| Author |  Topic  | |
andydeans3
V4 Guru
United Kingdom
2016 Posts |  Posted - 14 Nov 2018 : 22:37:10  
| If one decides to re-new the brake fluid is it possible to switch from DOT 4 to DOT 5?
I think that DOT 4 is not compatible with DOT 5, so I suppose the question is, is it possible to get all the DOT 4, out of the system?
Is there likely to be issues with the seals in the various cylinders, if the fluid is switched to DOT 5.
Andy
1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro |
|
greg124
V4 Fan
United Kingdom
173 Posts | |
andydeans3
V4 Guru
United Kingdom
2016 Posts | Posted - 15 Nov 2018 : 13:21:50
| Clive
Ah, very interesting. I see now that there is DOT 5.1, which is compatible with DOT 3 and 4, but DOT 5, (slicone based) which is not compatible, with DOT 3 and 4.
Only reason I was asking was that DOT 5 (Silicone) doesn't absorb moisture, whereas DOT 3 and 4, do. Which eventually corrodes the internals.
I was therefore giving some though to switching over to DOT 5 silicone, but I'm thinking now that it is not an option.
1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro |  |
|
greg124
V4 Fan
United Kingdom
173 Posts | Posted - 15 Nov 2018 : 20:39:13
| | I decided to stick with DOT4, and change brake fluid every other year to mitigate the effects of water absorption. Bit of a faff, but less so than replacing corroded gubbins | |
|
beardydave
V4 Fan
133 Posts | Posted - 15 Nov 2018 : 21:39:22
| Dot 5 is only really used on things like show hot rods and harleys where they are concerned about damaging the paint.
The reason normal brake fluid is hydroscopic is so that the moisture which always gets into the system is not able to corrode the inside of the pipes or calipers, and so it wont boil under hard braking which would lead to brake fade.
Using dot 5 its recommended to change the fluid more often than with normal fluids.
The dot rating relates to the "wet boiling point" of the fluid, which is the boiling point after absorbtion of a certain ammount of water supposed to relate to a typical length of usage. Using a better dot rating means it will resist fade better after prolonged length of installation.
It does not necessarily have a better dry boiling point. Some dot 3 fluids can be better than dot 4 or 5.1 when fresh, but are worse after a period of time. Racing fluids are a prime example of this.
To answer your original question, it is not possible to flush dot 3/4/5.1 fluid out to use dot 5 or visa versa. One will form sediment in the presence of the other. The only way to switch is to replace ALL parts of the brake system with brand new parts that werent assembled using the other type of fluid as a lubricant. |
Edited by - beardydave on 15 Nov 2018 21:41:54 | |
|
andydeans3
V4 Guru
United Kingdom
2016 Posts | Posted - 15 Nov 2018 : 22:15:51
| Beardydave.
Thank you sir for your most precise response.
I'll stick with DOT 4!
Andy
1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 15 Nov 2018 : 22:17:26
| quote:
Originally posted by beardydave
The reason normal brake fluid is hydroscopic [...]
[pedantic mode]"hygroscopic"[/pedantic mode]
www.saabv4.com | |
|
beardydave
V4 Fan
133 Posts | Posted - 15 Nov 2018 : 22:20:33
| | I never took Greek | |
|
| | Topic | |
Change the brake fluid from DOT 4 to DOT 5.
