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Brake Fluid
Posted by: Phil Fairman ()
Date: March 06, 2005 07:09PM

Next month I will be replacing all hard brake lines and brake hoses on my '66 Monza coupe. I have a new set of VelvetTouch linings and recently turned drums installed with new wheel cylinders and a new 7/8" bore master cylinder. All springs, adjusters, etc are new. I am currently using DOT3 fluid. With the total replacement of lines, this would be the time to change fluid type if desired. What are your thoughts/experiences with DOT5 silicone fluid? Is it a good idea to change to this fluid? I have been told that DOT5 does not absorb moisture and will not need frequent changes, but may change braking characteristics, IE: softer pedal...Any input appreciated.

Thanks,
Phil Fairman
'66 Monza 110/pg


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Re: Brake Fluid
Posted by: madgrinder ()
Date: March 06, 2005 07:12PM

I use DOT 4 + , it's made for European cars and has a much higher boiling point than DOT 3. It is compatible with DOT 3, so if you need fluid when in Dumaflotche, New Mexico you can mix as needed.

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Re: Brake Fluid
Posted by: David Clamp ()
Date: March 06, 2005 07:44PM

My car had DOT5 in it when I bought it. I haven't experienced any problems with it using all stock braking components.

DOT5 does not absorb moisture, but does more easily absorb air. While I had no trouble bleeding my brakes when I replaced the hoses and wheel cylinders, you do need to pour slowly so as not to caise air bubbles in the master cylinder.

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Re: Brake Fluid
Posted by: "UNSAFE" ()
Date: March 06, 2005 07:48PM

I would stick with the DOT 3 or 4. They are specifically recommended by most manufactures such as Wilwood,MPbrakes,NAPA and others.

It is very hard to get every last drop of old fluid out and the slightest amount when mixed with silicone DOT 5 will create slugs in the system that can cause problems.

DOT 5 is much more expensive.

DOT 5 may be harder to bleed due to aeration.

The one really good thing about DOT 5 is that it will not harm your paint or anything else! It is tough to remove the residue from trunk spatter paint though!

DOT 3 dry boiling point is 401 degrees,DOT 4 is 446 degrees and DOT 5 is at least 500.

If you're boiling your fluid , it's time for disk brakes anyway. gg

As usual these are just my opinions.

"UNSAFE"

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Valvoline Synpower Synthetic brake fluid
Posted by: Larry Forman ()
Date: March 06, 2005 09:00PM

Hi Phil,
My new favorite brake fluid is Valvoline's SynPOWER (NOT Syntec by Castrol) full synthetic DOT 3/4. From the Valvoline Synpower web site:

"SynPower High Performance Synthetic Brake Fluid is recommended for ABS, hydraulic drum and disc braking systems and hydraulic clutches requiring DOT 3 and DOT 4 fluids. Its premium, synthetic, low-moisture formulation provides superior anti-vapor lock protection. It has a high dry-boiling point up to 500°F that reduces the risk of fluid vaporization and possible brake failure.

Exceeds DOT 3 and DOT 4 specifications
For most ABS, disc or drum brake systems
High boiling point reduces risk of brake failure
Compatible with conventional brake fluids"

My personal experience with DOT 5, even when I REALLY wanted to love it, was that it and I were incompatible. I kept having spongy brake pedals on several vehicles despite WEEKS of bleeding, etc.

What most people don't tell you is that regardless of the non-hygroscopic nature of DOT 5, it STILL has moisture inside the brake system. This is because condensation will form naturally from the air and slowly contaminate the DOT 5 solution. It will not mix, but will still be there. Once there as it flows to the lowest points it can rust steels.

After basically giving up on DOT 5, I was told about Valvoline Synpower DOT 3/4 and LOVE it. On VV, or maybe it was here, someone did an experiment, (Bill Elliott?) and proved that it can slightly damage paint, but not as quickly as the non-synthetic DOT 3 or 4. The Synpower seems to have the best characteristics of Dot 5 but without the spongy pedal downside. It is not totally non-hygroscopic, but I still like it much better than having a spongy pedal. I think even with DOT 5, you should change it out from time to time, just longer intervals than the DOT 3 or 4 stuff.

-- Larry

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Re: Brake Fluid
Posted by: Phil Fairman ()
Date: March 08, 2005 04:19AM

Thanks for all the great input...from what I'm reading the Valvoline SynPower dot 3/5 seems like the way to go.

Great forum, answers & experience for everything Corvair (& more!)

Cheers,
Phil

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Re: Brake Fluid
Posted by: Bill Elliott ()
Date: March 08, 2005 08:28AM

I'll risk another post on brakes...

I have used Castrol GT/LMA DOT4 for years in all of my stuff.

Mixed experience with DOT5 (I think it's great for trailer queens, not so great for many drivers, including specific negative experiences in Corvairs).

However, I'm now with Larry. The new fully synthetic DOT3/4 compatible fluids seem the way to go. You can buy all sorts of expensive racing brake fluids made in this same genre, but the Valvoline Syntech is the only stuff that's generally available over the counter. Specs are not quite as good as the high priced stuff, but better than the best DOT4 (which is the GT/LMA in my opinion), so this is now what all of my cars get...even the race car.

Well, except for my Berkeley which came with DOT5 from the PO. Seeing how it's mainly a trailer queen and seals are difficult to get, I've not changed it over.

When it came out in 1956, the Berkeley registered the highest braking performance of any car ever tested...even though it had four wheel drums. (My later car has three wheel drums!) Why? Light weight (650lbs) and drum brakes designed for heavier cars. Sound familiar? ;-)

Bill

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Re: Brake Fluid
Posted by: Ryan Counterman ()
Date: March 08, 2005 08:31AM

I use silicone brake fluid, for 2 reasons. 1 is that it wont hurt my paintjob, and 2 its purple. I have it in all my cars and experienced no change in braking, and it was just as easy to bleed. Good luck!

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Re: Brake Fluid
Posted by: Packy ()
Date: March 09, 2005 09:17PM

Keep a close eye on your brake fluid. I ran it in my truck and it gelled and ruined the entire system. I have heard of it doing this to many other people as well.

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