Dot 4 or Dot 5 Brake Fliud?

[4spdragtop]

That's what I was thinking Casey, but not all hyd fluid is brake fluid(obviously).
I'm not sure if there is Dot 5 for non brake applications?

Hydraulic Clutch???


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[Johnny Mac]

Maybe showing my ignorance here, but why would Dot 5(or any other) brake fluid be used for TOB?

Hydraulic Clutch???


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Correct. Hydraulic TOB with clutch master cylinder.

 

[RustyRatRod]

That's what I was thinking Casey, but not all hyd fluid is brake fluid(obviously).
I'm not sure if there is Dot 5 for non brake applications?

Most all hydraulic clutches I've ever seen take brake fluid.

 

[Kern Dog]

I know we are only talking brakes here, but I have seen dot 5 eat the seals out of several throw out bearings. I have nothing to base my opinion on other than a guess, but I would guess a silicon based fluid isn't compatible in every brake caliper out there. Maybe I'm wrong. But I know 5 voids the warranty on more than one TOB manufacturer. Just something to ponder.

I called Silver Sport when I drained and needed to refill my Wilwood clutch master cylinder reservoir. I had some DOT 5 left over. They stated DOT 3 or 4 but absolutely no DOT 5 but couldn't tell me why.
I hate it when people tell you to do something a specific way but won't tell you the reasoning for it.

 

[junkyardhero]

I called Silver Sport when I drained and needed to refill my Wilwood clutch master cylinder reservoir. I had some DOT 5 left over. They stated DOT 3 or 4 but absolutely no DOT 5 but couldn't tell me why.
I hate it when people tell you to do something a specific way but won't tell you the reasoning for it.

the composition of some seals are not compatible with with the mineral based 5. basically the crux of the issue is that some material is compatible with glycol variants (3,4, 5.1) and some is compatible with the silicone based dot 5, but there isn't a synthetic material that is compatible with both.

there is also the issue that 5 compresses more and has a tendency to "foam" or aerate under repeated heavy load, it is also a gargantuan pain in the *** to bleed, or can be.

i'm guessing that their insistence on 3 or 4 is just to avoid potential problems from somebody that doesn't know what they're doing; or they're unsure of what seals the MC comes with and play it safe with the 3, 4 or 5.1

 

[CRUZE 418]

Then the manufacturers should offer products for both 4 and 5. Silicone based 5 has been around for awhile, time to get with the program.

 

[340six]

Then the manufacturers should offer products for both 4 and 5. Silicone based 5 has been around for awhile, time to get with the program.

I should have stated the last Silicone 5 I bought was NAPA Brand

 

[YY1]

I bought all mine while they were on "buy one get one 1/2 off" sale.

Bought out four Advance locations.

I should be good to go for topping off, or maybe do another conversion...or two.

 

[Kern Dog]

I bought all mine while they were on "buy one get one 1/2 off" sale.

Bought out four Advance locations.

I should be good to go for topping off, or maybe do another conversion...or two.

The DOT 5 stuff was over $34 a quart at the NAPA store near me. Ouch!

 

[RustyRatRod]

Then the manufacturers should offer products for both 4 and 5. Silicone based 5 has been around for awhile, time to get with the program.

Yeah and they should also offer Mopar guys an affordable header that actually fits. Keep dreamin. lol

 

[Johnny Mac]

I called Silver Sport when I drained and needed to refill my Wilwood clutch master cylinder reservoir. I had some DOT 5 left over. They stated DOT 3 or 4 but absolutely no DOT 5 but couldn't tell me why.
I hate it when people tell you to do something a specific way but won't tell you the reasoning for it.

Agree with you. Straight from my guys at McLeod also. It 1000% can eat seals. I have only seen maybe 3 internal tobs fail in my life, and all have been dot 5 induced.

 

[str12-340]

so I guess the less than 1% of us with a hydraulic clutch shouldn't use DOT5. I've yet to see a DOT5 induced brake seal failure... I wonder what the difference is?

 

[Johnny Mac]

so I guess the less than 1% of us with a hydraulic clutch shouldn't use DOT5. I've yet to see a DOT5 induced brake seal failure... I wonder what the difference is?

Your observstion is probably valid. I don't doubt it's a small number, and maybe brake piston seal rubber is simply different material. These are just old cars, with lord knows what kind of rebuilt, or aftermarket seals, just throwing it out there. I probably de-railed the thread a bit, but found it cautionary/interesting info to share.

