Many recent brake systems use DOT 4 Brake Fluid. Its synthetic and its advantage is that it supposedly doesn't hold moisture like std DOT 3 brake fluid. If a conversion was made to this fluid, it would entail draining and bleeding out the old fluid and introducing new DOT 4 fluid into a clean system. I believe that DOT brake fluid is a silicone based fluid. Has anyone tried using it and did it work correctly? Do the caliper seals and the Master Cylinder hold up using it ? There must be some advantage to using it but in a Fiero or older automobile it may not work well or will it? Thoughts on using it??
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I read that but it doesn't touch on my main point of whether all the seals MC/Wheel and the switch will be compatible with the DOT 4 fluid. I know guys have tried the silicone fluid in classic cars and it destroyed the brake switch and wheel cylinder seals. The Fiero has the brake switch on the pedal but also has a switch on the proportioning valve. My question is will the sensing elements in that switch be hurt by silicone fluid?
Many (most?) soft brake parts are made from EPDM. EPDM should be OK with silicone.
The prudent course of action when dealing with unknown soft materials is to soak the mystery parts in your fluid of choice, and then see if swelling or any adverse reaction occurs.
A one month soak should* be more than enough time to uncover any potential problems.
Originally posted by Dennis LaGrua: If a conversion was made to this fluid, it would entail draining and bleeding out the old fluid and introducing new DOT 4 fluid into a clean system. I believe that DOT brake fluid is a silicone based fluid.
This is incorrect. DOT4 brake fluid is chemically compatible with DOT3 fluid.
Originally posted by pmbrunelle: DOT 4 is glycol, just like DOT 3 and DOT 5.1.
DOT 5 is the silicone fluid.
Correct. DOT 4 fluid is "better" then any 3 fluid for normal street use and off road like mud crawlers. You find 3 w/ "higher" boil point then 4, even 5 and 5.1, but is only for Dry Boil. Many of these are "racing fluids" that expect to get change often.
You can run DOT 4 in cars call for 3 but Not other way around. If you read "expert level" doc's all say the same... Can run 4 or 5.1 in MC lid calling for DOT 3. Many recent vehicle calls for DOT 4... Can add 5.1 but not 3. Rarely car may call for 5.1 when true can't use 3 or 4. Some brands like Valvoline combine DOT 3 & DOT 4 in one product. Use them if you don't trust DOT4 label products.
I've been doing this for 20+ years and never had any problem. BUT If a vehicle has True ABS, I won't switch DOT #. Is very likely Technically Safe but ABS "Black Boxes" are so expensive is not worth to change DOT # and have ABS problems and people and dealers saying you did something wrong to Void a Warranty etc. ("Fake" ABS are used in some trucks etc w/ only an "load sense" prop valve tied to the rear axle. They are way too dumb to notice DOT # and related specs.)
Topping up the MC tank w/ 4 is no point... Only time you hope it makes a dif is when you "flush" old dirty fluid out until bleeders see clear fluid. Best after you replace hoses and/or calipers when you can empty calipers or have new dry calipers and can purge old fluid out of lines before connecting new parts.
I have a boil tester showing actual boil point of fluid in a car and many cars have very wet brake fluid and boils at very low temps. (This tool cost several hundreds of $.) The Only time I see Dry boil is when just test a new bottle or very new cars not driven much. Many times the Second New fluid is mix w/ old fluid the new D3 is so wet can't reach the wet spec on bottle or NHTSA's FMVSS specs. That's ever after you drain most old fluid for major repair/rebuild of the system. D4 handle old fluid better new D3.
Using DOT5 Silicone in any DOT 3 4 or 5.1 is bad on many levels. Won't make seals to swell like oil will but will cause problems, some are covered in cave page.
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Originally posted by theogre: Topping up the MC tank w/ 4 is no point... Only time you hope it makes a dif is when you "flush" old dirty fluid out until bleeders see clear fluid. Best after you replace hoses and/or calipers when you can empty calipers or have new dry calipers and can purge old fluid out of lines before connecting new parts.
