Sudden braking while in motion

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Mainlander

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Just the other day it seemed the vehicle braked on it's own while the car was in motion. This happened a few times during the same trip. Here were were three occasions on this half hour drive:

1. While braking slowly towards red light, moving <5 km/hr, seems the brakes just seized and i stopped abruptly. Heard some chattering...likely the tires on the pavement.
2. While coasting at around 60km/hr felt brakes engage for fraction of a second. This time it was scarier as I was going much faster.
3. While coasting at 20km/hr, same thing.

Seems to happen randomly at various times of the trip, regardless of braking or not. No warning lights came on. The E-brake was used right before I took off on this trip.

It has not happened since the last few trips, but I also have not used my e-brake since because maybe it could be that?

Do any of you have any ideas and how I should trouble shoot this? Could it be the e-brake system or maybe something else?
 

PaulLR3

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Probably not the e-brake. I had one seize on my LR3 and there was a strong "burning clutch" smell and smoke coming off the rear wheel.

The LR4 does have brake assist in panic braking and I've only felt it kick in once when someone pulled out in front of me. It seems to react more to how quickly you jump on the brake pedal as opposed to how far you push it.

Sounds like you could have an issue with the brake assist, but none of us (as far as I know) have ever had this issue. Maybe just try replacing the $50 brake light switch first. That used to cause all sorts of problems on LR3's.
 

Mainlander

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The situation feels more like something is actuating the brakes or e-brake momentarily, so likely an electronic issue? There was one more time about two weeks ago that this might have happened. Just backed out of parking spot, wheels cranked full one direction and in drive, while moving forward slowly I felt the wheel(s) bind up momentarily. Almost like I had it on 4x4 locked, however, it was in automatic mode. Again only lasted fraction of a second.

I'll look into the brake light switch and see if this could be it. It's low cost enough I can just replace it to see if it helps. I read somewhere on the Range Rover forums sometimes the e-brake controller acts up. Not really sure how to diagnose if this is the culprit.

I don't have the IIDtool yet, but for those who have one, does it give ability to show errors or help diagnose issues NOT showing up as a check engine light?

As a last resort, I'll bring it in the Land Rover and see.
 

jaguardoc504

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Sounds like you may have a binding caliper, or caliper slide pin.
The LR4 does not have any type of automated self braking, so it would seem near impossible (given the system design, and counter measures to prevent such actions) for the vehicle to randomly apply the brake itself.

A binding caliper may not be releasing properly. So that when you do apply the brake, immediately after these symptom would occur. Or if the vehicle had sat, where you applied the brakes to park.

Yes the GAPIID tool can provide all of the fault codes, even the ones that will not trigger any type of Malfunction Indicator Lamp on the dash.

Is it possible you are feeling the transmission shifting? As the LR4s get mile on them the transmission can have some weird intermittent feedback. This is usually resolved with a transmission fluid service.
 

PaulLR3

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Yes! I agree with jaguardoc504's idea...I forgot about the sticking brake caliper. I already replaced one of my rear calipers that was not releasing.
 

Mainlander

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Thanks for all your replies.

It almost could feel like a bad transmission shift, except I think the transmission shifts really smooth already. Only have 85,000 kms on it. However, I just bough some transmission fluid and will change it and see if that helps.

I'll also go ahead and dismantle the calipers to take a peak. Any special lube needed for the caliper pins? I know Toyota was very specific in it had to be their lithium soap base glycol grease. Can I just use the synthetic Permatex brake/caliper grease?
 

ktm525

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Check those slide pins. I replace two sets of rotors before figuring out it was a dodgy pin and some crap grease.
 

jaguardoc504

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I use Sil-Glyde every time I have the brakes apart (for brakes or other service)
buy it off of Amazon... https://www.amazon.com/dp/B0054DWS1W?tag=vglnkc3018-20
Same at what was used when I worked at Land Rover/Jaguar

The transmission, while normally feeling great, can have the odd shift every now and again.
How many mile on your LR4?
 

Mainlander

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I use Sil-Glyde every time I have the brakes apart (for brakes or other service)
buy it off of Amazon... https://www.amazon.com/dp/B0054DWS1W?tag=vglnkc3018-20
Same at what was used when I worked at Land Rover/Jaguar

The transmission, while normally feeling great, can have the odd shift every now and again.
How many mile on your LR4?

Thanks for the Sil-Glyde recommendation. Never heard of it, but from a bit of research seems to be great stuff. I'll have to pick some up if I can find it.

The transmission has been very smooth except maybe the first few minutes when it's warming up. It's a 2010 with 53,000 miles on it (85,000 kms).
 

XLR8TOR

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I had an issue similar to this on my 2014 and it was the E-brake causing it. The brake started dragging when I was going 75 MPH and the entire rear ended started shaking.
 

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