Standard brake fluid or silicone DOT5 brake fluid?

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Hi,

As part of my frame off restoration I made new brake lines and new cylinders everywhere. Now I have the choice to go DOT4 (standard) or DOT5 (silicone). The car is a 35 year old Toyota Hiace which will be an everyday car doing approx 10000 miles a year. When disassembling the old parts I noticed corrosion on the brake master cylinder and the proportional valve in the regions closest to the "outside air" suggesting that standard brake fluid attracts water and this will be a problem if not changed often.

Does anyone have hands on experience using DOT5 vs DOT4 brake fluid and can help me choose a way forward?

Lucas
 
Dot 4 is very common the US. Dot 5 is harder to find. You can't mix the two so if you have a leak, it's easy to run into a store and grab a bottle of Dot 4 or even Dot 3 if they don't have Dot 4. Much harder finding Dot 5. I'd stick with Dot 4 and just flush brake lines more often. Some suggest doing it every 2-4 years.
 
I've used DOT 5 in my old Studebakers since the early 90's with good results. I don't know that the rubber parts of the brake system last any longer, but the metal parts sure do. With DOT 3 or 4 water will mix with it, but DOT 5 since it is a silicone oil, water will not mix with it and will end up in the lowest parts of the brake system so a periodic flush is still necessary.
 
I ran DOT 5 in my Pontiac Sunbird 30 years ago. Had to completely flush the system to get the DOT 3 out. The DOT 5 performed fine, though. But since then, I have been running DOT 4 Motul RBF 600, and it does fine. I don't have to worry about a shop adding non-compatible fluid, as I would with DOT 5. But there is a newer specification; DOT 5.1, which is supposed to compatible with DOT 4 and 3. I think you should go with DOT 4, and bleed the brakes every 1 or 2 years to keep fresh fluid in the system, and eliminate moisture.
 
Im not worried about:

1. Mixing issues
2. Availability

I just want the best performance.

I know that water can settle at the lowest point and you need to flush anyway, so the question is, if it has an advantage anyway (DOT5)?
 
Originally Posted by LucasDK
Im not worried about:

1. Mixing issues
2. Availability

I just want the best performance.

I know that water can settle at the lowest point and you need to flush anyway, so the question is, if it has an advantage anyway (DOT5)?


You are over thinking it. Use Dot 4/5.1 and just flush more often.
 
I ran DOT 5 in my bikes for years, the big benefit in that case was if a leak occurred on the master cylinders the paint would not be damaged.
After 12 years in one of them there was no corrosion in any part of the system and no rubber deterioration (silicone lubricates rubber), braking performance was no different in a non ABS system.

For some reason the TÃœV requires stainless braided lines when using the DOT 5 which they can tell with its purple color, the TÃœV engineer said it has something to do with increased pressures (I took his word for it) so you may want to look into that.
I did run the braided with plastic covering to prevent sand from abrading the teflon liner core, never had an issue and it was TÃœV approved.

Personally I wouldnt think twice about running DOT 5 in that vehicle you have, it will prevent brake corrosion issues in the calipers and other parts. You may want to consider NiCopp/Cunifer lines instead of steel.
 
I would be hesistant about DOT5 on a daily driver due to the water issue. Not sure how much it matters, but I would be hesitant.
 
What water issue? Put some DOT 5 in a cup and put some water in, it doesn't mix. In a sealed reservoir how is water getting into it, the fluid does not absorb it from the air like other brake fluids.
 
Originally Posted by Trav
I ran DOT 5 in my bikes for years, the big benefit in that case was if a leak occurred on the master cylinders the paint would not be damaged.
After 12 years in one of them there was no corrosion in any part of the system and no rubber deterioration (silicone lubricates rubber), braking performance was no different in a non ABS system.

For some reason the TÃœV requires stainless braided lines when using the DOT 5 which they can tell with its purple color, the TÃœV engineer said it has something to do with increased pressures (I took his word for it) so you may want to look into that.
I did run the braided with plastic covering to prevent sand from abrading the teflon liner core, never had an issue and it was TÃœV approved.

Personally I wouldnt think twice about running DOT 5 in that vehicle you have, it will prevent brake corrosion issues in the calipers and other parts. You may want to consider NiCopp/Cunifer lines instead of steel.



