DOT 5 in aftermarket metering/proportioning valves

[Grady Cain]

Anyone having issues with leaks after using DOT 5 silicone-based brake fluid in the aftermarket valves from Inline Tube? I just had a PM conversation with a member here regarding this issue so I went to the source; a Support Tech. at Inline Tube and got some interesting answers to several questions I had:

I just got off the phone with Greg in Technical Support at Inline Tube and he told me NOT to use DOT 5 fluid in their metering/proportioning valves.

TAKE ALL OF THIS FOR WHAT IT'S WORTH - WHETHER OR NOT TO BELIEVE ANY OF THIS IS UP TO YOU. I AM ONLY REPORTING WHAT I HEARD DIRECTLY FROM HIM.

I asked him why this information was not on their website and he stated that this was something they have only discovered "...within the last 2 weeks" and that the common link to the leaks from each plaintiff was DOT 5 fluid.

I asked him if this was something the company was looking in to and he told me that they would be looking to their supplier/manufacturer of the parts to see if they are supposed to be or will be updated to be compliant with DOT 5.

I asked him if this only applied to recently manufactured parts (I told him I purchased mine in 2015 but haven't filled the system yet) and he stated that he would still NOT use the older parts. He said he had one that was purchased 6 months ago being the oldest one reported to fail.

I asked if the leak(s) appeared right away. He said, "No, they appear some time after being in service. The seals swell due to the silicone causing the leak(s)..."

I asked how Inline Tube was handling this issue regarding replacing parts that have leaked. He stated that they are shipping out replacements to anyone that had an issue.

I did not ask him how many people have had this problem but he did tell me that he had at least 5 persons calls this week with this issue.

Now be advised that if you go the DOT 5 route and have a leak in one of the valves and get a replacement part(s), you would have to completely flush out the entire brake system and go back to DOT 3/4 which is an incredible task to make sure there is no silicone left in any the components.

I would like to know if other manufacturers are having the same issues with their aftermarket metering/proportioning valves or if any other members have experienced this.

 

[moparleo]

For members unfamiliar with the different grades and applications of brake fluid, here is an article about the different fluids:
Brake Fluid

 

[aussiemark]

Back when I had to study brake systems as part of my training I was told that normal DOT 3 and 4 were hydroscopic fluids that absorb moisture during their service life and this lowers their boiling point so regular fluid changes were needed. DOT 5 does not absorb moisture so the moisture will collect underneath the brake fluid or the fluid will float on the moisture just like oil would. Because the moisture does this it would build up in the areas where it would do the most damage so regular fluid changes would be even more critical with this fluid this is why I never used it I would rather have the moisture absorbed by the fluid then separated the only benefit I can see is it won't ruin paintwork but if you don't have leaks and are careful with it it's not an issue anyway.