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Mon Mar 30, 2009 4:34 pm

Bently says not to use alcohol in the brake system because it will extract residual lubricant from the rubber parts, and cause premature aging of those parts.

I've seen several posts where people have flushed with rubbing alcohol.

What do you think?

Will it cause major break down of the braking system before it's time, or not?

Mon Mar 30, 2009 4:46 pm

I wouldn't do it. Just use fresh clean brake fluid. 8)

Mon Mar 30, 2009 5:44 pm

I agree, IPA can also carry moisture which will mix freely with the brake fluid, bad idea, use brake fluid.

Mon Mar 30, 2009 6:38 pm

i dont know why anyone would flush with alchohol. brake fluid flushes just as well

Mon Mar 30, 2009 6:51 pm

dansvans wrote: i dont know why anyone would flush with alchohol. brake fluid flushes just as well

I think brake fluid might work better - while bleeding my brakes this evening, the front drivers side wheel had a puddle of fluid around the tire - looks like at least one of the pistons sprang a leak (better to find it in the garage than on the road!)

Mon Mar 30, 2009 7:21 pm

No to Alcohol or anything else. Drain as much out as you can using a NEW battery filler into a can or jar and then wipe the inside of the top resevoir with a rag as best you can. Refill with the proper fluid and start bleeding the brakes until it comes out clean. Be sure to check the fluid level every few pumps. Do this once a year and your brake cylinders and master cylinder will last almost forever. Brake fluid is hydroscopic which means it picks up moisture - from out of the air too.

Sun Jul 08, 2012 1:21 pm

a few quick brake system flush questions:

- how much fluid to flush a 72 bus?

- just at the 4 wheel cylinder bleeders? i thought i read on Type2.com that there was a 5th on the master cylinder (will look myself)

- i just hooked a clear hose to an old water bottle. plan is to keep the bottle & hose higher than the cylinder. i will have help pushing the pedal and watching the reservoir. good?

- approx. how long/how many pumps to get to the RR wheel? my fluid is yellowish but not all that dark...i hope its obvious.

thanks

Sun Jul 08, 2012 2:55 pm

A 1 liter bottle of fluid is usually sufficient. It takes 6-8 full pumps to drain the reservoir and that's likely close or more than what's in the lines and cylinder at the back.

I usually do 5-6 pumps per wheel unless the fluid coming out is still funky looking.

Sun Jul 08, 2012 3:03 pm

More pumps for the first rear wheel you do than for the second, maybe 8-10 for the first wheel and half of that for the second. The fronts will require a couple pumps less each. I would guess that the late bay brake fluid reservoir would take more than 20 pumps to empty.

BTW, having caps for the bleeders can save a lot of hassle down the road with fighting bleeders that are rusted tight. You can make caps with short pieces of fuel line with one end plugged off with silicone if you don't have an easy source of replacement ones.

Sun Jul 08, 2012 3:14 pm

drink the Alcohol, use brake fluid for the rest. ever seen a grown man cry?

Sun Jul 08, 2012 3:15 pm

longlive356 wrote: ever seen a grown man cry?

Is that what happens when you drink brake fluid? :wink:

Sun Jul 08, 2012 3:35 pm

rustbus wrote:
- i just hooked a clear hose to an old water bottle. plan is to keep the bottle & hose higher than the cylinder. i will have help pushing the pedal and watching the reservoir. good?

thanks
I believe that your bottle can be below the cylinder, but the end of the hose wants to be in the fluid so no air gets back to the cylinder.

Sun Jul 08, 2012 3:40 pm

djspn wrote: rustbus wrote:
- i just hooked a clear hose to an old water bottle. plan is to keep the bottle & hose higher than the cylinder. i will have help pushing the pedal and watching the reservoir. good?

thanks
I believe that your bottle can be below the cylinder, but the end of the hose wants to be in the fluid so no air gets back to the cylinder.
Correct, even better with a wrap of teflon tape on the bleeder threads so they don't leak while it's open.

Sun Jul 08, 2012 4:02 pm

This is a handy tool for filling my '69 camper upper reservoir.

Aloha
tp

Sun Jul 08, 2012 4:04 pm

Alcohol may not be good for the rubber seals but there is more to a brake system than rubber seals.
My regulating valve was totally junked and gooped up and the internal valves were inopperable. They can't be fully taken apart to service. Repeated flushing with alcohol using a big syrenge finally got it immacuately clean and wonderfully working. It cleans it by acting as a solvent. Flushing with brake fluid did absolutely nothing. It was the buildup of the junk that needed to be loosened up.

BTW a quart bottle of brake fluid has been sufficient to flush the total system. Flush at each bleeder until the new clear fluid comes out and then a bit more.
Naturally you add more fluid in thru the upper refill reservoir but you don't need to or want to keep fluid in it. The only thing you want to do is not let air get into the MC. The bottom reservoir holds a lot so let it get almost empty of the old fluid before adding any new fluid. If you don't do that all you are doing is continually diluting the old fluid with the new. It will eventually get new fluid thru the system but it's still diluted with some of the old fluid.

Another way to think about doing it is just keep pumping and bleeding it until only air comes out the bleeders. Thet should get both the upper and lower reservoirs and a lot of the MC emptied of old fluid. then start refilling the system with new fluid. Naturally you will have to bleed the system but there will be very little of the new fluid diluted with some of the old.

