13 replies to this topic

[dasupersprint]

Hello,

 

To put you into context, my Mini is under a long restoration. Two years ago, I rebuilt the braking system, all in new, except for the master. I put DOT 3 or 4 fluid into the system.

 

Fast forward to last week, I decided to change the master too. I've been recommended to put DOT 5 fluid in my system.

 

My question is: Do I need to drain everything in the pipes before I put DOT 5 in them? Or could I put DOT 5 in the master first and push the pedal until the purple fluid comes out?

 

Thanks again!

[Gilles1000]

I wouldn't put DOT5 in my system, even if new.

- not compatible with other DOTs (think about having an issue on the road, you Must find DOT5...)

- does not absorb water, but I feel better opening one in a while mw system to check everything.

- maw cause problems withs gaskets and so on. If so wou can change all the system.

 

I will take DOT4 or 5.1 the day my car is so far.

[dasupersprint]

Is there any advantage to DOT 5 other than not dangerous for paint?

[Steve220]

Can you confirm you want to put Dot 5 or Dot 5.1 in, as there's a significant difference.

 

If it is Dot 5, then yes, the system will have be utterly dry.

Edited by Steve220, 28 February 2020 - 04:41 PM.

[Rorf]

Why complicate things - stick to DOT 4 and change it every 2 to 3 years.

[dasupersprint]

Can you confirm you want to put Dot 5 or Dot 5.1 in, as there's a significant difference.

 

If it is Dot 5, then yes, the system will have be utterly dry.

 

DOT 5 yes.

[dasupersprint]

I'm starting to think I better stick with the DOT 4 then. Plus DOT 5 is crazy expensive

[gazza82]

 

Can you confirm you want to put Dot 5 or Dot 5.1 in, as there's a significant difference.

 

If it is Dot 5, then yes, the system will have be utterly dry.

 

DOT 5 yes.

 

 

I think it's been said before but it needs repeating:

 

DOT 5 is completely wrong for our braking systems ..

 

It's DOT 4 or DOT 5.1 and even then you should really only use that with NEW empty braking systems!

[Spider]

DOT 5 is Silicon Based. All others are Glycol Based.

 

To get the best from DOT5, you need to replace all rubbers in the Brake System, though, with many DOT5, you can retro-fill the system as is, but any advantage of DOT5 won't be realised. You also usually need to top up the Master Cylinder quite slowly to avoid aeration of the fluid. Yes, it's fussy. But once in there, will virtually last forever.

 

I have one car on DOT 5.

 

Would I do it again ? No. There's nothing wrong with it, but it's silly money and just way too fussy for my liking.

 

As Rolf suggested, just use DOT 4 and replace it every couple of years.

[nicklouse]

DOT 5 also has water issues in that any water that gets into the system will sink to the lowest point(s) and cause rust.

The US forces that developed the stuff have been trying to work out how to get rid of it.

Take your pick of DOT3 or 4 or 5.1 they are all mixabke.

[dasupersprint]

Ok thanks to all of you, will not complicate things and continue with standard DOT 3/4 fluid

[Magneto]

The difference between the DOT 3, 4 and 5.1 is the boiling temperature, so if you're driving a street car and not going down mountain roads at 9/10 DOT4 is your best bet, it's also easy to find anywhere.

[dunkyb]

Hey guys, 

 

I have a 1965 MK1 which has DOT 5 silicone brake fluid (Atomec) which I assume was filled from dry when it was re-built prior to my ownership.

 

I am experiencing brake lock-on issues, now having read a lot of negative comments about DOT 5 am wondering whether it's eaten away at seals in the master cyl/brake servo.

 

If I wanted to move back to DOT 4 or 5.1, would bleeding all brakes with fresh DOT 4 be sufficient, or am I stuck with it?

 

Many thanks,

Duncan

[nicklouse]

Hey guys, 

 

I have a 1965 MK1 which has DOT 5 silicone brake fluid (Atomec) which I assume was filled from dry when it was re-built prior to my ownership.

 

I am experiencing brake lock-on issues, now having read a lot of negative comments about DOT 5 am wondering whether it's eaten away at seals in the master cyl/brake servo.

 

If I wanted to move back to DOT 4 or 5.1, would bleeding all brakes with fresh DOT 4 be sufficient, or am I stuck with it?

 

Many thanks,

Duncan

Strip clean and replace all seals the fit proper fluid. You may find your cylinders and calipers have rust inside now.