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Discussion Starter #1
If I am using the breaks quite strong, for whatever reason, the next breaking action gives a very strange reaction to the pedal : it goes almost to the metal so to speak, and it feels like there is a leak in one of the fluid lines. But, this is not the case and my garage says that it may be caused by some ABS related thing.

Hoewever, since I plan to go the the Alps next spring, I don't like this scary feeling of the breaks .
Is this a normal thing ? What is your experience ?
 

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That's not the way the system should work. What year is your Murano? I find myself wondering if you have a problem with the power brake (note spelling) booster. Perhaps applying the brakes is depleting the vacuum assist, and on the next application there is less assist available. In a hydraulic brake system, that could be either a faulty check valve that is not holding vacuum, or a bad brake power booster.
 

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If I am using the breaks quite strong, for whatever reason, the next breaking action gives a very strange reaction to the pedal : it goes almost to the metal so to speak, and it feels like there is a leak in one of the fluid lines. But, this is not the case and my garage says that it may be caused by some ABS related thing.

Hoewever, since I plan to go the the Alps next spring, I don't like this scary feeling of the breaks .
Is this a normal thing ? What is your experience ?
When you say you're using the brakes "quite strong" do you mean you are pressing them so hard that the ABS system is actually engaging (e.g. do you feel vibration in the brake pedal)? When you're not doing hard braking, do they otherwise feel normal in every day driving?
 

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Discussion Starter #6
Some twop years ago I had to brake hard and the ABS system engaged, so the car sort of stuttered and it was noticable in the pedal. But now, without engaging the ABS, I had to brak a little strong and arriving at my house and just slightly braking to get the car to a normal and calm stop the pedal was down the floor, although in the end there was a braking activity. Normally there was no problem whatsoever, but today it gave me a little scare .
 

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Discussion Starter #7
That's not the way the system should work. What year is your Murano? I find myself wondering if you have a problem with the power brake (note spelling) booster. Perhaps applying the brakes is depleting the vacuum assist, and on the next application there is less assist available. In a hydraulic brake system, that could be either a faulty check valve that is not holding vacuum, or a bad brake power booster.
THis is waht it seems, that the vacuum assist is depleted . Is there an easy way to check ?
 

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Some twop years ago I had to brake hard and the ABS system engaged, so the car sort of stuttered and it was noticable in the pedal. But now, without engaging the ABS, I had to brak a little strong and arriving at my house and just slightly braking to get the car to a normal and calm stop the pedal was down the floor, although in the end there was a braking activity. Normally there was no problem whatsoever, but today it gave me a little scare .
Is this just one incident with your foot going down to the floor or this is how the car is always acting now? Either way, this is not normal as the brake pedal should not drop low like that. If the ABS unit was causing this, I would think it likely a fault code would be thrown and the ABS light on the instrument panel would come on.

BTW...this happened today? You seemed to suggest in your first post that your mechanic inspected the brake system after this event?
 

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THis is waht it seems, that the vacuum assist is depleted . Is there an easy way to check ?
Yes. The tests for the brake booster are simple. See the attached PDF file. Let us know the results.
 

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Discussion Starter #10
Is this just one incident with your foot going down to the floor or this is how the car is always acting now? Either way, this is not normal as the brake pedal should not drop low like that. If the ABS unit was causing this, I would think it likely a fault code would be thrown and the ABS light on the instrument panel would come on.

BTW...this happened today? You seemed to suggest in your first post that your mechanic inspected the brake system after this event?
This happened today, the other time i went tot the garage and the mechanic gold me nog tot worry and that's IT would return tot normal , and it dus. So i was surprised to experience this today again
 

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Discussion Starter #12
Yes. The tests for the brake booster are simple. See the attached PDF file. Let us know the results.
THis morning I checked as per the schedule. First part of the operation was that in order to start I pressed the pedal which was deeper than normal The starting was okay and the pedal felt okay. Then the next test was as the test predicted, the clearance between a, b,and c was that the pedal came up and felt solid. . The next part was that after the start , so pedal pressed ( otherwise there is no start) , so I let the engine run for some time, and then, with the pedal pressed down I stopped the engine and the pedal remained in the same position. So, i took the car for a small spin around the block, and again when breaking the pedal just could go down to the floor , whilst braking slightly. So in fact the test seemed okay, but the problem remains. Any advice for a next step ?
 

