Brake Fade

keiron · Senior Member

Brake Fade

Whenarewethere · Guru

If it was 'spongy' when was the last time the brake system was bled.

yobarr · Guru

keiron wrote:
Last weekend in Wollongong, NSW, in high 30 degree temps I experienced what one might call "brake fade". The need to push extremely hard on the pedal which was spongy, and made little impact on retarding my progress. Fortunately I was only doing 10 - 15 kph in heavy traffic and was able to stop by going into neutral and hand brake mode. It did improve a lot after the brakes cooled from some "ram-air_ once we did get mobile.
I drive a 4.8litre Patrol, have drawers in the rear and was carrying 2 passengers. I had new pads fitted all-round about 5k ago, and all seem OK.
I have now arranged to have EBC Slotted / Dimpled Rotors with Yellow pads fitted to the front, which are designed for high temps and heavy loads, such as towing.
I would be interested in hearing from others who have experienced such a happening, and what was done to prevent future events.

Braided lines will help.Cheerd

markf · Senior Member

Funny you should mention this. We had an episode coming down to Omeo from Mt Hotham a couple of weeks ago towing our 18,000kg camper. It all started out very well but as we got to the steeper downhill parts near Omeo the drum brakes on the camper faded to next to nothing which left the Disco 2 brakes to do all the work which provided a "brown pants" moment until we could stop and let things cool off a bit.

We've never had this problem before and I'll lay the blame at the feet of the 12 inch drum camper brakes. They are not at all fade resistant so some more suitable brake linings are called for. Maybe a disc conversion although that'll be expensive. The Land Rover brakes are about as fade resistant as I can get and I've towed a heavier disk brake equipped trailer down there in the past with no problems.

erad · Guru

Spongy brake pedals - for sure you need to bleed the brakes, but a hard brake pedal - that sounds more like the brake booster failing. The fact that you were able to stop using the handbrake shows that at least something is working... Check the vacuum connections to the brake booster.

Did the brake pedal go to the floor when the brakes 'faded'? If they did, it was the brake fluid boiling in the brake calipers. You then need to replace all the brake fluids with new stuff, because brake fluid is hygroscopic ie it absorbs water from the air. A very small percentage of water eg 5% in the fluid can lower the boiling point from the nominal 255 Deg C down to 140 Deg C. The result of this is that as the fluid boils, it is the same as having air in the system and the pedal goes to the floor. Not nice. In addition, the presence of water in the fluid can cause corrosion of the wheel and master cylinders, resulting in leakage and certainly less braking. You should replace the brake fluid every 2 years to avoid problems like this.

Whenarewethere · Guru

markf wrote:
We had an episode coming down to Omeo from Mt Hotham a couple of weeks ago towing our 18,000kg camper.

At 18,000kg it must be decked out like Versailles!

dogbox · Guru

i would support the change brake fluid idea, fresh/clean fluid can make a big difference

PeterD · Guru

markf wrote:
Funny you should mention this. We had an episode coming down to Omeo from Mt Hotham a couple of weeks ago towing our 18,000kg camper. It all started out very well but as we got to the steeper downhill parts near Omeo the drum brakes on the camper faded to next to nothing which left the Disco 2 brakes to do all the work which provided a "brown pants" moment until we could stop and let things cool off a bit.

Sounds like you did not slow down and use a lower gear so that you did not have to use the for brake as much. I have travelled that road both ways many times including back when I had a D2. I have always pulled the gear selector back to at least 2nd gear and used 1st on the steeper pinches. I have never suffered brake fade on the van. All those of us who did a lot of hill driving with drum brake vehicles learnt to do that. There is now a tendency for driving instructors to poo-poo that idea. They reckon that with modern brakes down-changing is not necessary. That is why when you are at the bottom of a steep incline you will smell vehicles coming past like they have burnt out brakes. I always down-shift on hills like that whether I have a van in tow or are running solo. I believe in sparing my brakes for when I really need them.

PeterD · Guru

keiron wrote:
I have now arranged to have EBC Slotted / Dimpled Rotors with Yellow pads fitted to the front, which are designed for high temps and heavy loads, such as towing.

