Topic: How do I clean DOT 5 from my brake system?

[Zane]

I have a stock front disc system on my 400f.  A few months ago I cleaned the DOT 3 brake fluid out and switched to DOT 5, silicone brake fluid.  I now want to change back to DOT 3.  I found lots of info here regarding the first change (DOT 3 to DOT 5) but I can't seem to find any info that is helpful regarding cleaning DOT 5 out so it's okay to put the DOT 3 back in the system.

Does anyone know?  Varsol okay?

I'd appreciate it if someone who does know could help me with this.  (And I apologize if it's here somewhere - I couldn't find anything though ....)

Bill

[Dusthawk]

From what I've learned, there is no swap back. The silicon fluid permeates the rubber parts and gunks up the whole works if introduce back to DOT 3.

Not sure on this but it's what I heard,

Jeff

[supersport_CB400F]

Zane why do you want to change back to the old fluid?  The new stuff has less problems with water absorption and paint stripping qualities.

Cheerz

Dave

[Zane]

Jeff - I think you're correct about the rubber parts, but I plan to change all the rubber parts as part of the swap back.

Biffta - I am switching back because it appears the DOT 5 fluid has caused the caliper piston seal to swell a little.  In turn, that swelling inhibits the piston retraction, causing the brake to ride.

[hcritz]

Zane...
Silicone fluid is pretty inert...it shouldn't cause a problem with the rubber parts...I've used it in all sorts of applications with no problem...even old British stuff with live rubber seals...
Bet you have a corrosion problem in the caliper causing the sticking...seems to be a recurring thread here...I'm still sort of amazed that Honda didn't put a dust/water seal on the piston!!!
I have head that since water will not mix with the DOT 5 fluid any moisture that enters the system will end up at the bottom...
I've used it for years and have never seen any indication of corrosion in the system though.

[supersport_CB400F]

Thanks for the heads up, I was going to swap the fluid over, but I’ll use DOT3 now.

Cheerz

Dave

[Zane]

I'm a little confused by it all, actually.  There are no shortage of posts encouraging the (relatively problem free) use of DOT 5.  (That's why I chose to convert ...)

The piston is slick, with no marks.  It moves easily without the seal, and all seems to be within the tolerances stated in the manual.  I'm going to pop the thing apart again tonight and try again.  I've been holding off doing that until I could find a tube of the Dow Corning High Vacuum Grease mentioned and (highly) recommended by Two Tired a while back.  Now that I have the right grease for reassembly, I'll take it apart and compare the seal that's in there to the replacement seal, for starters.  I'll also triple check the inside of the seal channel and make sure it's free of residue.  (Maybe 400f seals are made from a different combination of natural and silicone rubbers than other models' seals ...??.)  And I suppose if I'm correct about the piston seal swelling, the 5 probably affected the rubber bits in the master cylinder too ...... aaarrrgh.

This has become a source of frustration for me, since I had no problems with a free spinning front wheel before I went to the DOT 5.  Having said that though, I'm certainly not completely convinced it is the DOT 5 causing the problem(s).  But I'm at a loss to explain why the brake works so poorly now.

[eldar]

I think I have dot 4 at this time. It is a synthetic fluid and it works very well. Might compress slightly more than dot 3 but I feel it gives me more precise control. I do need a new rubber seal and ring for my master though. Not because of the fluid but because the ring is cracked and so the diaphragm does not seal completely sometimes. I did use dot5 and never had an issue but I cleaned everything out and put on a new line and the synthetic I have now is what I found first.

When you pull the piston out. dry things well and look for anything white or offcolor. That is buildup which will cause the piston and pad to move poorly.

[TwoTired]

Bet you have a corrosion problem in the caliper causing the sticking...seems to be a recurring thread here...I'm still sort of amazed that Honda didn't put a dust/water seal on the piston!!!

Honda did!
They put on a high temp silicon grease for use as a water shed and dust block.  Many rebuilders ignore that, though, as it is not a common material found in auto stores.
The Honda manual clearly specifies using a silicone grease with specifications that match the Dow Corning High Vacuum grease. Pg 146 of the CB750 shop manual.

I got shouted down by DOT5 zealots in a previous thread.  The DOT5 conversion is a one way switch, as it is nearly impossible to completely remove silicone from the hydraulic system and is incompatible with DOT3 or glycol based fluids.  The American military would like to get rid of Dot 5, too as their entire fleet was converted many years ago.  There are studies in progress on how to flush systems.  But, so far no findings on an effective solution have been published (that I know of).  I think they're stuck with it as is anyone who who uses DOT5 now.

Ask any painter about the bane of silicone polishes and it's difficulty of complete removal.  The best they can do is add a wetting agent to the paint to minimize the fish eyes.  Flush blemished areas and respray.   Same problem with DOT5, the stuff is tenacious.

Best of luck!

