Brake Fluid
I noticed the brake fluid was a little low on MH and was going to add some when I notice what I have says DOT3 HIGH Temperature SYNTHETIC. Not knowing what the present fluid is will it make any dif...
Forum Discussion
All brake fluids re synthetic. The main difference is 5.0 is a silicone based fluid that is not compatible with the 3.xx and the 4.xx fluids. 5.0 isn't used in anything other than high performance vehicles.
You can't flush the system and switch to 5.0 because it isn't compatible with the rubber components in your system. If it's been more than 2 years since your brake system has been flushed I would flush it with DOT 4.0 brake fluid. If the system doesn't need to be flushed you can add either DOT 3.0 or 4.0 fluid. I would opt for the 4.0 since it has a higher boiling point and can be mixed with 3.0 with no ill effects. DOT 3.0 is considered obsolete and has been replaced by DOT 4.0
To me it would be a poor choice to use DOT5.0 in any braking system where the vehicle potentially sets for long periods of time. First of all it is not compatible with the rubber components in most master cylinders or brake cylinders. It can cause the rubber to swell or leak past it. Not being hygroscopic any water that enters the system will gravitate to the low points. It will sit there and start to rust any steel components like brake lines or calipers. If the weather is cold enough for water to freeze any water in the system will turn to ice. The last thing you want is a rusted through brake line, ice blocking the line, or a caliper literally frozen and inoperable.
It was originally developed for race cars that need a higher boiling point. It later was introduced to several high performance production vehicles. I am not aware of any motorhome chassis manufacturers that use it, or claim to have components that it's compatible with.
You can't flush the system and switch to 5.0 because it isn't compatible with the rubber components in your system. If it's been more than 2 years since your brake system has been flushed I would flush it with DOT 4.0 brake fluid. If the system doesn't need to be flushed you can add either DOT 3.0 or 4.0 fluid. I would opt for the 4.0 since it has a higher boiling point and can be mixed with 3.0 with no ill effects. DOT 3.0 is considered obsolete and has been replaced by DOT 4.0
To me it would be a poor choice to use DOT5.0 in any braking system where the vehicle potentially sets for long periods of time. First of all it is not compatible with the rubber components in most master cylinders or brake cylinders. It can cause the rubber to swell or leak past it. Not being hygroscopic any water that enters the system will gravitate to the low points. It will sit there and start to rust any steel components like brake lines or calipers. If the weather is cold enough for water to freeze any water in the system will turn to ice. The last thing you want is a rusted through brake line, ice blocking the line, or a caliper literally frozen and inoperable.
It was originally developed for race cars that need a higher boiling point. It later was introduced to several high performance production vehicles. I am not aware of any motorhome chassis manufacturers that use it, or claim to have components that it's compatible with.
