brake fluid

[atelic]

hi -

i did search for this and didn't find what would help me. this is a pretty simple question and, therefore, might be annoying.

i bought a GSX750 a couple of months ago. there's not much riding time left here (not for me, at any rate) and i'll be taking it in to a shop in the spring for some maintenance. i don't know of a good shop yet, though.

anyway, the brake fluid reservoir (i think that's what it is - on the handlebar) doesn't show any fluid. to get me thru a few more weeks, can i just add some fluid?

i don't notice any problems with the brakes or anything, and the guy seemed to have maintained it quite well. he was riding it to work a lot of days, so it hasn't been sitting or anything. but i'd hate to suddenly not have brakes!

if i can just add some fluid, do i simply pour it into the reservoir?? i know these are silly - i don't do my own bike maintenance. not because i'm a complete ditz with tools, etc., i just don't know how.

also, no manual came with the bike, so would i use DOT 3 or 4? it's an '82. ya'know, maybe it's a 650.

well, thanks for any help!

[koolaid_kid]

Yes, you can pour it straight into the reservoir. I suggest putting a cloth under it first, in case of a spill.
Go ahead and use DOT 3 fluid. It is doubtful that he used DOT 4, as it is more expensive and rare to find in any machine, much less a classic GS.
A picture might help us to identify the bike for you.
And welcome to GS Resources. Post in the New Owners section and be greeted by our unofficial greeter also.
You might want to fill in your location, in case a member is nearby and can provide some assistance.

[tkent02]

Top it up and then keep an eye on it. If the level goes down again you have something to fix over the winter. The fluid should be replaced routinely anyway. Old brake fluid contains water and causes rust inside calipers and things.
And get a manual, no one but yourself will fix these old bikes correctly, it's a D-I-Y- thing for sure.

[Pete Logan]

Clymer says DOT3 or DOT4, but warns against using the synthetic DOT5.

My reservoir is engraved 'Use SAE J1703 or 70R3 only'. This is DOT3.

[baco99]

my understanding is that you can use DOT5 synthetic is you flush out all the old stuff. the synthetic and dino brake fluids don't mix well and can corrode the lines.

[Steve]

my understanding is that you can use DOT5 synthetic is you flush out all the old stuff. the synthetic and dino brake fluids don't mix well and can corrode the lines.

That was probably true with the early formulations of DOT5, but there have been improvements.

I thought I would do a little research just so I would not mis-lead anyone, and found a well-written paper on the Ducati Monster site.
It lists the advantages and disadvantages of DOT3, DOT4, DOT5 and DOT5.1.


.

[marz]

does any one know

i just dont get this if its a new plastic bottle,then how does it become water fouled ..ie if i open a bottle and the use some then screw the lid on how apart from the air thats in the open bottle.how does h2o get in there?

[BentRod]

not all seals are perfect, and some water is bound to find a way in.

[Nessism]

Brake fluid is hygroscopic, meaning it is capable of easily absorbing moisture from the air. You want to be careful how much moisture exposure the fluid has had since the water will corrode brake system parts and has a tendency to boil off if the brakes get hot – leading to spongy lever feel. I’ve seen recommendations to not use brake fluid unless it comes from a new unopened container but I think this is a bit extreme. My own personnel rule of thumb is to try to use up the container of brake fluid within one year, but it’s not like I write the expiration date on the container or anything. I also like to change the brake fluid in the bike every 2-3 years or so. It’s easy enough to do, and provides a good opportunity to get rid of any residual air that may be in the system.

[Pete Logan]

my understanding is that you can use DOT5 synthetic is you flush out all the old stuff. the synthetic and dino brake fluids don't mix well and can corrode the lines.

Sure never mix them, but from an admittedly decaying memory there's something about DOT 3, 4 and 5.1 being designed for natural rubber seals and DOT 5 (synthetic) being designed for synthetic seals.

Of course, I could be totally wrong, and hopefully someone with some real knowledge will chip in.

I've used them all in everything I've ever owned and never had a problem - except don't mix DOTs 3, 4 or 5.1 with DOT 5 syn.

I suppose if it comes to it I'll flush the damn thing out and put DOT 5 in and report from beyond the grave :-D:-D:-D

To be honest, why bother, and why worry. Just put in what the book says (DOT3) and flush it every year as a normal part of winter maintenance.

