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RRC brakes and ABS


spiker3

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Hallo, I have just bought 1 1993 RR LSE overfinch that has been standing for about 2 years. The car seems to have a problem with its braking system. The brake pedal hardly moves and the ABS pump does not come on at all. I replaced the pads which were worn to nothing and pushed the pistons back in, this didnt help at all. If you drive at 20kph and push the brake pedal hard it takes quite a while to stop. Could it be that the pistons are seized due to standing for such a long time?

Is there a way that I can test the ABS pump to see if it working? if it isnt working could this be why the brakes are hard? I am hoping it is going to be an easy fix as I live in Botswana and in all my time here have only seen one other RRC, all the land rover spares workshops laugh when I ask for classic spares I even had a mechanic from the land rover dealer tell me he had never heard of a range rover classic and that I must have meant Range rover sport.

If anyone out there can help me get my dream car back on the road I would be very grateful.

Thanks

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Hi spiker3.

The fact that you manged to change the pads and push the pistons back in means that I don't think your calipers are seized.

I suspect that it may be your ABS modulator block (master cylinder) that has a seized valve or something in it. They don't apparently like being left unused for a long period of time.

If your pump was not running for some reason I think you would have pedal travel not a hard pedal. The pump has two wiring plugs. Unplug the one which is round and has two pins. Then just carefully apply 12V to the pins and it should run. I would probably disconnect the multiplug from the pressure to be on the safe side.

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Thanks alot.

If it is the ABS modulator block that has a seized valve, can I try to free it or do I need to get a new one? It is impossible to get RRC spares here in Botswana will one from a disco1 or P38 fit?

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I changed my ABS modulator block because it had a fluid leak into the drivers footwell. I bought the replacement from ebay. Could you not buy one and have it delivered in Botswana, excuse my ignorance of your country? For instance this will be the same as yours http://www.ebay.co.uk/itm/range-rover-classic-abs-system-v8-lse-/380430503358?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item58936ccdbe . The ABS modulator block is a pain to change but it is not difficult.

A Disco 1 master cylinder won't be the same. And although a P38 ABS block is made by the same company it would not be a direct swap, but you probably could get it to work if you used the pump and ecu as well.

First of all though I would check to see if the pump will run with direct 12 volts to it. It should run when you turn the ignition on.

Let us know how you get on.

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The pump should run for 30-45 seconds when you turn the ignition on after it has been stood a few hours. You need to find out if the pump has failed, it is lacking electrical power or the pressure switch on the side of the pump is faulty.

The RRC's system only uses hydrostatic pressure from the pedal on two of the four pistons in each front calliper - the other front pistons and all the rear pistons use pressure from the ABS pump. That means that you are currently using only half the front pistons and not getting any rear braking at all.

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Thanks for all your advice,

I unplugged the round plug from the pump and touched one of the pins with a wire connected to the positive terminal from the battery. I got a whirring sound which I assume is the pump working. It makes no sound at all when I turn on the ignition. I have already checked the 5A hydraulic pump relay fuse under the passenger seat and it is ok.

What is the next step in the chain of working out what the problem could be? I don't know if it is related or not but I noticed today whilst testing the pump that the brake lights seem to be on all the time.

Please keep up the good work trying to help me get the car back on the road, I d.ont have much of a clue myself

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Are you sure the pump was running? Could you feel it vibrating with 12V applied? Assuming it is;

Are you using a multimeter? I would also check for 12V being supplied to the pump in the other end of the 2 pin round plug that feeds the pump with the ignition on. I suspect that you won't have 12V if it runs when you give it 12V. So thats why I would check the fuses and relays next.

There should be 3 normal size fuses under the left hand front seat.

These are from the outside in to the centre;

One 5 amp fuse which is the hydraulic pump fuse.

A 5 amp fuse under the seat is the stop light switch, diagnostic plug and ECU pin 9 fuse.

And a Valve relay fuse. this is a 25amp white fuse.

There is also a green 30amp Maxi fuse. This is also another fuse for the hydraulic pump.

There will be 3 relays. One with a green base. This is the ABS warning light relay. A valve relay with a black base. And the pump relay with another black base next to the maxi fuse.

I would check the 30A green Maxi fuse. I would also check the white valve relay fuse. If those are ok, I would check the individual relays too to see if they work.

The brake lights operate from a simple switch attached to the pedal. Maybe it needs adjusting? Or is your pedal releasing properly?

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I forgot to mention it in the last post but the ABS light on the dashboard goes out as normal once the car is moving, does this mean the car thinks there is nothing wrong?

Yes. So the ecu and sensors are working. It also thinks that the hydraulic pump gets the system up to pressure.

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Had another look at the car this afternoon. All the fuses and relays under the passenger seat seem fine. I then checked the 2 pin round plug that feeds the pump. Running a wire from the battery to the pins definitely runs the pump. But putting a multimeter on the other side of the plug says that no power is getting to the plug.