From an inventory-control standpoint, I find it good to only stock the highest-spec fluid I need (such as DOT 4). This way I don't need to stock different bottles.
Also, once a bottle has been opened, it's best to use it quickly, before it picks up humidity. So keeping just one kind of brake fluid reduces the number of opened bottles I have.
Originally posted by pmbrunelle: From an inventory-control standpoint, I find it good to only stock the highest-spec fluid I need (such as DOT 4). This way I don't need to stock different bottles.
Also, once a bottle has been opened, it's best to use it quickly, before it picks up humidity. So keeping just one kind of brake fluid reduces the number of opened bottles I have.
True but quoted why?
quote
Originally posted by theogre: Topping up the MC tank w/ 4 is no point... Only time you hope it makes a dif is when you "flush" old dirty fluid out until bleeders see clear fluid. Best after you replace hoses and/or calipers when you can empty calipers or have new dry calipers and can purge old fluid out of lines before connecting new parts.
Again, Topping up the MC tank w/ 4 or any other is no point to think will change boil point because not enough new fluid.
Open bottles have "wet air" in them and pulls water from air after because of the cap mostly. Cap and its "Gasket" are not made to seal long term. Vs. Many MC caps have rubber to seal and allow fluid drop so never get fresh wet air on top of fluid. MC Caps have vent(s) to allow air equalization for the rubber but vent air doesn't make connect w/ fluid unless rubber is bad.
For "inventory..." For MC top off and other small jobs only use small bottles for this reason. Only use 1 quart bottles for major work that you use it all at once. Even then don't keep unopened plastic bottles of brake fluid in private inventory for months to years.
⚠️ Warning: Brake fluid is a HAZMAT and illegal to dump in most places. For "home use" can go to local HAZMAT drop-off many places often have only a couple times a years. Contact city etc solid wast management group even if normal trash is pick up thru 3rd parties.
Here's a boil test of my car today... Test 1 w/o warmup Note "Warmup" is test done but tool wasn't used in Months so tip is "covered" by very wet fluid so ignore first test. But get another sample as well.
CLICK FOR FULL SIZE
Test 2 & 3 w/ warmup. Test 2 is 287 but didn't take picture.
CLICK FOR FULL SIZE
Test Minimums...
CLICK FOR FULL SIZE
So seems is "bare minimum" for DOT 3 fluid right? But this car has completely refilled many times w/ DOT 4 and only drive ~ 1000 mile per year for last Decade. Last time was "flushed" was ~ 9 years ago when rebuild the system and filled from "empty" including empty rear calipers.
Test was done w/ small amount in a bottle because tester uses car battery and can't reach front of Fiero. Warmup is actual warmup as test heats small amount and likely purges the tip as don't use it daily. I waited a couple minutes each before tests 2 & 3.
I use Valvoline SynPower Dot 4 and Syn DOT 3&4 since dropping SynPower brand years ago.
[This message has been edited by theogre (edited 07-06-2023).]
You might want to check out Castrol SRF. It's compatible with DOT3 and DOT4 systems and has very high boiling points. 590*F dry and 518*F wet, so it's wet boiling point is still higher than most other fluids dry boiling points. It's pretty expensive though, and hard to find locally so I ended up going with Motul RBF660 (617*F dry and 400*F wet).
or "Gluten free" labels on Swedish Fish and many other candies that never had it.
Many "Synthetic" oils and other things used that term that means little or nothing thanks to Mobil 1 losing a lawsuit to Castrol.
quote
Originally posted by pmbrunelle: Next time I work on my car, I'm not going to go out an buy a bottle of DOT 3; I'm going to use my BMW buddy's DOT 4 leftovers first.
Any left over brake fluid will suck water right from air and "go bad" just sitting on a self. Often that doesn't take long too.
This "bad" fluid may not as low as wet boil but can't absorb wet fluid in a car during brake work and likely will reach wet boil or even boil lower then the spec sim to above testing.
Always Buy "fresh" fluid in factory seal bottle(s).
[This message has been edited by theogre (edited 10-17-2020).]
