Bringing FJ out of hibernation

[Pat Conlon]

Have you been replacing the fluid every year?
I've heard it doesn't absorb moisture that accumulates in the system and can cause corrosion if it isn't replaced annually.

Correct, DOT 5 is non- hygroscopic, meaning that it does not absorb moisture that gets into the circuit.
DOT 3/4 absorbs this water and holds it in suspension, (until you flush out the old fluid) and thus prevents corrosion and rust on the system internals.

The problem with conventional bleeding/flushing of DOT 5 is that the bleed ports are typically located in the upper part of the chamber, which is good for bleeding off any trapped air, however not so good for flushing out any accumulated water, which settles to the low part of the chamber.
I have found that a MityVac gives an aggressive suction which helps remove and trapped moisture in the system. Conventional bleeding via the lever squeeze, is not enough. You need to blast that water out.

That said...I've had DOT 5 in my '84 for about 20 years now and things are ok...so far...DOT 5 has a softer feel at the front brake lever. When I rebuilt my clutch slave, I noticed the bottom half of the cylinder bore was pitted from corrosion and that the steel piston has rust on it...caused by trapped moisture no doubt.
I live in the desert with low humidity and, excepting the 2011 WCR, very rarely ride in the rain.
So....from my experience, if you live in a wet climate or travel thru the rain, I do not recommend DOT 5.

It is kinda nice to splash DOT 5 on your paint and not freak out.....

[zz28zz]

I did a little research on the subject of swapping to DOT5. There was conflicting info abt what to use for the flush agent.
Haven't heard of using contact cleaner. I'll be going back with a completely dry system. Suspect I can just install the DOT5.

Have you been replacing the fluid every year?
I've heard it doesn't absorb moisture that accumulates in the system and can cause corrosion if it isn't replaced annually.

I've never had anyone tell exactly where they think that water is going to come from.  If the system is properly bled, there's no water there for sure.  If water were getting there from the outside, then you'd think there would be a problem keeping it bled, because air would surely be getting in, right?


The stuff was developed for military and other vehicles that might see long periods of storage between uses.  I've never found any water in my brakes and no problems with them.

The FJ clutch might be an exception, since I can see where it might draw water in past the slave cylinder seals.  We'll find out this fall, since I need to service the slave cylinder soon.

No, I don't change out the fluid every year.  YMMV

I've been scratching my head abt how moisture can get into the sys too.

The only way I can think of is by way of the reservoir. There's some air in there. When reservoir goes from hot to cold there would most likely be some condensation. Not very much, but over time it could add up. Kinda like how water collects in your exhaust pipes but on a much smaller scale.
Any condensation would go down to the bottom of the reservoir since it's heavier and slowly make it way to the lowest point. Just a theory, but seems plausible.

[FJmonkey]

Water in the exhaust comes from combustion, easy to see every morning as the tin tops are merging into traffic before the engine is warm enough to turn it into steam... Brake systems?? I am with you on that one, thought they were sealed till the cover was opened again....

[zz28zz]

Water in the exhaust comes from combustion, easy to see every morning as the tin tops are merging into traffic before the engine is warm enough to turn it into steam... Brake systems?? I am with you on that one, thought they were sealed till the cover was opened again....

I was ready to disagree with ya on that, but after a bit of digging, you're more right than I was. 
I've always been told the water coming from exh pipes was from condensation (which is correct), so I assumed it was from ambient moisture overnight. Apparently it is from the combustion gases condensing on the cold pipes during warm-up. As the exh gases leave the cyl head, the water is vaporized (even on cold engines), but when when the gases contact the cold exh pipes, the vapor condenses to a liquid. Once the pipes are hot, the water vapor stays in a gaseous state.

I'm feeling more edumacated now!! 