Does this mean that there is a break somewhere between the fuse/relay and the plug/pump? Would running another wire from the brown/red wire at the fuse relay end direct to the brown/red wire at the plug to the pump be a good idea? This would show if there is a break in the original wiring if the pump works??? Or really confuse me if the pump still doesnt work.

Does anyone have any other suggestions or theories that I can check?

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I would probably check voltages at the relay(s) both on the low current signal side and the higher pump side. I would also take the relay out and check its operation with wires applying 12 V to the terminals that energise the relay. You should then hear it click and with the mulitmeter you should see continuity across the high current terminals. If that is ok and you are getting 12V into the relay, then there must be a problem with the wires to the pump. If you could test that with the multimeter I would do that, but that depends on how long your test leads are.

Just do one bit at once and work logically. Then see what that finds.

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Thanks for the advice duncmc,

I did some more testing to day and am still not sure if I am getting things right. Let me tell you what I checked.

I attached a wire from the battery to the pump both sides of the plug, the pump worked.

I attached a wire to the wire by the relays and to the wire by the pump. the pump did not work.

I attached a wire to the wire by the pump and checked continuity by touching that wire and the wire by the relays. Got a beep from the multimeter.

Checked the relays with the multimeter and ignition on. Numbers 30 and 86 have 12 volts 85 and 87 nothing. When I turn on the ignition the relays click.

From this my untrained brain says that the pump and two pin plug are ok, the pump runs wired straight from the battery. There is continuity from the wire coming from the relay and the wire going into the plug, so there cannot be a break i that wire. If I bypass this wire the pump still doesnt work. Therefore surely the fault must lay with the relays? 12 volts at connector 30 means power is getting to the relays but not getting past them. If they are clicking can they still be faulty?

I am thinking of buying two new relays next to see if that helps. Is there anything else I am missing or can check? I am not too sure what you mean about the low current signal and higher pump sides and which terminals energise the relays.

Once again thanks alot.

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Not to familiar with the classic system but just finished hot wiring a P38 system so it runs as a stand alone system and I assume they are basically similar.

If all the lights go out once the vehicle is moving then the ECU and wheel sensors must all be working.

On the P38 this would also indicate the pump had pumped the system up to pressure?.

There must be a pressure sensor somewhere in the system which feeds the relay to turn the pump on and off. If you can locate this it is likely to either have one wire which goes to earth or not when it gets too pressure or two wires which connect with or with out pressure.

Hopefully some one with more knowledge of the classic system will be able to say where the pressure sensor is and how it works i.e. to earth when up to pressure or to earth to switch the pump on.

This is then worth a check as to me it sounds like the pump etc is all working but the sensor is saying the pressure is up already so the pump doesn't need to turn on, hopefully this might be as simple as a loose or damaged wire if not it might be possible to splice in a sensor from another vehicle if no correct spares are available, not something I would normally recommend but could work in the short term.

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The pressure switch is on the pump! :)

Same for P38 and RRC, if you 'hot wire' it, and negate to include this pressure switch then your pump won't last long at all.

As far as I know there's no warning from the ABS system light to say it is up to pressure, as the light goes out after you reach 8mph, and the pump can run for as long as 30 secs before pressurising.

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It sounds to me like the pressure switch on the pump is stuck in the pressurised position, stopping the pump and telling the ECU that all is well - with no ABS pump pressure, the three brake warning lights (aka three amigos - the red "!", amber ETC and red ABS lights) should all be staying on. It's normal for these lights to be on for upto 45 seconds after switching the ignition on while the system pressurises, staying on if the pump takes longer than that even if full pressure is reached.

The pressure switch is the cylindrical attachment on the pump body, usually anodised in green, with the lead with the black plug. You may be able to fix it rather than replace it by carefully stripping it down and cleaning up the parts. There is a guide on this forum of how to rebuild the entire pump. Failing that, replacing it with a second hand unit might be the next best option - I don't know if the pressure switch is available separately from the pump, but a complete pump costs £800 (plus taxes) new in the UK, so god knows what it would cost you if you can get one!

Have a quick look in the Range Rover or FAQ section of my blog here: http://www.nickslandrover.co.uk/range-rover-brakes-abs-pump-replacement/ . That will give you a bit more information.

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Lets try for the third time! Yeah it posted this time.

As Bowie69 says most likely to be your relays.

Have a read of this it will help you understand what is happening...http://www.autoshop1...forms/hweb2.pdf

Then, if you unplug the relay you usually see a little wiring diagram on the side of it. With that you can work out which terminals should be doing what. With the ignition on you should have 12V to the signal side, across one thin wire and earth (the car body). You should also have 12V to one of the load terminals (fat wire). Next I would take the relay out, and test it one the bench. Put the multimeter across the signal terminals and you should have continuity. Then apply 12V to them, and with the multimeter across the load terminals you should see the continuity change, and feel it click.

If you don't have 12V to the relay on both the load and signal sides, then it may be a pressure switch fault. If the relay isn't doing as it should change it and try again.

