Lancia Motor Club

About to change the brake fluid  on my Series 2 and have a couple of questions.
I am told Dot 4 is suitable for my application, which is normal road use, with a few mountain passes thrown in. I read somewhere it is vital to change the fluid every 2 years. Is this still the case if you use Dot 5.1.?
I understand it is better to raise the rear of the car when bleeding the brakes. How high please?
Many Thanks
Tim

It is important to have the rear brake bias valve in the open position, which means supporting the rear axle, rather than using the sill mounted jacking points. Richard

As Richard said raise the back by jacking and supporting the axle.

Fluid can take a long time to get through so I rig up a way of slighlty presurising the master cylinder (c2-5psi). As the master cylinder leaks air through the electrical terminals you will get a bit of a loss but do not over presurise or you will burst the master cylinder. I set the regulator of my air compressor to 5 psi. Also you need to ensure that the master cylinder always has fluid in it as you will find air will get into your refresh.

Dot 4 is vaguely hydroscopic and Dot 5 (silicone - dont use unless you are rebuilding the brake system) is not. I am not sure about Dot 5.1. Being Hydroscopic Dot 4 will take on water and this could allow the brake calipers could boil earlier. My Merc is maintained by a guy who tests the brake fluid (Dot4) and in 6 years he has not changed the fluid.

 Boiling point ranges (from Wiki)
Dry boiling point   Wet boiling point
DOT 3   205 °C (401 °F)   140 °C (284 °F)
DOT 4   230 °C (446 °F)   155 °C (311 °F)
DOT 5   260 °C (500 °F)   180 °C (356 °F)
DOT 5.1   260 °C (500 °F)   180 °C (356 °F)

I boiled my Dot 5 fluid on the descent of the Stelvio (the flowing west side) in a fully laden Fulvia Sport so I have also refreshed the fluid (6 years old at the time), and found nothing like any water present.... The brakes returned to normal after 15 minutes of cooling down - assuming the boiling vapour is reabsorbed?

Tim H

Many thanks Tim and Richard for your response. Much appreciated.
Regards
Tim

I recently put "Fay" in for a checkover in preperation for the Knights Rally in September, I specifically asked that the brake fluid be checked with the view of changing it if necessary, It was reported as being ok with no problems, last time fluid was changed was before going to Turin in 2006.


Brian
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Why does old brake fluid become very dark? Andrea

Oxydation process?? I assume you are referring to Dot 3 or 4??

Silicone is a light purple that fades a bit over time to clear.

Tim

Yes, I refer to Dot 3 or 4. Oxidation and moisture probably. Perhaps not enough to give fluid boiling and lack of pressure but enough to produce corrosion of the cylinder bores. BTW, I was checking over my Fulvia Montecarlo yesterday prior to an alpine event and noted that my battery is now 12.5 year old. Charge with engine off is OK. Not bad performance for a small alternator. Andrea

As it happens I just dropped a car in for a list of bits and bobs including a brake fluid change.  BMW have it down as a change every other year.

David

Most manufacturers have always recommend changing every two years, but I always have the fluid checked as I can't ever remembering finding it necessary to change as recommended.
I'm all for safety and checking, but IMHO it's just another one of those service items that are there to add to the profits.

Brian
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Hear hear!!!

Brian - What check do they do?

David

My merc guy says he measure SG (hydrometer)...

As a rule I tend to change the brake fluid in our cars roughly every 4/5 years or so - primarily because the fluid has darkened. To me, a darker fluid = contamination = shortened seal life and corroded wheel cylinders. I have never had brake fluid which has boiled.
On my race car, I change the fluid every 2 years because the front brakes do get very very hot and it is part of my regular pre-season checklist.
I have never used silicone fluid by the way as someone told me once that changing from Dot 4 to silicone would result in problems with seals although the change could be made the other way without any problems. Is this true?
Chris

I know David Thomas has the equipment to check the water content but my daughter had hers checked recently and they used a refractometer, I know when I volunteered at at Vineyard we used this for determining the sugar content of the grape to check when to pick them, no doubt Simon might know a bit more about it's uses.
See
http://www.amazon.co.uk/Brake-Refractometer-DOT4---motor-vehicle/dp/B00965Y8SK/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1372788380&sr=1-1-catcorr&keywords=refractometer+for+brake+fluid

Brian
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Chris I would not recommend Silicone fluid unless the whole of the brake system has been flushed and all seals replaced. I did this on both my Fulvias but not on the Flavia or Gamma as I kept a perfectly good system in place on those cars.

Brian,
We use a refractometer for our Pinello grapes to determine the sugar level is correct for picking before wine production. This scientific test is backed up by my neighbour, Alessandro looking very carefully at the colour of the pips in our grapes and he then chews them. My Italian is not good enough to understand what taste he is looking for but if he isnt happy we dont pick no matter what the refractometer reads!
Chris

If I used our refractometer for brake fluid, I suspect I would end up at the bottom of a tank ....

We do the same with the pips - brown good, green bad ! along with tension in the skin - the grape's not mine

Tim,
not forgotten your allocation, it is being bottled next week ! (Blend of 65% syrah 35% carignan and a very slight touch of oak ....)

I think the manufacturers two year recommendations are OTT! I suppose they have to go worst case for a business driver doing mega miles and who frequents mountain passes. Boiling brakes isn't good with water in the system as the water boils at a much lower temperature than the brake fluid and makes the brakes far less effective! A recipe for an accident and the manufacturer getting the blame!

On a brake related problem I had a nightmare several years ago trying to bleed the brakes on my Coupé. Fluid just wasn't coming out of one of the rear bleed nipples as freely as the others. It transpired that one of my brake hoses had actually collapsed internally (although externally it looked fine!) restricting the flow of fluid. I ended up replacing all the hoses from a safety perspective!

To add to the previous posts, the fluid in the resevoir is open to atmosphere at all times, so how about that absorbing moisture? Richard

Chris /Simon,
Wonderful!
Technology will never replace experience, at least if we have any sense.

Brian
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richard,
Yes it does and therefore it is necessary to check and replace if required, but it's the frequency of changing the fluid based on a period in time recommended by the manufactures, as opposed to the condition of the fluid itself after that period of time that is the question.

Brian
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