Icedmunkie Posted March 5, 2013 Share Posted March 5, 2013 Hi all Problem with a 1995 Classic 300Tdi manual, 179k on the clock Brake pedal is almost rock solid with very little movement and a delay in operation! The pump appears to chime in and out as it should. Am I right in thinking the accumulator is at fault? A local specialist suggested the module but some Googling of this has just added to my confusion. Over to you, people of LR4x4! Many thanks in advance Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted March 5, 2013 Share Posted March 5, 2013 The RRCs have very very little play in the pedal with a properly bled system, it may be that, if a new car to you, it is perfectly normal. Not sure what you mean by a delay in operation...? Quote Link to comment Share on other sites More sharing options...
Icedmunkie Posted March 5, 2013 Author Share Posted March 5, 2013 Thanks for the reply, I have driven plenty of ABS and earlier Classics and others and there is definately something amiss. By 'delay' I should have explained more clearly - you stamp on the brake and the pedal moves a fraction before the brakes apply. It's only a couple of seconds, but very disarming and obviously a fault somewhere. Or maybe it is just me! Quote Link to comment Share on other sites More sharing options...
duncmc Posted March 5, 2013 Share Posted March 5, 2013 I don't think it will be the accumulator causing a hard pedal, I would think a failed accumulator would leave the system pressure low, increased pedal travel and the pump running a lot/constantly trying to get to pressure. A hard pedal with a delay before brake application seems like either sticking valves in the modulator block, or maybe sticking pistons in the calipers? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted March 6, 2013 Share Posted March 6, 2013 Agreed, checked the caliper pistons for free movement/rust. Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 6, 2013 Share Posted March 6, 2013 Half of each front calliper is hydrostatic, not ABS/power brake, so if the vacuum pump on the engine block is not working, that would make the pedal very stiff as you will not have vacuum assistance. An accumulator issue could also cause problems. The accumulator should be charge with air initially, and only fluid filled once the system has pressurised. If the accumulator has been bled such that it is completely filled with fluid, with no head of air, then it will not function correctly - the ABS pump will run just for moments on start up, rather than for about 40 seconds, as the fluid is incompressible and thus pressurises instantly. This also means that there is no stored pressure, so the pump will cut in and out often, while the pedal remains firm because there is no system pressure for the power brakes. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted March 6, 2013 Share Posted March 6, 2013 I don't think there is a vacuum pump on an RRC, certainly not on the V8s, and no connection to the inlet manifold, all braking assistance is provided by the accumulator and pump. Quote Link to comment Share on other sites More sharing options...
duncmc Posted March 6, 2013 Share Posted March 6, 2013 The accumulator on the RRC system is filled with high pressure nitrogen gas. When bleeding the brakes as per the Landrover worhsop manual (which has to be followed to the letter for bleeding) all air is bled out of the accumulator. The pump then pressurises against the nitrogen like winding a spring up to provide a reservoir of pressure. On a normal system which has been released of pressure it takes 30-40 seconds to reach full pressure. There is only air in the accumulator when it needs bleeding, and normal should have NO air in. Sorry Snagger, but you are wrong there. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted March 6, 2013 Share Posted March 6, 2013 Picky point: The accumulator contains a flexible partition with nitrogen at ~2000PSI which is what the fluid is pumped up against, this then provides the assistance to the brakes. So no, no air but does contain a gas Quote Link to comment Share on other sites More sharing options...
duncmc Posted March 6, 2013 Share Posted March 6, 2013 Picky point: The accumulator contains a flexible partition with nitrogen at ~2000PSI which is what the fluid is pumped up against, this then provides the assistance to the brakes.So no, no air but does contain a gas Good point, didn't think along those lines.....and air is 78% Nitrogen.......... Quote Link to comment Share on other sites More sharing options...
