Hi, I have had a September 2012 CR 140 DSG now for just over a year. 36k miles. It does not appear to have ever had the brake fluid and coolant changed. All other oils and filters are 'up to date'.

Should I get these done as a priority? How often do others get these changed?

Thanks

Fats

 

No change interval as such for coolant: it gets changed with the water pump.

 

Brake fluid is first due at 3 years okd, and every two after that. On a 2012 it should have been changed twice by now.

2 hours ago, fatscoleymo said:

Hi, I have had a September 2012 CR 140 DSG now for just over a year. 36k miles. It does not appear to have ever had the brake fluid and coolant changed. All other oils and filters are 'up to date'.

Should I get these done as a priority? How often do others get these changed?

Thanks

Fats

 

 

Brake fluid as mentioned further up should be changed after the first three years and every two years after that and yes it is important as brake fluid is hygroscopic (absorbs water). If you don't this eventually causes other issues eg internal corrosion inc pipes, ABS, valves, calipers etc. 

 

I used to rebuild and or restore cars and some of the brake fluid I drained off from what had been someone’s family car was horrendous (milky white or brown, streaky etc).  

• One master cylinder reservoir look as though is was black - turned clear white when fluid changed. On the same car a dual circuit failure detector switch  was sticking in one direction due to internal rust. Fortunately this was a Volvo where the dual circuit was impressive with two separate hydraulic circuits in each front caliper.
• On another the car proved impossible to bleed as the front/rear compensator valve had rusted shut internally. The brake fluid came out milky white with streaks of rust. Just about had to replace the whole hydraulic system on this one.

My work was on pre ABS cars - the need for brake fluid change is even greater now.

 

Coolant is important (not safety though) but as mentioned above should be changed when the cambelt/water pump is replaced.

Edited 16 November, 20187 yr by bigjohn

Brake fluid in reality lasts far longer than the stated times. Some garages use a water test paper that when dipped in the brake fluid and then held against some heat should simply burn, if it "crackles" then there is water contamination in the liquid. This fine but does not checked the fluid at the ends in case water is being absorbed. This method is I presume done by old school type garages.

The test paper is how we used to test for water in oil transformers just one or two years ago . Well the principle is the same.

Edited 16 November, 20187 yr by Danny 57

4 minutes ago, Danny 57 said:

Brake fluid in reality lasts far longer than the stated times. Some garages use a water test paper that when dipped in the brake fluid and then held against some heat should simply burn, if it "crackles" then there is water contamination in the liquid. This fine but does not checked the fluid at the ends in case water is being absorbed. This method is I presume done by old school type garages.

The test paper is how we used to test for water in oil transformers just one or two years ago . Well the principle is the same.

 

Indeed the problem here it tests the fluid in the resevoir not further down the system. This fluid may be newer than further down in the system - especially if a caliper has been changed whilst clamping the rubber brake pipe and then just bleeding fluid from the one corner.

 

I agree that in reality it lasts without issue for longer than two years but this period has been set for a reason - some would say for the dealers to make money. Having seen the other end of the spectrum I can say if it is not changed for 10 years then it's pretty bad by then. So for me it's 3 then 2 years without fail.

 

If it was my family in the car...........

 

 

13 minutes ago, bigjohn said:

it is important as brake fluid is hygroscopic (absorbs water)

 

Just to be precise on this - DOT 5 brake fluid does not absorb water .. but it isn't compatible with ABS pumps ... all other DOTs (3, 4 & 5.1) are hygroscopic

So when will DOT 6 be on the market that does not absorb water and is compatible with ABS pumps.

 

Btw I do change my brake fluid as stated.

1 minute ago, Danny 57 said:

So when will DOT 6 be on the market that does not absorb water and is compatible with ABS pumps

 

I'd say about the same time as hydrogen fuel becomes available at your local gas station ...

5 minutes ago, vborovic said:

 

Just to be precise on this - DOT 5 brake fluid does not absorb water .. but it isn't compatible with ABS pumps ... all other DOTs (3, 4 & 5.1) are hygroscopic

 

I sort of ignored the silicone (DOT5) stuff as I tried it once and I had all sorts of problems. Any old seals or lurking DOT3/4 further in the system does not take well to it. It's supposed to be OK if you are starting from scratch with all new or stripped brake components/pipes but I didn't bother again after it caused havoc on a Morrris 1000. It was being sold as a magic bullet back in the day - it wasnt for me.

