twang?

Never ends.. just sorted a coolant leak, whiny diff, changed plugs and leads, new battery and was about to tackle rich petrol smell when I get this!

This morning heard what sounded like a guitar string break and felt a bit of a click as I tapped the brakes getting the car out of its parking bay. On the way to work noticed that every time i touched the brake pedal my ABS, TCS and Brake Warning lights flashed on. They went out as I pressed the pedal further. Now each time I use the brakes for the first time after the car has been parked for a while, I feel a slight click. Its only the first time and then no noise but as mentioned, the three amigos will flash. Pedal feels soft during initial travel and then firms up.

Based on experience in other cars I'd guess pressure loss but checked brake fluid and level seems fine. I was leaning towards pedal spring/pivot or even position sensor for the twang but then I just scared myself silly reading a 25 page thread over on rangerovers.net which says that bits inside the brake modulator are liable to disintegrate. Really, really hoping that's not it. I've also looked up all the posts on the 3 amigos here (overwhemingly Freelanders, some Discos and no RR!) but can't really find this combination of symptoms.

Anybody ever experienced the same? click, mushy pedal and 3 amigos? Would love some pointers.

Thanks!

'97 4.0 Manual.

bump!

I get that "twang" intermittently perhaps once a month or so, quite loud, seems to be from right front wheel but can't see any problem. No warning lights or anything though....no help to you really!

All P38 Owners with Vehicle Pre Mid 1999 Should Read This - Land ... is this of interest???

The link didn't work...do a search on LZ for P38 Modulator

f1roborbob said:

I get that "twang" intermittently perhaps once a month or so, quite loud, seems to be from right front wheel but can't see any problem. No warning lights or anything though....no help to you really!

Click to expand...

thanks for the support tho! from non LR experience yours might be sticky caliper or excessive pad wear. I'd have it looked at sooner than later cos its not a big fix but can become one if left untreated.

Irishrover said:

The link didn't work...do a search on LZ for P38 Modulator

Click to expand...

That's the 25 page thread I referred to! The link is:

RangeRovers.net • View topic - Please read all P38 owners up to mid 1999(brake modulators)

Its quite a long read so I saved an edited version on my laptop just for reference. I'm posting it here, with all credits acknowledged (mods - hope that's ok and nobody will get in to trouble?).

I've basically edited for space and made the following formatting changes for clarity:

Italics for questions

Normal text for answers

Bold for related information or possible alternative diagnoses.

---------

Could you please explain what the symptoms of the impending failure are?
At what age do the modulators fail?

Ok, symtoms are a stage or click in the pedal as you apply your brakes. Or any warning lights at any time.Basically be wary of any change in the brake process. From the cars I have fixed (5)they have been 95/96 models with drastically different klm's This is why a second hand replacement is a short term fix.

What is the part in the modulator that fails?

The component failure is in the hydraulic section of the brake modulator. When this fails you have a complete loss of brakes, only the handbrake to pull up.I will add to that repairing this situation prior to brake failure is recommended as once the failure has happened they is usually additional damage to the unit, in some cases rendering it useless.

How can we identify on which vehicles these are fitted?

I suspect the qualifying condition is that if the vehicle is 99 and has four wheel TC then it is fitted with the later Bosch Modulator.
If it's pre-99 then it automatically qualifies as 'possible failure'.
Yours, as '98 and no TC qualifies as 'possible failure'.


My 95 4.0 has had a rare but similar fault for the past two years.
Just occasionally, I have no pedal after startup.
It occurs only after sitting overnight and always is correctable with a couple of pedal pumps. It might manifest itself every day for a week, then dissapear for months.
I occasionally see the brake warning light, but only when the brakes are applied. Since I know my pads are getting low (and very shortly to be replaced along with the rotors,) I assumed that the warning system was bringing this to my attention , but now, I am concerned about imminent total failure.

Ok, the part on the left is the failed component.On the right is one that I have fixed.You'll notice that the left hand component has the smashed plastic component in the back ground.


