DOT 4 to help brakes?

[bsinmich]

My motorhome is useless right now. I have read that DOT4 will absorb moisture quicker than DOT 3. Would there be any reason to fill the system with DOT4 for a couple weeks and then flush that out with DOT3? Would the DOT4 absorb some of the moisture that apparently is in the phenolic piston so that I could at least use my expensive toy a little bit? After a couple weeks I would flush again with DOT3 and try to use it this summer since Workhorse doesn't give a darn about us.

[DriVer]

Quote:

Originally Posted by bsinmich I have read that DOT4 will absorb moisture quicker than DOT 3.

Bill, Please know that DOT4 doesn't absorb water quicker it just absorbs more water over time. I know your thoughts on this matter are in the right place but all you just need to do if you are going to go through all this trouble is just simply flush your system using DOT3. It'll take about 3 quarts or a little bit more.

If you replace the fluid it'll bring all the nasty stuff out of the system. See the article I wrote about my fluid change. Will this help suck up the water out of the phenolic pistons that may currently be contaminated? Short answer, No. If you replace the fluid I can guarantee that the situation will not get any worse. Some folks have changed their fluid and then promptly had a seizure. This is why we all need to be mindful to replace this stuff in a timely manner so that in the long run it'll make a difference.

I know you want to get going and this would be a good thing to get out of the way and it not gonna cost an arm and a leg to accomplish.

[k1hog]

bsinmich and DriVer why after flushing and refilling with DOT 4 fluid, would you in a few weeks replace the DOT 4 fluid with DOT 3. I thought DOT 4 was better then DOT 3?

Thanks Johnnie

[bsinmich]

I have always flushed my brake fluid since my '89 F350 in my Jamboree, which I got new, had a brake failure in '92. When I moved to Holland, MI. and a condo, with no place to do it myself, I have tried to get it done many places and they all laugh at me for changing brake fluid. Since my daughter & SIL have 10 acres I now have a place and help to do it myself again. I use Ford DOT3 since it has been highly rated and my wife gets a discount from Ford (Ford retiree). I really want to use my MH but after 3 times last summer, with fresh brake fluid, I am still a little reluctant to go more than 5 miles from home.

[bsinmich]

Quote:

Originally Posted by k1hog bsinmich and DriVer why after flushing and refilling with DOT 4 fluid, would you in a few weeks replace the DOT 4 fluid with DOT 3. I thought DOT 4 was better then DOT 3? Thanks Johnnie

Ford, using the same brake caliper from Bosch, recommends DOT4 while Workhorse recommends DOT3. My impression is that the piston will absorb the moisture from the fluid and would indicate that having DOT4 in there would only give a greater opportunity for moisture to be in the system. I just want to be able to go more than 5 miles before having a problem.

[DriVer]

Quote:

Originally Posted by k1hog bsinmich and DriVer why after flushing and refilling with DOT 4 fluid, would you in a few weeks replace the DOT 4 fluid with DOT 3. I thought DOT 4 was better then DOT 3?

Johnnie, The way I read the performance specs between DOT3 need DOT4 vs what is required is that these fluids are simply different. 4 is not better than 3 unless there is a need in your hydraulic system that requires 4. For the same reason we also see 5.1. Now add to this the marketing prefix "super" and an customer could really get confused pretty quickly. What if we saw "Super DOT3" ??

On new vehicles, the requirement for our hydraulic systems calls for DOT3. If an owner replaces their fluid every 2 years, the fluid will perform as if new for the life of the vehicle. The performance specifications of DOT3 meet or exceed the need of the system.

I am not at all certain if the fluid specification will change after the recall however right now Ford uses a Super DOT4 in their system with a maintenance advisory to replace the fluid every "2 years." Funny thing is both hydraulic systems are pretty much the same except that Ford uses a 73mm Bosch caliper on its front axle for weights of 24K and greater. It might be the case that the 73mm calipers generate more heat therefore the fluid requirement for Super DOT4 was set to meet that need of that caliper. The fact that DOT4's hygroscopic capability is more aggressive probably sets the maintenance need to replace the fluid every 2 years.

Workhorse uses a Quad piston Meritor caliper on GVWs of 24K and up that only needs to use DOT3.

[mrschwarz]

The difference between DOT 3 and DOT 4 brake fluid is the affect moisture has on its boiling point. When it comes to brake fluid, the higher the boiling point the better it is. Both types of brake fluid are hygroscopic (they absorb moisture). The more water they absorb, the lower the boiling point goes. DOT 4 is designed to have a higher boiling point than DOT 3 after absorbing the same amount of moisture. DOT 4 will always perform better than DOT 3 and the premium cost is marginal. If it were me and DOT 4 was available, I would always choose it.

[scoutmstr]

Quote:

Originally Posted by mrschwarz The difference between DOT 3 and DOT 4 brake fluid is the affect moisture has on its boiling point. When it comes to brake fluid, the higher the boiling point the better it is. Both types of brake fluid are hygroscopic (they absorb moisture). The more water they absorb, the lower the boiling point goes. DOT 4 is designed to have a higher boiling point than DOT 3 after absorbing the same amount of moisture. DOT 4 will always perform better than DOT 3 and the premium cost is marginal. If it were me and DOT 4 was available, I would always choose it.

Well and correctly stated. The only thing I would add is Castrol Dot 4 LMA gives high boiling point and Low Moisture Absorption. Search will bring up previous thread with link on tests.

[DriVer]

Quote:

Originally Posted by scoutmstr Well and correctly stated.

I agree 100% with the technical report on DOT3 and DOT4. Thank you!

What Workhorse owners need to keep in mind is if they buy the least expensive DOT3 they can find and flush it every 2 years, they will go a long way in maintaining the like new performance of their hydraulic brake fluid and system.

[oemtech]

DOT 4 or greater is NOT going to solve the "moisture" problem. It will allow you a bit of breathing room before your brakes start to fade. Me I added a set of Speed Bleeders and get 3 qt's of DOT 3 from Wally Word and flush and bleed the system yearly.

[al koffman]

At the risk of putting my foot in my mouth, I will still make this statement:

Regardless of which brake fluid you are using, if you are reaching the boiling point then you simply do NOT know how to properly use the brakes and/or downshift.

Al

[dieselclacker]

Quote:

Originally Posted by al koffman At the risk of putting my foot in my mouth, I will still make this statement: Regardless of which brake fluid you are using, if you are reaching the boiling point then you simply do NOT know how to properly use the brakes and/or downshift. Al

Al,


Dieselclacker

[Campingman]

Quote:

Originally Posted by al koffman At the risk of putting my foot in my mouth, I will still make this statement: Regardless of which brake fluid you are using, if you are reaching the boiling point then you simply do NOT know how to properly use the brakes and/or downshift. Al

You reading my mind?

[DriVer]

Probably for the same reasons that someone would choose to use Hi-test rather than Regular, fluids are specified to meet or exceed the need of the system. On our hydraulic brakes systems all we need to use is DOT3.

Ford uses a 80% similar brake system on their vehicles however their requirement for DOT4 is clearly labeled on the Hydro-Max. The label continues to state and use only Super DOT4.

Again, the fluid used meets the requirement set forward by the OEM.