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1995-2002 Range Rover P38A
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Discussion Starter #1
Hi folks

Bit of a long shot here but I'll ask for idea's as my wife isn't sure whether it's safe for to drive home or not. I'm 4000 miles away and she's spending the weekend on a remote island!

Everything has been fine with the brakes until yesterday when my wife said the brake pedal suddenly felt like there was nothing there, needing pushed right down to stop. Luckily she was just manoeuvring for parking at the time.
When speaking today she said that initially it was still spongy, but it has come good and feels like it's back to normal. But we're still concerned about her driving home tomorrow, although it's not very far so she can go real slow (home is where the nearest garage is anyway).

There are no dash warnings (other than SRS from a previous error on my part)
She's checked for no obvious leaks at the calipers, pipes or drips underneath (pretty difficult for a non-mechanical person with a self oiling chassis P38 :lol:)
Fluid level good, possibly too high.
I asked her to run the engine, stroke the brake pedal a few times and listen for the pump cut in/running - difficult for her who doesn't know what to listen for so she doesn't think she can hear it. A new accumulator was fitted a few years ago.
New discs and pads were fitted all round about 2 years ago (probably why the fluid is on the high side, I guess the garage apprentice may not have thought to pull some out...)

I know spongy is often associated with air in the system, but if there's no obvious leaks and the fluid is full then is this likely? And if there was air then it wouldn't just go away and the pedal firm up? While not really knowing how the internals work on P38 brakes, I'm wondering if some sort of seal could have failed in the internals allowing fluid bypass?

I'm out of idea's, has anyone got any suggestions both for me to ask her to check, and also to check myself once I get back home?

Thanks
 

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1995-2002 Range Rover P38A
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If the master cylinder main piston seal is tired, it can allow fluid to bypass the plunger and give that "Peddle sinking to the floor feeling" This would happen with a gentle push on the brakes, whilst a short sharp push can cause a better seal.
Your call, of course, but if the brakes are basically ok, and the wife is comfortable with it..........
Perhaps, have her drive it around the car park for a half hour braking a lot and see if the issue can be replicated?
As for the pump running, it would get very hard to brake if it was not working.
Why do these things happen to the missus when we are really far away???
Good luck!
 

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1995-2002 Range Rover P38A
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Discussion Starter #3
Thanks for that Bolt, and apologies for the late reply.

The next day the brakes were all working fine so my wife managed to drive home with no issue, and I pretty much forgot all about it until now that I've got back home. I've had a look myself and there is an issue, but I'm pretty sure it's with the brake system not pressuring up, the spongy feeling my wife described is just the brakes with no hydraulic pressure assist, and it is quite unnerving being so weak.
So it's intermittent, when they're not working correctly there are the 3 warnings on the dash - ABS, Brake and TC. At this time I cannot get the brake motor to run/pressure up. It appears to be every other start this appears, but on a test drive today of about 5 miles when starting off with it not working, it then started working all by itself - the dash warnings cleared and full brake pressure again. When the brakes are feeling as they should be, they pressure up solid so unlikely to be any master cylinder seal bypass.

While I have not yet checked any diagrams etc. I checked in the engine bay fusebox for blown fuses, relay issue's and every thing looked ok (I'd previously resoldered most of the connections in the fusebox board after having noticed the tell tale burnings under relays) does anyone have any pointers of where I should start to try and figure this out? With it being an intermittent fault, I'm thinking of a corroded connection or something?
 

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1995-2002 Range Rover P38A
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Relay 2 is the ABS power relay but the pump is turned on by relay 17 which isn't a standard 5 pin relay but a dual contact, high power, relay to cope with the high current drawn by the pump. That would be my first suspect, after that, have a look at the connections to the pressure switch although there is always the possibility that it could be a failing pressure switch.
 

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1995-2002 Range Rover P38A
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The first thing I'd do is re bleed the system, follow rave on this, it's not like other cars where you can pick a corner and start, it must be done by the book, if your garage did it before, have you been lucky all this time ?. There's bleed nipples on the accumulator which have to be bled, you can't even see them, I cut my insulation away and push back in afterwards.. have a search and print off the bleed process,, you and the missus can do it no problem,,
 

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+1 on the relay....Then the connectors and pressure switch.
An intermittent pump is not a symptom that can by fixed by bleeding.
As was stated, the term "spongy" was mis applied. brakes themselves are fine.....Booster pump issue......
The other thing that it could be would be brushes in the pump motor.
At this point, you can check for this by waiting for it NOT to run and then giving the pump motor a short sharp rap with something (Hammer?) If it fires up, it indicates worn out or sticking brushes.
 

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Discussion Starter #7
Thanks for the suggestions

Although the brakes are probably overdue a fluid flush, I'll leave that bit alone for now as when the system works then it's all solid.

I've had another look, and with the above and further online reading I went out a bit more aware of the system and I think it's now sorted. I gave the pump a tap with hammer but no change, I wiggled the pressure switch connector but no change (never got to the point of disconnecting, I was just trying to figure how to release it) but then I thought I'd have another check of the fuses and relays. When I was starting to remove the black relay 17 the pump instantly cut in, so out/in/out/in and the pump keeps pumping as it should. I somehow missed that relay yesterday so I'm thinking as it cut in the second I started pulling on it then it is likely to have been a dirty connection, probably on the coil terminals (with main contacts being parallel double pole - would've needed both poles to have been dirty). Anyway I have a spare complete fuse box so replaced the relay with the spare, sprayed some contact cleaner about it and everything seems to work fine now.

Thanks again for the suggestions, and I'll be taking care when driving until I get confidence back that it's sorted - it really is quite scary applying the brakes to find there's very little there.
 

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Discussion Starter #8
Arghh, wrote too soon...first drive after writing the above then I got the dash warnings then after several brakings I lost pressure again.

So I'm now hunting for some info on the pressure switch wiring, like what terminals to link to turn on the pump. There are 5 pins so which to check?
 

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It's all in the ETM, but one of the more irritating things is when people just advise to "Download RAVE", so I'll put up a pic to get you started:
abs.JPG
HTH
 

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Discussion Starter #10
Thats great, thank you. I do have a copy of Rave but it's been a while, and from memory I needed to use it on Windows XP which I was scratching my head a bit wondering how I'd get a copy of that loaded again.

So with that diagram I figured the pins and then linked 5 & 2 (it might have been 1 & 2 but I never bothered narrowing the grounds down as either was good for this purpose)

And for future help for anyone (or myself) then below is the pin layout - linking the top 2 brought the relay in which switched my pump on and off. So now it's looking like I need a new switch.

Many thanks once again everyone

Brake Pressure Switch.jpg
 

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I do have a copy of Rave but it's been a while, and from memory I needed to use it on Windows XP which I was scratching my head a bit wondering how I'd get a copy of that loaded again.
That's only the full install versions with ancient Acrobat plug ins. The version of RAVE in the FAQ stickie runs on any platform that supports any version of Adobe Acrobat. Yes, that includes Apple products and Android. It also includes Classic, L322 and Discos. The only thing not included are the accessories manual which most people never need. However since you have the full version you can browse to the accessories manual and still view it on newer version of acrobat. You just won;t have interactive abilities with the menu.
 

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Discussion Starter #13
Thanks for that part number and links, I'm in no hurry so I've ordered it from the US for £143 including post and import duty/charges, so should be here in a week or so.

I found the link for the PDF RAVE in the FAQ's, but the link just says error establishing a database connection. I'll try again over the next days incase it's just a temporary error.

Thanks once again folks.
 
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