The second shot is of the stainless steel replacement parts, above them is the original plastic part. I only have one or the originals in one piece.


The complete shaft and spring setup is part of the hydrualic section of the modulator and this component give the feel on the pedal, along with hydrualic pressure.


I imagine in addition to the part that fails in the modulator there are other parts which are disturbed when it is dismantled i.e 'O' rings, seals, gaskets etc. As you can only buy the modulator from Land Rover as a complete assembly and there are no individual parts or repair kits listed I would have thought these parts are only be obtainable from Wabco who if memory serves me correctly make the unit for L/R.

If there are such parts internally are you able to obtain these for inclusion in any repair kit you put together, otherwise it would be a bit like putting a new piston into a brake caliper and not replacing the seals.

As wabco will not provide any spare parts, replacing internal seals etc is hard. The 5 that I have repaired have been in perfect condition internally, as far as seals are concerned all rubber components have been nice and soft still with no damage. As you will see in one of my photo's a small aluminium piston can be damaged or smashed I have replaced this with a good conditon used item from another damaged modulator. This is what happens if you have complete failure and pump your pedal hard. In rave you'll read that LR recommend that you do not pump your pedal in the event of brake loss!!!

The clicking brake pedal is not a huge concern for me - mine did this for 3 years before it fixed itself strangely after I replaced a few bulging brake lines and a few fluid flushes.

What jsp said happened to this same car.It came to my workshop with almost no brakes and a horrible stage in the pedal.For two days a played with it trying to flush and manipulate the various parts electronically with faultmate, and still nothing.The next day I started the car and moved it, bingo brakes felt great.It only lasted for about a week and then full brake failure.The only reason I can put to this is by bleeding, flushing ect the broken parts move to allow normal braking process to occure.


Question, is there a reason for this part being plastic? Does it run against the bore of a cylinder, if so maybe its plastic is for no/low wear? Does it need to be Stainless? Brass or alloy perhaps? or even engineering grade nylon?? Are there hydraulic seals involved?

I can't see any reason. The components do not come in contact with the walls of the cylinder at all. The unit that is in my photo's is guided by a larger piston which it locks into. When wabco changed to stainless steel in the later modulators(mid 99 +). The later version is exactly the same in the hydraulic area but set up for 4 wheel traction control, which I think is purely activated by the update ecu. None of the seals are available from wabco, some are completely different from any that I have ever seen. I have not found the need to replace any yet as all have presented in perfect condition.


So this is the reason should I ever have any symptoms of pedal 'clicky-ness'?
Not always. I’ve had many cases where it was one of the sliding caliper pins starting to seize. Clicky-ness disappeared when pin finally seized. Didn't reappear when pin was unseized during pad replacement. Perhaps not all clicky-nesses are created equal. Would advise check all calipers for smooth free sliding before ripping any of the expensive bits apart.

Strictly a question trying to connect the dots... If Wabco changed this to SS for the newer model modulators, would it not be possible to replace earlier modulators with a newer one already setup with the SS assembly?

Yes you can, I pointed this out in a post. I have done one this way. Problem is there is a slight conflict in the electronics with 2 wheel TC vs 4 wheel TC. I'm trying to work out if it is just the ABS/TC ecu or the BECM as well.

In my case, fluid has been recently replaced. I still get clicking and I’m pretty sure its from around the pedal itself but unfortunately it does not occur at standstill so I can't stick my head in the footwell to confirm.

Ok, check your pedal spring and pivot point. Also make sure that its not the switch. I had a faulty switch a few weeks back that made some slight clicks.

Will there be any click feeling at the pedal? Because so far my brakes feels quit strong and pedal travel is minimal.

Generally the click feeling is in the pedal. The fact that the pedal is high, as in there is minimal travel, is not really an indication of failure or not. A minor click or staging in the pedal can be a failure of one of the plastic locating washers. In this case the brakes can sometimes function for a long period, but eventually they will fail.