Sun Jul 08, 2012 5:40 pm

Yall need to read better :wink:

Alcohol is perfect for flushing the brake system and washing the parts....but NOT isopropyl alcohol. Isopropyl is indeed hygroscopic (it absorbs and is a co-solvent with water just like acetone).

It is denatured alcohol that the manuals are speaking of...also sometimes called methylated spirits. It does not absorb water (extremely little)...which is why it is also the choice (and has been for about 200 years)....of painters when thinning shellac (real shellac). It prevents surface blooming from moisture absorption.

Use denatured alcohol for flushing the brake system. It works perfectly.

By the way denatured alcohol is ethyl alcohol (ethanol) doped with 5% or more methanol. Be sure you by 90% strength or better. Most hardware stores and paint departments have it. Ray

Sun Jul 08, 2012 6:25 pm

I would flush with brake fluid, and only brake fluid.

Sun Jul 08, 2012 9:57 pm

this is great, thanks for all the tips guys.

busdaddy wrote: djspn wrote: rustbus wrote:
- i just hooked a clear hose to an old water bottle. plan is to keep the bottle & hose higher than the cylinder. i will have help pushing the pedal and watching the reservoir. good?

thanks
I believe that your bottle can be below the cylinder, but the end of the hose wants to be in the fluid so no air gets back to the cylinder.
Correct, even better with a wrap of teflon tape on the bleeder threads so they don't leak while it's open.

you guys mean, so no air gets back into the cylinder, by accident, right? i mean with steady pressure and coordinated pedal pushings, there should be no reason air goes backwards into the cylinder, yeah?

if the end of the hose is in liquid, i gotta assume there is still air in the hose right? we're not priming the entire length of hose with fluid are we?

Quote: Naturally you add more fluid in thru the upper refill reservoir but you don't need to or want to keep fluid in it. The only thing you want to do is not let air get into the MC. The bottom reservoir holds a lot so let it get almost empty of the old fluid before adding any new fluid. If you don't do that all you are doing is continually diluting the old fluid with the new. It will eventually get new fluid thru the system but it's still diluted with some of the old fluid.

thanks DBM, i was wondering at what point to start adding new fluid....i'll just go for it until its nearly all the way down the tube in the cab. if i'm sliding around underneath and can keep an eye on the lower cylinder, i'll try to get that near empty before adding the new stuff....gotta watch that carefully i bet.

story is, my brake fluid must be about 10 years old....at least...i re-did the rear brakes 10 years ago when i got the bus and likely put maybe 5000km on it since then over the years. after getting the bus out of "storage", (dads barn) i found one rear cylinder leaking and it was replaced to pass safety inspection. before the rear brake work i had a leaky booster that was drinking my brake fluid like mad....

now i just want to replace the fluid as it is old..the system has been kept tightly shut so the fluid doesn't look terrible, but i suppose i will see soon how bad it is.

I never had any intent of flushing with alcohol, this is just one of few brake flush threads i found remotely relevant.

thanks all.

Sun Jul 08, 2012 10:23 pm

rustbus wrote: this is great, thanks for all the tips guys.

busdaddy wrote: djspn wrote: rustbus wrote:
- i just hooked a clear hose to an old water bottle. plan is to keep the bottle & hose higher than the cylinder. i will have help pushing the pedal and watching the reservoir. good?

thanks
I believe that your bottle can be below the cylinder, but the end of the hose wants to be in the fluid so no air gets back to the cylinder.
Correct, even better with a wrap of teflon tape on the bleeder threads so they don't leak while it's open.

you guys mean, so no air gets back into the cylinder, by accident, right? i mean with steady pressure and coordinated pedal pushings, there should be no reason air goes backwards into the cylinder, yeah?

if the end of the hose is in liquid, i gotta assume there is still air in the hose right? we're not priming the entire length of hose with fluid are we?
Now just how long is this hose?, I usually use one that's ~2' and it's got to have nothing but fluid in it before I consider the job done. As for no air getting sucked back in?, correct, it also keeps the fluid from drooling down the backing plate.

Mon Jul 09, 2012 9:38 am

busdaddy wrote: rustbus wrote: this is great, thanks for all the tips guys.

busdaddy wrote: djspn wrote: rustbus wrote:
- i just hooked a clear hose to an old water bottle. plan is to keep the bottle & hose higher than the cylinder. i will have help pushing the pedal and watching the reservoir. good?

thanks
I believe that your bottle can be below the cylinder, but the end of the hose wants to be in the fluid so no air gets back to the cylinder.
Correct, even better with a wrap of teflon tape on the bleeder threads so they don't leak while it's open.

you guys mean, so no air gets back into the cylinder, by accident, right? i mean with steady pressure and coordinated pedal pushings, there should be no reason air goes backwards into the cylinder, yeah?

if the end of the hose is in liquid, i gotta assume there is still air in the hose right? we're not priming the entire length of hose with fluid are we?
Now just how long is this hose?, I usually use one that's ~2' and it's got to have nothing but fluid in it before I consider the job done. As for no air getting sucked back in?, correct, it also keeps the fluid from drooling down the backing plate.

I had them chop me off 4'....i suppose i could cut that down a bit.

thanks again! - now to see if the misses can handle me bossing her around for 30 minutes. :P