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Sound like either the master cylinder needs to be replaced (Most likely, due to your description.) or you have an issue with the ABS (Unlikely).

The master cylinder has two systems, one for two tires and one for the other two tires. When one of the systems fails, the pedal will go almost to the floor before the other system engages the brakes.

From what I'm understanding from your posts that this is what has been happening. Applying the brakes hard enough to engage the ABS does put an extra strain on the master cylinder. When the ABS engages, the system actually cuts the master cylinder out of the system while it's engaged. Standing on the brake pedal while the ABS is engaged puts abnormal pressure on the master cylinder, potentially causing a partial failure down the road.

Good luck.

Have a good day.

PS When replacing the master brake cylinder, the brake system will need to be fully and properly bleed of air. Failure to fully remove the air will effect braking and could cause damage to the ABS unit if air is trapped in it. You will need at least 2 Qt. of DOT3 brake fluid for a full flush and bleed.
 

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Discussion Starter #15
Sound like either the master cylinder needs to be replaced (Most likely, due to your description.) or you have an issue with the ABS (Unlikely).

The master cylinder has two systems, one for two tires and one for the other two tires. When one of the systems fails, the pedal will go almost to the floor before the other system engages the brakes.

From what I'm understanding from your posts that this is what has been happening. Applying the brakes hard enough to engage the ABS does put an extra strain on the master cylinder. When the ABS engages, the system actually cuts the master cylinder out of the system while it's engaged. Standing on the brake pedal while the ABS is engaged puts abnormal pressure on the master cylinder, potentially causing a partial failure down the road.

Good luck.

Have a good day.

PS When replacing the master brake cylinder, the brake system will need to be fully and properly bleed of air. Failure to fully remove the air will effect braking and could cause damage to the ABS unit if air is trapped in it. You will need at least 2 Qt. of DOT3 brake fluid for a full flush and bleed.
In Europe prices for Nissan MUrano parts are extremely high, so it would be nice to know befoerhand if it is reallt the master cylinder. Is there a method to check and/or can the cylinder be repaired ? ( Just idea : from a non-Nissan supplier the cylinder costs around 200 euro, at the dealership it will be at least 300 euro)


It seems a bit strange that with my Murano having done 80.000 miles only such a part could die .
 

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Agree. It does sound like a problem with the master cylinder. If you put the car up on jack stands (all 4 wheels) with parking brake disengaged, you can test this if you have someone to help you. Have them press the brakes and go to each wheel and see if you can turn it (you should not be able to). The master cylinder has two pistons that each provide hydraulic pressure to two wheels as PaulDay stated--one front and one rear on the opposite side (e.g. left front/right rear and right front/left rear). So, if you can turn one front wheel and one rear wheel on the opposite side of the car then one of those pistons has failed.

If this is all too much then take the car to your mechanic, but I recommend towing it since it's not safe to drive in that condition.

Good luck and let us know what the final outcome is.
 

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Discussion Starter #17
Agree. It does sound like a problem with the master cylinder. If you put the car up on jack stands (all 4 wheels) with parking brake disengaged, you can test this if you have someone to help you. Have them press the brakes and go to each wheel and see if you can turn it (you should not be able to). The master cylinder has two pistons that each provide hydraulic pressure to two wheels as PaulDay stated--one front and one rear on the opposite side (e.g. left front/right rear and right front/left rear). So, if you can turn one front wheel and one rear wheel on the opposite side of the car then one of those pistons has failed.

If this is all too much then take the car to your mechanic, but I recommend towing it since it's not safe to drive in that condition.

Good luck and let us know what the final outcome is.
Thanks . Ik will see the mechanic next monday !
 

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Discussion Starter #18
Strangely enough this morning i chechrd again during a short round around the block and no problem!!!! Anyway, i Will Go and check with the dealership tomorrow. But is there no valve OR do that's will arrange the pressure , as per the previous suggestion ? Ik mean with the Brake booster ? If this may be blocked and needs cleaning ?
 

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Was it cooler this morning then during the day when you went for the drive? A worn master cylinder seal can still hold pressure under certain conditions, like when it's cooler then when the problem normally appears.

Try running in the heat of day and if it's cool where you are, let the car heat up before driving.

Good luck.

Have a good day.
 

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Discussion Starter #20
Temperaturen here is around 10 tot 15 Celsius, and around 8 during the nicht. Anyway, i Will have the m vhamic check, and before honing i Will do Dome emergency stops tot see what happens.
 
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