It's a pity you did not post here before you ordered the new bits. I agree with Whenarewethere. You need to have the brake fluid changed periodically. Brake fluid attracts moisture, even the later types do it. With the earlier types of fluid I replaced the fluid every 18 months to two years, I used to bleed the brakes in turn until the good colour fluid started coming out. Since anti-lock brakes I can no longer bleed them properly, you need them pressure bleeding. Also, the newer brake fluid lasts better so I get the fluid changed every three years or so. Changing the brake fluid may have fixed your problem, no water in the fluid means you don't boil the fluid. Changing the brakes will not help with your problem.

Whenarewethere · Guru

My mechanic does the brake fluid every 3 years.

We don't tow, but I still put the auto into a low gear for steep declines & it works well.

Jaahn · Guru

Hi smile

Well the brake fluid change is a good idea. The changing down and using the gears is another too(cheap too !!). But I would also point out that buying the cheapest brake pads might not be the best idea either. The material they use might be recycled horse poo for all we know. So be aware of using a quality brand when you change them. hmm What you described sounded to me like the brake pad material overheating and loosing friction which recovers as it cools. I am not sure about the caravan shoes either who makes them ??

Jaahn

oldbloke · Guru

keiron wrote:
Last weekend in Wollongong, NSW, in high 30 degree temps I experienced what one might call "brake fade". The need to push extremely hard on the pedal which was spongy, and made little impact on retarding my progress. Fortunately I was only doing 10 - 15 kph in heavy traffic and was able to stop by going into neutral and hand brake mode. It did improve a lot after the brakes cooled from some "ram-air_ once we did get mobile.
I drive a 4.8litre Patrol, have drawers in the rear and was carrying 2 passengers. I had new pads fitted all-round about 5k ago, and all seem OK.
I have now arranged to have EBC Slotted / Dimpled Rotors with Yellow pads fitted to the front, which are designed for high temps and heavy loads, such as towing.
I would be interested in hearing from others who have experienced such a happening, and what was done to prevent future events.

Been along time.since I practice as a mechanic.

But that does not sound like brake fade. Typically brake fade happens under very extreme conditions. As an example, I drove down a very long steep hill with brakes not working in my 20 foot van. At the bottom triton brakes were literally smoking but no brake fade, worked all the way down. My undies were were stressed though. Lol

Were you towing?

If so are you certain the van brakes are working?

Sound to me air in the system or as someone said boiling fluid. But again that only happens under very extreme conditions. As I described above.

Have a good mechanic look at them. The guy who fitted them may have stuffed up.

markf · Senior Member

PeterD wrote:
Sounds like you did not slow down and use a lower gear so that you did not have to use the for brake as much. I have travelled that road both ways many times including back when I had a D2. I have always pulled the gear selector back to at least 2nd gear and used 1st on the steeper pinches. I have never suffered brake fade on the van. All those of us who did a lot of hill driving with drum brake vehicles learnt to do that. There is now a tendency for driving instructors to poo-poo that idea. They reckon that with modern brakes down-changing is not necessary. That is why when you are at the bottom of a steep incline you will smell vehicles coming past like they have burnt out brakes. I always down-shift on hills like that whether I have a van in tow or are running solo. I believe in sparing my brakes for when I really need them.

Assumptive claptrap.

You know nothing about my driving abilities. You know nothing of my driving experience. Most importantly, you were not in the car with us.

As I said. Assumptive claptrap.

Jaahn · Guru

Well years ago I experienced brake fade like that on a hot day, in a Holden ute, doing a quick dash across the back streets in the city to pick up some parts in a hurry for the boss. Scared the bejeeses out of me when i came to an intersection and it would not stop properly, hard pedal little retardation. All below 60KPH. hmm

Guess what ! The brakes had been replaced only the week before by a well know brand shop but did a special price. The boss did not believe me so he went out for the same run and same result. So he took it back and told the shop to put quality linings on it not the cheapest rubbish. Never had any problems again on any of the utes. True story ! blankstare

