I've had my 79 for 20 years now and have never flushed the brake fluid so I figure it's probably past time. Doesn't get driven much but still. My question is what fluid should I use. I know the car has the better calipers that don't leak and stainless braid hoses. I remember something about silicone fluid but seems like that's not recommended anymore? DOT 3, DOT 4, now there's a DOT 5? Van Steel carries Amale DOT 3. Should I just use that? Thanks all

 

Clarification: DOT 5 is silicon; DOT 5.1 is glycol based. Silicon will not mix with DOTs 3, 4, or 5.1 and shouldn't be used in a 3/4/5.1 system without fully flushing out the glycol fluid.

To be sure you don't have silicon fluid now, a quick test is to put about a tablespoon of fluid from your reservoir into a container and mix in a like volume of water and give it a stir. If the two fluids separate then you have silicon and must replace with silicon. If the fluid and water mix then you have glycol-based. The reason folks are shying away from DOT 5 is that the seals can swell if the rebuilder doesn't use the correct EPDM seal material. But, silicon does have its advantages too.

The main differences between 3, 4, and 5.1 are the boiling points, which increase respectively. These can all be mixed so there is no concern matching with your existing fluid. I believe the down side of 4 vs. 3 is that 4 absorbs water more readily so should be flushed at shorter intervals -- like every 2-3 years rather than 3-4 years. I can't recall the pros and cons of 5.1.

As far as sources, I'd just buy from my local auto parts store - there's no quality difference as this stuff is tightly regulated. No need to spend money on shipping.

PS - Make sure the containers you buy are sealed. Opened containers should be discarded after ~6 months.

 

That's some very good info. Thank you, sir.

 

A couple really quick checks as per which fluid is in your system now. First, if it's all brown and looks more like mud than brake fluid. It's not likely silicone. And secondly, dot 3 and 4 smell like brake fluid. Very distinctive smell. Dot 5 silicone doesn't smell like anything. No smell.