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Anyone try DOT 4 Synthetic Brake Fluid? by Dennis LaGrua
Started on: 10-13-2020 09:55 PM
Replies: 20 (272 views)
Last post by: Frenchrafe on 10-19-2020 05:43 AM
Dennis LaGrua
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Report this Post10-13-2020 09:55 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
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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Report this Post10-13-2020 10:09 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
Ogre explained this in his Cave:
http://web.archive.org/web/...fierocave/brakef.htm
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Dennis LaGrua
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Report this Post10-13-2020 10:32 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by pmbrunelle:

Ogre explained this in his Cave:
http://web.archive.org/web/...fierocave/brakef.htm


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?
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Report this Post10-13-2020 10:47 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
DOT 4 is glycol, just like DOT 3 and DOT 5.1.

DOT 5 is the 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.

*I can't offer any sort of guarantee on that.
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Blacktree
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Report this Post10-14-2020 02:22 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
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.
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Report this Post10-14-2020 03:02 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
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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pmbrunelle
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Report this Post10-14-2020 08:55 AM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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.


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.
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Report this Post10-14-2020 10:58 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
My thoughts exactly. The DOT4 can also be used in clutch hydraulics. I see no reason to stock DOT3 fluid anymore.
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Report this Post10-14-2020 02:12 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
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.
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Report this Post10-14-2020 04:13 PM Click Here to See the Profile for SpadesluckSend a Private Message to SpadesluckEdit/Delete MessageReply w/QuoteDirect Link to This Post
Honestly if you have not drained/flushed your brake fluid in your Fiero now maybe now is a good time to do it, then switch it over to DOT4.
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Report this Post10-14-2020 06:24 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Here's a boil test of my car today...
Test 1 w/o warmup
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.

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.
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Report this Post10-14-2020 07:35 PM Click Here to See the Profile for Zac88GTClick Here to visit Zac88GT's HomePageClick Here to Email Zac88GTSend a Private Message to Zac88GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
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).
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Report this Post10-14-2020 07:36 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by theogre:
Topping up the MC tank w/ 4 is no point..


You don't add a bit of DOT 4 to an otherwise DOT 3 system in the hopes of raising the boiling point...

A typical scenario is my friend with a BMW who comes over to work on his car.

When he's done, he leaves behind half a quart of DOT 4 in the bottle.

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.
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Dennis LaGrua
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Report this Post10-16-2020 11:07 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Here is the confusing part about "synthetic"
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pmbrunelle
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Report this Post10-16-2020 12:08 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well of course brake fluid is synthetic; brake fluid is man-made.

Brake fluid is not like gasoline; extracted from oil that came from the ground.

Advertising synthetic brake fluid is like talking about "fat-free ketchup".
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Report this Post10-16-2020 12:28 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
... or gluten free meat
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Report this Post10-17-2020 01:01 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
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).]

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Report this Post10-17-2020 11:12 AM Click Here to See the Profile for Shho13Click Here to Email Shho13Send a Private Message to Shho13Edit/Delete MessageReply w/QuoteDirect Link to This Post
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.

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Report this Post10-17-2020 01:37 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
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...
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Report this Post10-18-2020 12:55 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
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
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Report this Post10-19-2020 05:43 AM Click Here to See the Profile for FrenchrafeClick Here to Email FrenchrafeSend a Private Message to FrenchrafeEdit/Delete MessageReply w/QuoteDirect Link to This Post
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.

Regards,
Rafe

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