Standard brake fluid or silicone DOT5 brake fluid?

[LucasDK]

Originally Posted by Trav

Soft copper line AFAIK is not allowed anywhere but if a Cunifer mixed metal type is used OE it is allowed, many of the high end cars use it. Soft copper is crap for all automotive lines, it work hardens, cracks, splits and corrodes.


1. In my search I had an interesting personal talk to a sales person in one of the biggest manufacturers/importers of brake lines in Europe (www.ojd.dk). They supply all countries in Europe and they offer both 100% copper and cunifer lines. Basically they ship 100% copper lines and no cunifer lines to all countries in Europe and all the way to Russia except for Germany.
2. I can safely attest that 100% copper lines are readily accepted by all TÃœV inspections in Denmark.Without question! And trust me, Denmark is heavily equally regulated by EU laws as Germany
3. When contacting the biggest OE spare parts supplier in Denmark (suppling/delivering spare parts 5x a day for 90% of all automotive workshops in Denmark), they did not have Cunifer lines in stock, only 100% copper lines suggesting that none of the automotive workshops use cunifer lines.
4. When contacting OJD an asking for a Danish shop where I could rapidly buy some cunifer lines, the answer was negative. They suggested that I buy them online in Germany!

Lucas

 

[Silk]

Originally Posted by Trav
. Soft copper is crap for all automotive lines, it work hardens, cracks, splits and corrodes.


Copper is legal in NZ, but has to, be secured every 300mm to stop flex which causes the work hardening. Preferred on boat trailers because salt water will rust a steel bundy tube pretty fast.

 

[Trav]

Cracking is the problem with copper, also the clamps used to secure it the copper can cause galvanic corrosion depending on the material and lead to cracking under pressure.
No OEM uses pure copper AFAIK, some of my cars have Cunifer OE they are Swedish and German cars. I wouldn't put soft copper brake lines on my car or anyone else's for any price.

https://vtauto.org/copper-nickel-brake-line/

 

[Trav]

Originally Posted by Chuckh
Isn't TÃœV similar to UL we have here in the USA?


Yes but they also inspect vehicles of all types, many of the TÃœV inspectors that inspect vehicles are degree engineers and only they can restore a certificate of roadworthiness if the vehicle has lost it for some reason eg being off the road for too many years, illegal parts (no ABE) or non approved repairs done, restored antiques,etc.

 

[djb]

An issue that is often forgotten: does it freeze where the vehicle is located?

If so, DOT5 is a poor choice. The separated water will form beads of ice that can plug the system.

This is one of the reasons that DOT5 is appropriate for show cars and race cars, but not daily drivers.

Personally I would stick to DOT4 fluid and change it every 2-5 years. It generally inhibits corrosion until a threshold of 5% is reached, which might take over a decade with an intact system. Corrosion happens rapidly above the threshold, so don't forget to change the fluid.

There is an inherent trade-off between dry boiling temperature and hygroscopic behavior/avidity. A high quality DOT3 fluid can potentially have a much longer service life than a DOT4 fluid. But it is cheaper to make a low quality DOT3 that sucks up just as much moisture, so you might as well just buy a good DOT4 fluid.

 

[Trav]

Where is this water coming from?

 

[djb]

Originally Posted by Trav
Where is this water coming from?


You are suggesting that something was left open? Yes, that would be bad. It is also obvious and is not the general problem.

A tiny bit at a time from everywhere.
Diffusion through rubber, even thick hoses and properly functioning seals. Through the fill cap, even with a diaphragm seal. A hot braking system that cools suddenly when driving through a puddle will suck a little moisture through the boot and seal. If that alone doesn't do it, tiny pockets of water trapped in the seal will flash into high pressure steam the next time the brakes get hot.

 

[LucasDK]

Originally Posted by djb
An issue that is often forgotten: does it freeze where the vehicle is located?

If so, DOT5 is a poor choice. The separated water will form beads of ice that can plug the system.

This is one of the reasons that DOT5 is appropriate for show cars and race cars, but not daily drivers.

Personally I would stick to DOT4 fluid and change it every 2-5 years. It generally inhibits corrosion until a threshold of 5% is reached, which might take over a decade with an intact system. Corrosion happens rapidly above the threshold, so don't forget to change the fluid.

There is an inherent trade-off between dry boiling temperature and hygroscopic behavior/avidity. A high quality DOT3 fluid can potentially have a much longer service life than a DOT4 fluid. But it is cheaper to make a low quality DOT3 that sucks up just as much moisture, so you might as well just buy a good DOT4 fluid.


Thank you, you nailed it with the ice argument. It will experience freezing temperatures. I will go with the DOT4.

Lucas

 

[Trav]

Funny, HD hasn't had any issues with water in the system over the many years of using it OE and I didn't either in 12 years in the same system.
The fact the master cylinders are exposed to the elements, they are sealed but still no water entered through the seals or hoses.
Sorry I am not buying it that is is getting in through the seals and hoses, too many people have been using this stuff for decades without issue.