I just bought a 78 FXS that has been in storage for 4-5 years. The front brakes were pretty much seized. When I took them apart I noted that the fluid appeared to be DOT 3 (yellow not purple) even though the shop manual says to use DOT 5. The front master cylinder is aftermarket chrome piece with no marking. The previous owner is dead (bought it from his widow) so I can't get any info there. I'm inclined to use DOT 3 but would like to know get some thoughts from people that may know better. Am I better off using DOT 5?
Thanks,
Scott

 

If you ain't sure what is in there, and ya need to work on it anyway...Flush, rebuild, Use dot5.
Or Just dump some in and see! Dot3 has some advantages...Paint remover comes to mind!

 

Dot 5 doesn't stay purple for long..after a short time it looks kinda...yellow. I wouldn't put 3 in anything with nice paint.

 

exactly.. DOT5 turns tellow in time

 

you can determine what's there by stirring a few drops into a shot glass of water - dot 3 will dissolve but dot 5 will not

 

Dot 3 has a distinctive smell and feels kinda warm on your fingers , I quit using 5 and went to Dot 4 on everything now. Better hang time and not a touchy as 5 and won't remove paint like 3.

 

Will remove paint exactly like 3...both are polyglycol ether...4 has more borate to increase the boiling point.

 

The inside cover of the reservoir says DOT3 only. Shop flushed it and put DOT5 in , said it didn't matter.

Just stating my experience, brakes have worked fine so far. Is it right, wrong or what?

 

If you've done a complete flush you'll be 100% okay