Dot 4 has a higher boiling point than 3.
Both are same basic fluid other than that and are completely interchangable Just avoid Dot 5
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New hydroboost still no brakes c10
- Thread starter Landon730
- Start date
Both are same basic fluid other than that and are completely interchangable Just avoid Dot 5
Just another note on the subject.
Last week I had to replace the Master Cyl in my K5. Original was dot5.
While trying to find a "dot5" compatible replacement I found that other than fluid type used there is no difference.
Decided after a good bit of research to move to Dot 3.
To do so I drained and flushed the entire system with denatured alcohol, once with Dot 3. Installed the new master (front calipers we're done 2 weeks ago) and refilled and bled the system. After driving for 1 day I re-bled all 4 corners and now my brakes are far better than ever.
Takes a while so give yourself half a day anyway.
I also used low press air for my flush.
(10psi)
I blew through the lines from master to each pair of slave cyls
Then again one at a time to insure that a Max of dot 5 was gone.
To Flush each slave with alcohol, I used the fluid container from my hand Vac Pump, adapted so I could use my 10 psi air to push the fluids through the system. Filled each slave and blew it dry twice with alcohol.
After alcohol I again flushed the system in the same manner with fresh Dot 3.
After the flush I refilled the plumbing and slaves, installed the new bench bled master and carefully vacuum bled each corner checking for any sign of contamination.
First day it developed a bit of spongy pedal. Re-bled and found a bit of air in the rears, none in front.
Brakes have never been better.
Even better, brake fluid went from $11.00/pt to $6.85/qt
I used about 1/2 gal of alcohol and 1 qt of Dot 3.
If you have been under the impression that the different fluids require different seal materials (as I was).
A little research on line will educate you on the real differences.
Last week I had to replace the Master Cyl in my K5. Original was dot5.
While trying to find a "dot5" compatible replacement I found that other than fluid type used there is no difference.
Decided after a good bit of research to move to Dot 3.
To do so I drained and flushed the entire system with denatured alcohol, once with Dot 3. Installed the new master (front calipers we're done 2 weeks ago) and refilled and bled the system. After driving for 1 day I re-bled all 4 corners and now my brakes are far better than ever.
Takes a while so give yourself half a day anyway.
I also used low press air for my flush.
(10psi)
I blew through the lines from master to each pair of slave cyls
Then again one at a time to insure that a Max of dot 5 was gone.
To Flush each slave with alcohol, I used the fluid container from my hand Vac Pump, adapted so I could use my 10 psi air to push the fluids through the system. Filled each slave and blew it dry twice with alcohol.
After alcohol I again flushed the system in the same manner with fresh Dot 3.
After the flush I refilled the plumbing and slaves, installed the new bench bled master and carefully vacuum bled each corner checking for any sign of contamination.
First day it developed a bit of spongy pedal. Re-bled and found a bit of air in the rears, none in front.
Brakes have never been better.
Even better, brake fluid went from $11.00/pt to $6.85/qt
I used about 1/2 gal of alcohol and 1 qt of Dot 3.
If you have been under the impression that the different fluids require different seal materials (as I was).
A little research on line will educate you on the real differences.
Will L.
Well-Known Member
@86 CUCV
I am not sure on sucess rates going from dot 5 to 3 or 4. Hopefully good.
I have seen and delt with many switches from 3 to 5- and it rarely is good after a couple years. People are normally pleased the first year. Depending on use it is usually sometime in the second year that problems start. Every flexible component failed. Master orings, slave seals, caliper orings and seals, rubber hoses.
Idk what the chemical reasons- just dealt with the results.
I feel your pain on the silicone dot 5 price. Being hydrophobic and over 1.5 times the weight of water, simple master cylinder inspection identifies moisture in the system as opposed to the hygroscopic dot 3,4,etc the moisture gets pulled through the system and simply lessens the ability to retain pressure and promotes rust and oxidation inside the system. But the fix is easy- flush and bleed every few years and it is cheap enough to do it.
On rigs like my hummer or racing applications where the higher operating temps could be present- dot 5 makes sense. On the cucv- no. The only reason it was done is one type brake fluid in military fleets- which is a good reason imo.
Please anytime you do brakes or it hits you it has been 6 months- post up on this thread to relay if any soft failures occured or hopefully that nothing is wrong and all is well.
I would love to hear going from 5 down works better than 3/4 up to 5.
I am not sure on sucess rates going from dot 5 to 3 or 4. Hopefully good.
I have seen and delt with many switches from 3 to 5- and it rarely is good after a couple years. People are normally pleased the first year. Depending on use it is usually sometime in the second year that problems start. Every flexible component failed. Master orings, slave seals, caliper orings and seals, rubber hoses.
Idk what the chemical reasons- just dealt with the results.
I feel your pain on the silicone dot 5 price. Being hydrophobic and over 1.5 times the weight of water, simple master cylinder inspection identifies moisture in the system as opposed to the hygroscopic dot 3,4,etc the moisture gets pulled through the system and simply lessens the ability to retain pressure and promotes rust and oxidation inside the system. But the fix is easy- flush and bleed every few years and it is cheap enough to do it.
On rigs like my hummer or racing applications where the higher operating temps could be present- dot 5 makes sense. On the cucv- no. The only reason it was done is one type brake fluid in military fleets- which is a good reason imo.
Please anytime you do brakes or it hits you it has been 6 months- post up on this thread to relay if any soft failures occured or hopefully that nothing is wrong and all is well.
I would love to hear going from 5 down works better than 3/4 up to 5.
I'll own the DOT3 to DOT5 "OOPS! from: the Skool of Hard Knocks" The DOT numbering system is too damn close to engine oil weights that really don't matter so much. So too easy to confuse with the marketing label claiming high temps on 3,4, and 5. First when you mix them they look weird with new brake fluid in the reservoir. So flushed the system with DOT5... 6 Months Later: replaced the brake system: master cylinder, calipers, rear wheel cylinders... Everything leaked.
@86 CUCV - you spent more on converting the system than you will save in fluid costs. It's not a bragging point of being cheap on brakes. Simply from the perspective of cost to replace the entire system if the seals don't like the change. The MC on my OOPS! completely failed to "No Brakes" so there is some real risk of a panic stop pushing the 'iffy' seals past failure. Adjusted and working parking/E-brake saved my ass.
Sure you read "Everything's Fine" with seals that are tested NEW. 30-40 year old seals may not like the change. Point of fact synthetic oil is enough to make an old engine leak. And then you have to ask was it the change or OLD seals just giving up?
Just saying you are doubling your odds of failure with "old seals" and a "fluid type" change.
@86 CUCV - you spent more on converting the system than you will save in fluid costs. It's not a bragging point of being cheap on brakes. Simply from the perspective of cost to replace the entire system if the seals don't like the change. The MC on my OOPS! completely failed to "No Brakes" so there is some real risk of a panic stop pushing the 'iffy' seals past failure. Adjusted and working parking/E-brake saved my ass.
Sure you read "Everything's Fine" with seals that are tested NEW. 30-40 year old seals may not like the change. Point of fact synthetic oil is enough to make an old engine leak. And then you have to ask was it the change or OLD seals just giving up?
Just saying you are doubling your odds of failure with "old seals" and a "fluid type" change.
point taken all of my seals are new in the last 30 days. Should have mentioned it My bad
As for the time spent, to me it was worth it. I now have better brakes new seals and a system that will provide safe reliable operation for some time to come.