 

[Kern Dog]

I switched to the DOT 5 simply for the reduced chance of paint damage. The clutch reservoir is near the booster in my car...

 

[RustyRatRod]

I switched to the DOT 5 simply for the reduced chance of paint damage. The clutch reservoir is near the booster in my car...

View attachment 1716157633

And that's a great reason. You got lotsa fine paint to worry about!

 

[YY1]

DOT 5 does not strip paint like others.

Whatever you do, DO NOT mix DOT 5 with any other.

My DOT 5 conversion has been going strong for almost 10 years.

Just a slight bit of sponginess and a slight bit of additional pedal travel.

@jos51700

What part of my personal experience do you disagree with?

 

[jos51700]

Use whatever you feel is best, but whatever you decide, never mix the glycol based fluids with DOT 5.

Wrong.

DOT 5 does not strip paint like others.

Whatever you do, DO NOT mix DOT 5 with any other.

My DOT 5 conversion has been going strong for almost 10 years.

Just a slight bit of sponginess and a slight bit of additional pedal travel.

That sponginess is your car, not the fluid.

We had a master cyl leak onto firewall and bubbled paint. Went right down and got Dot 5. Added it directly and bled brakes until Dot5(purple) came out. Zero issues 11 years later. Factory disc front, rear drum.

This, like a ****.

Steve, it's not just the internet. It's every single service manual that goes in depth talking about brake fluid differences. That's all I was doing was stating technical fact.

Now, as far as what you said, I agree 100% and that's how I would do it if I ever swapped to DOT5. But I'm not going to recommend someone do it that way.

I've never understood why manufacturers do this.

You're a parts guy, see my post below.

the composition of some seals are not compatible with with the mineral based 5. basically the crux of the issue is that some material is compatible with glycol variants (3,4, 5.1) and some is compatible with the silicone based dot 5, but there isn't a synthetic material that is compatible with both.

there is also the issue that 5 compresses more and has a tendency to "foam" or aerate under repeated heavy load, it is also a gargantuan pain in the *** to bleed, or can be.

i'm guessing that their insistence on 3 or 4 is just to avoid potential problems from somebody that doesn't know what they're doing; or they're unsure of what seals the MC comes with and play it safe with the 3, 4 or 5.1

Compresses more? Yeah, no. Fluids are effectively incompressible, that's kinda part n' parcel to how the hydraulic brake system works.




For everyone in this thread (and all the threads' cousins that nobody ever searches for):

There is ONE major manufacturer that has extensive experience with DOT5, and converting to DOT4: Harley Davidson.

Harley used DOT5 from AT LEAST the mid-70's until the mid 2000's. When they swtiched, I used the opportunity to put this issue to rest.
In Harley world, the -XX part of the part number is the first year the part was introduced, the letter is the revision number.
From the 2010 Harley FXDWG parts manual:

The cover kit, reference number 24, is where the '05 model changed to reference that Harley had switched to DOT4 (the label on the lid changed, hence the new part number).
The rebuild kit, reference number 17, shows 1996 year of introduction (before DOT4 even existed in HD's inventory by a decade)....and there it is, a DOT5 set of seals and cups and everything, spec'd by a manufacturer in a DOT4 system. The soft parts are compatible with either fluid. At the time, I checked brake hoses, piston seals, and everything.

I've swapped several systems, mixed fluids in a jar on the bench, done everything I could to 'turn seals to mush', 'cause seals to swell', make 'fluids turn to gel', etc. I've never seen it happen. The DOT specs full miscibility, as I cited in other threads on this matter. Run the DOT5, and don't sweat it. Flush n' fill, top off, full rebuild, however you want to do it.

And to put the issue to bed forever....DOT4 has one expected 'benefit' to Harley riders:

Harley-Davidson Recalls Motorcycles for Brake Concerns

Harley-Davidson is recalling 2008-2011 Touring, CVO Touring, and VRSC motorcycles equipped with ABS. Consumer Reports gives the details.

www.consumerreports.org

 

[jos51700]

@jos51700

What part of my personal experience do you disagree with?

The sponginess in using DOT5, mainly. I've ridden thousand of Harley's and driven several converted cars, and that was never an issue.