I flushed and did a complete DOT 4 conversion when I replaced all my brake hoses and calipers on my car a few years ago back I overhauled the brakes... Works perfectly fine. Been about 6 years now.
DOT 4 is compatible with DOT 3 and can be mixed.
DO. NOT. ADD. DOT. 5. DOT 5 is completely different and *will* break things.
------------------ "Discord" Red 1988 GT under restoration!
Originally posted by theogre: Any left over brake fluid will suck water right from air and "go bad" just sitting on a self. Often that doesn't take long too.
This "bad" fluid may not as low as wet boil but can't absorb wet fluid in a car during brake work and likely will reach wet boil or even boil lower then the spec sim to above testing.
Always Buy "fresh" fluid in factory seal bottle(s).
I will usually go through a bottle of brake fluid within about half a year of opening it.
What's the difference between half a year stored on a shelf with the cap closed, vs. half a year extra on the vehicle?
I didn't think that my habit of keeping opened brake fluid bottles on the shelf for half a year was so bad, given that you have people driving around on 10+ year old brake fluid.
I guess the real answer to this question is that I have to buy a brake fluid tester like yours. I already have too many auto parts/tools, and not enough places to store this stuff...
Originally posted by pmbrunelle: I will usually go through a bottle of brake fluid within about half a year of opening it.
What's the difference between half a year stored on a shelf with the cap closed, vs. half a year extra on the vehicle?
I didn't think that my habit of keeping opened brake fluid bottles on the shelf for half a year was so bad, given that you have people driving around on 10+ year old brake fluid.
I guess the real answer to this question is that I have to buy a brake fluid tester like yours. I already have too many auto parts/tools, and not enough places to store this stuff...
Most bottle caps won't seal even if have "gaskets" in them. Threads etc wet w/ fluid have a easy path for water to get at the rest of bottle. Remember B-fluid attract water then move it so everywhere = out that water... like water will seek level everwhere. Depended on where stored open bottles can reach wet boil spec in a few days because Many keep in basements, garages, and other places w/o AC allowing local weather to get at the open bottle.
Fluid in cars w/ good caps etc will take a lot longer to see wet boil. Above test is DOT 4 after ~ 20 of only Dot 4 in the system and "flushed" nearly 10 years ago. But Leave Bottle and/or MC cap open, more so w/ these GM Brake MC and its huge cap, and can be at Wet Boil or lower Very fast. Depending on weather can be super fast meaning Hours to 1 day to see wet boil or worse.
I got tool above from shop went bankrupt. Boil tool above and related are way out price rage for most DIY. OTC, Mactools, and more makes/sells several types including "rebrand" of tool shown above (Like OTC 3890) often at ~ $350 or more. Seem some "knockoffs" of tool above available for ~ $100.
Are "Cheap" test methods but many are specific to fluid used. IOW Many only work in 1 DOT X fluid or results mean nothing. Some "cheap" testers are unreliable and break easy. Example: Ones that are "pen size" make sure only the probe tips are in fluid. Otherwise fluid can get into it and ruin the guts.
Side Note: OTC 3890 Brake Fluid Tester is used by Porsche and likely other car brands... https://static.nhtsa.gov/od...MC-10166922-0001.pdf SPX/OTC likely bought original maker of above tester also now owns Kent-moore that made nearly all GM specialty tools in all FSM
Hi everyone, Just my experience: I've been using DOT 5 (silicon) brake fluid in my car for years. On and off the track! Never had any problems or seals failing.
Originally posted by Frenchrafe: Hi everyone, Just my experience: I've been using DOT 5 (silicon) brake fluid in my car for years. On and off the track! Never had any problems or seals failing.
You just got lucky. Because very likely have pools of very wet DOT 3 4 or 5.1 or even Water migrate to any low areas and if is in calipers or drum slaves this can boil very easy w/o warning and have little or no brakes.
Thanks Ogre. Ever the optimist😉 Next time I end up in the gravel at the end of the long straight, I'll be thinking of what you said 👍😁
No seriously, my entire brake system is replaced with new lines and calipers. It has never seen any other fluid but DOT5. Before I upgraded the rear calipers, I managed to get the old pads glowing red at one race! The friction material was crumbling off the backing plate. The pedal was always there, no fluid boiling, just severe pad and disc overheat. DOT5 works in my case is all I'm saying.