Jaahn

Tony LEE · Guru

"You know nothing about my driving abilities. You know nothing of my driving experience. Most importantly, you were not in the car with us." . . . Exactly. Then tell us the circumstances leading up to the incident because even under extreme driving situations provided they are handled competently, brakes don't fade to the extent that you can't come to a halt

erad · Guru

This topic has developed into a bunfight. the OP problem has not been addressed in letter posts at all. But to continue on the bunfight, look at Mt Hotham and braking as you go downhill. it seems that the caravan brakes were smoking or whatever, not the car. When you put your foot on the brake pedal, an electrical signal tells the caravan brakes to apply. The intensity of that application varies according to the rate of deceleration at the time. If you are braking hard, the accelerometer will sense this and say that the van should help too and give a bit more braking than if the rig was gently stopping. Great - that is what it does. But if you are going down a steep hill, the accelerometer will sense this as hard braking and thus apply the brakes hard as well. So even if the driver is only lightly pushing the brake pedal, the van is sensing hard braking required and will give it all.

Obviously, the answer is to not use the brakes very much and to use the car's engine to control the rig, dabbing the brakes occasionally as required. If the driver goes down the hill with his foot on the brakes all or most of the way down, the caravan brakes will be working all or most of the time as well, and because of the gradient, working at maximum braking effort, and of course will heat up. Drum brakes are not the best choice, but they work adequately, given some understanding as to how they are working in that situation. And, of course, if the driver is not using the engine effectively to slow the rig, the brakes will be on more than necessary and although the car brakes may take this (modern cars with disc brakes are fairly good), the van won't be able to match it nd the van brakes will overheat.

rgren2 · Guru

My Patrol was the 3L CRD, I recently fitted the 4.8L front brake pads. A huge improvement. The yellow pads are a good choice, bit dustier and quicker wearing.
I also have braided lines.
Lots of information here. www.patrol4x4.com/search/401496/

Magnarc · Guru

Markf PeterDs observations were sensible ones. Perhaps you would like to tell us did you use brakes only????????? Steep inclines need lower gears when towing to be safe. No ifs or buts mate, just common sense driving.

PeterD · Guru

erad wrote:
This topic has developed into a bunfight. the OP problem has not been addressed in letter posts at all. But to continue on the bunfight,

I think that no one has had anything more to add for the OP and that is why little extra has been addressed to him. However when someone else poses another question then that question must also be answered. However, if markf had not taken my suggestion as to what could have happened and misread it as an attack on him and then got on his high horse with the attitude of "I know how to drive and no one is going to tell me how to drive" attitude it would not have turned into a bun fight.

Erad, your suggestion has merit but I have not had that problem with proportional brake controllers. Maybe when I had the first generation of proportional controllers with pendulums I did not set the pendulum as finely but had them back a bit so slopes did not affect them as much that way. The Tekonsha Prodigy and similar controllers with the decelerometers do not have that problem as their mechanism self adjusts on climbs or descents. However, if Mark has one of the synchroniser type controllers your suggestion is a distinct possibility if he was driving in low gear and feathering the brakes most of the way he would have had his caravan brakes working at maximum capacity for most of the way. In that case most of his descent retardation would have been done by the van brakes and that would have explained the brake fade. This is one of the reasons I recommend not using synchroniser brake controllers. I don't know why they are still being produced, probably it is to satisfy the demands of the Luddites.

-- Edited by PeterD on Thursday 28th of January 2021 03:20:53 PM

rgren2 · Guru

PeterD wrote:
erad wrote:
This topic has developed into a bunfight. the OP problem has not been addressed in letter posts at all. But to continue on the bunfight,
I think that no one has had anything to add for the OP and that is why little has been addressed to him. However when someone else poses another question then that question must also be answered. However, if markf had not taken my suggestion as to what could have happened and misread it as an attack on him and then got on his high horse with the attitude of "I know how to drive and no one is going to tell me how to drive" attitude it would not have turned into a bun fight.
Erad, your suggestion has merit but I have not had that problem with proportional brake controllers. Maybe when I had the first generation of proportional controllers with pendulums I did not set the pendulum as finely but had them back a bit so slopes did not affect them as much that way. The Tekonsha Prodigy and similar controllers with the decelerometers do not have that problem as their mechanism self adjusts on climbs or descents. However, if Mark has one of the synchroniser type controllers your suggestion is a distinct possibility if he was driving in low gear and feathering the brakes most of the way he would have had his caravan brakes working at maximum capacity for most of the way. In that case most of his descent retardation would have been done by the van brakes and that would have explained the brake fade. This is one of the reasons I recommend not using synchroniser brake controllers. I don't know why they are still being produced, probably it is to satisfy the demands of the Luddites.
I did give very relevant information and a link with a lot more from dedicated Patrol owners.

