, if some prat has left the car and the rear cylinders have binded (or bound if ye unnerstan that better) then overheating could have caused distortion.

My experience wi the RAV has been that it has eaten up front discs. Aye, we had new pads - ahm no that skint.

It came doon tae the front calipers piston and caliper assembly binding causing the pads no tae retract and the discs tae heat up tae the point waur they distorted. Ah gut less than 2000 miles oot the last set o discs (Rotordisc) which is why I went fur KAD calipers and discs. Cost a wee bit but (swear wurds excluded in case the mud-erator fines me) bleedin hall, the brakes work well. 6 pot calipers wi Ferodo pads an I can drive along wi-oot the RAV feeling as if its about to turn tail over nose due to drag.

Simple but ye mind want tae check yer front calipers for properly freeing aff - ye need tae make sure that the whole thing moves as it should...and of course when they have been used ( as I assume you use the brakes frum time tae time) an heat builds up, the calipers still need tae be able tae operate. Ma man at The Garage (nae promoting intended but he's the first guy that telt me aboot the caliper problem wots quite common) is that the 2 bolts an rubbers need tae be clean and rust free and use the proper grease - I had used copper grease an it didnae work wi the immense heat wot the calipers produce...the calipers jist seized an ma RAV drove nose down wi a helluva vibration from the front oan the motorway as the discs and all heated up tae whitever temperature.

Wi-oot being cheeky, ye micht want tae check that altho its difficult if yer driving alang at 60mph.

As fur the straicht jaickit, the NHS have tried that an failed. See, ahm strong; drink whisky an Guinness an use ma Cobra sports seats n 4 point harness tae keep me in place. nae need fur anither jaickit. An ahv got a seatbelt exemption certificate as weel - bet ye don't have wan o them!!

Mad Max frae near Motherwell

[taff_rav]

Thanks to all for advice especially bothwell (even tho had to bring in translator)

I'll let you know how i get on.

[bothwell_buyer]

Thanks to all for advice especially bothwell (even tho had to bring in translator)

I'll let you know how i get on.

Nae bother big man. Comin frae near Newcastleland, reminds me o the maths lecturer whit came frae there. I cuidnae unnerstan him an failed ma maths - diffrent language Geordy is!

[taff_rav]

Just thought i would update you all

Checked o/s front abs sensor cleaned crap and cleaned exciter ring also removed caliper and checked operation all fine refitted tyre went for spin,big improvement but slight pulsing vibration on braking.

Did same with n/s front caliper etc and all fine.Removed sensor and again removed (large piece of)crap.When cleaning exciter noticed one tooth looked different and on further inspection moves slightly with a small screwdriver.Looks like it has cracked near this tooth.Not sure what it should sit like or how to remove this,does it come as part of whole drive arm?

Tried car and braking ok but annoying slight shudder and more often and not pulsing vibration.Any advice anyone before i commit to specialists. :(

[anchorman]

Taff

I'm still not sure if you are getting vibration from ABS modulation or Judder.

ABS modulation is more like a high frequency pulsing many times faster than wheel rotation and regardless of speed. The pedal may also feel strange and appear to go down a bit lower than usual. This is generated by the ABS unit and is intended to make you aware that modulation is taking place.

Judder tends to be at the same frequency as wheel rotation (usually once per revolution and reduces with vehicle speed) and may be felt via the steering wheel. This can be caused by a wharped disc or DTV (Disc Thickness Variation) where the disc is worn thick/thin. Maria has also highlighted a very valid point that the tyres can cause you horrendous problems and must be checked for true. The best way is as she has described;

jack up one front wheel

FULLY APPLY THE HANDBRAKE

Start the engine and engage second gear then carefully release the clutch until the speedo stabilises.

Go around the front and without putting yourself at risk, observe the tyres.

The rule of common sense applies so don't get hung up about a small amount of run out but anyhting bad enough to cause a problem will be obvious.

Repeat the other side

Good luck and let us know what you find.

Which does yours do?

[taff_rav]

ok just got in from half hour test drive to try and confirm problem.

Definately not high frequency pulsing, more like dull knocking/thudding that is in relation to wheel revs.

If i am travelling at 50 mph and apply brakes gently, knocking does not start until down to 20 mph and the same if applied more harshly.same for 45,40 and 30 mph does not start knocking until 20.

If travelling slowly at 20 mph and apply brakes knocking starts instantly.

Can feel it on brake pedal but not steering.

Have brand new discs and pads on.(very warm at moment),but tyres are legal (just) and are probably due for change in January.Going to try tyre check now.

[taff_rav]

OK..............you will not believe this!

Tried tyre test,ok, must have 2 of the most concentric tyres around, just about perfect, but..

after testing 1st tyre noticed abs light had came on, tested 2nd tyre light still on, so went for test drive and knocking problem GONE!

Wait for it..... turned last corner into our street, braked and knocking was back and lo and behold abs light out!!!????

So, when abs light comes on does it deactivate abs?

why would light come on when testing tyres individually?

Am i going to the nutty farm with this problem

[shcm]

So, when abs light comes on does it deactivate abs?

why would light come on when testing tyres individually?

suppose I should leave Anchorman to answer this one, but I know a little about ECU design .

