Best brake fluid?

[bams50]

I'm doing a brake job, everything new- all 4 wheel cylinders and dual master conversion, all new lines and hoses. What's the preferred brake fluid for an all-new system?

I know there are plenty of old threads on this subject, and different opinions. But these things sometimes evolve, so I'm wondering what's the LBS (latest, best science) on the subject.

What do you say?

Robert (Bob) Andrews- on the IoMT (Island of Misfit Toys)
Parish, central NY 13131

[Skip Lackie]

I've had silicone brake fluid in a couple of vehicles for more than 30 years with no problems whatsoever. Some people have reported that they've had a higher brake light switch failure rate with silicone, but that has not been my experience.

Skip Lackie
Washington DC

[Rerun]

For an "all new" system, I would definitely go with DOT-5 silicone fluid. The standard DOT-3 fluid is hygroscopic and will entrain moisture, leading to rusted and stuck cylinders. This is particularly important for a vehicle that may sit unused for months at a time.

I used DOT-3 on my first total brake rebuild on my '63 Avanti. Three years later, I had to do it again. The second time, I used the silicone fluid and the system was still fine when I sold the car about 10 years later. Don't worry about the stoplight switch. There are DOT-5 compatible switches readily available.

Jim Bradley
Lewistown PA
'78 Avanti II

[bams50]

Yes, I'm thinking longevity. I have a young guy that's working with me, and he was shocked when I pulled back the boots on the wheel cylinders and a big pile of rust/powdered piston fell out[:0]

Robert (Bob) Andrews- on the IoMT (Island of Misfit Toys)
Parish, central NY 13131

[fmarshall]

I use dot 4, flush the system every two years, and have all stainless lines. The next brake job will get brass sleeves in all cylinders, calipers and MC.

========================
63 Avanti R2, 4-Speed, 3.73 TT
Martinez, CA

[sweetolbob]

Put my vote in for DOT 5 Silicone. I've used it in all my old cars since the late 70's and have had no switch failures, leaks or gelling of the fluid.

It's in the SBC powered 39 Ford Standard Coupe, 1961 Austin Healey 3000 and the 54K I currently own. Also used it in others that I've since sold. Spitfire GT6, Fiat 850 coupe, 1972 Ford Bronco.

Every one had new lines and cylinders installed, I value good brakes.

By the way, if you spill it, it won't eat the heck out of your paint.

Bob

[Swifster]

If you flush your brake fluid at regular intervals, Ford's Heavy Duty brake fluid is great. It is DOT 3, runs about $6 a can (you'll need 2). I've always used this in my race car and never had a problem.

I flush the fluid in my vehicles at least every 30K or two years, whichever occurs first. I've never run into rust problems, wheel cylinder failures, etc. Clean fluid is the key.

---------------------------------------------------------------------------------------------------
Tom - Mulberry, FL

1964 Studebaker Daytona - 289 4V, 4-Speed (Cost To Date: $2125.60)

[Rerun]

The DOT-5 eliminates the need to periodically flush the system or to sleeve the cylinders. However, be ready for "sticker shock" as the DOT-5 is typically about $40 for a quart. Well worth it in the long run, though.

Jim Bradley
Lewistown PA
'78 Avanti II

[53k]

quote:Originally posted by bams50

I'm doing a brake job, everything new- all 4 wheel cylinders and dual master conversion, all new lines and hoses. What's the preferred brake fluid for an all-new system?
I know there are plenty of old threads on this subject, and different opinions. But these things sometimes evolve, so I'm wondering what's the LBS (latest, best science) on the subject.
What do you say?

Like Skip, I have had silicone in two of my cars for a LONG time with no brake light switch failures. However, I have had problems with leaks (silicone fluid can find smaller "holes" than DOT3). On one Avanti (since sold), I had trouble with leaks at the fittings on the caliper cylinders and on bleeder valves. On my '53 I have had wheel cylinder leaks. I had all the wheel cylinders sleeved by White Post (in brass) and they recommend against using silicone. I already had silicone in the system so I ignored their recommendation. Also, silicone seems to be harder to bleed (get out all the air). As expensive as it is it is painful to seemingly waste a lot.
FWIW, I bought a gallon jug of DOT 5 for $25 many years ago and I'm still using from it.




