Is DOT 3 Fluid OK?

[jj]

Yes, that is a fair assumption. Since the DOT5 is not hydr, uh, doesn't absorb water, it can tolerate sitting around much better than DOT3. The DOT3 fluid mixes with moisture that gets into the system then causes corrosion. When the moving parts move they sieze on the corrosion, and you get frozen wheel cylinders and calipers. Since the moisture that gets into the DOT5 doesn't mix, it just settles in the low points of the system. Yes it will cause corrosion there, but it doesn't seem to be as big a problem. I think because the "low points" tend not to be the moving parts.

 

[Stretch44875]

I found the wheel cylinders will collect the water that gets in DOT 5, and cause them to rust. When I first got my deuce, it had DOT 5 in it, and all the wheel cylinders had a little water in them, with the fronts needing honed. I was told that DOT 3 will slightly swell the seals, and they will seal better.

I flushed and changed to DOT 3 in the deuce a couple of years ago, due to the expense and availability of DOT 5. Haven't had any problems.

 

[jj]

You know,Stretch i got to thinking this last trip about what you said, and you are probably correct. Any water that gets into the system will migrate to the low points of the system. On most of the vehicles i've been under the low points are in the plumbing, but that is only going to matter if the water gets into the master cylinder. The water will accumulate in the low spots and stay there until you start bleeding brakes at a later time. Normally the fluid in the system doesn't really "flow", it just compresses. But, any water that gets into the wheel cylinders will tend to stay there, too. And, arguably, the wheel cylinders are exposed to much more water than the rest of the system. So DOT5 brake fluid really won't do much to protect the system from corrosion, except to the extent that when the DOT5 gets put into a vehicle that didn't start out that way, it usually involves putting new parts in too. Like new wheel cylinders and calipers with shiny new (read tight) seals. This is probably protecting the system from corrosion, by preventing water infiltration, more than the DOT5 fluid is. I think i just talked myself out of spending 25 bucks a quart next time any of the vehicles need brake work.

 

[sprucemt]

DOT 5, surplus, is $25.00 to $35.00 per GALLON, not qt. I would strongly suggest re-reading D Dolye's post and the US Military study done on this subject.

 

[jj]

Maybe $25-$35 per gallon as surplus but at the local NAPA store where i satisfy my cravings for instant gratification it is twenty-five American dollars per QUART. And they smile profusely when they take the money!

 

[allrevup]

All brake fluids absorb moisteur and degrades with heat, DOT 5 is the most inactivity, heat/cold fluctuations and moisture resitant but none the less it too will degrade, never used any fluid from a open unseal container, should be flush every 2 years as you also have degrading seals and metal contaminating the system, even the fluid in cans is suseptible to decay from the old metal containers ( Beware I have seen some OLD military stuff for sale in the internt) not shure of the shelf life of any...

 

[hobie237]

DOT5 does not absorb water. The water therefore collects at the lowest point(s) of the system (wheel cylinders and calipers) instead. That's one of the many differences between silicone fluid and regular brake fluid.

 

[Jake0147]

I have seen several vehicles with dot 3 and dot 5 mixed. I can not vouch for the sludge formation. I can't say that it can't happen, however I've seen mixes go for years with no issues of any kind.
I've also seen more than once where mixing of any proportion means that you must go by the wet and dry performance of the DOT3 used (since it won't "mix", the properties won't "average out".) I would think that the presence of jelly in the brake lines would be a more immediate concern than the jelly's boiling point.

I can tell you this with certainty. If you get power steering fluid in there with DOT 3 brake fluid (which used to be sold in a bottle that looked very, very similar), it WILL immediately make a nasty, gooey, alergy snot looking mess. If it's old and darkened brake fluid, it darkens even worse and the sludge is more like globs of sludge than an even mix. This steering fluid concoction (and I SUSPECT other petrolium products, but can't say for sure) most definately does attack rubber parts of the braking system. Master and slave seals first, but anything rubber is fair game.

I have never seen it in a real world brake master cylinder, but dot 5 does not seem to mix or care if there's power steering fluid or oil poured in with it. They stay separate.

 

[jdmcgowen]

Here is link to an interesting post on this subject. Please let me know what you think.
John
http://www.motorcycleproject.com/motorcycle/text/cows-brakefluid.html

 

[hobie237]

Short version: unless you think you're going to NEED the DOT5's benefits (higher boiling point, heat/cold resistance), it's stupid to run it. It's more expensive, more likely to lead to corrosion in the system, easier to get full of bubbles, and gives crappy, crappy pedal feel (this is why most sports car groups don't recommend, or even ban, DOT5 on race tracks). One of these days I may get around to flushing the truck's system out so I can dump in 3/4, if/when I get around to it.