At power up the ECU will most likely do a system check, one item of which is almost certainly a sanity check on the wheel speed sensors. When the vehicle starts to "move", it will expect to see some speed signal from each sensor. In this case it won't see that and with therefore decide there is a system fault.

It's very likely that the system will be deactivated under these conditions IMHO.

Cheers

[taff_rav]

Thanks shcm

Well if your right and when system is deactivated problem goes away, that proves that when activated abs is causing fault either by correct diagnosis(not in this case though because not locking brakes)or faulty diagnosis i.e. sensor picking up damaged exciter ring or dodgy sensor or fault within ecu(is that electronic control unit?) or something else in system.That would surely bring up fault light though, wouldn't it?

Can system be deactivated manually just to prove point?

This is a good fault finding excercise if nothing else.

Ah the joys of motoring

[shcm]

Yes, ECU is electronic control unit.

My system knowledge is not as good as it should be, it's been some years since I did any ABS ECU design and I have to agree it does not sound like ABS modulation.

But (never start a sentence with but), ABS sensors come in a least 2 kinds, VR (Variable Relutance) and Hall Effect.

Variable Reluctance sensors are robust, but generally don't work well at low speed. To a first approximation, their amplitude (output level) goes up and down as wheel speed goes up and down. So I am wondering whether you do have a faulty sensor (i.e. it has enough output to drive the ECU input above 20mph, but not below) and hence the "knocking" at low speed. I don't know what sensors are on the 4.1 RAV. Earlier ABS systems generally had VR, I believe.

I'm not that convinced though. (Doesn't feel right) Maybe if the ABS ECU is fused separately, you could pull that fuse and try it.

Thing is, I'm not familiar with the elec architecture on the 4.1. If there is anything else in the vehicle that expects to see for example CAN bus messages from the ABS ECU (if it even talks CAN), then I don't know what else might happen if you pull the ABS fuse and I don't want to give you advice that might make your problems worse.

Cheers

[anchorman]

shcm knows a lot more about electronics than I do so I don't intend getting into the technicalities of that aspect. I am not surprised that your ABS light came on as generating a voltage at one wheel will probably make it thing that the other 3 are defective when it can see an input from the speed sensor.

What I do not understand is how it can generate that kind of low frequency knocking with the system active.

shcm - do you think that if the system failed to see a voltage for part of a revolution at one station that it could modulate during that period? That would give the sensation that it was "per revolution" when in fact it was modulating normally for part of a revolution.

I wonder if the air gap is too big on that exciter that appears to be broken. During this phase the voltage disappears and modulation starts and then stops when it picks up on the good teeth??? It might climb through it as the speed increases above 20mph.

Taff - In this case you need to ask Kingo if they are a seperate item. I know that later ones have moulded teeth but I think you describes an external punched steel ring attached to the CV joint - right? That might be replaceable.

[shcm]

shcm - do you think that if the system failed to see a voltage for part of a revolution at one station that it could modulate during that period? That would give the sensation that it was "per revolution" when in fact it was modulating normally for part of a revolution.

I wonder if the air gap is too big on that exciter that appears to be broken. During this phase the voltage disappears and modulation starts and then stops when it picks up on the good teeth??? It might climb through it as the speed increases above 20mph.

To me, that sounds like the best explanation so far.

[bothwell_buyer]

OK big man....

there's lots of good info flying aboot here and we have 2 of the top experts in the country when it comes to braking systems...or is it 3.

Anyway, I had a look at the Haynes USA manual wot i have -

Quote

"The front speed sensors are mounted on the steering knuckle in close relationship to the toothed sensor rotors, which are integral with the outer constant velocity joints."

The ABS ECU is mounted behind the passengers side kick panel. Faults show up as a light on the dash and a fault code will be stored in the ECU. Codes can be retrieved without special tools....on 2000 and earlier models the code can be accessed by turning the ignition key to the off position; remove the short pin from the data link connector then connect a jumper wire to terminals E1 and Tc of the data link connector. If need be i can scan the pics and send them to you. Turn ignition key on and observe codes on the ABS warning light on the dash. The code is the number of flashes indicated on the ABS light. Its a mixture of flashes then pause then flashes. There then follows 2 more paragraphs and a full page of ABS trouble codes.

From what you've posted, maybe its something to do with the broken tooth on the ring. the system is also full of relays and solenoids.

I am now even more thankful that I bought my front brakes from KAD racing and don't have the hassle of ABS. I just hit the brakes and hope the eejit behind can stop as fast as I.

let me know if ye'd like the 3 pages scanned and sent to you.

[taff_rav]

Once again thanks to all who have contributed, sorry for late reply just got in from 12 hrs graft

Both,although this sounds fairly straight forward isn't it only confirmation of what we know?feel free to send over the 3 pages pm me for my e mail address and i wil give it a go. How do i contact kingo for parts update?and any info on getting cv joint off would be very welcome.

by the way...Great site! :D

[dave.m]

Hi Taff, send him a PM , his correct screen name is Partsking. ;)

[taff_rav]

Thanks but coming up as no member name???