Converting from DOT 3 to DOT 5 brake fluid

S

Sneaks

New member
Since my backup solenoid valve failed on the Pacific trailer, I'm considering a switch to DOT 5 while it's down for repair.

The DOT 5 label procedure involves draining the DOT 3, "flushing" and then filling and bleeding with DOT 5. Flushing with what? Some say alcohol, some say DOT5 (at $30/qt.)

There are a few tech articles like this one around but none really pertain to boat trailers which, IMHO, are perfect candidates for DOT5.

Bottom line: Has anyone here done the DOT3/DOT5 conversion? Any tips? I'm encouraged by the fact that any possible mixing isn't the "end of the world", so I'll probably do as NAPA recommended: Drain the DOT3, pour in and flush with a few bottles of alcohol normally sold to remove water from fuel, blow out the lines and start filling/bleeding with DOT 5.

Don
 
I just replaced my wheel cylinders(one was stuck) and considered the switch to DOT-5. I opted for a compromise. DOT-4. I'm convinced that my W.C. stuck due to water in the fluid. It was ugly when I drained it. Dot-4 is puportedly less hydroscopic than DOT-3 and less expensive than DOT-5($12.99/QT). It is also compatible. I never heard of using alchohol for flushing. I assumed I'd flush with DOT-5. That MIGHT have changed my calculations.
 
There is a big difference in the viscosity between DOT 4 and DOT 5. Dot 5 is much thicker.

Changing from DOT 3 to DOT 5 is acceptable, but changing from DOT 3 to DOT 4 may have unforseen cosequences. I found this out the hard way on a KTM bike. The rear brake would not work when I changed from DOT 4 (recommended) to DOT 5.

It may work, but I'd stick with the manufactures recomendation. They know the difference. If your brakes don't work, the cost difference is immaterial.

Boris
 
journey on":3f722pba said:
It may work, but I'd stick with the manufactures recomendation. They know the difference. If your brakes don't work, the cost difference is immaterial.
Boris
Click to expand...

I just spoke with Atwood customer service, maker of my 6,000 lb. actuator.

They do not recommend switching to silicon based DOT 5. Their reason? "Decreased brake performance" and the fact that the silicon based brake fluid does not break down any water that might enter the system.

I did not ask about glycol based DOT 5. (it does exist.) Oh well, it will make my job a lot cheaper.

Don
 
I have a 1982 shorelander tandem axle trailer under my SeaRay and
after inspecting the wheel cylinders and master cylinder they were
severely rusted. I replaced all of the wheel cylinders and master
cylinder (Atwood) in 1995 and flushed out everything and used DOT 5
Silicone brake fluid. I did not notice any deterioration of stopping
performance. The inside of the master cylinder looks like new
inside and I have not observed any water when I flushed the system.
Note: Silicone does not absorb moisture like conventional glycol
based brake fluids. I am very picky when it comes to brakes.
That's my $.02 worth.

Mike
 
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