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Brake Fluid

caravelle

Member
Hi folks, just doing a complete overhaul of my Caravelle brakes and just wondering if there are any tips on brake fluid type.
I have always used Dot 5 but thought i would ask just in case.
Thanks everyone
 

caravelle

Member
Silicone, so you may be stuck with it, depending on what has been replaced.
Thanks, i am doing a complete overhaul, new seals etc. I will drain system of all old fluid.
Just not sure if there is any new thoughts out there on what fluid to use these days.
Rob
 

Breitie

Member
Thank you for this interesting question Mr caravelle, as it motivates me to learn something new today.
I have never considered Dot 5 silicone brake fluid, because Dot 4 was usually specified for all cars and motorbikes that I have ever serviced.
I have now learned that Dot 5 does not absorb moisture over time, which is good, but is not recommended for ABS systems because of compressibility or something. It is also said to be much more expensive but for that you get a pretty purple colour.
However, I would hesitate to use it because most mechanics routinely top up/refill with the industry standard common Dot 4 glycol stuff.
 

JoBo

1000+ Posts
Years ago we had a Nissan Prairie from new. I changed to silicon brake fluid pretty soon after we got it. After about 10 years i got so curious i dismantled the the master and wheel cylinders and all looked pristine.
I used standard Aussie silicon fluid at first, don't think any other stuff was available at the time. After a few years when BelRay became available here i replaced the original for BelRay.
I only use recommended fluid i.e. the hygroscopic stuff in our ABS cars now because of uncertainty.... BelRay claim that their stuff is compatible with ABS...
 

pink panther

New member
be careful, I believe Dot 5 is silicone purple Belray which I've had in my caravelle for years. But Dot 5.1 is not I read somewhere, and would not be compatible. Motorbikes tend to use these products
 

JohnW

Too many posts!
I've had Dot 5 in the 4CV for 30 years. After 25 years I changed the brakes themselves - everything inside was perfect. Full stop. About 10 years ago I changed the R8 to Silicone, it being done in parallel with a complete overhaul with new everything.

Personally I wouldn't use anything else. I keep fluid that comes from the bleeding process, filter it and re-use it. For your Caravelle, like our R8, a key issue is corrosion of the alloy calliper behind the 'o' ring, since that is exactly where the other fluids, which are hygroscopic, absorb moisture over time and, bingo, corrosion. I don't believe that regular fluid changes get into the recesses of the calliper either. Dot 5 doesn't take paint off.

And yes, Dot 5.1 is NOT silicone. I was at a brake place the other day and see Bosch offers a multipurpose fluid that is compatible with most fluids including Dot 5.1. The young bloke behind the counter was telling a customer it was OK for Dot 5, which sounded very odd, so I went and looked at the label. Sure enough, it was Dot 5.1 not Dot 5. Then I intervened, carefully. This was a specialist brake place......

Heaven knows why they've introduced a Dot 5.1 that is not silicone - dangerous confusion can result.

My two bob's worth.
 

JoBo

1000+ Posts
Just soak the rubber bits in the silicone fluid first to see that the rubber is compatible (most are). I did introduce it to a Wetczech (skoda) once and the seals swelled up - not good, no brakes.
 

caravelle

Member
Wow, lots of schools of thought there. On pulling out the pistons they are all in good nick. Giving them a good clean and new seals.
Looks like Dot 5 is still the goods.
Thanks for all your thoughts folks and hope to see you all out n about one day.
 

COL

Alpine A110
Hi folks, just doing a complete overhaul of my Caravelle brakes and just wondering if there are any tips on brake fluid type.
I have always used Dot 5 but thought i would ask just in case.
Thanks everyone
I have just re-read your first post about doing a complete overhaul.

I would be flushing the whole system out with some methylated spirit to make sure you have all the old brake fluid out along with any crud that is in there and then blow out with compressed air.

Assemble everything with rubber grease and then use your brake fluid of choice.
 

Artificer

Member
DOT 5 is silicone & DOT 5.1 is NOT silicone & they do not mix.
I love DOT 5 for all the reasons previously stated & the need to not flush every couple of years.
Be aware DOT 5 [silicone] should NOT be used in systems that incorporate a hydrovac or ABS.
 

Dano

1000+ Posts
Artificer,

I had already decided to use Dot 4 fluid instead silicone in my 404. This was mainly because the brake company that pressured tested by Hydrovac unit, used Dot 4. As a matter of interest, why do you suggest not to use silicone in a Hydrovac system?
Not questioning your knowledge, just interested.

Cheers

Dano
 

JoBo

1000+ Posts
DOT 5 is silicone & DOT 5.1 is NOT silicone & they do not mix.
I love DOT 5 for all the reasons previously stated & the need to not flush every couple of years.
Be aware DOT 5 [silicone] should NOT be used in systems that incorporate a hydrovac or ABS.
From memory so i may well be wrong - BelRay say that their stuff is ok with ABS? The general answer i got for not using Silicone in ABS is that it is more compressible than Dot 4, 5.1 etc. Don't know if there are 'rubbers' or seals inside the ABS that may not be compatible? Never dismantled one.
 

seasink

1000+ Posts
DOT 5 can aerate, which the ABS manufacturers deprecate. Instead of absorbing water like the others, it absorbs air.
 

JohnW

Too many posts!
DOT 5 can aerate, which the ABS manufacturers deprecate. Instead of absorbing water like the others, it absorbs air.
I think that might be it. You do have to be careful in handling and pouring it gently in my practical experience. I don't believe what is written about compressibility at all, but aeration is certainly an issue and would impart compressibility. I've seen the warnings about vacuum assist but have never seen an explanation of why.
 

Artificer

Member
A leaking hydrovac master cylinder will cause burning of brake fluid & silicone becomes sand & will wreck your engine, tout suite.
As far as the ABS unit read the owners manual it'll tell you not to use DOT5.
The ABS rapidly applies & releases brakes & this causes silicone fluid to foam & the result is the same as air in brake fluid. Not what one wants on any braking system.
 

JohnW

Too many posts!
A leaking hydrovac master cylinder will cause burning of brake fluid & silicone becomes sand & will wreck your engine, tout suite.
As far as the ABS unit read the owners manual it'll tell you not to use DOT5.
The ABS rapidly applies & releases brakes & this causes silicone fluid to foam & the result is the same as air in brake fluid. Not what one wants on any braking system.
That makes sense to me! Thanks. Happily no hydrovac on the 1964 R8.....
 

Artificer

Member
Another thing:
If one chooses to use Dot 5 after a rebuild or full flush DO NOT pump bleed. Vacuum or pressure bleed, only.
Pump bleeding aerates the silicone fluid & makes for a soft pedal.
 

JohnW

Too many posts!
Another thing:
If one chooses to use Dot 5 after a rebuild or full flush DO NOT pump bleed. Vacuum or pressure bleed, only.
Pump bleeding aerates the silicone fluid & makes for a soft pedal.
That is SO interesting. I've just vacuum bled the R8 and have the best "pedal" I can remember for years. The key hint from me is very heavy silicone grease on the bleed nipple threads so it doesn't suck air past them. Thank you Mr A.
 

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