-- Edited by rgren2 on Thursday 28th of January 2021 01:37:56 PM

markf · Senior Member

PeterD wrote:
erad wrote:
This topic has developed into a bunfight. the OP problem has not been addressed in letter posts at all. But to continue on the bunfight,
[deletia...]
However, if Mark has one of the synchroniser type controllers your suggestion is a distinct possibility if he was driving in low gear and feathering the brakes most of the way he would have had his caravan brakes working at maximum capacity for most of the way. In that case most of his descent retardation would have been done by the van brakes and that would have explained the brake fade. This is one of the reasons I recommend not using synchroniser brake controllers. I don't know why they are still being produced, probably it is to satisfy the demands of the Luddites.

And that is exactly the situation. The irony is that I have a Tekonsha P3 that I haven't installed yet.

The controller came with the car and has been good for around towns, highway and freeway travel but as this trip demonstrated it's no good on extended steep downhill sections where you tend to feather the brakes a bit even in a low gear and I was in 2nd at the time.

The "brown pants" moment came at the bottom of the steepest bit where there is a sharp right hand bend that I needed to slow down a bit more for. When I applied the brakes there was nothing from the camper and the poor old D2 had to do it all. I never had a problem on the same road with the old D2 with a P3 installed.

As for driving experience - I've driven heavy trucks up and down those roads more than I care to remember without incident.

PeterD · Guru

Hi Mark, thanks for that reply. My first guess was wrong, I offered that as it is the problem that most of our members have when they experience brake fade or smelly brakes. My second guess seems to have been on the ball. Thanks for confirming my suspicions that synchroniser style controllers can be a danger and should not be used for towing, particularly in mountainous country.

By the way, most of my towing over that stretch was with a D1 and then a D2. Since I have had the Nissan I have only been over there once.

keiron · Senior Member

Thanks to everyone for your comments, and I add the following for clarification purposes;

I was NOT towing anything when I experienced the "brake fade".

I had used the Auto select to descend the mountain (Bulli Pass) mainly using 2nd and 3rd gears. Occassional brake usage only.

I had 2 adult passengers plus myself.

Temperature outside around 38-40 degrees.

My Patrol is 4.8 litre Petrol Automatic.

I hope this clarifies my original enquiry, and removes any ambiguity. Cheers again. KB

Brownie2 · Senior Member

Brakes can fail due to overheating. Brake fluid is "hydroscopic" and absorbs water over time. Under extreme conditions the water will boil and the brake pedal disappears. Many years ago, as a motor mechanic, we trialed a brake fluid that was used by the army (a silicon based product) but it was never taken up on a big scale to my knowledge. So, everyone should have the brake fluid changed regularly. I qualify this by stating that I've not been practicing motor mechanics for a long time, so will love to be informed on new data.

PeterD · Guru

keiron, it definitely sounds like a brake fluid problem to me. Patrols don't have brake fade problems with their brakes in good order under unless you are flogging them and not downshifting on descents. If you are going ahead with the new parts they should replace all the fluid as part of the service.

erad · Guru

Kieren wrote: "I was NOT towing anything when I experienced the "brake fade"."

Kieren: Try to describe the brake fade. Did the pedal go to the floor, or did the pedal stay hard? If the pedal stayed hard, did the 'take-up' point of the pedal stay at the normal height or did the hard point of the pedal come right at the top of the pedal travel?

If the pedal went to the floor, that is the brake fluid boiling - either due to reduced boiling point or due to reduced airflow to cool the discs.

If the take-up point of the brake pedal remained at 'the normal level', the vacuum boost was still working, but if the pedal got hard right at the top of the pedal travel, you had no vacuum boost to the brakes.

