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Warped Discs

Warped Discs

Postby iandvl » 05 Feb 2015 16:53

Hi Patrol gurus.

More questions brake-related. Hope I'm not annoying anyone with my incessant posting, but it is super frustrating sitting in Kenya with the Patrol in the shop.

Vehicle in question is a 2001 4.5 GRX.

I had it at the dealers for a complete checkup and similar after purchasing the thing. All-in-all it's fine, but there were a few nigglies I am sorting out.

One was the brakes. The felt very spongy. Dealership mentioned the master cylinder (my post here: http://patrol4x4.co.za/viewtopic.php?f=47&t=5191) and this was re placed. However, I had a friend go with the wife when they called to that the 'trol could be collected, and the brakes were still incredibly spongy. Since then, it's been at the dealership, and they've been investigating (I should have taken the 'trol to Graham from the start).

They've just called me. Apparently, they've eventually managed to get the vehicle bled properly. However, they've told me the discs are warped, and therefore the new brake pads only grip on 30% of the disc and this also contributes to the "sponginess" of the brakes. Is this possible ? I would not have expected warp discs to cause a spongy pedal. At the very least, I'd have imagined one would have felt this on the brake pedal...

The discs are still in-spec, so they're going to give them a skim tomorrow. If that doesn't sort it out, I'm settling my bill and taking it to Graham.

Ian
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Re: Warped Discs

Postby David M » 05 Feb 2015 17:26

iandvl wrote:
The discs are still in-spec, so they're going to give them a skim tomorrow. If that doesn't sort it out, I'm settling my bill and taking it to Graham.

Ian


So they have actually done nothing to sort out the problem but are going to present you with a bill. If the discs are that warped you would feel the brakes take and release if you apply them softly.

I would tell them to keep their bill until the problem has been identified by an expert (Graham)and then pay them for what actually needed doing.
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Re: Warped Discs

Postby Peter Connan » 05 Feb 2015 17:32

I guess it depends on how the discs are warped.

If they have gone "wobbly" (wich is almost always the way it goes), then it you can definately feel uneven braking when coasting very slowly and applying the brakes softly. Sometimes the pedal may feel spongy and you might also feel feedback, almost as if the ABS is working, particularly at low speed. If this is the case, generally most of the pad contacts the disc at some point in the roation of the wheel though. Braking force is reduced and it becomes difficult to accurately modulate the brakes, and skimming is certainly recommended.

On the other hand (in theory), if the disks have somehow become either concave or convex, it might more accurately describe the symptoms. You will not feel a wobble as described above, and new pads will not seat correctly. One will seat on the outer edge, the other on the inner. Brakes will feel spongy as in reality you are flexing the calipers to align with the discs. However, once the pads are worn in, the symptoms will dissappear.

I have however never actually seen a disc warped like this, and don't know if it can really happen. Kinda doubt it, but I am not prepared to put anything on a block.

Also note that a caliper mounted skew (due to dirt under the mounting points or similar) would produce exactly the same results and is far more likely to happen...
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Re: Warped Discs

Postby iandvl » 05 Feb 2015 17:51

Mini Patrol wrote:So they have actually done nothing to sort out the problem but are going to present you with a bill. If the discs are that warped you would feel the brakes take and release if you apply them softly.

I would tell them to keep their bill until the problem has been identified by an expert (Graham)and then pay them for what actually needed doing.


David,

I'm battling to arrange something else at this point as I am in Nairobi. I'm going to have the wife settle any bill there is tomorrow, and if the vehicle is not correct, I will take it to Graham. And then Nissan will have a very angry me on their hands.

We'll see.

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Re: Warped Discs

Postby iandvl » 05 Feb 2015 17:52

Peter,

Thanks for the feedback. I'll see what happens tomorrow. Incredibly frustrating in being away from home with all of this going on.

:/

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Re: Warped Discs

Postby AndriesS » 06 Feb 2015 07:05

Is it Spongy while the engien is on? I find on mine that if the engine is off and I've pumped the brakes 2 -3 times to get the power assist out of the way then the pedal is very hard and high, but once you start it it feels spongy to a point, I normally blame the booster, that said even pumping it will not increase the pedal height and if it would it is generally a clear indication of some brake problem.

Also I normally find that driving my wifes car or some of my other cars , the first time I step om the patrol's brakepedal there is a bit of oops what's wrong thought as it takes a bit lower than modern or non assisted cars.
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Re: Warped Discs

Postby iandvl » 06 Feb 2015 16:28

Well, in a nutshell:

The wife collected the Trol. The brakes feel even worse (according to her). Got a friend to baby it home, and it is now in the garage at my house. I will give Graham a call on Monday when I am back from Kenya, and arrange to take it to someone who knows what they are doing.

Needless to say, Nissan has not charged me a cent.

Still, I am incredibly annoyed about this all.
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Re: Warped Discs

Postby iandvl » 09 Feb 2015 08:45

I got back from Kenya pretty late on Saturday evening. Took the 'trol for a drive yesterday, but I think the wife is over-reacting.

The brakes seem fine, so I assume Nissan did get the issue resolved.

I assume it is the difficulty in trying to get stuff like this sorted out when one is far away...
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