Dot 5

Post by **markattard** » Thu May 28, 2009 8:39 am

Just wanted to know if it is possible to fill up a brand new brake system, new m/c, new pipes and new slaves, with dot 5 fluid without no adverse consequences

Post by **Stig** » Thu May 28, 2009 9:36 am

If by dot 5 you mean silicone then yes, I've filled a brand new system and a partly new system with no adverse effects at all.

I've heard people warn against using it with old seals but it always seems to be "I read it somewhere once.." etc. rather than "I did it and had a problem...".

Post by **markattard** » Thu May 28, 2009 9:47 am

Hi stig tanx, So I think its very usefull to convert to silicone, at least it does not eat away the paintwork when spilled and I heard it would last much longer than the old dot 3 and 4

Post by **bmcecosse** » Thu May 28, 2009 10:24 am

It doesn't give as good as a pedal - the manufacturers don't use it on new cars! And - it costs a lot more! Best just use DOT4 - don't spill it - and bleed a wee bit through each year during the MOT prep!

Post by **markattard** » Thu May 28, 2009 10:31 am

our advice much appreciated BMC, so dot 5 what is it good 4 anyway?

Post by **bmcecosse** » Thu May 28, 2009 10:35 am

Well - I did use it in a specialised ultra high vacuum unit I had at work !! It was basically boiled up - sprayed down a 'christmas tree' where it absorbed the last few molecules of air!
But it IS used in classic cars - expensive and unnecessary is my view - but it's your choice!

Post by **markattard** » Thu May 28, 2009 11:04 am

I only got interested because it does not harm the paint. My problem is andjusting the m/c plunger travel, usually when filling up a new system for the first time. I end up having fluid out of the m/c cap till I get a decent adjustment.

Is there a way to avoid this?

Post by **Stig** » Thu May 28, 2009 12:13 pm

Well I haven't noticed a particularly soft pedal in either car.

bmcecosse wrote:- the manufacturers don't use it on new cars! And - it costs a lot more!

That'll be why they don't use it then.

markattard wrote:I only got interested because it does not harm the paint. My problem is andjusting the m/c plunger travel, usually when filling up a new system for the first time. I end up having fluid out of the m/c cap till I get a decent adjustment.

Is there a way to avoid this?

I'm confused as to why you're adjusting the plunger travel, it's usually set once and left alone. If the filler cap is on and the fluid level isn't too high (it doesn't need to be up to the brim) then I wouldn't expect fluid to squirt out. Maybe you're just overfilling it, I'm sure the manual says what the level should be. Or someone else who has a better memory than me...

Apart from not harming the paint it's principal advantage is that it doesn't absorb moisture so doesn't need changing regularly like mineral fluids.

Post by **Leo** » Thu May 28, 2009 12:31 pm

Mark
My advice is to go for Silicone, I have been using it in various classic cars for well over 10 years with no problems. None of that peeling paint and nice clean fluid all the time. Just important to introduce it when the complete system is renewed.
It can be bought at a reasonable price if you shop around.

Leo

Post by **jaekl** » Thu May 28, 2009 1:19 pm

I switched my three over in the 80's. Went from usually at least one cylinder that needed to be unseized to none. Definetly reduces maintenance and is best for the occassional car. Due to the nature of water absorption of reglar fluid, once saturation is reached water starts coming out of solution and falls since it is heavier than the fluid. Not a problem for the wheel cylinders since they are vertical, but in the master cylinder the water drips out of the reservoir through the ports and causes pits directly below.
If you use the car alot and know you will freshen the fluid, regular fluid is probably best. However, for a car that is not used alot or you know yourself better and know you probably won't get around to freshening the fluid, silicone can reduce the annual maintenance.
The drawbacks I encountered is if you have a leak, it's a bit tough to locate it since silicone likes to migrate quickly. Also after 25 years I'm finding a need to rebuild the brakes. After these years some fluid has managed to get past the seals and now the shoes are less effective. Not sure whether is just the time or the fact that I'm in a spell of less Morris driving. The problem is the seepage occurs so slowly it can go unnoticed except the brake performance suffers.
Finally, I'd say it would be best to be prepared to do a rebuild every ten to fifteen years. There is no clear choice but my experience is less need for repairs and maintenance. It's probably the silicone migration that keeps the clyinders free to move, but it eventually contaminates the brake lining.