 

I think al the others are glycol based.

 

 

 

4 minutes ago, bigjohn said:

 

Indeed the problem here it tests the fluid in the resevoir not further down the system. This fluid may be newer than further down in the system - especially if a caliper has been changed whilst clamping the rubber brake pipe and then just bleeding fluid from the one corner.

 

 

There is really only one way for water to enter the braking system and that is via the brake reservoir. Most modern caps seal fairly well but extreme heat changes could allow the cap to breath with expansion and contraction of fluid. I expect once water is absorbed, it will spread fairly rapidly throughout the entire fluid. High humidity, formation of dew overnight, rain, too much washing,  etc are the times that water could get absorbed. If these can be avoided, e.g. garage your car, then less of a problem.

 

 

1 minute ago, xman said:

via the brake reservoir

 

Which are mainly out of plastic, and the plastic can have a crack somewhere over time (doesn't even have to be a sealing cap in question)

If your reservoir is cracked, then you have more than water to worry about.

1 minute ago, xman said:

If your reservoir is cracked, then you have more than water to worry about

 

True, but the crack can be above the fluid level (near the cap), retaining the brake fluid in place, but allow outside water/condensation to enter the reservoir

11 minutes ago, xman said:

 

There is really only one way for water to enter the braking system and that is via the brake reservoir. Most modern caps seal fairly well but extreme heat changes could allow the cap to breath with expansion and contraction of fluid. I expect once water is absorbed, it will spread fairly rapidly throughout the entire fluid. High humidity, formation of dew overnight, rain, too much washing,  etc are the times that water could get absorbed. If these can be avoided, e.g. garage your car, then less of a problem.

 

 

 

I've seen hygroscopic materials in the lab (phosphorous pentoxide) pull moisture through a screw cap that was sealed outside with parafilm (stronger stretchier clingfilm) while sitting inside a dessicator jar that was sealed as well. Screw caps don't seal as well as people would like to believe and it's very possible for a braking system to draw in water over time.

41 minutes ago, xman said:

 

There is really only one way for water to enter the braking system and that is via the brake reservoir. Most modern caps seal fairly well but extreme heat changes could allow the cap to breath with expansion and contraction of fluid. I expect once water is absorbed, it will spread fairly rapidly throughout the entire fluid. High humidity, formation of dew overnight, rain, too much washing,  etc are the times that water could get absorbed. If these can be avoided, e.g. garage your car, then less of a problem.

 

 

 

Not 100% true. It is mostly through the resevoir but also through microscopic pores in rubber brake pipes which get hammered with water from the road (there are better sorts to try and avoid this) and from moisture/condensation on caliper & master cylinder walls that enters the systems as the hydraulic pistons move over the cylinder surfaces.  Also through moving valves with an external operation - I experienced this with a rear suspension height compensator valve.

 

In addition the resevoir cap cannot seal as it has a vent to allow the brake fluid level to drop as the brakes are operated (and rise on release)

 

Edited 16 November, 20187 yr by bigjohn

Motorbikes well mine anyway have flexible rubber seals on the inside that allow air to enter on one side but not through to the fluid. In theory that is the idea. I am very careful replacing my seal to ensure that it sits correctly under the cap which is secured by screws. I know that air will gradually pass but it is minimised.

2 minutes ago, Danny 57 said:

Motorbikes well mine anyway have flexible rubber seals on the inside that allow air to enter on one side but not through to the fluid. In theory that is the idea. I am very careful replacing my seal to ensure that it sits correctly under the cap which is secured by screws. I know that air will gradually pass but it is minimised.

 

I think on bikes this is more to keep the brake fluid in on leaning rather than moisture out however probably would protect against this. Maybee it's time to fit this to cars! 

 

 

 

 

 

"Leaning" I don't lean as I do not have the skills. Bikers with those skills and balls have what the call the chicken strip. How near they can get to the curved edge of their tyres. My bikes chicken strip is about three inches either side. 

 

Thanks Chimaera.

 

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