As for moisture entering brake sys, I did find this from http://www.afcoracing.com/tech_pages/fluid.shtml:

MOISTURE IN THE BRAKE SYSTEM
Water/moisture can be found in nearly all brake systems. Moisture enters the brake system in several ways. One of the more common ways is from using old or pre-opened fluid. Keep in mind, that brake fluid draws in moisture from the surrounding air. Tightly sealing brake fluid bottles and not storing them for long periods of time will help keep moisture out. When changing or bleeding brake fluid always replace master cylinder caps as soon as possible to prevent moisture from entering into the master cylinder. Condensation, (small moisture droplets) can form in lines and calipers. As caliper and line temperatures heat up and then cool repeatedly, condensation occurs, leaving behind an increase in moisture/water. Over time the moisture becomes trapped in the internal sections of calipers, lines, master cylinders, etc. When this water reaches 212º F the water turns to steam. Many times air in the brake system is a result of water that has turned to steam. The build up of steam will create air pressure in the system, sometimes to the point that enough pressure is created to push caliper pistons into the brake pad. This will create brake drag as the rotor and pads make contact and can also create more heat in the system. Diffusion is another way in that water/moisture may enter the system.

Diffusion occurs when over time moisture enters through rubber brake hoses. The use of hoses made from EPDM materials (Ethlene-Propylene-Diene-Materials) will reduce the amount of diffusion OR use steel braided brake hose with a non-rubber sleeve (usually Teflon) to greatly reduce the diffusion process.

[FJmonkey]

Good info, thanks for posting it.

[rktmanfj]

MOISTURE IN THE BRAKE SYSTEM
Water/moisture can be found in nearly all brake systems. Moisture enters the brake system in several ways. One of the more common ways is from using old or pre-opened fluid. Keep in mind, that brake fluid draws in moisture from the surrounding air. Tightly sealing brake fluid bottles and not storing them for long periods of time will help keep moisture out. When changing or bleeding brake fluid always replace master cylinder caps as soon as possible to prevent moisture from entering into the master cylinder. Condensation, (small moisture droplets) can form in lines and calipers. As caliper and line temperatures heat up and then cool repeatedly, condensation occurs, leaving behind an increase in moisture/water. Over time the moisture becomes trapped in the internal sections of calipers, lines, master cylinders, etc. When this water reaches 212º F the water turns to steam. Many times air in the brake system is a result of water that has turned to steam. The build up of steam will create air pressure in the system, sometimes to the point that enough pressure is created to push caliper pistons into the brake pad. This will create brake drag as the rotor and pads make contact and can also create more heat in the system. Diffusion is another way in that water/moisture may enter the system.

Diffusion occurs when over time moisture enters through rubber brake hoses. The use of hoses made from EPDM materials (Ethlene-Propylene-Diene-Materials) will reduce the amount of diffusion OR use steel braided brake hose with a non-rubber sleeve (usually Teflon) to greatly reduce the diffusion process.

So, then, with the use of braided Teflon lines and DOT 5 should keep moisture to a minimum, huh?

I'm gonna change out the front brake lines this winter anyway.  The old covers on them have yellowed and look pretty crappy, and the DOT 5 has been in there long enough (5 years or so) that it has lost almost all color.  I'll try to capture all of it I can when I drain the system, and see if I can detect any moisture.

[zz28zz]

The teflon lines and fresh fluid should go a long ways I would think.

I will go with DOT5 in the clutch for now. In a year I'll do a quick and dirty bleeding and then give her a bath.

If I like it, I'll switch the brakes over when I rebuild the calipers and master.

[SlowOldGuy]

I converted both of my FJs to DOT 5 many years ago.  I converted the front brakes on my '85 sometime in the '87 time frame.  That fluid remained in there, untouched and unbled, until about 2002 when I swapped the front end and went to monobloc calipers (using DOT 5 in them also).

When I disassembled the stock calipers, they were sparkly clean and had absolutely NO rust or corrosion whatsoever on any of the components (after 15 years!).  

