Brake Fluid DOT 3 and DOT 5

[Super Warrantman]

Hello. I have a 1977 M882 Dodge and I have what might be considered an obvious question. Long story shortened down considerably, I had my brakes repaired by a local Dodge dealer. I didn't have the equipment and the tools to make a proper job of it if I had attempted to do it myself. The truck now stops OK but I am concerned on one point and that is I don't know for sure what type of brake fluid the shop used. Was it DOT 3 which is the usual stuff everybody has in their cars' brakes, or was it DOT 5 which is what the military had specified? I know I had mentioned it to the service writer at the time the shop took on the job but I don't know which flavor they used to accomplish the job. Is there a way one can tell?

I have learned in my reading in the car hobby that DOT 5 is a fluid that doesn't attract moisture as much as DOT 3 and is a better fluid to use if the vehicle is subject to long term storage (which is probably why the military specified it) It is my understanding too that one shouldn't mix DOT 3 and 5 fluids although I'm not sure what would happen if you did. I have been told that the brake system in my Dodge will work fine with either DOT 3 or DOT 5 fluid but it has to be one of the other.

Yes, I have heard that DOT 5 is more expensive.

So, if I need to top up my master cylinder at some future date is there a way to tell what fluid is already in there so I don't mix fluids? Suggestions?

 

[phil2968]

Put a small amount of it in a glass, add a drop of water. If the water is absorbed it is 3. If it stays separate it is 5.

 

[michigandon]

DOT 5 is purple, DOT 3 is amber.

 

[porkysplace]

DOT 5 is purple, DOT 3 is amber.

The purple fades over time .
this is a good thread on how to tell the difference ;
[h=3]Brake fluid -how to tell which kind you have DOT 3 or DOT 5[/h]

 

[Flyingvan911]

My first instinct would be that they used DOT 3 since that's what the put in every car that comes into the shop. Unless you told them it takes DOT 5.

 

[Bob H]

jeez, give the service tech the benefit of doubt.
Your truck have those yellow stickers on it that say Use Silicone fluid only?
He may have noticed.
What was written on the repair bill?
Could simply stop in and ask the service guy.

 

[whiskey357]

Greetings and the right dot stuff makes a big difference on cost not results.......go ask the repair what he added...simple fix...

 

[Super Warrantman]

Thank you all for your replies; especially Porkies Place. My truck still has the yellow sticker under the hood that says it is supposed to take silicone brake fluid only so it is possible the tech noticed it. I did say something about it to the service writer too, but there was nothing on the work order to indicate what kind of brake fluid was actually used in the repair. I will have to stop by the shop and ask what was used I suppose to be sure.

 

[Gunzy]

If it has been mixed just empty the system and flush with DOT3 then thoroughly bleed the system with DOT3 and stay with it. Would cost less than do it all with DOT5. JMO

 

[Bob H]

If it was DOT5 & they added DOT3, it should have blended by now & would look nasty.