P38 Brake Query

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PAW

New Member
Posts
5
Hi,

This is my first posting, and I would be grateful for any advise on a brake problem I am encountering.

I have recently purchased my first Range Rover, a 1997 P38 4.6 HSE auto.

The problem seems to be an intermittent one with no real pattern.

On starting the vehicle, even after a short stoppage, the brake system takes approximately 20 to 30 seconds to achieve full hydaraulic pressure and is ready to drive. Generally the TC instrument light on the dash extinguishes to indicate its ready, however the ABS light remains on until the vehicle exceeds approx 4 mph. (If the brake is applied before the hydraulic pressure is reached, there is excessive pedal travel with virtually no braking force).

Subsequently when driving along, (at both low and higher speeds), and the brake pedal is applied the ABS and TC lights flash on for approximately half a second. However this is intermittent and seems to have no relationship to length of journey, speed or applied braking force. Additionally, but again intermittent, the level of force required on the brake pedal seems to change as does the brake pedal travel.

Any advise would be much appreciated.

Many thanks,

PAW
 
First of all change accumulator see if that sorts problem, i am 99% sure it will. It is normal for ABS light to stay on until vehicle reaches approx 7mph.
 
Further to the above, don't be conned by the rip-off merchants on e-Bay who seem to want at least £150+ for a new accumulator or £100 for a second-hand "tested" one.

Big bug-bear of mine is the incessant inflation of prices for almost everything Range Rover related on eBay...still the sellers wouldn't do it if people didn't buy at those prices...

The major LR specialists do brand new ones for rather a lot less; Island 4X4's website show new Wabco (ie. OEM) ones for £90 and IIRC Paddocks were very similar.

I've got a similar issue and plan on doing mine shortly; and have been doing my homework. Conveniently Island 4x4 are pretty close to me so I even save the postage costs!

Malcolm
 
Many thanks to everyone for their advise so far.

I've just placed an order with Island 4x4 for a new accumulator.

Hopefully I will be able to fit it this weekend, and I'll let you know if it cured the problem.
 
Is this part normal? It happen to me when the car is stop over night. But I don't have any indication of malfunction.
(If the brake is applied before the hydraulic pressure is reached, there is excessive pedal travel with virtually no braking force).
 
jlsplinter said:
Is this part normal? It happen to me when the car is stop over night. But I don't have any indication of malfunction.
(If the brake is applied before the hydraulic pressure is reached, there is excessive pedal travel with virtually no braking force).
Click to expand...

get it fixed
 
jlsplinter

power assisted brakes. On virtually every other car or van on the market the 'power assist' comes from the engine. On a Rangie there is a separate pump that fills a reservoir of compressed air (accumulator. Your system is leaking and overnight has enough time to empty. The accumulator is the sensible place to start but do it soon because if you really need your brakes whilst driving, on a long downhill road for example, your pump might not be able to keep up with demand and you might run out of brakes.


Quick story -
Had a weird fault with Merc van about 15 years ago and a few of the drivers refused to drive it as they said that the brakes faded away. Had it checked by Merc dealers - no fault found, checked by Merc national engineer from H.O. - no fault found, checked at a Ministry commercial testing station - no fault found.
Then one poor lad, driving through Bristol thumped into the back of large saloon, hard. He said that he'd run out of brakes but also that the bloke in the car was refusing to exchange details so my lad had called the cops. Two bobbies turned up but the 'other' driver refused to speak to them. Then a sargeant, then an inspector, then some bloke with scrambled egg all over his cap. Meanwhile my lad was being kept well away by the bobbies. Then two very well dressed gents arrived in a big Audi, my lad's details were taken and he was told to go away! We found out later, from our insurers, that the car he'd concertina-ed belonged to a "government agency" and was a covert surveillance vehicle and the boot was stuffed with the kit. Without the car the insurance claim was for over £70,000.

As I was responsible for the vehicles and the driver I had the van towed to an old mechanic friend of mine and explained the situation. He found the pinhole leak in the brake servo that would cause the brakes to fade away with frequent use. By the time my company and the insurers were finished Merc got a VERY large bill.
 
dogsbody said:
jlsplinter

power assisted brakes. On virtually every other car or van on the market the 'power assist' comes from the engine. On a Rangie there is a separate pump that fills a reservoir of compressed air (accumulator. Your system is leaking and overnight has enough time to empty. The accumulator is the sensible place to start but do it soon because if you really need your brakes whilst driving, on a long downhill road for example, your pump might not be able to keep up with demand and you might run out of brakes.