If you ask me, the TÃœV guys in Germany are crazy: As the only country in Europe, copper brake lines are not approved in Germany. You have to use original steel brake lines, or on a good day Cunifer (90% copper, 10% nickel). If there is no approval from the vehicle manufacturer, they will not accept it. And no vehicle manufacturer approves 100% copper lines. But among the remaning +400 million people in Europe and their corresponding inspections its OK to use copper :-D
 
Originally Posted by buck91
I would be hesistant about DOT5 on a daily driver due to the water issue. Not sure how much it matters, but I would be hesitant.
Flush your brakes like you are supposed to every two years and there are no issues.

If I had an old car that had completely drained brake hydraulics, I would strongly consider it. It makes sense for an old car that might be hard to get parts for in the future. How often do you top off your brake fluid anyway? If you need new fluid, chances are it will be during a service.
 
Originally Posted by LucasDK
Originally Posted by Trav
I ran DOT 5 in my bikes for years, the big benefit in that case was if a leak occurred on the master cylinders the paint would not be damaged.
After 12 years in one of them there was no corrosion in any part of the system and no rubber deterioration (silicone lubricates rubber), braking performance was no different in a non ABS system.

For some reason the TÃœV requires stainless braided lines when using the DOT 5 which they can tell with its purple color, the TÃœV engineer said it has something to do with increased pressures (I took his word for it) so you may want to look into that.
I did run the braided with plastic covering to prevent sand from abrading the teflon liner core, never had an issue and it was TÃœV approved.

Personally I wouldnt think twice about running DOT 5 in that vehicle you have, it will prevent brake corrosion issues in the calipers and other parts. You may want to consider NiCopp/Cunifer lines instead of steel.



If you ask me, the TÃœV guys in Germany are crazy: As the only country in Europe, copper brake lines are not approved in Germany. You have to use original steel brake lines, or on a good day Cunifer (90% copper, 10% nickel). If there is no approval from the vehicle manufacturer, they will not accept it. And no vehicle manufacturer approves 100% copper lines. But among the remaning +400 million people in Europe and their corresponding inspections its OK to use copper :-D

Copper is not allowed in the USA either, but Nicop is popular with the aftermarket and repair crowd. I think its the same as your Cunifer .
 
Originally Posted by LucasDK
Originally Posted by Trav
I ran DOT 5 in my bikes for years, the big benefit in that case was if a leak occurred on the master cylinders the paint would not be damaged.
After 12 years in one of them there was no corrosion in any part of the system and no rubber deterioration (silicone lubricates rubber), braking performance was no different in a non ABS system.

For some reason the TÃœV requires stainless braided lines when using the DOT 5 which they can tell with its purple color, the TÃœV engineer said it has something to do with increased pressures (I took his word for it) so you may want to look into that.
I did run the braided with plastic covering to prevent sand from abrading the teflon liner core, never had an issue and it was TÃœV approved.

Personally I wouldnt think twice about running DOT 5 in that vehicle you have, it will prevent brake corrosion issues in the calipers and other parts. You may want to consider NiCopp/Cunifer lines instead of steel.



If you ask me, the TÃœV guys in Germany are crazy: As the only country in Europe, copper brake lines are not approved in Germany. You have to use original steel brake lines, or on a good day Cunifer (90% copper, 10% nickel). If there is no approval from the vehicle manufacturer, they will not accept it. And no vehicle manufacturer approves 100% copper lines. But among the remaning +400 million people in Europe and their corresponding inspections its OK to use copper :-D


Soft copper line AFAIK is not allowed anywhere but if a Cunifer mixed metal type is used OE it is allowed, many of the high end cars use it. Soft copper is crap for all automotive lines, it work hardens, cracks, splits and corrodes.
 
Use a (non-silicone) DOT 5.1 fluid like Wagner Severe Duty or Bosch ESI6
smile.gif


Another good choice is Castrol DOT 4. It used to be called LMA and is supposed to absorb moisture more slowly than other brake fluids. About $10 from Walmart online.

You should be replacing the brake fluid every few years anyway. I usually flush it when replacing pads and rotors.

Silicone DOT 5 can foam
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