If you have 12V to the load side and the relay works, but you don't have 12V to the pump motor plug then the wiring is faulty.

If you do need to check the pressure switch it is isn't too complicated. They are fairly tough, I dropped mine and it still works!

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Thanks guys. My last reply seems to have got lost, here goes again.

The 3 warning lights (3 amigos) go off once the car is started and driven, does this mean I have ABS pump pressure? Snagger your blog looks like it might be helpful.

duncmc, your advice to look at autoshop101 helped me check the relays properly, they all seem to be working properly. I did the two tests autoshop101 suggested and the results prove the 3 relays are fine. I also checked 12v to the load and signal side for the relays as you suggested. The two relays closest to the 30a fuse both had 12v, the first relay, the blue one, only had about 2v on the load side and nothing on control side. According to the relay though this is a normally closed relay as opposed to the other two normally open relays. Does this mean the pressure switch is at fault? I will check 12v to the pump tomorrow as it is dark outside now.

Thanks

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Thanks guys. My last reply seems to have got lost, here goes again.

The 3 warning lights (3 amigos) go off once the car is started and driven, does this mean I have ABS pump pressure? Snagger your blog looks like it might be helpful.

duncmc, your advice to look at autoshop101 helped me check the relays properly, they all seem to be working properly. I did the two tests autoshop101 suggested and the results prove the 3 relays are fine. I also checked 12v to the load and signal side for the relays as you suggested. The two relays closest to the 30a fuse both had 12v, the first relay, the blue one, only had about 2v on the load side and nothing on control side. According to the relay though this is a normally closed relay as opposed to the other two normally open relays. Does this mean the pressure switch is at fault? I will check 12v to the pump tomorrow as it is dark outside now.

Thanks

Great. Good results. And you are getting somewhere now. The fact the three lights go out does mean the ecu thinks the system is at pressure. That could be a faulty ecu, pressure switch, wiring or something else I don't know.

I'll check on mine tomorrow to see what I get on each relay as I am not 100% sure without checking, just to make sure we are talking about the same things. It could be the pressure switch, but when I have looked at mine and re-read your above post I will post back.

I will also see if you can test the pressure switch without unscrewing it which would be useful.

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Thanks guys. My last reply seems to have got lost, here goes again.

The 3 warning lights (3 amigos) go off once the car is started and driven, does this mean I have ABS pump pressure? Snagger your blog looks like it might be helpful.

duncmc, your advice to look at autoshop101 helped me check the relays properly, they all seem to be working properly. I did the two tests autoshop101 suggested and the results prove the 3 relays are fine. I also checked 12v to the load and signal side for the relays as you suggested. The two relays closest to the 30a fuse both had 12v, the first relay, the blue one, only had about 2v on the load side and nothing on control side. According to the relay though this is a normally closed relay as opposed to the other two normally open relays. Does this mean the pressure switch is at fault? I will check 12v to the pump tomorrow as it is dark outside now.

Thanks

The main brake warning light (hand brake and "!" ) should go out with the hand brake off only once the system is up to pressure - that red light has four triggers: the hand brake lever; pad wear sensors; the reservoir fluid level sensor; the ABS system pressure. As your pump is not activating, the system cannot be pressurised and so the ECU is receiving a faulty signal that the pressure is up. This is why your ABS (and ETC, if fitted) lights extinguish once the vehicle reached approximately 4mph (the self-test speed for the ABS wheel sensors) - the ABS light should remain lit if the pressure is low, a fault in the wheel sensors or ECU is detected. This false pressure signal is the reason that the relay for the pump is not being activated. If you do have ETC on the rear brakes (as mine does), then the yellow ETC light doesn't need motion to go out, but it still needs ABS system pressure, so again, if that light is going out after start, then there is something wrong with the pressure sensing circuit.

If you run a wire from the battery to the control terminal on the relay, the pump should activate, proving the relay and the pump wiring. This will isolate the fault to the pressure switch, its wiring to the ECU, the wiring from the ECU to the relay or the ECU its

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Loads of rain and no time to get out to see what voltages I had on my relay today I'm afraid. However this hopefully will help;

This is the pressure switch.

IMG_0796.jpg

Here you can see it screwed into the pump body. Note the 5-pin multiplug attached to it.

PIC_0001.jpg

The 5 pins

IMG_0798.jpg

To see if the pressure switch is faulty, unplug the 5-pin connector. Then looking at the wiring connector (not the bit on the switch above) so that you have got 2 pins on the top row and 3 on the bottom row, jump the pin top right to the bottom right pin, but don't bend the pins. If the pump runs then your pressure switch is faulty. Be careful if it does run, not to let it run for very long, as it will not stop as the pressure builds and that obviously could be very dangerous. Also check for continuity across the corresponding pins on the switch, low pressure it should be continuous. If having jumped those two pins it still doesn't run, then you are back to looking at the relays and wiring.

When I had my pump apart, I tested my switch with the multimeter by pushing the plunger in......quite difficult to do.

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