Dot 4 and Dot 5.1 brake fluid. What is the difference?

[Rubce]

Hi All

Went to purchase some brake fluid today. Can someone please explain the difference between Dot 4 and Dot 5.1? Both containers said they were silicone. Which type do people recommend?

On a futher point, what type of brake bleeding kit do you guys recommend? The shop sells the Gunson Easybleed gizmo which uses compressed air from your spare tyre. Any good? Worth the money?

Thanks

Bruce

[SGN]

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Hi Bruce
Have a look here -

http://www.ldparts.co.uk/shop/shop.php?c=viewproduct&pid=474&cat=30&maincat=1&start=0&sid=sid5c2851304ccafda1c54cd86759b46329

Cheers
Steve

[V Mad]

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The problem with pressure based brake bleeders is getting a good seal on the master cylinder cover, then you get fluid all over the place.

[jpyke]

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V Mad wrote:

The problem with pressure based brake bleeders is getting a good seal on the master cylinder cover, then you get fluid all over the place.

I'll second that - I've got an eazibleed and I've always found it very good but of course it doesnt have a cap adapter for a stag master cylinder. I ended up getting a 2nd hand cap and needed 2 rubber seals in there and screwing on quite tight to stop any leaks. That said it worked very well, wouldn't use anything else these days.

I think you can get bleeders that work the other way around and attach to the nipple and suck the fluid through (queue the dodgy comments :shock. Think they may be a more expensive option though worth investigating.

I find you still need to pump the pedal once or twice during bleeding to ensure you get all the air out of the master cylinder.

[Gresley]

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Hi Bruce

I have a Sykes Pickavant equivalent of a Mityvac. It creates a vacuum and then draws the fluid into a container via the bleed nipple. I have used it this evening to bleed my brakes and it is easy to use and effective. It also pressure tests things if required.

A good tool and worth having IMHO.

Brian

[marshman]

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Hi Bruce,

Look at this thread re:bleeding brakes:

http://stagownersclub.mywowbb.com/vi...ber+tube+bleed

I only ever use a split rubber tube with the end blocked off and an old milk bottle half full of fluid. Never failed to bleed brakes or clutches on any car in a few minutes.

Roger

[stoutgoose]

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I've used DOT5 silicone brake fluid in Lucas Girling brakes before and it caused the rubbers to swell, which resulted in the brakes sticking on. This was on a full rebuild using all new callipers, cylinders and seals.

When I spoke to Lucas about it and mentioned the DOT5 the chap immediately told me that was the problem, and he was right. I flushed through with DOT4 standard fluid and the problem never resurfaced. It's strange, because I'd previously used the fluid in an old Mazda 929 with no problems.

I know it's appealing that it's non-agroscopic, however I would put up with the bi-annual fluid change for reliability.

[mad cyclist]

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DOT is the 'american dept of transport'

its the standard at which fluid boils, the higher the number the higher the temp it will take, all to do with severity of braking.....i think..

[elvimto]

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DOT 5 is a standard silicone fluid the wet boiling piont is 500 F or 260 C I talked to a lot of owners in the States who use it and they have no problems also it will not damage your paint why the guys with the really expensive paint jobs use it. Do not use DOT 5.1 it is not a silicone based fluid that will mess up your seals Use DOT 5 One owner swears by it has had it in his car for years it does not absorb any moisture therefore no rust and longer seal life. I changed to it no problems. I think depending on your seal material they may reference DOT 3 for natural rubber check out LD Parts they have an opinion on this

Stuart

[Rubce]

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Hmmmm, a few months ago I noticed that the clutch master cyclinder on the GT6 was nearly emply. In my ignorance I topped it up with Dot 5.1. Since then I am having to top up the reservoir on a fortnightly basis. I have finally lost patience with it and purchased a new cylinder yesterday.

I am wondering if the Dot 5.1 has made the situation worse? Or just a coincidence and that the cylinder seals were on the way out anyway?

I see from the link that Steve posted that LD Parts are recommending Dot 5.1 whilst Stuart is saying don't touch it. I am confused:shock:

I need to make a decision as to what to fill the GT6 clutch up with it and also first virgin fill of the Stag resto clutch and brake systems.:?

Bruce

[elvimto]

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Bruce
DOT 5 is silicone the rest are not I did some reading on a US phorum and the guys who have changed to DOT 5 stand by it. I changed my rear seals and replaced the the flex brake lines and overhauled the PWDA switch. Most of the old fluid had drained out, I flushed out the lines with a good solvent and blew them with air. There would be some residual but going by a good source on Stags over here he said it would not be a problem. My source claimed he had one car go, not a Stag, over 150K miles and naver had to change the brake fluid. Same guy has two Stags and uses DOT5 in both no problems.
In the end its your decision but I thought about it and if they put DOT 5 in all cars etc, the brake repair buisness would lose a ton of money on replacing wheel cyclinders caliper rebuilds etc just because the fluid is contaminated and has taken out a seal.

Cheers Stuart

[stoutgoose]

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http://www.teamtorquesteer.co.uk/fie...uid-dot-5.html

The link above leads to the fluid I used both times as mentioned in my last post; in the Mazda (with only new front callipers) it was fine, yet in the Lotus with all new (Lucas/Girling) rubbers it caused swelling and brake lock.

It is DOT 5, and from a personal point of view and after advice from Lucas who stated that they would not accept any warranty claim in respect of brake parts with which it had been used, I would not recommend this stuff to anyone!

[mad cyclist]

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Rubce wrote:

Hmmmm, a few months ago I noticed that the clutch master cyclinder on the GT6 was nearly emply. In my ignorance I topped it up with Dot 5.1. Since then I am having to top up the reservoir on a fortnightly basis. I have finally lost patience with it and purchased a new cylinder yesterday.

I am wondering if the Dot 5.1 has made the situation worse? Or just a coincidence and that the cylinder seals were on the way out anyway?

I see from the link that Steve posted that LD Parts are recommending Dot 5.1 whilst Stuart is saying don't touch it. I am confused:shock:

I need to make a decision as to what to fill the GT6 clutch up with it and also first virgin fill of the Stag resto clutch and brake systems.:?

Bruce

like oil use what was about at the time the car was new.

rgds Nick

[marshman]

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Rubce wrote:

Hmmmm, a few months ago I noticed that the clutch master cyclinder on the GT6 was nearly emply. In my ignorance I topped it up with Dot 5.1. Since then I am having to top up the reservoir on a fortnightly basis. I have finally lost patience with it and purchased a new cylinder yesterday.

I am wondering if the Dot 5.1 has made the situation worse? Or just a coincidence and that the cylinder seals were on the way out anyway?

I see from the link that Steve posted that LD Parts are recommending Dot 5.1 whilst Stuart is saying don't touch it. I am confused:shock:

I need to make a decision as to what to fill the GT6 clutch up with it and also first virgin fill of the Stag resto clutch and brake systems.:?

Bruce

Stick with what you know and trust - Dot 4 - and change it every few years or so. At least that way the bleed nipples shouldn't become seized upalso you should always be able to find a "top up" if you need one.

Roger

[elvimto]

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It must depend on the composition of the rubber seal material. Lucas Girling parts must not like the DOT 5 silicone fluid then. I did not buy Lucas Girling parts the seal parts were aftermarket so they must be made from a different material composition. Might be an idea to try different fluids on a sample and see what the reaction is. I have seen this on pump seals ando rings where the material is not compatible at work we use viton o rings where we used buna before. Some more research required.

Cheers Stuart