Which DOT of Brake Fluid???

I just about have my brakes finished and got to thinking... What brake fluid does this thing take?? I looked in the manual but didn't see anything listed by DOT. We had a contract years ago to work on the postal Jeeps and I remember they used a different DOT of fluid and I was told back then not to mix the different DOTs or it would swell the seals in the system. ??? If this is true then I probably need to switch to a civy style master cylinder since I changed all of the wheel cylinders out to the Ford style and just run DOT3.

Thanks
Tim W.

Use dot 3 or dot 5. I use dot 5 in my trucks. I have heard the no-mix myth for a while. I haven't seen any actual facts that specify that they can't be mixed. Dot 3 obviously is the most readily available. Dot 5 has a higher boiling point (for high performance/high heat applications) which doesn't benefit the M715 much but is also less likely to absorb moisture that results in a rusted out braking system. This is a major benefit to us when the trucks sit for extended periods. This is why the military specifies dot 5 in all their applications.

I'd go with DOT5 were it me. That way moisture isn't as much of an issue, particularly if the truck isn't driven regularly.

The only issue I have ever thought might actually have some merit in mixing the two fluids, is the boiling point. Other than that, they both do the same job of non-compressible fluid.

DOT 5 it is. Thanks again guys

Tim W.

Look at the surplus places to get DOT 5 by the gallon at about the same price as the parts stors charge for a pint.

Will do, thanks for the tip!

:)

Check over on Steel Solders. 1 gallon cans were going for $25 + ride.

i was going through the truck i just bought and i noticed the master cylinder was low on fluid. checked on here and saw DOT 5 was the stock spec. I also saw not to mix DOT 3 and DOT 5. I called the local parts store and they only had a pint of DOT 5 and i called the previous owner and he said he couldn't remember what he put in when he did the wheel cylinders, probably the more common DOT 3. so i didn't know what to do... i didn't think a pint would be enough the flush the system of whatever was in there and leave it full afterwards. then someone on here said to get DOT 4 because it is compatible with DOT 3. so i didn't know what to do and went with DOT 4. i haven't put anything in yet and i think it probably has DOT 3 in it... but it may have DOT 5 so adding more DOT 3 could cause compatibility issues. what should i do? try and track down enough DOT 5 to flush and fill?

Silicon fluid didnt exsist when the 715 was made so they didnt use it. it could of course have been changed over later, it is purple in color when new to differentiate it from conv. fluid. here is an article about brake fluids-
http://www.afcoracing.com/tech_pages/fluid.shtml

Also it is reccomended that if u r changing from silicone to conv. or vise versa that u flush all lines and parts w/ alcohol and dry before installing the new fluid.