Front O/S Caliper Getting Hot

[innercry666]

For a while I have noticed that the front off side caliper / disc / alloy has been getting noticeably hotter than it used to do. I picked it up from the tyre pressure increasing and thought it was odd. The wear on the disc is noticeably increased as well and mpg is down. The conclusion was a caliper that was binding. Audi had the car in and apparently cleaned up the caliper and regreased the pads but the problem is still there.

I've taken some temperature measurements and the difference between the front calipers is over 10 degrees C with the discs and alloys being about 8 degrees C different with the O/S front having the highest temperatures. Rears are less 1 degrees C difference. Clearly there is an issue.

The car is with Audi at the moment and I have had the phone call to say that it is a normal characteristic of the car, to which my response was b****cks. They then tried to claim that they had another RS4 on site and the temperature difference across it's fronts was 12 degrees C! I smell BS. They clearly don't want to resolve the issue.

Has anybody else had this or a similar issue with the brakes? Any ideas as to what the cause may be? Any ideas on a resolution to the issue? I will collect the car thursday so have a day to understand the issue as much as possible before I collect so that when I get the arguments from Audi as to why this is 'normal' I can provide a strong response to the contrary so any help is appreciated.

[johnnydog]

Assuming that the pistons aren't sticking in the caliper, the next thing I would be considering is whether the flexi brake hose to that wheel has collapsed on the inner wall, therefore not allowing the brake fluid to return sufficiently to allow the pistons to fully release following a brake application. It's hard to physically check this, but any softer spots on the hose are a sign the wall may have collapsed inside.
It's just a suggestion, and a cheaper alternative for Audi to replace before looking at replacing the caliper.
A master cylinder fault would affect all four brakes, not just one.
I don't know what type of flexi hoses our cars have, whether they are braided or have a coil outer but short of replacing the caliper that is all I can suggest.

[innercry666]

Thanks for the reply Johnny, I appreciate your input. I did mention to Audi that I wanted to change to braided brake hoses and see if a fluid change improved things so I may go down that road. Audi however recommended that I don't move away from the standard components due to warranty issues.

Audi have come back and advised that one caliper getting hotter than the other is, "a normal characteristic of the car" due to the water pump and radiator being located on that side of the car. Granted it is warmer behind that side of the bumper in the wheel arch but it doesn't explain why the caliper is the hottest component of the whole wheel assembly!

I smell the Audi BS a mile away but even calling them on it doesn't appear to influence the outcome.

I think the caliper has been sticking slightly. Audi cleaned the calipers up and ground down the lip that had been generated on the disc the last time they had the car which did bring about improvements, but not enough to fully resolve the issue. I could spend a lot of life chasing Audi to resolve the issue but I think I'm going to go to a specialist for a second opinion. See if we can nail down the problem and then see what the best solution to the problem is first and then worry about the cost and who pays second.

[forestek]

Pulling up this topic, not sure what was the conclusion with OP issue, I just wanted to share that I'm going through the same thing. I bought my RS4 2014 few months back and during the first spiritated drive in the mountains, I got brake fade and overheating/smoke on the Front Right brake, very bad. I knew the front rotor were skimmed a year ago and discs were anyway ready for change so I change my 4 rotors with Girodiscs 380mm in front and new ones in the rear with the Girodiscs Magic pads hoping it will all go away.
After the first drives, no issues with fading but still Front right wheel hotter than the left one by ~10 degrees, so I thought issues with brakes, I got the brake lines changed with HEL stainless steel and still same.

I notice it's the entire front arch which is much hotter like there is a source of heat and/or no cool air is coming to the brakes. I had my workshop to look at everything and couldn't find anything wrong at all, I drove the car on the motorway for a while and stopped without touching the brakes, both were at same temperature, cool so no caliper issue. I went in the mountains and could feel and smell front right much hotter but because of big discs and good brake fluid no fading.

My conclusion is, nothing wrong, just more heat on that side from engine compartment and poor brake cooling, but it should be same to all cars.

Anyone else has seen such issues and even take some temp measurements?

Thanks
Kenny

[Nige_RS4]

Is 10 deg really an issue when the braking components are subject to temps over 300+ degs under hard braking? As mentioned above, it could be down to slightly less air being flowed to one of the wheel arches? Clearly the OP had something sticking / binding if you could actually feel the difference with your hand, but it would have to be quite a bit more than 10 deg imo.

[forestek]

Hi Nige,

I agree 10 degrees is not much but I need to measure after a fast drive, I really lost confidence in the front brakes since the fading appeared the first time. But if you have a RS4 B8 do you also notice the front right of car is much hotter around the wheel?

[innercry666]

Certainly sounds like a similar issue to what I experienced. It turned out that the caliper was sticking on that side. I was able to check it with the wheel off whilst with Audi and the disc was difficult to turn in comparison to the nearside. Audi didn't want to know. It certainly seems to be a common issue with the RS4. I was going to get the discs skimmed whilst in situ on the car and get new pads but sold it before I go to it. I would either do that or go for aftermarket discs and pads.