[Bob Wessner]

as it is not a common material found in auto stores.

Where does one get it?

[Zane]

Well Two Tired - I'm going to take that as a good news/bad news post for me.  Is it only the rubber bits that hold the silicone, and make it impossible to get rid of once introduced?  If it is only the rubber bits, in your opinion, would I be okay if I changed the caliper piston seal ring and the master cylinder piston assembly?  (I don't think there are any other rubber bits in the system (unless the brake light pressure switch has some rubber in it).

Or maybe the stuff gets into the braiding in the stainless lines?  Yikes!  My intuition told me (very subtley) that the whole DOT 5 conversion thing was too good to be true, but I bulled on ahead anyway.

I say again ...... aarrrggghhhhh!

[Zane]

Bob - I found it by getting the list of distributors for Dow Corning that operate in my area.  I started calling them and by the eighth call I found a company who would sell me a single tube.

The DOW internal product number for the stuff is 1597418.  I gave that number to the order desk at BDI (the Bearing Distribution company who I called eighth) and up it popped on his computer.

And one more thing - if it becomes troublesome finding it, go to the DOW website and use the "live chat" feature.  (I know what you're thinking, but it's not that kind of live chat - silicone or no silicone so to speak....).  That service was the determining factor in helping me find the stuff.

Good luck ....

[supersport_CB400F]

I'm sure SS lines have rubber linings 

[Bodi]

SS lines usually have teflon linings, there may be other plastics used though.
I've switched to DOT5 and back again to DOT3, no apparent problems but I have teflon braided lines and redid the master cylinder and caliper seals.
The caliper piston was sticking BADLY with DOT5.

[Zane]

..... and here's little ol' Canuck me trying to solve a problem that has the US military messed up!   Yeeesh!

It's gonna take some more thought, that's for sure.  Maybe I should have thought just a bit more before I swapped ....

You'd think that the lining on a modern line would be something ..... well, .......... something modern.  Is silicone indeed so "tenacious" as to stick to such stuff?


So thanks Bodi - I'm pretty sure that's what I'm going to do too - swap all the rubber.  Your symptom(s) sound identical to mine.

Which brings me back to my original question - did you use anything to clean the lines, cylinder reservoir, and caliper bits before you went from 5 to 3?

[hcritz]

Hey T-T
The silicone grease is a bit hard to find...but I can find a product called Sylglide at most "Real" parts stores(NAPA)...great for lots of different uses...really good on cables etc...pretty resistant to most things...water and solvents...

I still think that a simple rubber dust/water seal would have cured many of the stuck caliper ills that seem to happen and would have been worth Honda's time...of course these were some of the first bikes to use Disk too.

I do a lot of restoration work...and many of the cars sit for long periods of time...brake component corrosion was always an issue with older cars and the DOT3 fluids . With single circuit systems...one component failure means NO BRAKES.
One thing we don't have to worry about here with bikes is brake pull from side to side...aways an issue with drum front brakes on an auto...throw in the fact the the steering and braking of the earlier cars is questionable at todays traffic speed...It can be dangerous.
Seemed one of the wheel cyl. was always sticking with the old fluid and causing problems or leaks.
I do a lot of old British cars too and they use live rubber for the seals...(hopefully not anymore) and using the wrong fluid ruined them.
Now I use DOT5 and silicone paste grease on pistons, seals and bores (Sylglide) and the car can sit for a year and the brakes work as designed. There are issues with the DOT5... seems it doesn't have the lubricating properties that the DOT3 does and can cause a strange feel to the brakes but the sylglide seems to cure that. It also prevents messed up VERY expensive paint work under the hood too.
It's not a cure-all, but It's not a bad product either...If people would flush systems as they should etc...either type would be fine.
Just like the infamous dino/vs/syn oil...if change regularly...either work fine.

Oh...by the way...I'm running DOT3 in my 750...was out of DOT5 when I cleaned out the caliper. Which was of course stuck with lots of crud and grunge...still had the silicone grease there though and it's 29 years old!!!
Now if I could get the DAMN BRAKES TO QUIT SQUEALING!!!! Yes the plastic piece is there and I even surfaced the rotor!
Maybe new pads!!!!!!!

[hcritz]

Zane...
After my last post something crossed my mind that might explain the sticking brakes after going to DOT5.
I mentioned that the lubricity seems to be less with the DOT5 and I had noticed a strange feel to the brake peddle.
I'm wondering if your Master Cyl isn't returning all the way to the end...that would keep the tiny little bleed port from opening and hold residual pressure... and cause brake drag.
In actuality...the rubber seal in the caliper is supposed to be very tight and actually deforms when you apply the brakes...when you release the brake...the seal is supposed to go back to it's original shape and help pull the piston back slightly and move the pads from the disk.
Something that might be worth a try before spending a lot of time and money!
Drain the fluid from the master cylinder and and pump as much of the evil fluid out as you can...put in a very small amount of some
PFTE (Teflon) additive into the master cylinder and work that in well...that should lube the master cyl. seals and make sure it's returning all the way out...then add your DOT5 back and bleed... see if the brakes still stick...
Did this with one of my personal vehicles...made things work very nice!