Quick story -
Had a weird fault with Merc van about 15 years ago and a few of the drivers refused to drive it as they said that the brakes faded away. Had it checked by Merc dealers - no fault found, checked by Merc national engineer from H.O. - no fault found, checked at a Ministry commercial testing station - no fault found.
Then one poor lad, driving through Bristol thumped into the back of large saloon, hard. He said that he'd run out of brakes but also that the bloke in the car was refusing to exchange details so my lad had called the cops. Two bobbies turned up but the 'other' driver refused to speak to them. Then a sargeant, then an inspector, then some bloke with scrambled egg all over his cap. Meanwhile my lad was being kept well away by the bobbies. Then two very well dressed gents arrived in a big Audi, my lad's details were taken and he was told to go away! We found out later, from our insurers, that the car he'd concertina-ed belonged to a "government agency" and was a covert surveillance vehicle and the boot was stuffed with the kit. Without the car the insurance claim was for over £70,000.

As I was responsible for the vehicles and the driver I had the van towed to an old mechanic friend of mine and explained the situation. He found the pinhole leak in the brake servo that would cause the brakes to fade away with frequent use. By the time my company and the insurers were finished Merc got a VERY large bill.
Click to expand...

Really do think you need to read up on accumulator powered braking systems. Range Rover brakes don't use air at any stage of operation. That would be an air over hydraulic system. Range Rovers use a pure pressurised fluid system.
 
wammers said:
Really do think you need to read up on accumulator powered braking systems. Range Rover brakes don't use air at any stage of operation. That would be an air over hydraulic system. Range Rovers use a pure pressurised fluid system.
Click to expand...


Good story though...... And I suppose its prudent to point out that the pressure accumulation is via the medium of compressed nitrogen in the accumulator.
 
PAW said:
Hi,

This is my first posting, and I would be grateful for any advise on a brake problem I am encountering.

I have recently purchased my first Range Rover, a 1997 P38 4.6 HSE auto.

The problem seems to be an intermittent one with no real pattern.

On starting the vehicle, even after a short stoppage, the brake system takes approximately 20 to 30 seconds to achieve full hydaraulic pressure and is ready to drive. Generally the TC instrument light on the dash extinguishes to indicate its ready, however the ABS light remains on until the vehicle exceeds approx 4 mph. (If the brake is applied before the hydraulic pressure is reached, there is excessive pedal travel with virtually no braking force).

Subsequently when driving along, (at both low and higher speeds), and the brake pedal is applied the ABS and TC lights flash on for approximately half a second. However this is intermittent and seems to have no relationship to length of journey, speed or applied braking force. Additionally, but again intermittent, the level of force required on the brake pedal seems to change as does the brake pedal travel.

Any advise would be much appreciated.

Many thanks,

PAW
Click to expand...


PAW i was having exactly same problem as you,all the same symptoms and indications, after looking on here for help most people pointed to the accumulator, however i took it to garage for a check up and on intensive investigation it turned out to be the ABS pump switch, main dealer price £238 + VAT!!!! they are not repairable either, i bought a tested second hand unit- pump, switch and accumulator for £250, had it fitted and now all works as itis supposed to, i would have been pretty peed off forking out for an accumulator for it not to fix problem- itmay be worth getting it checked on a fault reader before spending any more dosh.
 
rewmer said:
Good story though...... And I suppose its prudent to point out that the pressure accumulation is via the medium of compressed nitrogen in the accumulator.
Click to expand...

Yes indeed, compressed Nitrogen inside a rubber ball. And fluid is pumped in against this pressure to form a reservoir of pressurised fluid for use by the master cylinder/ABS modulator. Quit where he gets air from i do not know.
 
Get it sorted ASAP, I left mine to late, then the ABS booster pump went, cost me an arm an leg because it's all link together.

Len :cool:
________________

1998 4.6 HSE
 
if you want to see if it is the accumulator you can hear the pump running sounds like a servo for the airvents but press the brake peda land pump will run let go press again pump will run you hear it every time you brake thats what mine was doing replaced accumulator and problem solved
 
Thanks to all.

Can anyone write here the normal behavior of the pump? Shouldn't it pump every time I brake to be sure it have enough pressure?
 
Last edited:
jlsplinter said:
Thanks to all.

Can anyone write here the normal behavior of the pump? Shouldn't it pump every time I brake to be sure it have enough pressure?
Click to expand...

No it should not. How often the pump comes on in a healthy system depends on brake application. It takes upwards of thrity brake applications with pump off to deplete the pressure supply. Fluid is stored at 170 bar 2466 psi. If you brake gently not much pressure is lost from the accumulator. If the ABS operates then a lot of pressure will be lost. But no way under normal conditions should the pump come on everytime you brake. Only when the pressure drops below a minima does the pump actuate. If the pump comes on everytime the brake is applied it is a sure sign that the nitrogen charge is low. The accumulator is charged at 80 bar 1160 psi with nitrogen. Minimum nitrogen charge below which sphere must be changed is 50 bar 735 psi.
 
jlsplinter said:
Great info. Thanks a lot. I'll be looking to replace that accumulator then.
Click to expand...

If anybody needs an accumulator they can have it for the price of the postage : no guarantees. I replaced one in a step by step attempt to fix my ABS problem ( it turned out to be the pressure switch.) can't remember where I acquired the second one but I don't think either is absolutely decesased but I wouldn't want to sell them claiming to be effective.
 
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