Re: D.O.T. 3-4 vs. D.O.T. 5 for a '56 Patrician

Posted by HH56 On 2015/9/15 13:20:05

IMO, there is no proof one way or the other. Just anecdotal evidence that those who change the fluid and use 5 seem to report having a brake switch failure not that long after the change. Whether the failure is due to the fluid or the switch was on the way out before the fluid change and would have gone anyway is unknown.

The silicone is slightly thinner fluid so conceivably it could seep into the inner workings or there may be an incompatible substance that is damaged by the silicone. I don't know if anyone has ever taken a failed switch apart to see if they can spot what happened.