My wife's Golf was serviced by the local VW dealer today including 2 yearly brake fluid change. I got home from work early so took a look under the bonnet. All was well, except just a moment what is that damp patch on the offside strut? Eye drawn to the brake master cylinder - full to the brim with evidence of seepage from the top - sure enough below it on the chassis leg a small pool of brake fluid.
I phoned the VW dealer and they sent someone straight out. I thought they would arrive with a small syphon - but no - a rag stuffed into the top of the master cylinder to soak up the excess until it was down to the MAX line. Then he poured a little (I mean a little) water over the chassis leg - when I questioned this he told me that brake fluid is no longer corrosive - IS THIS TRUE?
Edited by Pugugly {P} on 18/02/2008 at 20:59
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Can't be sure if it's corrosive, but it makes a mighty fine paint stripper. Just checked my new bottle in the garage for you, it has a warning on it not to spill onto paintwork for this reason.
If I were you I would wash down the affected area of the engine bay with your usual car wash compound and a soft brush and then swill copiously with plain water. You never know if some small amount of brake fluid has got into a body joint where it will strip the paint - this in turn might allow corrosion to start.
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Pass!
The silicone based fluids are more expensive (£25-40) and it is possible they may not be corrosive, however, most silcones are irritants or corrosive in their liquid form - e.g. Bathroom sealent (silicon acetate) and not sand!
QUESTION: If the fluid used were not corrosive then why did the chap attempt to wash off the excess? Don't think brake fluid washes off very easily with water anyway? (Does it?)
All "normal" brake fluids are corrosive. I doubt a routine service on a routine car would involve the use of silicone fluid. I may be wrong (please see disclaimer)
Best thing to do would be to ask the dealer for the Material Safety Data Sheet for the fluid used to back up their claim.
Guy
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PS. Apologies to "Jon" - I am not an expert in the field of brake fluid and the above advice is to be taken as that of a friend/stranger at the bar in any anonymous hostelry in the UK (incl. Northern Ireland). Any loss or damage caused by the advice given is that of a DIYer and the advice giver does not accept any responsibility. The advice given is purely an "opinion" of the author and does not represent the opinons or business ethos of either HJ, The Daily Telegraph or Mr Lacey's employers. Any reference to persons sharing the same name as Mr Lacey is purely coincidental and the author apologises for any offence taken.
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Or would you rather be a fish?
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I think my disclaimer could do with some amendment by our Brazilian friend - methinks I have just accepted responsibility for any damage caused as opposed to the reverse, as I intended!
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Hey Mr Eckie - whatever it is you're taking - can I have some?
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So it's a b*****d, then?
PJ
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Just to clarify - silicones are not corrosive, but some are classified as toxic, harmful or irritant. The reason they make good paint strippers is that they are excellent solvents for certain chemicals. They are also a pig to remove from surfaces like glass, since they repel water.
Andy
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Well at least they came out ,a bit unusual for VAG.I should send them a bunch of flowers
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Steve,
Just because brake fluid is not corrosive, does not mean it will not melt your paint. But the paint melting effect is fairly rapid, and if you can wipe a clean rag over the affected area without leaving any paint on the rag, don't worry!
Modern brake fluid seems to be far less eager to strip paint than stuff of old. Water based paints such as on the Golf IV may well not suffer - when you spill 15yr old brake fluid from your cellulose paint based MGB all over the engine bay you can see the paint melt before your eyes, and wiping it off produces a distinctly body coloured rag. Spilling the 'latest' DOT5 silicone based stuff gives a nice polished effect and does no damage at all though.
So why don't manufacturers use silicone brake fluid from new? Apart from expense, two reasons I've heard are that some bodyshops won't have your car on their premises without silicone fluid because it wreaks havoc with the paint process. And because DOT 4 is hydroscopic (water absorbing), water is removed from the braking system every 2 years with a fluid change. DOT5 silicone is supposed to never need changing, as it doesn't abosorb water. But any water that does get in will corrode more aggressively as the brake fluid won't absorb it. I would also venture that if any work does need to be done on the brakes and the bleed nipples haven't been freed for several years because silicone is in the system, trouble is ahead.
Regards,
Rob F
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Checked out the Bosch Automotive handbook this morning:
It is a requirement of FMVSS116 that brake fluids must not initiate corrosion to any metals commonly found in braking systems. Therefore, brake fluid has never (in recent history) been corrosive. The fluid contains corrosion inhibitors.
The reason silicone fluids are not used by oems is that it presents a considerably higher compressibility index than glycol or mineral oil based fluids.
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CC
I've heard this one about greater compresibility, but I must say that I've always though it a bit odd. At the sort of pressure in a braking system I would expect the difference between the compressibilty of two fluids to be negligible, and unlikely to be noticable at the pedal.
Not only that, but silicone fluid is US DOT 5 approved, so there can be no safety issues and it is apparently used by the US military.
Regards
John
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I think I'm a 'fool jumping in' but:
CC - brake fluid isn't corrosive in itself.
It's just a really good paint stripper. The bare metal then corrodes naturally. [1]
Hopefully an angel won't fear to tread on this subject.
[1] Appologies to Jon if this view from an amateur is incomplete inncorrect or in any other way irritating to him.
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