Splangj
Well-Known Member
Yep! Wasn’t aware of dot 5.1.
Dot 5 mixing
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steve340
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DOT 5 silicone fluid is OK to use in classic car brake systems but it must be used from day 1 when all components are fresh and new. That is my understanding anyway and I have never tried to flush 4 out to replace it with 5.
I have also read articles were RE advises its use 0f 5 - but I don't recall him ever advising they can be mixed. It is routinely fitted to brake systems in colder climates I read because it will not freeze - but it does not absorb water at all so any water in the system stays in little globules.
My GTX with Bendix discs has 5 it in and nice firm brake pedal - no issues.
The DOT 3 and 4 are compatible as far as I know but should never be mixed with silicone based DOT 5.
I have never liked working on brakes so I take no chances screwing something up.
I have also read articles were RE advises its use 0f 5 - but I don't recall him ever advising they can be mixed. It is routinely fitted to brake systems in colder climates I read because it will not freeze - but it does not absorb water at all so any water in the system stays in little globules.
My GTX with Bendix discs has 5 it in and nice firm brake pedal - no issues.
The DOT 3 and 4 are compatible as far as I know but should never be mixed with silicone based DOT 5.
I have never liked working on brakes so I take no chances screwing something up.
I'd say give it a go. Mix 'em up.
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While I like RE, and have bought stuff from him in the past, in this case he is incorrect. The DOT specs do specify composition, and that's the reason why DOT 3 and 4 are clear or light amber, while DOT 5 is purple, to make sure people are aware there's a difference when they grab a bottle.
And then fluid bulk modulus (compressibility):
DISADVANTAGES OF SILICONE FLUIDS
DISADVANTAGES OF SILICONE FLUIDS
- Compressibility — Silicones have a poor bulk modulus. In practice, this means they can compress up to three times more than conventional fluids when pressurised in a brake system. This results in a “spongy” feel to the brake pedal, together with long pedal travel. These effects can be countered by fitting over-sized master cylinders but this is expensive and produces non-standard components.
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^^^THIS^^^
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I've been using DOT 5, starting with a brand new system, for five years now. I did notice a slight bit of give in the pedal versus Dot 3 or 4 but not by much. It's like having a 1/2" of play in the pedal before its solid when you would have no play using DOT 3. It's also supposed to tolerate heat better than a glycol-ether fluid. It's why they use it in racing applications.
Someone brought up the fact that any moisture in the system won't be absorbed and it separates. I haven't seen this in this system yet.
And as far as reacting with paint, I've had a slight leak from the master cylinder cap periodically and I painted the MC before installing it. Not even any discoloration has taken place.
Someone brought up the fact that any moisture in the system won't be absorbed and it separates. I haven't seen this in this system yet.
And as far as reacting with paint, I've had a slight leak from the master cylinder cap periodically and I painted the MC before installing it. Not even any discoloration has taken place.
Ok, you guys that want to mix.
Grab a pickle jar or any small glass jar and pour a inch of DOT 3 in it.
Now pour a inch of 5 in.
Stir it up and go back later and check it out.
Grab a pickle jar or any small glass jar and pour a inch of DOT 3 in it.
Now pour a inch of 5 in.
Stir it up and go back later and check it out.
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Already did this in another thread.
Mixing Dot 3 with Dot 5 it just wants to separate. If I stirred it, it would turn into a thin jell but soon after it would separate again.
Dot 3 and Dot 5 together.
After stirring
After sitting for awhile.
Ok then
In a brand new system, on my 70 Charger
DOT 3 or DOT 4
What is the consensus??
In a brand new system, on my 70 Charger
DOT 3 or DOT 4
What is the consensus??
They are the same with 4 being a higher boiling pt.
I use 3 or Super 3 in everything.
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The original spec is the safe choice. There is no down side if you never have any leaks and do proper maintenance.
For a street beater where damaged paint in the engine bay isn't a concern, DOT 3 or 4 is fine.
I repainted my engine bay last year and prefer to keep it looking good so I went with DOT 5. New front calipers, master cylinder anyway, so....
For a street beater where damaged paint in the engine bay isn't a concern, DOT 3 or 4 is fine.
I repainted my engine bay last year and prefer to keep it looking good so I went with DOT 5. New front calipers, master cylinder anyway, so....
I guess I’m leaning toward the DOT 3
I will have to check out this Super 3 plus do a bit more research before I go charging the system. All the years I’ve been playing around with cars, I’ve never had the misfortune of spilling brake fluid
I know that there’s always a first time
That being said,I’m always on high alert when brake fluid is involved
I will have to check out this Super 3 plus do a bit more research before I go charging the system. All the years I’ve been playing around with cars, I’ve never had the misfortune of spilling brake fluid
I know that there’s always a first time
That being said,I’m always on high alert when brake fluid is involved
It washes off with water.
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DOT 4 is just better, but no ill effects if you use it instead of DOT 3. It's like putting premium gas in your 318 instead of regular - not going to hurt it.
Yes
I figured it must be better since it’s “4” lol
But I read in those side posts up above that you could add Dot 4 or 5.1 to Dot 3 but couldn’t add Dot 3 to 4 or 5.1
Thanks for your reply Photon440
I’ll check them out once I get home and do a bit of research
I figured it must be better since it’s “4” lol
But I read in those side posts up above that you could add Dot 4 or 5.1 to Dot 3 but couldn’t add Dot 3 to 4 or 5.1
Thanks for your reply Photon440
I’ll check them out once I get home and do a bit of research
YY1
Well-Known Member
DO NOT MIX.
I used DOT 5 in my Satellite for the paint protection also.
VERY tired of having a rusty master cylinder and streaks of rust on the firewall.
I installed new calipers, wheel cylinders, hoses, MC, and new front brake lines.
I blew out the line on the axle and the line from front to rear, as well as the prop valve, then flushed all of the above with brake-kleen three times.
I am VERY happy with it this way.
The pedal is just a bit spongy with slightly more travel, but I can live with it.
I also swapped boosters and that may also have something to do with my pedal feel.
The master cylinder is still painted black almost 10 years later!
The firewall still looks like the day I painted it.
That's NOT gonna be the case with other spec fluids.
I used DOT 5 in my Satellite for the paint protection also.
VERY tired of having a rusty master cylinder and streaks of rust on the firewall.
I installed new calipers, wheel cylinders, hoses, MC, and new front brake lines.
I blew out the line on the axle and the line from front to rear, as well as the prop valve, then flushed all of the above with brake-kleen three times.
I am VERY happy with it this way.
The pedal is just a bit spongy with slightly more travel, but I can live with it.
I also swapped boosters and that may also have something to do with my pedal feel.
The master cylinder is still painted black almost 10 years later!
The firewall still looks like the day I painted it.
That's NOT gonna be the case with other spec fluids.
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