Emulsification of Brake Fluid

[John northcott]

I have a 1976 Toyota Landcruiser I use on a farm. I found the brakes not to be working at all this morning and opened the master cylinder reservoir to find it full of brake fluid that had turned to a consistency of custard. I had to pull the whole master cylinder apart and some of the brake fluid had even turned to a sticky substance like chewing gum which I had to peel off. After cleaning the master cylinder and putting it back on, I attempted to bleed the air from the brake system as per usual but found that the pipes to the four wheels are also blocked and I will have to clear them by reverse purging with compressed air and possibly Methylated spirits. This is the second time this has happened to me and am wondering what I am doing wrong. Perhaps the brake fluid is too old or what? It seems to have happened suddenly but understandably takes a lot of work to fix. Anyone have any thoughts on the problem?

[John northcott]

Yes I understand the hygroscopic tendency, and the brake fluid is not that old. I have completely rebuilt the hydraulic system including new cylinders on wheels and rebuilt the master. This seems to be something else. Part of the fluid had turned to a sticky gum that I had to scrape off with a sharp screwdriver and the rest in the master cylinder was a thick past like thick cream, grey in colour. Gum was quite hard and was in the centre of the cylinder between the two rubber plungers. Looks like a chemical reaction of some sort. I have not alternative nut to clean the whole system and use new fluid.

[John northcott]

Ok Thanks guys for the thoughts. 'Not that old' means months, not years, but it may have been mixed up with older fluid. Some is kept in farm sheds and who knows how old. Possibility of oil contamination did cross my mind. I use both for brakes. A tractor uses Castrol Mineral oil for brakes and the rest of my farm equipment uses brake fluid. So, possible. I will be careful not to cross contaminate with silicon and glycol fluids too from now on. Wasn't aware of the problem until you pointed it out. It is common to grab a bottle of 'brake fluid' and whack it in the master cylinder without reading the fine print. Thanks again. I'll take it all on board.