5ive0

Ok so I understand that brake fluid absorbs moisture and becomes less effective over time. So especially on cars that are being tracked, I get it, it needs to be changed.

Having said that there are many other cars out there which have never had their brake fluid changed and they are fine 10-15 years later.

Can someone educate me on the reason for the frequent changes on our cars and other German brands? I like to keep my cars well maintained, but I like to be educated on why I am doing things.

So what happens if its done every 5 years for instance. Is there some exposure to hoses that degrade? Or is it simply about stopping effectiveness only, because I've never heard of brake fluid abruptly failing.

Educate me.

993GT

brake fluid attracts and holds moisture...bleeding it purges the moisture out and protects the metal system components. The Euro brands specify it more frequently as many rely on heat capacity of the brake system for Autobahn usage...fresh fluid has a much higher boiling point than old/moisture-laded fluid

craig001

IIRC Porsche recommends a fluid flush and fill every two years. It's a good thing since in addition to absorbing water a lot of crud can build up in the lines and calipers.

jbossolo

I track mine 1-2 times a year. I change all fluids before every event, tranny oil once per year.
It's cheap compared to the alternative.

Macster

Even if one accepts that cars have gone for years with no brake fluid change and there are no problems I am reluctant to gamble the brakes and braking performance of my Porsches for the sake of saving a few dollars in brake fluid.

Have to point out that for some Porsche models the clutch shares the fluid with the brake system.

Based on my first hand experience with my Boxster and letting its brake fluid go just 2.5 years (lost track of time) without a flush/bleed while the braking action was apparently unaffected as it turned out clutch action was negatively affected.

The symptoms were I was unable to move the car from a stop smoothly no matter how hard I focused on my clutch work. And shifting became crunchy as if I was not depressing the clutch all the way or my timing of when I pushed the clutch pedal down and shifted was off.

An overdue brake/clutch fluid flush/bleed eliminated the problems with the clutch and shifting.

While as I noted above braking action before and after was as far as I could tell the same the transformation of the clutch and shifting action was remarkable and convinced me the 2 year brake fluid flush/bleed is very important.

Even in a Tip/PDK equipped car I see no benefit in skipping this service. I am not anxious to have to deal with brake problems arising from the lack of proper fluid servicing even if braking performance is unaffected. And one might not know braking performance was affected until too late.

Kevinmacd

if moisture absorbtion is an issue, using a DOT 4 synthetic will surely fix the issue. Motul makes a dot 4 synthetic.

Macster

While the synthetic brake fluid does not absorb water any water that gets into the system will sink down to the lowest point which has to be the brake calipers/piston area. Upon hard braking and high temperatures the water there will boil at 212F (vs. the ~500F boiling point of synthetic brake fluid) and affect braking.

Thus one should still perform a periodic brake fluid flush/bleed.

Also, synthetic brake fluid is my info primarly used by the military due to its superior low temperature performance. In spite of this there is some indication the military is desirious in moving away from synthetic brake fluid and moving back to DOT 4 fluid. If this happens then synthetic brake fluid could become extinct with the fall off in demand from the military.

This could be a problem as I understand it the recommendation is once one switches to a synthetic brake fluid there is no going back.

There is too the risk of moving to synthetic fluid in an older car. The brake system likely has sludge -- especially if the owner is one who has skipped the regular brake fluid flush/bleed services -- and the synthetic fluid will combine with this sludge and could cause sticky pistons.

There is nothing wrong with good old DOT 4 fluid. All that is needed is a regular flush/bleed and the braking system should perform properly with no other attention for years and years and hundreds of thousands of miles.

Given the risk of moving to a synthetic fluid, along with the necessity of doing a flush at least to push any water out of the calipers, staying with a DOT 4 fluid seems the lesser of two evils.

Fishey

All brake fluid even synthetic except dot 5 silicon will absorb water. They sell testers for contamination after 2 years generally your looking at 2% . Cheap fluids will start at 1% always use good fluid I suggest oem ATE products. The water contamination can cause corrosion in the brake pistons as well as cause failure of the abs valves. I have seen both happen if the systems are neglected for to long. I always do mine every 2 years. If your car is kept in climate control you will find most ire contamination isnt as bad or if you live in a place that doesn't see big temp changes.

5ive0

Plus the possible effect on the brake lines. This makes sense. I'm convinced. Thanks for all the replies.


What are people paying these days for a brake flush?

Fishey

Hour labor plus fluid cost

z06801

The thing is with brake fluid is, SRF never a problem

Kevinmacd

Thats just it regular brake fluid actually acts like ethanol in gasoline, it absorbs moisture from the air ( hygroscopic). If you use true synthetic mineral based, it does not pull moisture from the air, non hygroscopic or known as hygrophobic, therefore the amount of moisture is nil as compared to standard brake fluid. Not advocating mineral,oil base is compatible with our cars So the degradation on the braking system is minimul. It doesnt load up in the bottom as you stated since the amount is negligable. Yet considering dot 5 and 5.1 not mineral oil based does have its negative side, one being compressibility.

SteveMFr

Silicone based brake fluids tend to entrap air (dissolved air, not air that can be bled out of a brake system). They also tend to expand at significantly lower temps than their actual boiling points. Both of these items lead to soft, spongy pedals. This is why they are not used in performance applications or race cars.

If this was a cure-all, Porsche would have sent the cars out of the factory with silicone based brake fluid.

Fishey

The only things I have seen with silicone brake fluid are military vehicles. They are not well known for braking prowess.

Kevinmacd

First off no one has said silcone based brake fluid is a cure all. The discussion was about moisture. Secondly mineral oil based synthetic is totally different than silicone based. Not advocating mineral oil based brake fluid is compatible, just pointing out the characteristics.
Staying with a high qualty dot4 per Porsche is the way to go for all round performance.