I have a related problem, when I start the car, I initially have no brakes! After about a minute or two they come back aided by some pedal pumping.

It sounds like you have a failing accumulator. It's taking longer than normal to build up brake pressure. Try this test. Leave the car in park, release the handbrake, start the engine. Time how long it takes for the brake light on the dash to go out. If it's up near 45 seconds (owners manual says they will go out in 3 secs but this is rarely so) , I'd say the accumulator is on the way out. After the light goes out, you will have brakes.

I have a dash brake light error already so I don't think this test will work for me. Any suggestions? Also is this kit you sell for what you think could be my problem. And also what damage could be done already that would make it not repairable? When I said brake failure, The pedal felt hard to the ground but it was very hard to stop

Given that you have a brake light error I would think, from your symptoms that your system is down on pressure. This can be the ABS pump and or accumulator.

I currently have brake fluid that is just below the min line. WIth that in mind, I have had several symptoms mentioned here, as well as another. I'm trying to figure out if it's the low fluid, the accumulator, or the Plastic part in the "hydraulic modulator" (or whatever it's called). I have had the "no brake pressure for a moment just after putting it in drive" intermittently. I also have a clicking sound at times...almost like the abs is engaging when I stop. The 3rd symptom is where I thought its the accumulator (from what others told me here)...at speed, I step on the brake, and the 3 lights on the dash flash for a moment.

Ok, generally the red brake light will come on when braking due to the accumulator/lack of pressure. All lights coming on indicates faults in all systems or insufficent pressure thoughout the system. The click will be the plastic locating washers failing. The pressure issues could also be caused by the plastic components breaking up and lodging within the modulator. Hard to be exact without stripping the unit down. My suggestion would be repair the modulator you have in the car, then see how it reacts. Then look at the abs pump and accumulator.

I have TC ABS and now the brake error light on. And they stay on all the time although when this first occured the brake error light came on, then after I restarted the car about 5 minutes later went away and I had brakes. Then very quickly it came back and I did not have brakes. Do you suggest I start with the accumalator or the pump first?

I would suggest that with all lights on and little or no brakes you have a pressure failure some where. Can you get the car to a brake shop to tesst the output pressure of the pump??? you can have a faulty pressure switch and or a faulty pump. If it where mine I would start by the modulator fix and then the pump and accumulator, but either way it sounds like you have more than one area failing.



Hello gents, just another item to check. Have just be made aware of a modulator leak problem. If any of you that are experiencing fluid loss that can't be explained, check under the body of the modulator. I have not heard of this before but a 97 HSE has presented a leak in the sealed soleniod compartment. There are seals that hold and seal each solenoid in place. The give away symptoms will be fluid loss. This would appear to be rare at this stage but another thing to check whilst doing the repair.

It took me the best part of ten hours from draining the system to bleeding back up, with a few interuptions along the way. Job went very well, all parts came to pieces quite well. I was being extra carefull in the dismantling as I was conscious that to damage any part could mean game-over and potentially a new modulator at £1800ish! The pins holding the assembly at the rear were quite tight to punch out, but with care and a little WD40 they gave in.
My little plastic filter was also very tight but working it gently with my fingers it too slowly eased off.
Now for the main components, the plastic washers. Mine initially appeared to be both fully intact. However, when I came to remove the first one nearest the collet, I discovered it had actually got a crack through it from the outer edge to the centre. Both washers were also extremely brittle and took no effort to break off the shaft with finger pressure only.
So on with the new s/s washers, new o-rings and carefully all back together. I choose to fit the reservoir tank to the unit prior to fitting back to the car and managed to line the bolts at the rear back up ok. I bled the system through about three times as I couldn't seem to shift some air which was causing the abs pump to make the clicking sound mentioned in the bleed instructions in RAVE. All sorted now and pedal nice and firm.