task Posted March 6, 2013 Share Posted March 6, 2013 Do you get any vibration through the pedal? What fault codes are stored in the ECU? Do the lights operate correctly on the dash? Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 7, 2013 Share Posted March 7, 2013 Yes, there is a vacuum pump on the 300Tdi connected to the ABS valve block, and thank you Bowie for correcting me that it is nitrogen, not air, but affirming that the accumulator should have a gas precharge and that if lost, it will fail in the manner I described. If the power braking or vacuum servo are lost, the pedal will be very hard but should still move the calliper pistons. If the pistons are seized, then the pedal will be hard even with power and vacuum assistance. I suspect the accumulator - it explains the delayed application of the brakes as the pump catches up with demand placed on a failed accumulator. Check the calliper pistons first, though - accumulators aren't cheap and the system is a pain to bleed. Quote Link to comment Share on other sites More sharing options...
jad Posted March 7, 2013 Share Posted March 7, 2013 The pedal in my dads rrc doesnt move at all. The breaks are astounding though. If you break hard enough u will stall the engine and its an auto! The MOT guy didnt believe my dad till he went and tried if for himself. The ABS does only work once though and then then car has to be restarted to "re-arm" it.... Jad Quote Link to comment Share on other sites More sharing options...
Icedmunkie Posted March 7, 2013 Author Share Posted March 7, 2013 Thank you for all replies. There is no vibration through the pedal and I have not checked for fault codes - I will get this done though. The dash lights operate correctly. It does pull very slightly to the right when braking hard. I will whip the wheels off and investigate further. Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 7, 2013 Share Posted March 7, 2013 The calliper pistons are very prone to rusting and seizing. If this has occurred, and I would be suspicious of the left calliper if it is braking weakly on that side, then I'd recommend rebuilding the callipers with Zeus Engineering stainless pistons rather than buying new callipers - it'll be cheaper and last much longer. I have a calliper rebuild post on my blog which may be of help. The fact that the three amigos are behaving doesn't rule out an accumulator fault. It shows that you are getting valid wheel sensor inputs, that the pump is producing adequate pressure within 45 seconds of start up, and that there is enough fluid in the reservoir. There are probably other inputs, but I don't know what they are. I can tell you that there is not sensor within the accumulator, though - the system assumes it is at pump output pressure, so with no compressed gas charge, the accumulator pressure will drop off the moment the pedal is pressed. This would reactivate the pump, but because it has no gas head to compress, the pressure would be re-established extremely quickly, so the ECU check won't time-out and the warning lights will stay extinguished. It's just a possibility, though one you can test by repeatedly braking with the engine off and ignition on, listening for the pump activating momentarily after each application. But as I said before, look at the callipers first and replace the accumulator if a calliper rebuild doesn't cure the fault. Quote Link to comment Share on other sites More sharing options...
Icedmunkie Posted March 20, 2013 Author Share Posted March 20, 2013 Dear all A pair of rebuilt front calipers did the trick. Fresh MoT obtained. Thanks for all the replies. Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 21, 2013 Share Posted March 21, 2013 Well done. Quote Link to comment Share on other sites More sharing options...
duncmc Posted March 21, 2013 Share Posted March 21, 2013 Good news. Quote Link to comment Share on other sites More sharing options...
paintman Posted March 27, 2013 Share Posted March 27, 2013 I don't think there is a vacuum pump on an RRC, certainly not on the V8s, and no connection to the inlet manifold, all braking assistance is provided by the accumulator and pump. Earlier injected V8s - mine's a 1986 3.5 EFi - have a hose from the inlet manifold (ram housing) to the brake servo. No accumulator or pump. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted March 28, 2013 Share Posted March 28, 2013 Earlier injected V8s - mine's a 1986 3.5 EFi - have a hose from the inlet manifold (ram housing) to the brake servo. No accumulator or pump. Yes, the earlier V8s had servos, but then they didn't have ABS/pump/accumulator system at all, as the OP's is a 1995, it would have ABS and therefore pump/accumulator system. Quote Link to comment Share on other sites More sharing options...
paintman Posted March 30, 2013 Share Posted March 30, 2013 . Quote Link to comment Share on other sites More sharing options...
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