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Low Brake Pressure at Startup

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Old Aug 30, 2012 | 08:43 AM
  #1  
jmason's Avatar
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Mudding
Joined: Aug 2011
Posts: 110
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From: Toronto, Ontario, Canada
Default Low Brake Pressure at Startup

Hi All,

Quick question. Starting yesterday, I noticed something when I first started my vehicle. I park on a slanted driveway, with the front of the car higher than the rear. As I was reversing down the driveway, I went to slow down to check if the other car's doors were locked. I realized that the vehicle wasn't really stopping (but slowing), and then I noticed my brake pedal was nearly fully depressed. I continued to hold the brakes until the vehicle was stopped, threw it in park, and let go of the brakes. After putting it back in reverse at the bottom of the driveway, everything worked properly again. I drove the rest of the day, and the brakes worked seemingly normally.

As I reversed out of the drive again today, I felt like the brakes were again not as powerful as they usually are. Maybe it was just in my head, but I'm pretty sure they weren't working as properly. It almost felt like the brakes weren't warmed up properly, but after a couple jabs to the brakes, things started to work the way they should.

A bit of background, I installed new rotors and pads earlier this summer. Additionally, I had it all apart a week or so ago when installing my new diffs. Could these indicate anything else?

Does this sound like an accumulator or pump, or is this just a quirk of the vehicle?

Thanks,

John
 
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Old Aug 30, 2012 | 03:56 PM
  #2  
strongdynamics's Avatar
6th Gear
Joined: Aug 2012
Posts: 6
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From: Kansas City, MO
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I have lived with this "quirk" for about 2 years now. I'm pretty sure it has to do with air in the lines and the ABS system. It is probably worth taking it to an independent shop and have them bleed them one more time with a machine if you know what I mean. I think I will do the same. I guess I've just gotten use to it.
 
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Old Aug 30, 2012 | 04:13 PM
  #3  
Hinnadr's Avatar
1st Gear
Joined: Aug 2012
Posts: 1
Likes: 0
Default Discovery 1994

Hi I am looking for a manuel for this jeep a 3900cc i specially need the brake system just got a new master cyclinder kit and realized that couple of the leads on the old one are off. so need them check thourghly before cruising
thanks
 
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Old Aug 30, 2012 | 05:31 PM
  #4  
Savannah Buzz's Avatar
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Joined: Jan 2011
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From: Savannah Georgia
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Land Rover Manuals

and links to RAVE (factory shop manual) in my signature. Should cover all the bases. I think the 95 and 94 are very similar.
 
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Old Aug 31, 2012 | 07:26 AM
  #5  
04duxlr's Avatar
Pro Wrench
Joined: Nov 2011
Posts: 1,462
Likes: 32
From: Duxbury MA
Default

Originally Posted by jmason
Hi All,

Quick question. Starting yesterday, I noticed something when I first started my vehicle. I park on a slanted driveway, with the front of the car higher than the rear. As I was reversing down the driveway, I went to slow down to check if the other car's doors were locked. I realized that the vehicle wasn't really stopping (but slowing), and then I noticed my brake pedal was nearly fully depressed. I continued to hold the brakes until the vehicle was stopped, threw it in park, and let go of the brakes. After putting it back in reverse at the bottom of the driveway, everything worked properly again. I drove the rest of the day, and the brakes worked seemingly normally.

As I reversed out of the drive again today, I felt like the brakes were again not as powerful as they usually are. Maybe it was just in my head, but I'm pretty sure they weren't working as properly. It almost felt like the brakes weren't warmed up properly, but after a couple jabs to the brakes, things started to work the way they should.

A bit of background, I installed new rotors and pads earlier this summer. Additionally, I had it all apart a week or so ago when installing my new diffs. Could these indicate anything else?

Does this sound like an accumulator or pump, or is this just a quirk of the vehicle?

Thanks,

John
Not a quirk. You likely need a new accumulator. The brakes in a P38 are pretty amazing when they work correctly. They store fluid pressure against a nitrogen charged bladder. When you press the pedal, the stored pressure activates the brakes. This system also alows the traction control to work very quickly as you don't need to wait for a pump to build up pressure to clamp the caliper at the spinning wheel. In the later years of the P38 with the 4 channel system, the traction control system is practically like having lockers.

Your ABS pump should build full pressure in maybe 45 seconds after startup, with the system developing enough pressure to work the brakes in about 15 seconds. If the ABS pump runs more than 5 or 10 seconds every time you use the brakes, that is another indicator. Check the link I posted on the other forum for diagnosis and repair tips. Also, you should change out the ABS relay while you are at it.
 
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