Brake fluid service

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ams

Active Member
Joined
Dec 12, 2009
Messages
94
Location
London
Car
W207 E250 CDI Coupe
Only had brake fluid service done 2 years ago and have done about 5K miles since.

Mercedes are saying its due again. Does it really need changing again?
 
Maybe because it is hygroscopic (water absorbing) not related to miles covered.

You can buy a tester for about £20 to test it for yourself, if it tests okay you can leave it a while longer.
 
ams said:
Only had brake fluid service done 2 years ago and have done about 5K miles since. Mercedes are saying its due again. Does it really need changing again?

It's due every two years at Mb.
 
Maybe because it is hygroscopic (water absorbing) not related to miles covered.

You can buy a tester for about £20 to test it for yourself, if it tests okay you can leave it a while longer.

I always wondered about these brake fluid testers - they test the brake fluid that is in the reservoir, which is usually nice and fresh, but not the fluid at the callipers, which is usually dark and looks dirty....

Unlike coolant or oil, brake fluid does not circulate in the brake system, but rather stays where it is. It is possible that any moisture will be distributed equally throughout the fluid - but is this the case? Otherwise the brake fluid testers would be pointless... no idea.
 
Only place water vapour can get into the brake fluid is the reservoir cap , so IMHO if the fluid in the reservoir tests OK and the brakes do not get spongy when used hard (thus getting the fluid really hot) there's no reason to change it every 2 years. IMHO it's just another CYA and money maker for the dealer!
 
I like to do brake fluid every 2 years to keep all the nipples nice and free.

Doesnt take long to do and should cost much if combined with a service.

We charge £50..
 
I tend to just bleed some out of each calliper (until it looks fairly clean) whilst keeping the reservoir topped-up.

Keeps the system nice and firm and gets rid of any cooked fluid from heavy braking.
 
In short - yes, it need doing.

Why would you want to compromise on a safety related item. It's not that expensive to get the fluid changed.

Bet you spend more on bling for your car.
 
If you've ever after a bit of spirited driving had the brake pedal go to the floor and gotten all the braking effort a strong headwind, you'd change the fluid.
 
IF the pedal goes long or spongy, of course it needs attention, but in all the cars I've owned over the years, it's only since I came to MB that I've had anything in the manual about changing brake fluid every 2 years - until my Porsche (ex) indie tried the same thing last time (and it will be the last time!) he serviced my 968 cab. He tested the fluid, it was OK, the brakes are fine - so if it ain't broke, why "fix" it?? After all, although it's "only" £50, that's a nice meal out and a couple of drinks for wife and I!!
 
As far as I am aware (almost) all makes of cars require brake fluid change either every 2 or 3 years.

I have seen arguments online against the need to change the brake fluid, to be honest I don't know enough to pass judgement who's right, but for the record - manufacturers do stipulate brake fluid change every 2 or 3 years.

And as others said - for the cost, seems false economy to even debate it.
 
Change your brake fluid every two years and your braking system will be trouble free for years. Most garages do not do this service if not requested.

Of course if you intend selling the car in the near future why bother:fail
 
IF the pedal goes long or spongy, of course it needs attention

It may then be too late. When the fluid has moisture in it, it boils to a gas and you'll lose brakes. I'm not saying "it goes a bit spongy". If your brake fluid contains moisture, you're only one hard stop too many away from the pedal hitting the floor and you're ploughing on regardless.
 
It's probably worth noting that if the pedal goes spongy because you've boiled the fluid, that's different from going spongy because there's moisture in the lines. - Boiled fluid will cool and the brakes them come back.
 
It's probably worth noting that if the pedal goes spongy because you've boiled the fluid, that's different from going spongy because there's moisture in the lines. - Boiled fluid will cool and the brakes them come back.

The moisture reduces the boiling point of the brake fluid:



Source: Epic Bleed Solutions - Bleed Brakes for Less!
 
So testing the water content of the brake fluid is in principal OK, but again how do you know that the moisture level you testing at the reservoir bottle is the same as the moisture level at the calliper and hoses? I understand that there an assumption that moisture cant penetrate into the hoses/callipers, only the reservoir bottle, is this a fact?
 
I like to do brake fluid every 2 years to keep all the nipples nice and free.

Doesnt take long to do and should cost much if combined with a service.

We charge £50..


Would that £50 be for a R230 SL500 too?
 
Quite apart from the safety aspect of the lower fluid boiling point due to the absorption of moisture over time, the moisture also promotes corrosion of the brake system components - especially the alloy in the calipers and master cylinder.

After seeing the corrosion in various motorcycle brake systems that haven't had the fluid changed regularly I always change the fluid on all my vehicles every 2 years.


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We charge 85 for cars with sbc.

Thanks for the rapid response.
 

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