Which brake fluid

[Galwaylotus]

If cost was the issue for manufacturers they wouldn't use long-life engine oil and platinum plugs, carbon fibre panels and brakes. High end GT car manufacturers (Ferrari, Lambo, Porsche, Corvette, AM, etc.) are not concerned with the costs if the component is better than its alternative. People like Carroll Smith, Fred Puhn and the SAE don't recommend silicone brake fluid and that's goo enough for me.

[bcmc33]

If cost was the issue for manufacturers they wouldn't use long-life engine oil and platinum plugs, carbon fibre panels and brakes. High end GT car manufacturers (Ferrari, Lambo, Porsche, Corvette, AM, etc.) are not concerned with the costs if the component is better than its alternative. People like Carroll Smith, Fred Puhn and the SAE don't recommend silicone brake fluid and that's goo enough for me.

Well made point.
But just to get things clear - all those marques (and others) do use synthetic fluid in their respective race cars, but not in their road cars. Race cars get the fluid changed after each race, road cars do not get changed on a sufficiently regular basis - synthetic fluid is potentially very dangerous in regular road cars.

[oldelanman]

Well made point.
But just to get things clear - all those marques (and others) do use synthetic fluid in their respective race cars, but not in their road cars. Race cars get the fluid changed after each race, road cars do not get changed on a sufficiently regular basis - synthetic fluid is potentially very dangerous in regular road cars.

Now I'm really confused, I thought most Dot 4 fluids are synthetic these days aren't they - or did you mean silicone fluid ?

[bcmc33]

Well made point.
But just to get things clear - all those marques (and others) do use synthetic fluid in their respective race cars, but not in their road cars. Race cars get the fluid changed after each race, road cars do not get changed on a sufficiently regular basis - synthetic fluid is potentially very dangerous in regular road cars.

Now I'm really confused, I thought most Dot 4 fluids are synthetic these days aren't they - or did you mean silicone fluid ?

You're quite correct, Roger. Another simple brain fart, I'm afraid. I normally blame my dyslexia, but I can't spell that either.

[Chancer]

I thought that I had read all the links and opinions in the thread, expanding my knowledge in the process but I cannot see where you are coming from in saying that silicone fluid is potentially dangerous in a road car unless perhaps you consider that it is going to rot the seals.

To save me reading it all again can you explain why you consider it (potentially) dangerous please?

Not looking for an argument or to score points, just to understand and respect your opinion.

[alexblack13]

Well made point.
But just to get things clear - all those marques (and others) do use synthetic fluid in their respective race cars, but not in their road cars. Race cars get the fluid changed after each race, road cars do not get changed on a sufficiently regular basis - synthetic fluid is potentially very dangerous in regular road cars.

Now I'm really confused, I thought most Dot 4 fluids are synthetic these days aren't they - or did you mean silicone fluid ?

You're quite correct, Roger. Another simple brain fart, I'm afraid. I normally blame my dyslexia, but I can't spell that either.

looks no bad to me Brian....


I'm just completely befuddled.. I nipped out n checked and Ahemmm ...Err .4 in the brakes and ? in the clutch. I will find the container...Now not sure whether silicone or synth??? I have it noted in the book somewhere but not looked there yet. Off to London in the morning to watch the boy run the marathon... Thanks to all who helped and donated by the way..Total is over 3K...

Head really nips now and its all your Fault.

[ardee_selby]

I'm just completely befuddled..

Don't worry Alex. You are not alone. I feel the the same...and hope the Wiki will effect a cure.

Cheers - Richard

(Go Craig Go....!)

[UAB807F]

(Part Quote)
To save me reading it all again can you explain why you consider it (potentially) dangerous please?

I don't think it's actually "dangerous" but there are potential snags, the biggest for me is that you can't mix with normal 3,4 or 5.1 fluids so there is a potential for someone (that would be me ) to inadvertently top up with the wrong type. Being serious, that's not a problem if you DIY, but it potentially is if it's garage maintained.

As I posted earlier, I just buy dot 4 but I did look into dot5 when it came out as like everyone else, I've had rusted caliper pistons. I think back then it had 2 claims, firstly it had a big 30C boiling point advantage over dot 4 so better for the racers, but it was sold to the classic car crowd on the hydrophobic (water repelling) properties in the hope it would stop internal corrosion. The normal stuff was water absorbing and to combat corrosion they added inhibitors but they couldn't do much about the absorption lowering the BP & degrading the inhibitors other than change fluids regularly. Dot5 doesn't absorb water therefore doesn't have inhibitors to degrade or the lowering of BP either, so it looks an obvious choice.

So why didn't I buy it ? Several reasons. Firstly I've never had internal piston corrosion on a sealed system that I've bled every few years, the inhibitors seem to do their job. When I thought about it, all the piston sticking was due to corrosion between the seal & dust cover which the fluid never comes into contact with, so it wouldn't help there.

