Brake Fluid Top Up?

[dm222]

Hello, Please can someone advise? I have been told by a garage that my brake fluid is low, although there is no warning light on the system. I drive a B Class 2018 model, so it is still under warranty. The garage is quoting a lot of money which seems very unreasonable. In order to maintain the warranty and benefit from the Roadside Assistance programme do I need to get the brake fluid topped up by a garage which used original parts? The brake fluid is not replenished at service - so is it necessary to use only mercedes approved brake fluid or can a local cheaper garage do it for the warranty and roadside assistance to be preserved? Thank you.

if the car is under warranty check if it has any leaks so it gets fixed under warranty because I don't think its normal for the fluid level to go down

 

[Crossthreaded]

I don't think its normal for the fluid level to go down

without wishing to give any offence, I would beg to differ. As the pads wear they become thinner so the caliper pistons come to rest protruding further from their bores. The more worn the pads are the further the pistons protrude from the caliper bore when at rest. To compensate for this fluid is transferred, little by little, from the reservoir to the calipers. Therefore, when the pads are well worn it's not unusual for the reservoir to look around half empty. This varies depending on how big the reservoir is on any individual vehicle, but, in my experience, even if you were not to top the reservoir up it wouldn't become dangerously low by the time the pads require renewing. Personally I'm not obsessed by keeping the brake fluid reservoir topped up to the full mark because I know that when it comes around time to replace the pads, if you keep topping up, you're only going to have to syphon the excess fluid out to stop it cascading out of the reservoir as you force the pistons back into their bores to accommodate the new pads. Of course a bit of common sense needs to be applied to this thinking. For instance, if the level is dropping noticeably quickly or you suddenly notice the reservoir is nearly empty, then don't ignore it as you likely have a leak!

 

[dm222]

without wishing to give any offence, I would beg to differ. As the pads wear they become thinner so the caliper pistons come to rest protruding further from their bores. The more worn the pads are the further the pistons protrude from the caliper bore when at rest. To compensate for this fluid is transferred, little by little, from the reservoir to the calipers. Therefore, when the pads are well worn it's not unusual for the reservoir to look around half empty. This varies depending on how big the reservoir is on any individual vehicle, but, in my experience, even if you were not to top the reservoir up it wouldn't become dangerously low by the time the pads require renewing. Personally I'm not obsessed by keeping the brake fluid reservoir topped up to the full mark because I know that when it comes around time to replace the pads, if you keep topping up, you're only going to have to syphon the excess fluid out to stop it cascading out of the reservoir as you force the pistons back into their bores to accommodate the new pads. Of course a bit of common sense needs to be applied to this thinking. For instance, if the level is dropping noticeably quickly or you suddenly notice the reservoir is nearly empty, then don't ignore it as you likely have a leak!

If the fluid is low enough to be a concern then probably its not just wear of the pads...
He should definetly check for leaks to be on the safe side, if he doesnt find anything great!