Home » Public Forums » GMCnet » Flushing Brake System
| Flushing Brake System [message #278851] |
Mon, 01 June 2015 16:02  |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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Considering changing the brake fluid that the P.O. installed in my coach with DOT 4. He installed DOT 5, harder to find and much more expensive. Other than pouring DOT 4 in and pushing it through the system, what other headaches can I expect to run into.
I am moving to 80mm Calipers on the front this week. Coach has OEM front brakes and I would like a litttle more stopping power, since I now have a Toad.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: Flushing Brake System [message #278852 is a reply to message #278851] |
Mon, 01 June 2015 16:45  |
rickmike
Messages: 252
Registered: September 2011
Location: United States
Karma: 0
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Stick with the DOT5. You don't have the moisture problems of regular brake fluid.
Rick M.
1974 26' Canyonlands
aka "The General"
Clinton, TN
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| Re: [GMCnet] Flushing Brake System [message #278866 is a reply to message #278852] |
Mon, 01 June 2015 20:17 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Tom,
Here's a link to DOT 5 that sells for $21.85 for a quart:
http://www.amazon.com/Motor-Medic-Gunk-M4032-Silicone/dp/B00200C5SI/ref=sr_1_1?s=automotive&ie=UTF8&qid=1433206821&sr=1-1&keywords=d
ot+5+brake+fluid
that is only $6.00 more than my favorite DOT 4:
ATE DOT 4
http://www.tirerack.com/brakes/brakes.jsp?make=ATE&model=Type+200+Amber+Brake+Fluid
If I were you I'd get one of Jim Hupy's pressure bleeders:
http://www.bdub.net/jhupy/
and flush the DOT 5 every 3 years
In my opinion best practice when changing from DOT 3/4 (or vice versa) is to disassemble, clean, and reassemble all the parts in the
system then fill it with DOT 3/4.
You are going to get a lot of responses contradicting my last statement which will be "I changed from DOT 5 to DOT 4 and all I did
was flush out the system with DOT 4 and it's been working fine since I did it." Or "I purged the DOT 5 with air and then flushed the
system with alcohol then DOT 4 and it's been working fine since I did it.
Rick,
DOT 5 has moisture problems as well.
DOT 4 is hydroscopic and will absorb water which will lower the boiling point and cause brake components to rust internally if not
flushed regularly. Regularly is defined by the brand of fluid you use. I use ATE and they recommend flushing every three years:
http://www.gmcmhphotos.com/photos/aa-miscellaneous-photos/p41972-ate-brake-fluid.html
DOT 5 is hydrophobic and will not absorb water, HOWEVER, if water gets into the brake system it can gather at high points and if it
freezes you got a problem!
For many years Harley Davidson used DOT 5 brake fluid because if you spill it on paint it is innocuous, they reverted to DOT 3/4
because of the problem noted above.
Here's a bit of extra reading:
http://www.epicbleedsolutions.com/resources/faq/difference-between-dot4-and-dot51-brake-fluid/
Regards,
Rob M.
The Pedantic Mechanic
-----Original Message-----
From: Richard Michelhaugh
Stick with the DOT5. You don't have the moisture problems of regular brake fluid.
Rick M.
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Flushing Brake System [message #278868 is a reply to message #278866] |
Mon, 01 June 2015 20:27 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I suggest that you build yourself an experiment. Take equal amounts of DOT3/4 and DOT5. Mix it in a small jar and see what happens. I have been told it will turn to goo. I have never seen it myself but you might see and try it for yourself before installing it in your coach.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Flushing Brake System [message #278897 is a reply to message #278871] |
Tue, 02 June 2015 02:15 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Matt Colie wrote on Mon, 01 June 2015 20:47Here I am again....
And, I have two things to add.
One is that Rob is wrong by a little. The sg of DOT5 is about 0.96, so the water will settle to the low points where it can do the most damage.
The other is seal swell. Just about all elastomers swell when exposed to just about anything. Rubber seals and brake fluid fit here. So, the system seals have all absorbed some DOT5 and now have the accumulated swell. When you change the fluid to DOT4, all the parts that soaked all the DOT5 that they could will now add the swell of the DOT4 to the show. Ergo, changing to DOT4 may not be the best answer. I have had trouble that I thought I was avoiding changing brake fluid both ways.
