Brake Fluid Question

[Bob_Roller]

Flushed the brakes and clutch on the oilhead, then on to the R65, for it's yearly brake flush .

Got down to about an inch or so of fluid in the bottle, I wanted to get the brake system done today on the LS .

I went out to get some more Castrol LMA GT/4 fluid, the only place in my area that carries Castrol brake fluid, now only carries GT/LMA synthetic fluid .

Not a problem with the LS, seeing as how the brake system is completely dry, but I'm wondering about any future problems with the other vehicles, when you get a mix of the two fluids .

[Barry]

Things were straightforward at one time you couldn't mix the old style DOT 3/4 Poly glycol brake fluids with the silicone Dot 5 type.

It's got more confusing recently as there are now non-silicone synthetic fluids available (maybe this GT/LMA synthetic fluid) which manufacturers claim are fully compatible with old type poly glycol fluids so you should be OK to mix them.

If that isn't complicated enough there is now a DOT 5.1 standard which is not a silicone type and can be mixed with DOT 3/4 type.

I've just bought some good old DOT 4 stuff it's much simpler as long as you don't spill it.

By the way I don't know if the DOT standards are universal but the basic differences in chemistry must exist in all markets.

[Bob_Roller]

I've been using Castrol brake fluid since I started performing vehicle maintenance, I haven't changed brands since then, that's about 40 years now .

I just thought it was odd, that I can't find the 'old' standard glycol based fluid anymore from Castrol .

Got the LS front brake system bled, and it feels pretty good, I'll do the old trick, of putting a rubber band on the brake lever for a few days to release any residual amount of air left in the system .

Only casualty of the process, was the vacuum pump, I got the hoses on the reservoir swapped, and sucked brake fluid into the vacuum pump, I think it's ruined .

[DeeG]

I was told by a mechanic that you cannot mix the silicone with the non silicone, and that if you want to go straight silicone (DOT 5, not the DOT 5.1), you have to swap out all the rubber and such.  Basically start with a brand new system.

Not sure how much of that is true, he just said that the two fluids were incompatible and something about they compressed differently and even if there was a little bit of the non silicone in there, it would "f" up the brakes.   :-/

[Ed Miller]

You must missed a Harbor Freight sale for about 16 bucks for a vacuum bleeder.

I wish I knew where to get new attachments, those things that fit over the brake bleeding nipple, as mine wear out and stop sealing well.  

[Bob_Roller]

Ed.

I don't need a vacuum pump, until I do the brake flush next year, so I'm sure something will come up by then .

I stopped using the accessories that came with the pump, I just use clear hose, and it works just as well for me .

I also put a wrap or two of teflon tape on the threads of the bleeder screws, seems to help the flushing process  a bit .

Bleeding the dry system on the LS went pretty quick, until I let the fluid reservoir run dry !!!!

[nhmaf]

I 've also gone with the "keep it simple" philosophy with brake fluids - I stick with straight DOT4 stuff for the airhead, and even then I try not to mix brands.   Actually, it is rather aggravating as I always end up with a bit left over, and once the container has been opened, if it is more than a month old, it goes into the hazardous waste section @ the recycling center.

[montmil]

Mike, you can keep your brake fluid left overs from absorbing moisture -the term is hygroscopic- by shooting a couple seconds worth of propane into the can and sealing the cap. Displaces the air. No air, no moisture.

This works with oil based paints and varnishes, too. Saves me quite a bit of bucks I used to waste on left over polyurethane.

Monte

[nhmaf]

My wife may suggest that I use an alternative source of heavier-than-air combustible gases.
 

[montmil]

No sparks, Mike!

[Bengt_Phorqs]

Actually nitrogen is the preferred inert gas to dispel oxygen.  All oil tankers have an inert gas system that layers over the crude in the tanks.   And I understand that now since a lot of new cars have nitrogen only tires the nitrogen is available at service centers.  

Personally, I'll just take it to the recycle center if I haven't used it in a month or two.  It's cheap enough to buy it fresh.