TwoDogs
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Wednesday, August 28, 2019 4:00 AM
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DOT3 Brake Fluid.
At Wakefield on Friday I was discussing brake fade with another punter (non MR2) and he suggested I get better pads
and get fluid with a higher boiling point. I am fairly confident the brake fluid was not boiling but it made me wonder.
My car is 91Turbo, stock brakes and I believe Toyotas of that time used seals which do not tolerate Dot4. I presume that means "swelling" and then brakes sticking, but maybe just leaks.
If this is true, and I am limited to DOT3, then do some brands have a higher boiling point than other brands ??
I know it is very common to replace the original brakes with bigger and I may do that at some point. Liekwise rip out the crappy ABS. The fade I experienced was relatively minor but likely to increase/intensify when the car has semi-slicks (another lesson learnt) and is going faster.
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Admin
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Re: DOT3 Brake Fluid.
Wednesday, August 28, 2019 7:48 AM
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I use regular dot4 in my time attack car with stock master cylinder and callipers. I bleed each wheel with 10 pumps before every track day. I've never had an issue with fluid by using this method. Pads are very important. If the compound is too soft, they will melt.
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Guest
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Re: DOT3 Brake Fluid.
Wednesday, August 28, 2019 10:53 AM
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Previous MR2’s used super dot 4 - not experienced an issue.
Admins car is pushed in race conditions and listed above regular dot 4
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TwoDogs
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Re: DOT3 Brake Fluid.
Wednesday, August 28, 2019 1:27 PM
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Ok thanks for the responses, I think I need to go back to the brake specialist in Hornsby to clarify why he said Toyotas have a problem with Dot4.
As for pads overheating, which pads do people recommend ?
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Guest
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Re: DOT3 Brake Fluid.
Wednesday, August 28, 2019 8:08 PM
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I think the specialist has an opinion :) like all of us.
Dot 3, Dot 4, Super Dot 4, Dot 5.1. Only one not compatible is Dot 5.
Key to success is service, from memory prior to every two years (as in full flush).
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Falcon
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Re: DOT3 Brake Fluid.
Thursday, August 29, 2019 9:49 AM
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What Glen says. That should get rid of any accumulated water from the hydraulic system.
Using a similar strategy I have not experienced any hydraulic fade issues.
I did get some pad fade while using standard Toyota pads but they coped with a fair bit of hard use before they gave up and recovered once I eased off for a couple of laps. They are perfectly fine for road use.
I have recently fitted Forza FP3.pads all round and bedded them in. So far they feel really nice just road driving but I won't know how they go until after Wakefield Park track days on 7th and 8th October.
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TwoDogs
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Re: DOT3 Brake Fluid.
Friday, August 30, 2019 4:20 AM
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Thanks all, I just searched again "Toyota Dot4" and there are very many hits all complaining Toyota seals and Dot4 are not compatible. I don't know why you have not encountered problems unless your seals are not OEM ??
I believe you when you say you have not had any problems. I had a piston seize and when the brake guy blew it out for me was when he mentioned that I should not be using Dot4. That is not proof that Dot4 caused my problem, but I was quick to revert back to dot3 anyway.
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Reddtarga
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Re: DOT3 Brake Fluid.
Friday, August 30, 2019 7:30 AM
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Have used Castrol react super Dot 4 for years with no issues. OEM Toyota parts used.
A full system flush done every couple of years, and the old fluid has always come out clean with no discoloring.
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TwoDogs
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Re: DOT3 Brake Fluid.
Tuesday, September 03, 2019 6:06 AM
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Thanks all.
I suspect the problem of boiling fluid in short track day sessions is more to do with accumulated water content than the Dot 3. So I will heed the advice and flush old fluid out, if I then have overheating issues, will move to Dot4.
I don't think my son and I encountered fluid problems, but pads more likely.
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5SGTE
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Re: DOT3 Brake Fluid.
Saturday, September 07, 2019 1:59 AM
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Jump on the oil websites, nulon datacheck, penrite datacheck etc, they spec a dot3 for the reason your brake mech suggested.
That said heaps of people, myself included, have used other options without too much issue. I'd suggest regular changes are key.
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TwoDogs
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Re: DOT3 Brake Fluid.
Sunday, September 08, 2019 8:49 PM
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Thanks 5sgte. I had a look at those references and some other references on brake fluid being hygroscopic. I had the same thought when someone asked "why use a fluid that is hygroscopic ?" (absorbs moisture). The explanation is that the absorbed water is distributed throughout the brake fluid and does not affect the fluid's boiling point. The worse alternative, a fluid that rejected moisture, would cause the moisture to pool and boil at 100c.
Nulon suggest replacing their Dot3 every 2yrs.
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