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Discussion Starter #1
My pedal needs to be mashed to stop the truck....what can I do? The front rotors have a lip but pads are great on both front and rear. If i dont keep my foot pressed hard on the brake pedal at a light, the truck begins to move forward little by little. Fluid seems ok.
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

an enormous vacuum leak will cause loss of power to your brake booster. Also will generate check engine light.
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

Although I have no idea about the real cause, I'm pretty sure it's not caused by a vacuum leak!
The brake servo on a P38a isn't operated by a vacuum booster, but by a high pressure abs pump.

Does your brake pump run at start up/after some pedal presses (you can feel if it runs by touching the black ball next to the EAS box)?

Maybe air in the system, if it is you'll hear a ticking sound from the ABS pump if it's running.

Sigi
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

afox04 said:
My pedal needs to be mashed to stop the truck....what can I do? The front rotors have a lip but pads are great on both front and rear. If i dont keep my foot pressed hard on the brake pedal at a light, the truck begins to move forward little by little. Fluid seems ok.
This is one of those times when you take it to a professional. While there may be a number of causes, if you need to ask here then it's time to put safety before DIY. BTW why are you still driving it !!

Harsh, yes but at 4600lbs you gotta have them brakes at 100%.
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

I think its the abs pump based on the description, but as previously stated it could be a number of things. Are there any faults displaying on the information display? And are the three lights "abs, traction, brake" lights displaying on the dash board?
 

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Discussion Starter #7
Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

Funny you should mention the ticking sound it totally happens a lot when running. The triple lights r only on at startup and shortly dissapear. The abs light does stay lit until I hit about ten mph it seems.

This might be q dumb question but do we have a forum post on how to bleed the brakes? I vaguely recall it to be a process.
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

The bleeding process is described in RAVE and on the main page.

Did the ticking sound appear suddenly?

Maybe your accumulator is bad and has flooded the brake system with nitrogen (ask me how I know...)?
Do you know if it was ever replaced?

Sigi
 

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Discussion Starter #9
Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

I found the process here actually. rangerovers.net/maintenance/brakebleed4.html
I don't think accumulator is bad only BC it went on my old one and what happened was that in am the pedal was to the floor and the first time I troed to brake it wasn't working well.

In guessing the last person didn't bleed properly when they changed fluids.
I'm going to do this this weekend. Anyone know if I can bleed calipers without tires off?
If anyone has any other info or advice please post.
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

munichp38a said:
Although I have no idea about the real cause, I'm pretty sure it's not caused by a vacuum leak!
The brake servo on a P38a isn't operated by a vacuum booster, but by a high pressure abs pump.

Does your brake pump run at start up/after some pedal presses (you can feel if it runs by touching the black ball next to the EAS box)?

Maybe air in the system, if it is you'll hear a ticking sound from the ABS pump if it's running.

Sigi

You're right. I was working on another truck recently and the brake booster was powered by the vacuum system of the intake. Had it in my brain.

Probably just a bleeding issue.
 

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Discussion Starter #12
Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

I think the symptoms are different for the modulator, the 3 amigos on the dash light up. let's hope a successful bleed will fix it.

Stay tuned! :)
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

afox04 said:
I think the symptoms are different for the modulator, the 3 amigos on the dash light up. let's hope a successful bleed will fix it.

Stay tuned! :)
thought the 3 lights was the accumulator?
 

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Discussion Starter #14
Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

i thought that's what he said. must have misread. then what's the symptom of a bad modulator?
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

Just as an fyi. The lip on the rotors is the same for ours. AFAIK this is standard oem practice. I have also seen it on some ford lincolns I believe. I have not seem an aftermarket rotor with this lip. My guess is that it may keep a little more crud or rainwater out of the pad contact area. So it is very unlikely that your rotor is so badly worn to cause this lip. Other slight possibility is the chance that caliper pins are frozen/seized. Also as a quick check , release front bleed screw on brake booster and see if air comes out. Then close, of course. This returned my brakes to normal. Not meant to be a cure, but a start. Good luck.
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

The three lights coming on at startup and switching off after a few seconds (abs light will switch off after you've reached 5 or 6 mph once) is the normal behaviour.

When they come on when you're braking/braking hard you have a bad accumulator (black ball on top of the pump).
To clarify, the modulator is the big metal block with all the brake pipes going into it and the reservoir on top of it.

Sigi
 

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Discussion Starter #17
Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

munichp38a said:
The three lights coming on at startup and switching off after a few seconds (abs light will switch off after you've reached 5 or 6 mph once) is the normal behaviour.

When they come on when you're braking/braking hard you have a bad accumulator (black ball on top of the pump).
To clarify, the modulator is the big metal block with all the brake pipes going into it and the reservoir on top of it.

Sigi
Righto sigi. What are symptoms of a bad modulator? I had a bad accumulator on my last one and those were the symptoms.
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

diff said:
Just as an fyi. The lip on the rotors is the same for ours. AFAIK this is standard oem practice. I have also seen it on some ford lincolns I believe. I have not seem an aftermarket rotor with this lip. My guess is that it may keep a little more crud or rainwater out of the pad contact area. So it is very unlikely that your rotor is so badly worn to cause this lip. Other slight possibility is the chance that caliper pins are frozen/seized. Also as a quick check , release front bleed screw on brake booster and see if air comes out. Then close, of course. This returned my brakes to normal. Not meant to be a cure, but a start. Good luck.
my guess is a dangerous statement when it concerns brakes, no guessing here on brakes, lip on rotors means they are wearing and all disc's are marked with a min thickness allowable for safe use
 

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Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

The only modulator failure scenario I know of is failure of some internal plastic parts, leading to complete brake failure, but as you are still able to stop it this doesn't seem to be the case, especially since you have a lot of air in your brakes.

If you want to be scared, read this thread about this topic: viewtopic.php?f=3&t=23569

Try bleeding it first and hope that this will fix it.
But then there's the question where the air came from, if it happened suddenly...

Sigi
 

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Discussion Starter #20
Re: Brake pedal needs to be MASHED to stop truck/keep it stopped

Okay all. My old friend the Land Rover dealership shop foreman did me a favor and said there is no sponginess in my brakes. They are good, but he said they do kinda require a little more foot pressure to keep it stopped at a light without slowly lurching forward. HOWEVER....

He did say that the abs PUMP was cycling about every third pedal press. The accumulator is good, but I'm thinking about rebuilding it anyway because I have to take the accumulator off...I thought it was the EAS compressor...not so much... Here's the symptom for future people having this problem and successfully using the wonderful search function on our beloved forum: You hear the pump turning on after you press the pedal. he said you know it has to get replaced when it turns on every time you press the pedal. I'm about to look for replacement instructions.
 
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