[Zane]

I think I might try that hc.  Since I'm planning to change the master cylinder works anyway, all it would cost me is the PFTE stuff.  (Speaking of which - where would I get that PFTE Teflon stuff?)

[TwoTired]

You will kick yourself later if you use syl glide in the caliper.  See:
http://www.sohc4.us/forums/index.php?topic=10620.0

Syl glide is mostly propylene glycol and castor oil with some silicone added.  It may lubricate at 600 degrees, but it will flow like thin oil at about 200 or below.  If you like your disk and brake pads well lubed, syl glide will do it!  I didn't like mine lubed that way.  Had to throw away the pads and flush the rotor about 20 times with alcohol.  Syl glide will stay put as long as it doesn't get hot.  But then, working brakes do get hot!

I fell prey the slick marketing methods of the sylglide people, too.

Good luck with your choice!

I still think that a simple rubber dust/water seal would have cured many of the stuck caliper ills that seem to happen and would have been worth Honda's time...of course these were some of the first bikes to use Disk too.

I disagree.  All the caliper problems I've seen on Honda calipers with the correct silicone outer lube, were caused by issues inside the hydraulic vessel.  I don't believe a dust/water seal would have had any effect on the breakdown and crystalisation of the fluid inside the containment vessel.
Did you find corrosion or crud under the 29 year old grease on your 750 caliper?  Or, was it only where the DOT3 made contact?

Cheers,

[Bob Wessner]

Zane,

Thanks for the info on locating it.

[Zane]

You're more than welcome - all the great info you folks have given me during my first year of motorcycle ownership - it's the least I could do eh?

If you're in the Toronto area you can get Dow Corning High Vacuum Grease through BDI Canada Incorporated in Brampton.  Call BDI at 905 459 - 5202 and ask to speak to someone at the order desk.  When you speak to that person, tell them you need a single tube (or however many tubes you need) of Dow Corning High Vacuum Grease, Dow Corning product number 1597418.

They'll take your name, address and number, and if you want you can pay by credit card.  Then they'll give you the address of the place where you can go and pick it up (and pay, if you didn't by phone).  (The pick-up spot is also in Brampton.)  They will also give you a shipping number, which you'll need to give to the shipper at the pick-up place.

And that's all there is to it.......

Oh yes, it's $16.34 Canadian bucks plus gst & pst (unless of course you're pst exempt).  They take debit at the pick-up spot.

If a whole boat load of local SOHC folks want the stuff, I'll go out on a limb, buy a case, mark it up a bit (just to cover my expenses) and sell it by mail to those who want some.  Anybody in 416 - 905 - 519 area buy it if I did that?

[TwoTired]

Well Two Tired - I'm going to take that as a good news/bad news post for me.  Is it only the rubber bits that hold the silicone, and make it impossible to get rid of once introduced? 

The trouble is, silicone sticks to everything and finds pores to hide in, even with metal surfaces.  If you are determined to switch back, continued high volume flushing to wash it away seems like the only Semi-thorough way to remove it.  Crevases like the stop switch diaphram will likely be the hardest to scrub.  Having never done it, but, knowing something of silicone's properties, I would suggest repeated filling and/or flushing of the brake components with lots of denatured alchohol.  That's my best guess.  Perhaps Bodi could share his method?

Best of luck,

[Zane]

Thanks a lot Two Tired.  I'm sorry I wasn't better able to discern your thinking on this issue before I swapped.

And yeah, what about it Bodi?  Any more tips?  Did you also change that pressure switch at the same time you changed the o-ring and master cylinder guts?

[Zane]

Yes Two Tired - I would say that I'm determined to have a properly functioning front brake - really determined.  As for swapping back to DOT 3 - well, after reading the posts here, it seems that will be somewhat more difficult to do than I had hoped.  I guess the worst case scenario is replacing the whole system.  I don't want to do that, but  will if it comes to it .....

I think I may try hc's trick with the PFTE and see if that works.

One thing I haven't mentioned until now (because I didn't think it was relevant - but it might be now) is that that brake pressure switch never really worked properly with the DOT 5 after the first couple of weeks.  It will work very briefly right after I bleed the lines, but it progressively gets harder to switch on (squeezing the lever) until it doesn't come on at all.  I swapped the switch and the same thing.  Swapped back - same thing.

Have I said  aaarrrrggghhhh yet?

[TwoTired]

Well, I just gotta ask.

Did you spill any DOT5 on your paint?  If so, maybe a little less argh.

Cheers,