GTIN Code: 889545069518 Liquid Measurement: 16.9 fl. oz. Brake Fluid Type: DOT 4 Sold in Quantity: Each Notes: Dry Boiling Point: 626 F. Wet Boiling Point: 417 F. Dry Boiling Point: 626 °F Wet Boiling Point: 417 °F
This is the fluid I use on my Fiero, Abarth (which I track 3 to 6 days a year) and my kart and NEVER had the brakes fade. I personally don't bother with DOT5 fluids. It's more expensive and it can't mix it with DOT3 or 4 in case of an emergency. Whether you run 3, 4 or 5 and you track your car more than twice a year or drive it spirited, it's good practice to flush your system with fresh fluid yearly.
Originally posted by Frenchrafe: Thanks Ogre. Ever the optimist😉 Next time I end up in the gravel at the end of the long straight, I'll be thinking of what you said 👍😁
No seriously, my entire brake system is replaced with new lines and calipers. It has never seen any other fluid but DOT5. Before I upgraded the rear calipers, I managed to get the old pads glowing red at one race! The friction material was crumbling off the backing plate. The pedal was always there, no fluid boiling, just severe pad and disc overheat. DOT5 works in my case is all I'm saying.
Replace everything is maybe the Only time using 5 is "OK." Most try to "flush" old parts and causes problems said above because Silicone Does Not mix w/ others and allows them to sink and stay wherever and often get wetter and wetter too.
Originally posted by La fiera: This is the fluid I use on my Fiero, Abarth (which I track 3 to 6 days a year) and my kart and NEVER had the brakes fade. I personally don't bother with DOT5 fluids. It's more expensive and it can't mix it with DOT3 or 4 in case of an emergency. Whether you run 3, 4 or 5 and you track your car more than twice a year or drive it spirited, it's good practice to flush your system with fresh fluid yearly.
Don't you mean can mix?
[This message has been edited by theogre (edited 10-20-2020).]
Originally posted by La fiera: I meant 5 won't mix with 3 or 4.
Ok and correct.
Bit confuse because Wilwood anything is more expensive too. $21.47 for 16.5 oz at Wilwood vs Valvoline and others DOT 4 ~ $8 per Quart (32 oz.)
Also Brake Fade has little to nothing to do w/ Fluid used. Fade is caused by overheated pad/shoes etc. and most times won't cause low pedal. Might feel spongy or not during fade problems. With "cheap" pads/shoes often is easy to have this w/o glowing rotors etc.
Fluid Boil will produce instant "Air"(steam) in the hydro and will causes low/spongy pedal and often won't work right again until you bleed them at minimum. Boil fluid is trash and likely have fix other brake problems too.
Bit confuse because Wilwood anything is more expensive too. $21.47 for 16.5 oz at Wilwood vs Valvoline and others DOT 4 ~ $8 per Quart (32 oz.)
The boiling point is much higher than generic DOT4 fluid.
According to FMVSS116 standards, DOT4 brake fluid must have a minimum dry boiling point of 230°C and a minimum wet boiling point of 155°C. The Wilwood fluid has (advertised) boiling points of 330°C and 214°C, respectively. That is significantly higher! For someone who does road racing, that will be worth the expense.
Also Brake Fade has little to nothing to do w/ Fluid used. Fade is caused by overheated pad/shoes etc. and most times won't cause low pedal. Might feel spongy or not during fade problems. With "cheap" pads/shoes often is easy to have this w/o glowing rotors etc.
Yes, if High-Temp fluid is to be used is logical to get the correct pads to make the entire system work efficiently. In the Fiero I use Hawk DTC 30 pads along with the Wilwood fluid. My little Abarth comes with very aggressive Ferodo pads from factory and the replacement of the stock DOT4 that it comes with (which I have no idea what if its high temp) along with replacing all the rubber hoses for stainless steel gave the brake system a more positive, firm and direct brake pedal with no fade whatsoever.