The extra 30C operating range didn't bother me either, if I really wanted a higher range fluid then these days 5.1 is even higher than 5.0. (is that what the racers use ? it was in the Elise and that had a 12 month change interval)

I have read that because it's hydrophobic any moisture present will form a separate phase and potentially freeze/corrode (no inhibitors). Whether that's true or not I have no idea but it would make sense with the advice to use only in a clean, new system.

Brian

[bcmc33]

These are my words to paraphrase what I understand about brake fluids:

The old DOT 3 fluid is glycol based and had a bad reputation for easily boiling. By with some additives DOT4 improved the boiling situation for average driving.

DOT5.1 (often called super DOT4), remains a glycol based fluid with a boiling point similar to DOT5, and can be mixed with DOT3/4 without a problem

DOT5 is silicon based fluid developed for racing with a much higher boiling point, but has the disadvantage for some people in that it is compressible which results in a spongy feel at the pedal, and cannot be mixed with DOT3/4/5.1.

Now a lot of talk is made about the water getting into the system and mixing with the fluid ? now this is a fact of life, and will happen for all the fluids. What was always called a disadvantage, in my younger days, is now considered an advantage for the DOT3, 4 & 5.1 fluids as the water is absorbed due to hygroscopic action, and as a result will be more difficult to boil.
The water enters the system through the caliper seals and maybe a little through the reservoir vent. In the case of the silicon DOT5, the water is not absorbed in any way, and just sits there as water ? in an ideal position to be boiled when the caliper gets hot enough.
For most of us that use a glycol based fluid is that we probably don?t drive hard enough to get the calipers sufficiently hot to cause a problem, but with DOT5 fluid and water the temperature may be more achievable for boiling to take place.

If I were to use DOT5 I would bleed the calipers on a regular basis to expel whatever water is in the system. As it happens, I do bleed through my DOT5.1 fluid at the start of each summer season.

[TroonSprint]

It is very confusing to bears of little brain like me. All I know is that I have used silicon fluid in my MGB V8 (200 bhp) for 10,000 miles (3 years) now and it hasn't given me the slightest cause for concern. A pal who also had a V8 MGB had silicon fluid in his car for 17 years and sold it on with absolutely no brake trouble in all that time, the fluid never having been changed.

What am I going to put in my Elan when I get round to building it?

[Chancer]

I never ever changed or bled through the silicone fluid in my race cars or my road kit car, to me it was fit and forget, had I ever experienced any problems I would naturally have done so.

Up to 5 years on the racecars (in my ownership) and 10 years with the kit car which was often used in anger on track test days and no problems, I expect that most of them still have the same fluids.

I have experienced water contamination on a road car which had glycol fluid, it was one of the first Ford Galaxies and the rain would drip onto and enter the master cylinder and then find its way to the lowest point of the system, the calipers, clearly it was not absorbed by the hygroscopic fluid, I lost the brakes whilst towing the trailer and race car down Detling hill in Kent. i immediately purged the system and was shocked at how much unmixed water came out of the calipers, subsequently the clutch slave cylinder which shares the same reservoir failed through water corrosion, Ford eventually begrudgingly did a recall on these vehicles.

The amount of water that may enter a braking system via the caliper seals and brake hoses is miniscule compared to what I had been driving with.

At the end of the day whatever route you choose its important to have peace of mind and confidence that your brakes will perform if ever they are called on in extreme conditions, one single emergency stop is unlikely to expose any deficiencies but long descents with the vehicle loaded and/or towing will do so as will several spirited laps on a circuit.

[elanmac]

According to the leaflet in Automec silicone brake fluid it can be mixed with dot 3,4,5.1. but you lose all the benefits. It must not be used in systems that require mineral based fluid. Another plus for silicone is that it doesn't strip paint.
Mac

[jono]

Well guys, I popped into my local Wilkos and bought 4 litres of Comma DOT 4 (8 x 0.5 litre bottles) at ?3.28/0.5 litre.

Brakes have come up a treat once I removed the air lock in the MC outlet pipe and got the new MC primed. In practice used less than a litre for the brakes and clutch and have got nice firm pedals on each. Off to Wilkos now to take 6 bottles back.

I used a simple non return bleed valve for a couple or quid and 'the job's a good un' as they say (or rather as we say up north )

Incidentally I ditched the servo - the guy at Classicar Automotive told me "good lad" when I mentioned this.

Jon

[AHM]

Jon, I usually buy it in wilko also. This morning however, I was in Tesco - ?7 for 0.5l and Halfords ?10 fo 1l I ended up buying 5l at halfords for ?17.50 (?3.50/l) mentioned to to the assistant at halfords that they had the most expensive brake fluid on the planet!

Simon

[mikealdren]

Non Silicone brake fluid is hygroscopic, it absorbs moisture from the air as well as through direct contact.

As a result, it can also absorb water while in a half full can, i.e. its shelf life isn't great. Think twice about buying large quantities and storing for a long time. Having said that, in an airtight plastic container it should be fine.

Mike