DOT 5 in an 84??
 

I have a completley new brake system from the master cyl, new lines, valves, calipers and drums. I am ready to bleed the system. Is there any reason not to run DOT 5 brake fluid? I like the idea of the extended life you get with it. Is it safe in older style systems like on my 84?

Re: DOT 5 in an 84??
 

the military CUCVs 1983-1987,(K30s and K5s) run Dot 5 in their brake systems . . .

Re: DOT 5 in an 84??
 

I bleed older vehicles with Dot 4 all the time and haven't seen any problems yet. I'm sure Dot 5 would be the same. It should have a label on the bottle to let you know if it's compatible.

Re: DOT 5 in an 84??
 

don't do it man.

dot 5.1 o.k, but dot 5 has a tendency to eat seals in certian brake systems.
it might work, but i'd rather stay on the safe side and use 3, 4, or 5.1.

Re: DOT 5 in an 84??
 

Ya what they said, it's very good!

Re: DOT 5 in an 84??
 

I have been using DOT5 exclusively in all my vehicles from a 69 Chevelle up to and including my 84K 20 with great results. What you must do though is make absolutely sure the system is "clean"! No DOT3 left over anyplace. Rebuild or replace the MC, calipers and cylinders, flush lines with alcohol, or replace with stainless like I did and use the DOT5. Make sure you tag the MC so if you get oil changes at a shop they don't touch the MC and add DOT3. Also DOT5 will not attack the paint and works real good in locks. jim

Re: DOT 5 in an 84??
 

First of all, James McClure is absolutely right, they do NOT mix well at all. You must be sure that every part of the system is new or rebuilt and completely clean.

Second, where did you get the idea that DOT5 fluid has a longer life? From what I understand, the opposite is actually the case. DOT5 fluids are "silicone" based and as such will withstand higher temperatures, not do they absorb water from the air like "glycol" based fluids (DOT3 & 4). But there are trade-offs (negatives) By not absorbing the water in the system, it is free to corrode the steel parts. This factor alone means that is requires more frequent fluid changes, not less.


willett is mostly on track. DOT5.1 is really the best way to go. It is a glycol based fluid that meets DOT5 heat requirements. It's not that the DOT5 will hurt the seals, but that it allows the moisture to rust the steel parts.

Personally I use DOT5 in my motorcycles because of "paint" issues. Having one master cylinder hanging out over my gas tank and another bolted to the side of a color-matched frame makes it worth it to me. It has mostly aluminum parts and all braided lines, so I don't really have corrosion worries.

In a car/truck I would stick with DOT4 or the newer DOT5.1 if you feel the need.