One last question or two, How long does it usually take you to do this? I was going to see if my mechanic would do the repair for me, but need an idea of the time involved so we could price out the labor. Oh and do you have a list of tools required to complete the full job as I still may choose to do the work myself? I got your RAVE bleeding instructions, and was suprised that it didbt require a "Bleeder" to acomplish. Thanks for those! May be I am making this "mole hill" into a Mountian as the saying goes. I look forward to your reply as always. Thanks!

Ok, a qualified mechanic with all facilities at hand should take about 10 to 12 hours tops. This would take into account having never seen this repair before. As I'm sure by now you would have looked through the instructional manual, it's very detailed so this should dramatically save time. If your undertaking the repair yourself, and not knowing your ability. I would give yourself two full days so you can take your time.
Tools required are quite basic.
Metric spanners and sockets-10-11-13-17
Allen keys/hex heads 4 to 6mm by memory
Screw drivers flat and phillips(star) depending on what hose clamps are on your car.
Hammer
A drift or punch as seen in the cd.
Long nose pliers
A bench vice helps.
Thats about it. I always use a bleed tube/valve when working on any brake or clutch system. Brake fluid is extremely corrosive and makes a big mess if squirted all over the place. Some of the bleed process is done under the ABS pump pressure so if a bleed tube is not used the fliud is leaving the bleed screw at great pressure. If you do not have one, they are very cheap to buy from an auto parts outlet. If possible get one with the one way valve, this helps to make sure that no air returns into the system. Hope I have answered to your expectations.

I finally fitted my modified spare modulator almost without any problems, thanks to your instructions, but would like to highlight two areas:

1) Two long bolts mount the modulator to the two right angled firewall brackets, one of which has the two nuts welded to it. On my LHD car, the bracket with the nuts is on the right hand side (looking towards the rear of the car) which means the bolt heads are behind the engine and VERY difficult to get at with a socket wrench. I suspect this is the standard LR assembly arrangement for the British design as it places the bolts easily accessible on a RHD car.
When the modulator is out, it is not much of a job (Using a 1/4" drive extension with a knuckle) to switch the two brackets to make remounting and future work easier. Looking at the firewall from under the dash, the lefthand nuts should be tightened fully and the right hand left a little slack until the modulator bolts are in place, to avoid any alignment issues. The right hand nuts are still accessible after the modulator is in. The brackets are identical and symmetrical so there is no problem with doing this, just note that the nuts are the self locking type with the outer threads deformed, so they do not spin off easily and it takes a spanner to get them all the way to the end of the studs.

2) The importance of resetting the brake light switch after replacing the modulator should be highlighted. If this is not done, apart from the brake lights remaining on all of the time, the EAS will not operate as it will not change the car height if the brakes are on and it receives its signal from the brake light switch. I know you refer to the resetting in the last pages of your instructions but, once I had the modulator out, I didn't refer to them again and it cost me another hour trying to find out what was wrong with the EAS afterwards.

The LHD bolt coment is great. I have not worked on a LHD vehicle so I'm sure this will help with those who are.

1. The brake light switch can now be refitted. Pull the end of the switch away from the body of the switch. It’s on a ratchet which will automatically reset to the correct length when refitted. Fig 39. Figure 39.

2. Partially press the pedal down, and at this time refit the switch. Release the pedal and the brake light switch is reset.

IMPORTANT: Failure to reset the brake light switch will result in inoperable EAS.
Also, I found that the switch plunger needed a REALLY good pull to get it to extend and, for a while, I thought my car maybe had a different type to the one you were referring to. It might be worth mentioning this.