The DOT 5 I used in the monoblocs during installation remained in those calipers, again untouched and unbled, until last week when I changed front brake pads.  I went to the trouble to pop the pistons out of the calipers to clean everything up and guess what?  Absolutely NO rust or corrosion on anything (after 10 years!).

So, given 25 years of using DOT 5, I'll venture to say that unless you decide to piss into your master cylinder while changing the fluid, the chances of suffering corrosion with DOT 5 fluid is remote (unless you store your FJ underwater).

And it's HUMID in the Dallas area during summer, and I wash my FJs a LOT so the calipers and master cylinder are frequently exposed to water.
FWIW,
DavidR.

[FJmonkey]

So, given 25 years of using DOT 5, I'll venture to say that unless you decide to piss into your master cylinder while changing the fluid, the chances of suffering corrosion with DOT 5 fluid is remote (unless you store your FJ underwater).

And it's HUMID in the Dallas area during summer, and I wash my FJs a LOT so the calipers and master cylinder are frequently exposed to water.
FWIW,
DavidR.

Sounds like a smoking gun there, if the system is sealed (as it should be) then Dot 5 is the way to go. As long as you don't mind the brakes being slightly less crisp in the feel over Dot 3, 4. Good info David.

Anyone with bad experience using Dot 5?

[rktmanfj]

So, given 25 years of using DOT 5, I'll venture to say that unless you decide to piss into your master cylinder while changing the fluid, the chances of suffering corrosion with DOT 5 fluid is remote (unless you store your FJ underwater).

And it's HUMID in the Dallas area during summer, and I wash my FJs a LOT so the calipers and master cylinder are frequently exposed to water.
FWIW,
DavidR.

Sounds like a smoking gun there, if the system is sealed (as it should be) then Dot 5 is the way to go. As long as you don't mind the brakes being slightly less crisp in the feel over Dot 3, 4. Good info David.

Anyone with bad experience using Dot 5?

I've never understood the 'lack of crispness' comments, either.     

David, you don't have 'urine cup' M/Cs, right?  Does your DOT5 fluid still have the original color?

Mine is almost perfectly clear in the front brakes.  The clutch is still purple after the first year.  I just wondered if it was UV exposure or what.

[FJmonkey]

Wait!!! If I switch to Dot 5 for my clutch I won't know when to rebuild the slave. With Dot 3 I can see the paint bubbling up before I get air in and can't change gears. Pros and Cons eh?

[rktmanfj]

Wait!!! If I switch to Dot 5 for my clutch I won't know when to rebuild the slave. With Dot 3 I can see the paint bubbling up before I get air in and can't change gears. Pros and Cons eh?

Yeah, good point.  You'd better stick with DOT3.   

[SlowOldGuy]

Still have the stock masters.  DOT 5 still clear to slightly purple-ish.

I rebuilt the clutch slave cylinder 3 times in the first 5 years of ownership.  I finally gave up, bought a new slave, and converted the clutch system to DOT 5.  I haven't had a single clutch slave problem since the late '80s.

The "mushiness" is absolutely unnoticeable.

Just once, can we try to NOT spout the same old crap everytime someone asks about DOT 5?  I've had exceptional performance from DOT 5.  Unfortunately, that message gets lost everytime someone posts all the "truths" that they read about it on the internet.

I post this same argument everytime this comes up because someone who doesn't use DOT 5 has to give an UNinformed OPINION.

Finally, NEVER use "racing" brake fluid.  You don't need it and it goes bad WAY faster than regular fluid.  Racers change their racing brake fluid before EVERY race.

DavidR.

[fj11.5]

dot 5 seems to have a lot going for it 

[SlowOldGuy]

All I can do is relate my personal experience with it.  I know Gary Forman (who started the Yahoo FJ List) didn't have the success I had with his clutch using DOT 5.

Youir performance may vary depending on how well you flush the system and try not to spill your beer into the master cylinder when you bleed it.  :-)

DavidR.