Paul Johnson, Wild and Wonderful West Virginia. '64 Daytona Wagonaire, '64 Daytona convertible, '53 Commander Starliner, Museum R-4 engine, '62 Gravely Model L, '72 Gravely Model 430

[Bud]

I've been using DOT 5 fluid in my Studebakers since the stuff was first sold and have had very good luck with it. It will find leaks faster than DOT 3 or 4, but the life of the metal parts in the brake system is almost infinate. I have had problems with the brake light switch in my Avanti, but the switch in the 62 GT Hawk hasn't failed in 15 years. Get ready for sticker shock if you decide to use DOT 5 fluid. Bud

[rockne10]

In addition to silicone fluid finding all possible leaks, it is not hygroscopic. Hygroscopic fluid allows moisture to disperse evenly throughout. Hence, it won't freeze but you need to flush it from time to time.

Silicone, without hygroscopic properties, should moisture find its way in to the system, it will collect in the low spots. How many years, or decades, would it take to accumulate sufficient moisture to create a frozen "plug" in the line? In New York state, who knows? Hopefully, you should live so long.

[Gunslinger]

Most performance car automakers specifically prohibit the use of silicone brake fluid. These cars, when driven hard and competitively have problems where air bubbles form in various parts of the system and cause pedal sponginess. For some reason it causes problems with anti-lock brakes as well. Not that I expect old Studebakers have those issues, but whichever type one chooses, the entire system must be completely flushed of the previous type of fluid. Mix DOT 3 and DOT 5 silicone fluid and you get a milky, cloudy mess and gunk that creates serious braking issues.

Avanti Motors began using silicone brake fluid as factory fill about 1970 and advertised that fact in their literature. They must certainly have been comfortable doing so. It does make me wonder how many Avanti owners unknowingly mixed fluid types leading to problems such as poor braking performance. It could be at the root of much unhappiness with the original design brakes, when it may not be the design at all, just lack of communication in proper servicing. It could even be the root of some collisions...just speculation on my part.




Poet...Mystic...Soldier of Fortune. As always...self-absorbed, adversarial, cocky and in general a malcontent.

[Guest]

Silicone will hold air bubbles forever (or close to it), never shake the can, never pump mutiple times when bleeding and not too good for performance use (if it boils you're done). I let mean ol mister gravity do most of the work when bleeding. Takes a while but all the air comes out of the system without the chanc of introducing bubbles. Do one wheel at a time starting at farest point, use a hose and catch can. My 62 Bird took almost three days but it was air free and had a very nice pedel feel.

Bill, Many Fords and one great Stude!

[WCP]

Used Dot5 fluid in my everyday drivers ('76 Jeep Cherokee &'73 Chev Biscayne wagon) from probably 1981 to 1997, when the Jeep was sold for farm service. No problems winter or summer! Put 100,000 miles on the Jeep after conversion without ever touching the hydraulic system, other than to adjust fluid levels after pad and shoe changes. I always kept any used fluid and filtered it through laboratory filters (or a couple of coffee filters) and used that for master cylinder topup. Back then Dot5 was not readily available in Canada and pricy. I've had my Studebakers on Dot5 since the mid to late '70s, with no problems, including brake switches. When I did the conversion on the daily drivers, I performed a solvent flush of the lines with some volatile solvent (can't remember which) and dried the lines with compressed air, and then installed new rear cylinders and remanufactured calipers. In the past 10 years, I've been tempted to convert my current daily drivers, but have held off due to the more complex ABS systems, and lack of experience info fron anyone else that has done it. For the older cars, I wouldn't use anything else. I think most problems with Dot5 are the result of poor conversion techniques, such as simply doing a flush with Dot5 fluid on an Dot3 system. Bob, if you are replacing the brake lines and installing new cylinders, that is the time to introduce the Dot5 fluid.

[Thomas63R2]

For a completely new and dry system on a normally driven car, Dot 5. As noted, take care not to trap air bubbles in silicone fluid.

Use a quality regular brake fluid in an aggresively, or competitively, driven car.

The people who never flush a Dot 5 system, you are not doing your braking performance any favors. Just because silicone is not hydroscopic does not mean that moisture will not enter the fluid. As noted, what it does mean is that the moisture will gather in low spots rather than mixing throughout. I can guarantee that any long time silicone fluid will reveal moisture when drained. It is natural laws at work: when you use your brakes heat is generated and passed on to the fluid. As the brake fluid goes through heating and cooling cycles condensation will occur - you can't stop nature.

For a light or normally driven car the water accumulation in a silicone filled system is not problematic. However, your brake fluid boiling temperature will be lowered, So repeated high speed stops will suffer. Practically no car gets repeated high speed stops unless you live in the mountains.

Thomas

Long time hot rodder
Packrat junk collector
'63 Avanti R2 4 speed