Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Brake fluid for 4/4 sport

I am about to start annual service on 2009 4/4 sport which includes bleeding the brakes/clutch. The handbook I have which includes 4/4 to Roadster models. refers to A P Universal Brake Fluid and on the reservoir tank the tag states Dot 4. I have sourced AP Universal brake fluid on the internet where there is AP racing 600 Dot 4 , an high spec fluid for racing. Looking at Dave W superb breakdown of servicing where he is bleeding fluid I notice that the bottle of AP fluid being used refers to AP Formula which seems to be Dot 5.1 brake fluid. AP technical data , on the Dot 5.1, does state it's compatible with Dot's 3 & 4. As AP formula Dot 5.1 is not a silicone based fluid can this be used instead of the 600 Dot 4 ?

I get my brake fluid from Demon Tweeks - mainly because it's quick delivery!
I decided that I would go for 5.1 as the best option (for me)!
"Dot 5.1 is AP Racing’s high performance non silicone based brake and clutch fluid. Recommended for use in the hydraulic brake and clutch systems of all cars, for which a non petroleum based fluid is specified.
Suitable for high performance applications including vehicles fitted with ABS and ESP, is suitable for road and track day use".



I believe that the packaging may now have changed to yellow.

Thanks Dave for the info

Eddie

Dot 5 is essentially for competition cars as it has a higher boiling point.
Downside is that it absorbs moisture quicker and therefore will need changing more often. It is also more expensive.
I would stick to Dot 4 personally.

All non-silicone brake fluids absorb water , it is just a question of how quickly, and what is the resultant boiling point.

Personally I would recommend changing the fluid every year, or maximum 2 years.

I would rather have "fresh" DoT 3 than old DoT 4 or 5.1 which had absorbed a lot of water.

The fluid also contains inhibitors against corrosion against certain metals , these are consumed over time as they "pacify" the metals in the system, you really do want fresh fluid to ensure this process is kept going.

Sounds klaxon, aroogah aroogah...

DOT5 is silicon and must never be mixed with 5.1, 4, or 3.

DOT5.1 is miscible with DOT4 etc and is normal brake fluid. If the car has ABS, the handbook might specify DOT5.1 as it has lower viscosity than DOT4.

I did look up rates of water absorption, but got nowhere. Nothing I looked at gave any figures and nothing suggested 5.1 was any worse than 4 (or 3).