dot 4 brake fluid safe in 1986 cruiser?? (1 Viewer)

[blurr1604]

did a swivel hub rebuild/longfield install the other night, it was about midnight by the time it was all finished went to sort out he brakes, bleed etc, realised i only had dot 4 brake fluid, and the cap said dot 3, i stupidly assumed the dot 4 would be fine, but i also needed the car to be roadworthy the next day

the dot 4 says in general it is suitable for all dot 3 applications,

should i drain the whole system and refill with dot 3???

or will it be ok?

thanks !

 

[Ron R]

To my knowledge there is no problem in mixing Dot3 and Dot4.
The only difference between them two is the boiling point. Dot4 has a higher point so it's even 'better' than Dot3.

Note: Dot 5 should never be mixed with other fluids as it is a different kind of stuff.

 

[jb BJ73]

i've heard that dot 4 will swell the seals in toyotas. not sure how much truth there is in that though, heard it from one of my tech college lecturers

 

[blurr1604]

i've heard that dot 4 will swell the seals in toyotas. not sure how much truth there is in that though, heard it from one of my tech college lecturers

s


hopefully someone else can elaborate/confirm this

cheers

 

[Eric Winkworth]

I frequently have Dot 4 fluid sitting around, for when I work on 4 wheelers / Dirtbikes, so it did go into the cruiser once when I needed on a whim similar to your situation, no issues!

I've read on several forums "DOT4 is a premium version of DOT3, and they will mix. A lot of newer vehicles spec DOT4 in the brake or hydraulic clutch systems, so check to see what your specific application calls for. Quick side note: DOT5 brake fluid is the one that WILL NOT mix with DOT3 or DOT4. "

As far as swelling seals, I call BS on that! but i've been wrong before!

 

[dgangle]

good read

no the sky isn't falling and yes you can use DOT 4 in place of DOT 3. It's DOT 5 (silocone based) that cannot be used in the 3 or 4

This sums it up pretty well. Good read:

DOT 5.1 - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/DOT_5 "Using DOT 5 in a DOT 3 or DOT 4 system without proper flushing will cause damage to the seals and cause brake failure."

 

[Hulsty]

I've used dot 4 for ages and no problems, always flush and refil with one type of clean fluid. Mix only in emergencys, its just good practice.

 

[Dieseler]

I use DOT 5 only...so far so good the rumor is it does not absorb moisture like DOT 3 and 4 does and I have had moisture ball up and plug my master in the past to the point were I lost pressure in my pedal when I was in the bush.

 

[blurr1604]

great thanks guys !

 

[Toyota Kijang]

As far as swelling seals, I call BS on that!

I agree some ppl are so melo-dramatic unnecessarily overexageratting stuff...

 

[jb BJ73]

i'm kinda skeptical on the seals swelling as well but i did hear it from someone who is supposed to know what theyre talking about so i thought i would mention it

 

[cambelt]

Its 100% true about the seals swelling, using DOT4 fluid in any toyota with tired cylinders will fail in time . Im not sure if you guys have the hydraulic boosted master cylinder but over here in AUS many failures have resulted from DOT4 use.
That said if yr cylinders are healthy DOT4 works fine but itsSTILL no good for the seals.
Cant people understand that if a maker specs DOT3 ''ONLY'' you would have to be dumb to use otherwise.
Dave

 

[dgangle]

I call BS. What is your source?

 

[Dieseler]

This may be true I had a seal on my slave go last summer when I loaded up the reservoir with DOT 4 it went without warning no leaking just a blow out.
After rebuilding the slave I switched to DOT 5

 

[beislebub]

I've seen brake fluid out there that won't eat your paint if you spill , is that Dot 5 ? (silicone based) Can't remember what it was but my dad used it in his 10 year long restoration (1967 Plymouth Belvdere).


Joel.

 

[Dieseler]

DOT 5 is a silicone base fluid not sure if it eats paint like 3 and 4 does.

 

[dgangle]

99.9% of these questions could be answered if one read the info in the 2 links I posted in #6 above. As for the claim of 4 damaging seals accustomed to 3, I am still waiting for a credible reference.


"DOT 5.1, like DOT 3 and DOT 4, is a polyethylene glycol-based fluid (contrasted with DOT 5 which is silicone-based). Polyethylene glycol fluids are hygroscopic and will absorb water from the atmosphere."

"Unlike polyethylene glycol based fluids, DOT 5 is hydrophobic. Its chief advantage over other forms of brake fluid is that silicone exhibits a more stable viscosity index in extreme temperatures. It is widely used in the antique automobile arena as well as it does not damage paint."

 

[cambelt]

20 years of being a toyota mechanic is my source ,I think ive seen just a few cylinders , also the fact that all toyotas state on the filler cap , USE ONLY DOT3 FLUID.
Dave

 

[dgangle]

...and exactly at what part of your professional training as a Toyota mechanic was this information presented to you and by whom?

I have worked on all the Toyota's I have owned for nearly 3 decades. Does this make me a "Toyota mechanic"?

To further prove my point with fact, not conjecture, read this article from Bendix at www.bendixbrakes.com/download/pdf/right-stuff.pdf


"DOT 4 fluid meets the criteria set for DOT 3 fluid as well as higher standards so it’s safe to use DOT 4 in systems that specify DOT 3. But don’t use DOT 3 in place of DOT 4 because boiling point protection won’t meet the vehicle maker’s specs. If someone wants to stock one brake fluid type that can be used in the vast majority of vehicles, that would be DOT 4."

This debate is over and I have won.

 

[roscoFJ73]

Its 100% true about the seals swelling, using DOT4 fluid in any toyota with tired cylinders will fail in time . Im not sure if you guys have the hydraulic boosted master cylinder but over here many failures have resulted from DOT4 use.
That said if yr cylinders are healthy DOT4 works fine but its no good for the seals.
Dave

Tired cyls are gonna fail any way. Ive had no probs with dot 4
Where the hell is "over here"?