Ok, all back together. took @5hrs upto this point. All that remains is the bleeding/flushing of the system. All went according to plan (for a change). Excellent instructions and all parts fitted like a glove My plastic parts were intact, but were EXTREMELY brittle when i removed them. Had to use a little 1000 grit on the piston to get them to slide easily.
The large allen headed bolt was actually recessed a little on mine (instructions refer to counting exposed threads!), i counted 4.5 turns to refit to the same location. i punched 3 lines from the head to the body of the modulator before removing, and counted turns.
Notes so far.......and this is for LHD only.
You need to remove the duct work from the airbox to the throttle body.
Removing the cruise control cable will give you a little more wiggle room.
Be carefull of the AC lines that run next to the assembly, they look easy to break (and no i didnt, thank god!)
Get a 10,11 and 13mm line wrench. they have the cutout to slide over the brake lines and will be a lot easier on the lines than an open end wrench. I didnt have any issues, just a thought.
While the resevior was draining, i went ahead and disconnected the brake switch, save a little time as it was taking forever!
I used a vernier caliper to measure where the collet was positioned on the shaft before i dissasembled it. makes reassembly a lot easier and more precise IMO.
people may want to get the following items before taking it all apart...
new clamps for the line going from the resevior to the abs pump. the clamps on mine were one time use deals, junk. luckily i had a hose clamp to resecure it.
new copper washers for the banjo bolts. i reused my old ones, but new ones would sure make me feel better! there are 4 in total.I didnt think to measure them, but i am sure russell could supply that info.
Its a lot easier to leave the resevior off during installation, those bolts are a PIA big time!
leave the 2 lines off the front of the assembly until after the resevior is refitted. gives a lot more room. number 12 is ok to refit beforehand though. i ended up removing those other two to fit the resevior back on.
the hardest part was removing the 17mm bolts that hold the whole shebang to the firewall. whoever thought of that was an idiot big time!
Well, off to brake bleeding heaven for me, will reply again after it is all said and done!
thought i would post up while it was fresh in my small memory!


You can re-use the copper washers thus; Heat them to 'cherry red' with a propane torch or stove top flame, dunk em in cold water and they will be as soft as butter and receptive to re-sealing.
You can only do this once or twice however as the copper will stretch at each tightening and eventually will will be a loose fit on the banjo fitting.

During the preparation I machined the plastic part that holds the smaller spring also from stainless steel, and fitted this instead of the original. I assumed if the washers can crack so can the other plastic part. This failure will most likely not have complete abcense of brakes as a result but just for my own peace of mind.

my brake lights were stuck on....so i assume i innadvertantly adjusted the rod?

The normal cause of brake lights being stuck on is brake switch 'failure'.
Sometimes it does fail, but in addition there appears to be a ratchet mechanism inside the switch to give a measure of self-setting. If you push the plunger when the switch is dismounted you can destroy this setting.
To reset, pull the plunger out of the switch, then re-install the switch CAREFULLY, you will probably hear the ratchet move, either on installation, or the first time you move the pedal.


Is the brake rod adjustable?

Hey Martin, there is no adjustment in the rod. You need to reset the brake switch. Pull the plunger out, it's on a ratchet. install the switch and release the pedal slowly. This will reset the switch and allow normal functions of both brake lights and EAS.


How can I tell if its running on the backup brake system? Brake pedal is very hard.

Hi Ken, in my experience with these Wabco systems. I would say your RR is suffering from lack of maintenance(sorry). These braking systems require a full caliper flush every 12 months depending on usage. Of late every RR that I have worked on has had very average brake fluid in the system( dirty, discoloured and even water within the system). Most of these having full logs!!! It's really simple to flush the system and ensure fresh clean fluid is being circulated throughout the life of the car.
The backup system within the brakes is hydraulic, this means that if you have a complete electrical failure (no abs pump) you can still have reasonable brakes (hydrualic no pump assistance).

feckin hell, if thats edited.....

gavbriggs said:

feckin hell, if thats edited.....

Click to expand...

and that's just from the first 11 pages! didn't even bother reading the remaining 14!

anyhoo, frightening as that is and all, i was really hoping that someone on here might have some experience in the matter and be able to throw in alternative suggestions? no?

Curiously, car has been fine for two days.



EDIT: And ABS apparently works. Silly man on a bicycle is probably grateful. ound:

EDIT 2: Three years on I have finally had the dreaded modulator failure. But I'm far more confident about fixing it now plus the kit is now widely distributed, on eBay and others.