Silicone Brake Fluid.

[HWade]

I recently replaced the wheel cylinders on a Dodge WC53 having them machined and relined and rebuilt, at Past Parts. After getting them home and fitting them I then proceeded to fill the master cylinder with silicone brake fluid, well after bleeding the system and fitting the drums, all seemed fine. It was only the next morning i founds pools of fluid under each drum. On investigation the fluid appears to be getting past the seals.I tried another set of seals but still the same problem. I phoned past parts only to be told that the seals they use do not recomend the use of silicone brake fluid. Shame they didnt say this at the time of buying the brake fluid.They also pointed out because of this it can lead to spongy brakes or even total loss of brakes. I am now going back to Dot 4. Has any body else had this problem. Howard

[spanter]

I know a few of my friends have had these problems recently while swapping to the longer lifed silicone fluid in classic cars, I just wish the people who rebuild the cylinders would say what fluid resistant seals they put in at the time, had it with light aircraft as well.

 

Steve

[N.O.S.]

This makes for interesting reading, Howard:

 

http://www.adlersantiqueautos.com/articles/brake1.html

 

Mr. A is seemingly not a big fan of silicone (you were right - dot 5 :thumbsup:)

 

The point about engine contamination from leakage past hydrovacs is worth noting - on the plus side it could be a lazy way of deglazing bores :cool2:

 

Then again here is a well-balanced assessment worth a read:

 

http://www.buckeyetriumphs.org/technical/Brakes/Fluid/Fluid.htm

 

The claim by PP that some seals can be affected by DOT 5 is a bit very concerning - and a maybe bit of a cop-out? My thinking is that if after all these years of dot 5 use there really was an issue, then product liability would have kicked in and the likely-to-be-affected seals or the fluid quickly withdrawn from the market.

 

But since some people have used silicone successfully for many years it might suggest some variation in the spec of rubber seal materials used? What did the seals you removed look like compared to new?

[N.O.S.]

I know a few of my friends have had these problems recently while swapping to the longer lifed silicone fluid in classic cars, I just wish the people who rebuild the cylinders would say what fluid resistant seals they put in at the time, had it with light aircraft as well.

 

Steve

 

Which lends more weight to the variation in seal compatibility claim. Makes you wonder if the market is contaminated with counterfeit seals of dubious quality - especially suppliers of older style seals who may have no choice but to source from non - OEM manufacturers?

 

There is no excuse for a supplier of seals and silicone brake fluid not to make the compatibility issue clear at time of purchase of either or both.

 

Tony

[HWade]

Hi Tony

 

I did try the original seals that the cylinders had in originally, and i have to admit they had a bit more meat on them, but they still leaked. What i have done now is to order four brand new cylinders and i am going to measure the bore size, if the resleeved ones are right they should be the same size. I have a sneaky feeling they have been bored slightly over size. But i may be wrong. But I am not taking the risk of dot 4 fluid leaking all over the back plates. Hence fitting the new cylinders. Howard

[Pete Ashby]

Not come across this problem before Howard thanks for flagging it up I'd be very interested in your final findings with the new cylinders. I know there are issues when changing over to Si if the whole system is not thoroughly flushed washed out and the old seals replaced however Iv'e not heard of non Si compatible modern seals before.

 

A question for the Moderators; depending on Howard's finale conclusions given the potential serious nature of the consequences is there any way this thread/information could be given a higher visibility for the benefit of all forum members new and old?

 

Pete

[Baz48]

Not come across this problem before Howard thanks for flagging it up I'd be very interested in your final findings with the new cylinders. I know there are issues when changing over to Si if the whole system is not thoroughly flushed washed out and the old seals replaced however Iv'e not heard of non Si compatible modern seals before.

 

A question for the Moderators; depending on Howard's finale conclusions given the potential serious nature of the consequences is there any way this thread/information could be given a higher visibility for the benefit of all forum members new and old?

