Club 80-90 Forums

I know that mixing DOT4 and silicon fluid is a big no no, has anyone changed over to silicon on a system that previously had DOT4 in it?

How do you flush out all the old fluid, or is it a case of draining the system as much as possible and then bleeding loads of silicon through?

Cheers

Ian

IIRC you can get DOT 5.1 silicon thats "compatible" with DOT 4...

I also seem to remember... The point about ridding the system of DOT 4 is prob more to do with it lowering the boiling point and still absorbing water... replacing as much of the system as possible (and cleaning out the rest) will enable a much reduced contamination.. to be fair... unless I was fitting all new components I wouldnt bother with silicone... use a quality brand of DOT 4 and change it every 2-3 years... that will keep the system in good shape..

Thanks Tomanytoys

Thats confirmed what I had thought.
Just thought it would be good to fill the system with some thing that had a higher boiling point and that did not rot the pipes, also though silicon would keep the rubber seals in better shape.
I do change the fluid in my vehicles about every 18 to 24 months, so shall keep doing the same until I get round to a complete strip down.

Cheers

Ian

sandwedge wrote:I know that mixing DOT4 and silicon fluid is a big no no, has anyone changed over to silicon on a system that previously had DOT4 in it?

How do you flush out all the old fluid, or is it a case of draining the system as much as possible and then bleeding loads of silicon through?

Cheers

Ian

As far as I know, it is not mixing the types that is the problem, it is the seals etc in your vehicle. DOT5 has the silicon and can rot/swell seals in systems designed for DOT4. The upgrade to DOT4 is DOT5.1 (higher boiling point). My motorbike states DOT4 on the cap and the workshop manual states DOT5.1 is fine. If upgrading I would just push plenty of DOT5.1 through and not worry about draining and introducing air to the system as they can mix ok.

Hope that helps.