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Brake fluid
Posted: Mon Nov 20, 2017 1:06 pm
by RolandRat
Hi all, What brake fluid should I use? I am thinking DOT 3 or DOT 4 ? (1942 CCKW353) Thanks, Roland
Re: Brake fluid
Posted: Mon Nov 20, 2017 1:08 pm
by Bill_Wolf
DOT 3. Flush every year
Re: Brake fluid
Posted: Tue Nov 21, 2017 7:22 pm
by RolandRat
DOT 3 it is.. Ta very much.
Re: Brake fluid
Posted: Thu Nov 23, 2017 2:25 am
by mudflap
Hi RolandRat,
What kind of fluid is in the truck now? Are you just topping off? Or is this a system that has been rebuilt and you are starting from scratch?
If just topping off, first see what is in there now. It is probably DOT 3. Hopefully if the system has DOT 5, (silicone based) there will be a tag or some other indication on the master cylinder alerting you to that fact. As Bill mentions, its a good idea to flush every year. DOT 3 is hygroscopic ( just loves to absorb water). Since the CCKW's brake system is not sealed, it is easy for moisture to enter.
DOT 4 has a higher operating temperature than DOT 3. I don't see where this would be a factor on a drum brake vehicle like a CCKW.
If you are doing a ground up rebuild, you may want to consider DOT 5. Silicone based fluid does not absorb moisture like DOT 3, although it is still a good idea to flush every few years just to ensure that any stray moisture that may have entered the system gets purged. The other advantage of DOT 5 is that it won't take the paint off everything it comes in contact with like DOT 3.
Some will argue against DOT 5 over the concern of possible engine damage in the event of a hydrovac internal seal failure - which could cause brake fluid to be sucked into the engine. However, in a newly reconditioned system, I think the likelihood of this is rather low. DOT 5 is also more expensive than DOT 3.
When I rebuilt my system several years ago I used DOT 5, and have not had any problems.
Best Regards.....
Re: Brake fluid
Posted: Sun Nov 26, 2017 4:44 am
by RolandRat
Hi, don't know what fluid was used in the past. I lost the fluid and assume its the Hydrovac seal issue mentioned in another thread.
This was some years ago and I am now sorting through the braking system. 2New wheel cyl. 2 cyl repair kits, Master cyl repair kit. All hubs off so new hub seals.
Issue I have is knowing how to strip down the Hydrovac unit !! I'll ask in a spate thread.
Thank, Roland