I have not tried Ken's experiment.
Matt
I also have not tried it. I have always stayed away from DOT 5 so I have none around here to try.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Flushing Brake System [message #278898 is a reply to message #278871] |
Tue, 02 June 2015 02:43 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Matt,
DOUH - oil floats on water!
As far as Ken's experiment goes all I can say is AHA! Now I know why one Harley I worked on had "jelly" in the front brake master
cylinder on the handle bars!
Regards,
Rob M.
-----Original Message-----
From: Matt Colie
Here I am again....
And, I have two things to add.
One is that Rob is wrong by a little. The sg of DOT5 is about 0.96, so the water will settle to the low points where it can do the
most damage.
The other is seal swell. Just about all elastomers swell when exposed to just about anything. Rubber seals and brake fluid fit
here. So, the system seals have all absorbed some DOT5 and now have the accumulated swell. When you change the fluid to DOT4, all
the parts that soaked all the DOT5 that they could will now add the swell of the DOT4 to the show. Ergo, changing to DOT4 may not
be the best answer. I have had trouble that I thought I was avoiding changing brake fluid both ways.
I have not tried Ken's experiment.
Matt
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: Flushing Brake System [message #278960 is a reply to message #278851] |
Tue, 02 June 2015 20:33 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Dot 5 works well in antique and street rods that are not used much. It keeps the system nice and clean and mostly moisture free. It doesn't work as well in the motor home unless you flush it on a regular basis just like 3&4. My street rod has the same dote 5 in it for a ton of years. I had it in the gmc but I lost the brakes on a steep down hill decent due to moisture in the front caliper. The moisture doesn't mix with the dot 5 but it will be in a pocket and you will loose your brakes if they are over heated. I had to bleed the front calipers in Kings canyon national park in order to continue down the mountain or wait till they cooled enough to continue then worry about the peddle going to the floor again. I pumped dot 3 thru the system when I got home to displace it as dot 5 costs too much to replace every couple of years.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Flushing Brake System [message #278971 is a reply to message #278851] |
Tue, 02 June 2015 23:46 |
Adrien G.
Messages: 474
Registered: May 2008
Location: Burns Flat, OK 73624
Karma: 1
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Senior Member |
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tphipps wrote on Mon, 01 June 2015 16:02Considering changing the brake fluid that the P.O. installed in my coach with DOT 4. He installed DOT 5, harder to find and much more expensive. Other than pouring DOT 4 in and pushing it through the system, what other headaches can I expect to run into.
I am moving to 80mm Calipers on the front this week. Coach has OEM front brakes and I would like a litttle more stopping power, since I now have a Toad.
Tom, MS II
Thomas,
FWIW I've been using DOT 5 on a 87 Goldwing, 65 Corvair, for about 20 years with flushes every 3 to 4 years. And now on a 75 Glenbrook.
I've never experienced any problems using it. Being Hydrophobic in mature, I think it would make it a better choice in high humidity areas.
Just what I've done.
Adrien & Jenny Genesoto
75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior Rebuild
Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6
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| Re: Flushing Brake System [message #279018 is a reply to message #278971] |
Wed, 03 June 2015 15:44 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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OK. I'm convinced nothing to be gained by changing from DOT 5. Lower Alabama is a high humidity area, almost all year around. Mobile, AL is one of the wettest spots in the nation.
Ordered two qts from OReilly's. At $14 per qt, better than pints at $10.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] Flushing Brake System [message #279026 is a reply to message #279018] |
Wed, 03 June 2015 18:40 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Tom,
There you go - If it's not broke, don't fix it!
I am of the opinion that the key to a long lived braking system is flushing it as recommended by the brake fluid manufacturer be id
DOT 3, 4, 5, or 5.1,
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
-----Original Message-----
From: Thomas Phipps
OK. I'm convinced nothing to be gained by changing from DOT 5. Lower Alabama is a high humidity area, almost all year around.
Mobile, AL is one of the wettest spots in the nation.
Ordered two qts from OReilly's. At $14 per qt, better than pints at $10.
Tom
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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