 

Pete

 

Had the same problem with relined cylinders on a C-15A

[HWade]

Well I got around to removing the cylinders that had been resleeved , and after inspection the machining of the sleeve is a bit to be desired, the sleeve is distorted. Whether thats the reason for the leaks I cant say, but they will be returned for a full refund. I fitted the new replacement cylinders today and after bleeding the system there are no leeks. It may well be interesting to do a small survey as to the problems people have had with silicone brake fluid. has problems been on resleeved cylinders or new untouched cylinders. Hope some of these findings help, after all, we all need are brakes to work correctly. Howard

[HWade]

Well I took the cylinders that were at fault to Past Parts and they were in agreement that they had not been rebuilt correctly. They issued me with a full refund for the cylinders and the loss of the silicone fluid. I have now fitted new cylinders and have no leaks. However, just remember that the makers of some seals do not support silicone fluid. Howard

[paul_bish]

Might be worth noting that for later US Vehicles, M series such as M35 or "REO", they specify the use of Silicone Brake Fluid.

[lowfat]

not the first time ive heard of problems with resleeved cylinders either... its not any easy operation.

[Sean N]

Must admit I'd take an NOS original cylinder - or even a good used one - over a sleeved one every day, and fit new seals if necessary.

[gas 44]

I think there are for and against re the re sleeving. True if new/nos were available (I would have thought so for a Dodge) then I would buy them. But if parts are not available then re-sleeving/overhaul may be the only option. However after reading some reports over the years re silicone I would always go for DOT 4.

If as is reported dot 4 absorbs water then in real terms its really no great shake to change the fluid every 2/3 years.

Progress..........

[N.O.S.]

The real benefit of s/steel sleeving must be its use on vehicles used very infrequently. Often standing idle is the killer of original type cylinders where water sits in one position.

[gas 44]

The real benefit of s/steel sleeving must be its use on vehicles used very infrequently. Often standing idle is the killer of original type cylinders where water sits in one position.

 

We dont have vehicles that are used infrequently......If we dont intent to use them we dont buy them.....simple.

[N.O.S.]

We dont have vehicles that are used infrequently......If we dont intent to use them we dont buy them.....simple.

 

That's good - less brake cylinders for you to worry about, and more vehicles available for the rest of us to squirrel away On the other hand if you don't intend to use a vehicle it doesn't need any brake cylinders at all! I would think that possibly 70% of all restored mvs out there sit for long periods of time out of use, e.g. over winter months.

 

I've had cylinders reclaimed by sleeving on one very infrequently used vehicle. It was far more effective in both cost and time to get the cylinders sleeved - also we're trying silicone fluid in that one. Since then we've had two other vehicle sets sleeved (cost similar, main advantage was time over trying to source replacements and the advantage that they will never suffer with water issues), but went for DOT4 as they will be used more regularly.

 

Oh hang on - was it one DOT 4 and one silicone? I do recall being very indecisive about what fluid to use, I must make a note to check and mark the reservoirs!!

 

The very infrequently used vehicle with silicone stopping power, despite having a good turn of speed, has no suspension and solid tyres - so is not the first choice for nipping out to the pub in.

 

I'm not keen on the idea of silicone fluid in non-s/steel lined cylinders, because I'm led to believe that water (e.g. from condensation in reservoir) will tend to collect in one place in the system and therefore increase risk of corrosion at that point. Apparently with mineral based fluid (e.g. DOT 4), water tends to disperse more uniformly throughout mineral oil. Or so someone told me……..

Edited May 30, 2015 by N.O.S.

[Richard Farrant]

Apparently with mineral based fluid (e.g. DOT 4), water tends to disperse more uniformly throughout mineral oil. Or so someone told me……..

 

Hi Tony,

A correction here, DOT4 (as well as DOT 2 and 3) are not termed "mineral", they are a synthetic.

The systems that use a mineral fluid are Rolls Royce, Citroen, etc and certain military vehicles used by the British Army (and others!), which is a very low viscosity hydraulic oil.

 

I also understand that water can be absorbed into silicone fluid so not as good as we were led to believe. Also have to remember that although you might have cylinders sleeved with Stainless Steel, the pistons could still be a ferrous steel.

 

regards, Richard

[N.O.S.]

Hi Tony,

A correction here, …..

 

Ah damm - I thought it was Half Term this week …...:cool2:

[Richard Farrant]

Ah damm - I thought it was Half Term this week …...:cool2:

 

9/10 for effort Master Tony

[Degsy]

9/10 for effort Master Tony

 

Yeah, but how many for content Richard:???

[HWade]

Yes Tony, The small vehicle with Solid tyres is on Silicone, and the other 4 wheeled vehicle is on Dot4. Howard