2010 2.0 Diesel Scout Brake Fade after prolonged use of Cruise Control

[bigladwigan]

Hi guys, I'm hoping someone else has knowledge of this. I've taken the car to garages who've confirmed the brakes are in perfect working order.

 

When I use cruise control on longer motorway distances say 40 miles or more I get brake fade and  the longer the journey the worse the fade is. In normal everyday use the brakes work well enough, but whenever I travel on motorways using cruise I lose braking power. The pedal is normal but response from the car is massively reduced to the point that I nearly failed to stop altogether when entering the services on a trip home from London which was the very first time this occurred. The pads, disks and fluid are all in perfect condition, ABS works as normal I can and have done emergency stops since this started and was successful.

 

Has anyone had this before and identified the cause or able to make suggestions as to what could be behind this problem?

 

Thanks in advance for your help.

 

Ady

[KenONeill]

Can you smell over-heated brake linings? If not, then you don't have conventional brake fade.

 

I can't see why this should happen, but could the cruise be draining vacuum from the servo?

[bigladwigan]

No bad smells at all. The first time this happened there was no warning whatsoever and we were very lucky it didn't end badly. I think this Scout may be jinxed, I've only had it since last may done 9k and it's have a new egr cooler, keeps blowing headlight bulbs, brake failure, constants slow punctures thanks to the proteus alloys, I'm pretty sure the DMF is failing and there's something odd with the clutch. I've had 2 previous octavias one with 3 times the mileage of this one that only went as it was written off in an accident neither car gave me any trouble other than wear and tear.

[pikpilot]

Your symptoms sound to me like you are losing vacuum for brake assist.

Just guessing but perhaps worth checking out. On the 2.0L diesel I believe there is a vacuum pump on the end of the camshaft on the right hand side.

Under cruise control the engine revs are lower for a longer time so the pump is turning slower. I would look for damaged/rubbing or split hose as well as the pump itself. As I say just a guess!

[reverse]

Might not be any fault at all with the car. Have you considered the weather conditions? If you don't use the brakes for a long time, and it's wet outside moisture will accumulate on the discs and you get that fade. That is the reason why some agressive sporty Audis (RS6 for example) have a system that keeps the brakes always at optimal temperature and dry. So in case you really need them, they are there at 100% of their power.. next time try it by applying just a fraction of pressure on the brake pedal (so there is contact between the pad and disc) wait a few seconds (give it time to heat up and do its magic) and then push harder - the fade should be gone and brakes bite like normal. I experience this on a long haul (no brake usage for 30 minutes or longer) and when its time to get off the highway, I already know that the first attempt to brake is rather.. interesting

[radders567]

Have you checked that none of your brakes are binding causing the brake fade ?