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10th October 2017, 05:11 PM
#1
Hard Pedal - Poor Brakes
Hi All
I've got a GQ patrol with terrible brakes. The pedal is very hard, but the braking performance is way below acceptable. It doesn't seem hydraulic as the pedal is nice and firm and doesnt sink to the floor if you keep your foot on it.
If I do press really hard, it will pull up, but the front left consistently locks. I do have to try hard to get that to happen.
I've tested the booster by pressing the pedal and than turning on the engine. I can feel the booster working and pulling the pedal down further. Aso if I turn it off and wait a minute I can feel the booster work and after a few pedal pumps the vacuum assist is gone.
So...any ideas what it could be. The discs and pads do need replacing, but I would of expected better brakes than that.
cheers
Damo
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10th October 2017 05:11 PM
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10th October 2017, 06:23 PM
#2
Legendary
How do you know front left consistently locks?
I have trouble processing brake pedal being very hard and being nice and firm at the same time.
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10th October 2017, 06:30 PM
#3
I am wondering about piston condition in the calipers - are these free to move? Maybe you have checked this, but you will need the calipers off and then slide the spools by hand - they could be nearing a seize condition, hence the excessive hydraulic force required to actually slow down. This would explain perhaps why one wheel locks before the others - it could simply not be as seized as the others.
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typo368 (7th November 2017)
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10th October 2017, 06:54 PM
#4
Patrol God
I recently had to clean the rear caliper slides and replace the pistons due to a rubber seal being ripped. Fairly simple to do. The search function is your friend. Here are some threads I found :
http://www.nissanpatrol.com.au/forum...t=brake+slides
http://www.nissanpatrol.com.au/forum...=brake+caliper
Last edited by mudnut; 10th October 2017 at 11:40 PM.
My advice is: not to follow my advice.
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10th October 2017, 07:37 PM
#5
Diesel or petrol? Determines how the vacuum is generated.
Could also be glazed pads.
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Last edited by Turtle_au; 10th October 2017 at 07:41 PM.
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10th October 2017, 11:21 PM
#6
Originally Posted by
dom14
How do you know front left consistently locks?
I have trouble processing brake pedal being very hard and being nice and firm at the same time.
Because when I brake hard, that wheel locks up.
The pedal is hard and wooden in use. I was making the point that is doesnt sink to the floor, so not leaking past seals in Master Cylinder.
Originally Posted by
PeeBee
I am wondering about piston condition in the calipers - are these free to move? Maybe you have checked this, but you will need the calipers off and then slide the spools by hand - they could be nearing a seize condition, hence the excessive hydraulic force required to actually slow down. This would explain perhaps why one wheel locks before the others - it could simply not be as seized as the others.
I do need to replace the disks and pads. I'll check that when I do it on the weekend. Just got the parts this week.
Originally Posted by
Turtle_au
Diesel or petrol? Determines how the vacuum is generated.
Could also be glazed pads.
Petrol. I've just bought the GQ, and I'm thinking its been sat un-used for a while. I expect that glazed pads may be the case.
Thanks for all the comments. I have a feeling replacing the disks and pad will help a lot.
Greasing the caliper pins will probaly be a good thing too.
cheers
Damo
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11th October 2017, 09:26 AM
#7
Legendary
Originally Posted by
Damo
Because when I brake hard, that wheel locks up.
The pedal is hard and wooden in use. I was making the point that is doesnt sink to the floor, so not leaking past seals in Master Cylinder.
You obviously understand how the brake system works and the possible culprits.
I can suggest the slide pins from my experience. They do get jammed after losing the lubricant(copper or rubber grease)
I had fair bit trouble pulling out the jammed one(it was basically welded) and then spending a fair bit of time polishing the sliding pin hole and sliding pin using smooth sand paper and then smooth grinding paste.
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PeeBee (11th October 2017)
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12th October 2017, 02:01 AM
#8
Originally Posted by
dom14
You obviously understand how the brake system works and the possible culprits.
I can suggest the slide pins from my experience. They do get jammed after losing the lubricant(copper or rubber grease)
I had fair bit trouble pulling out the jammed one(it was basically welded) and then spending a fair bit of time polishing the sliding pin hole and sliding pin using smooth sand paper and then smooth grinding paste.
It was doing my head in because none of the expected problems were the problem. Also I'm used to toyotas where you can just pop the wheel off swap the disk and pop it back on. All 4 disks and pads in a couple of hours. The GQ looks to be a big pain in the @ss to get the whole hub off to swap disks.
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12th October 2017, 08:46 PM
#9
Legendary
Originally Posted by
Damo
It was doing my head in because none of the expected problems were the problem. Also I'm used to toyotas where you can just pop the wheel off swap the disk and pop it back on. All 4 disks and pads in a couple of hours. The GQ looks to be a big pain in the @ss to get the whole hub off to swap disks.
Front is bit of a PITA, rear is normal & can be done it 15 minutes.
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15th October 2017, 10:28 PM
#10
So....I got the disks replaced on the front. Not so bad. But I couldn't find any pads in stock for the twin piston GQ calipers so will need to wait a couple of days for them to come in for a trial.
It looks like the problem was the disks have rusted pretty bad in the past and the pads and disks suffered for it. I've just bought the car and think its sat for quite a while before I bought it. The disk surface looks "wierd" so hoping that was the problem.
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PeeBee (15th October 2017)