Either way, if you lost braking effect due to the pads overheating, it is possible that the pads are not the correct pads for that application. In my younger days (over 55 years ago), I had Triumph 2000 sedan. A friend used to work for Lucas Motorsport and he got me a set of competition pads for the front wheels (the rears had drum brakes). I decided to test them out one night coming down the hill to Tumut Pond Dam. It is not particularly steep, but many corners, so it was hard on the throttle, then hard on the brakes , throttle, brakes etc all the way down. The brakes didn't fade, the pedal stayed firm (so the fluid was not boiling) and the brakes worked well all the way down. Whilst crossing the dam, I saw something in the side reflection from the headlights and stopped to check. The front discs were glowing red hot! Oh dear - what to do? I decided to continue driving slowly (it was uphill by then anyway) and let the discs cool down normally. Now, these were competition pads so presumably they were designed for these temperatures, but normal pads may well glaze up under similar conditions. I never repeated this test again either...

Many years later, I was receiving some driver training from the Aust Federal Police in Canberra at their test track. They were using standard VP Commodores direct from the CommCar fleet. The coppers were teaching us threshhold braking, where you stand hard on the brakes and make the car's nose dip. This loads up the front wheels as the weight of the car lurches forward. At this point, you press really hard on the pedal and wait until you hear a wheel lock up, You then ease up slightly on the pedal and when the wheels are all rotating again, repeat the process until again you get lockup. The distance where you could stop the car from 80 km/h was astonishing. We had theory sessions describing this process and then practical sessions. he coppers got us to get up to 80 km/h, brake hard, then straight back to 80 and then stop again. On the third braking effort, the pedal went straight to the floor. Standard VP Commodore. Scary as hell, but anyone who drives like we did deserves to run out of brakes. BUT - if the brake fluid was contaminated with moisture from the air, the boiling point could be lowered to a point where you could not stop even once from the 80 km/h speed. And anyone coming down a step hill relying totally on the brakes can soon reach that fading point....

oldbloke · Guru

keiron wrote:
Thanks to everyone for your comments, and I add the following for clarification purposes;
I was NOT towing anything when I experienced the "brake fade".
I had used the Auto select to descend the mountain (Bulli Pass) mainly using 2nd and 3rd gears. Occassional brake usage only.
I had 2 adult passengers plus myself.
Temperature outside around 38-40 degrees.
My Patrol is 4.8 litre Petrol Automatic.
I hope this clarifies my original enquiry, and removes any ambiguity. Cheers again. KB

Driving sensibly you should not get brake fade under those conditions with disc brakes these days. Not high speed, low loads. And 40c is not going to matter much.

Take it back to where you had the brakes last worked on.

Your hand brake worked so your front discs are faulty.

Modern brakes are as good as race cars 20 years ago, or better.

Whenarewethere · Guru

It can't be the front brakes as the hydraulics is a dual system diagonally. Front right & rear left. The other half is front left & rear right.

Greg 1 · Guru

I am not sure where you have got the idea that the split brake system is diagonal. Pretty much every car that I know it is split front and rear. It needs to be this way to be able to balance the braking forces in the car. The fronts usually do about 70 to 75% of the braking effort. It would be extremely difficult to get that balance correct across the diagonals. With regards fade, you can get what is called pad fade with new pads that have reached a high temperature. The pads degas giving off gas and this has the effect of holding the pad clear of the disc surface. It will show itself by the fact that you still will have a good pedal but the vehicle will not pull up. This is the reason that discs have slots cut in them to allow the gas to escape and to keep the surface of the pad deglazed. Cross drilling does the same thing but I would not recommend that as I have seen discs disintegrate due to heat stress cracks propagating from the holes. Quite a few race drivers have been caught out by pad fade. Usually an off on about laps 2 or 3 can be suspected of being caused by this phenomenon.

Whenarewethere · Guru

From my Freelander's manual:

Vehicle braking is achieved with a vacuum assisted, hydraulic circuit connected via an integrated ABS module and HCU, to the front and rear disc brake calipers.

For increased safety, the hydraulic system is designed as a diagonally split dual circuit.

This provides a primary and secondary braking circuit connected between the master cylinder and each front and opposing rear wheel.

The braking system provides anti-lock control to aid the driver, and to make sure the vehicle remains in control during all driving conditions and manouevres.

The sophisticated ABS functionality also integrates with other vehicle software controlled systems, to provide stability assistance and control when driving off-road.