Takes all of 10 minutes.

[atelic]

Thank You!!

wow - thanks everyone! i'm just going to get a bottle of DOT 3, take the top off the reservoir, and pour some in. it has gone down (from the line in the reservoir window) in the last couple of months, so i'm guessing there's some leak somewhere, although nothing ever under the bike. i just want to get thru this month.

i know a guy who should be pretty good at working on an older bike, and he's supposed to be opening a shop again. (i'm in southern Wisconsin.)

it's not the bike i was hoping to find, but it's in quite good shape, so i'll probably be looking for some stock parts for the very few things that need to be replaced. and, if the guy doesn't have the manual somewhere (going to check with him and see if he forgot it), i'll order one at some point.

lol - no picture, and i was too lazy to go out to the garage and look, or pull out my file with the title in it. i'm thinking it's a 650 because when i got it i was thinking it wasn't as big as my old Shadow. but...senior moments happen even at my age!

again, thanks very much!

[baco99]

true, DOT3 is the safest bet, but the synthetic is supposed to have a higher resitance to both heat and water absorption, making braking more consistent.

i just rebuilt my calipers with new seals and i plan to use DOT5, so i'll report back if i have problems. i used DOT5 on my 89 GS500E and didn't have any issues.

[Pete Logan]

Yeah - does anyone know what the supposed issue is with using DOT5 ?

I have a nagging memory that it's something to do with rubber seals, but I've used DOT 5 in vehicles from the '70s with no problem (as long as you flush the system out).

What is the issue here ?

I ask because I would rather use DOT5.

[Nessism]

Yeah - does anyone know what the supposed issue is with using DOT5 ?

I have a nagging memory that it's something to do with rubber seals, but I've used DOT 5 in vehicles from the '70s with no problem (as long as you flush the system out).

What is the issue here ?

I ask because I would rather use DOT5.

DOT 5 is synthetic and requires complete clean out of the old fluid from the system. It tends to lead to a spongy feel at the lever due to traped air in the fluid.

DOT 4 is the hot ticket to use - higher boiling point than DOT 3, compatable with other brake fluids (except DOT 5), fairly cheap.

[spyug]

One thing I think folks missed in this thread is that if the reservoir was completely empty you will create a bit of a problem by just pouring in fresh fluid. There will be air in the line which will act as a buffer between existing fluid and new resulting in poor brake feel and ineffective actuation i.e. your brake may not function properly when you really need them. Very dangerous.

If you have added fluid in this scenario, you do need to bleed the lines to force this air out and have a solid fluid filled line from caliper to master cyclinder.

To do this:
a) place bike on center stand or bike lift so bars are parallel to the ground.
b) cover body work with rags or shop towels to keep fluid from paint which it can disolve or otherwise ruin.
c) get a length of 3/8" diameter clear hose long enough to fit over caliper nipple and into a clear jelly jar.
d) pour fresh fluid into the jelly jar so the end of the hose is immersed. The hose needs to stay in the fluid at all time.
e)loosen off nipple on caliper just enough to have fluid start to run.
f) fill reservoir with fresh fluid and pump lever. Do not let fluid completely drain from reservoir, top it up as it goes down.
g) watch what comes out of the tube. Big bubbles then smaller then hopefully none. When clean clear fluid is running and before the reservoir drains hold down the lever and lock off the nipple.
h) top off the reservoir and pump the lever a few times. When the lever feels solid you're done. If lever is still spongy repeat from e) onward.
i) if you have two front brakes you will need to bleed from both calipers and if anti-dive mechanisms are fitted these need to be done as well. Please get a shop manual to explain this in more detail.

It will help if you have an assistant to fill the reservoir and pump.

The first time you do this you may need a bottle or two of fluid. Do not reuse it as it comes through the circuit. Only use fresh fluid. Fluid that has been flushed will bring "gunge" from the mastercyclinder, hose and or caliper with it.

Brakes should never be fooled with. Learn to do it right (its not difficult) or have a pro do it. As others have mentioned fluid will become ineffective in a season or two especially in climates with high humidity. Make changing the fluid a seasonal thing. At the start of or end of each season.

Remember, your life could depend on it.

Ride safe.
Spyug