dath

So I was at the auto parts store the other day and noticed they have synthetic DOT3/4 compatible fluid that has a higher dry rating. I don't recall what the wet rating was (I should probably check), but I was curious what peoples thoughts were in regards to synthetic brake fluid and which fluids would be a good choice for use?

Also, I am replacing the calipers, hoses, master cylinder, and the lines leading to the calipers (just the short ones)... I would like to flush out the brake system very thouroughly, does anyone have a recommendation on how to do this? I ask because the first time I had the system open I flushed more than a quart of fluid through the system and now my fluid looks dirty again...

PatG

Well with replacing all of those items you are almost there. When I switched to DOT5 I removed all of the lines from the pressure switch block just below the MC and flushed with alcohol and blew it out with compressed air. Make sure you have someone hold a rag over the end of the line when you blow it out because you do not want the DOT3 brake fluid on your paint.

john V. zemba

use denatured alcohol and with the lines open pour it in the reseviors until it looks clear coming out. On my 78 I used about a 1/2 gallon, then put my new fluid in. It took a few minutes for it to work thru the first time but it cleaned it out and won't hurt anything in your system.

PatG

I think the original post mentioned replacing the MC. I would not flush a brand new MC and it is much easier to fluch the system with it completely opened up.

mrvette

I have been a stong backer of silicone brake fluids...DOT 5, for a LONG time now....much better than normal 3-4 stuff, as it does NOT rust out the system over time...it's not water absorbtive...'hydroscopic'....apparently normal 3-4 fluids will absorb water/moisture through the rubber brake lines, it's that bad...

at any rate, some years ago I switched to DOT 5 fluid...i'ts a silicone based oiley crap of some sort....In chemistry, it's allways a poly-can't-pronounce-it, and for sure this parrott can't pronounce it.... :D :D

at any rate, I know nothing of this new product you mention above here, I"m highly interested in it....anyone???

GENE

dath

Yes, I will be replacing the master cylinder and I do not have any intention to flush the new one with anything. My brake system is completely open at the moment, so it sounds like I'll be flushing the system with denatured alcohol. Does the alcohol need to be completely out of the system before putting in new fluid? I would otherwise assume so.

mrvette: I had thought of using the silicone based DOT5 fluid, but I've heard so many complaints about squishy brakes and trouble getting all of the air out of the system... My car fits nicely into the driver catagory, so I'm thinking that the regular DOT3/4 compatible fluids are the best choice for my use...

I had actually read the same thing about absorbing water through the rubber hoses, that is quite impressive I have to say. If you've ever had brake fluid on your hands, I'm sure it isn't much of a surprise, that stuff sucks liiquid.

Disco_Mike

I had to replace the rear calipers last year. Silicon DOT5 was recommended to use. Ive had no problems. I have even had a few 'brake tests' in traffic.
I am pleased.

mrvette

You may be on to a better solutiion there with that 3/4 new fluid there, as long as it's not hydroscopic....that would be GREAT.....I frankly have had NO troubles with soft pedal that is proven to be caused by the DOT5 fluid....
it does seem to hold bubbles when poured rapidly, but the settle out quickly, and after a few days the pedal is hard as a rock....mine is, anyway...


GENE

PatG

I have yet to see it proven. My brakes are great with the DOT5. Can't see any reason not to use it, unless you like brake fluid that eats paint and turns to muck in the master cylinder.

thejaf

As far as flushing the open lines, I had good luck using nylon tubing and a large syringe. Just be careful and don't drip anything on your paint.

Rockn-Roll

You may want to check with your states Bureau of Automotive Repair and also the manufacturers of master cylinders and calipers to make sure that the seals will not deteriorate from alcohol. I would not recommend using anything other than brake fluid to flush a system. Brake fluid itself is a solvent so in my opinion flushing with alcohol is just a waste of time and money, and unless you are getting pure alcohol (illegal in most states) you will be introducing contaminates into the system most obviously the chemical(s) that go into denaturing alcohol. If you are installing new calipers, hoses, m/c, etc. then I would definitely not try to run anything else through the lines other than what you are going to be using as brake fluid. You should run the brake fluid through the lines BEFORE installing the calipers and hoses. I recommend installing the m/c, fill with your brake fluid, and pump like 4 to 8 oz through the lines. Then install hoses and calipers then bleed as normally.

dath

Good point. I want to make sure things are thouroughly cleaned this time though... Last time I "flushed" the system with over a quart of fluid, well, it's dirty looking again... Maybe I didn't flush the whole system evenly as that isn't exactly why I put so much fluid through :bb