brake fluid

[trini]

Hi , I would like to find out which  type of brake fluid is better suitable for the 1928 Dodge cars ?  Is it DOT 3, or Dot 4 Synthetic.  What is the advantage and disadvantage ? The Dodge will be not be regularly driven.

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Cheers and have a nice day.

 

[keiser31]

You may want to do a search on this forum as it has been discussed many times.

[Frank DuVal]

DOT 5 (Silicone-based)  is best for cars that sit.

 

OK, that is MY opinion. Based on using it in vehicles for over 30 years. No Issues with it. As Keiser says, many discussions on DOT X brake fluids here and other forums, it seems everyone has an opinion...

 

[Spinneyhill]

In general, each DOT spec. has higher boiling point and less affinity for absorbing water. Thus DOT 5.1 is better than DOT 4, which is better than DOT 3. DOT 5 is synthetic and does not absorb water. Read the Wikipedia entry on "Brake Fluid".

 

Here is one such discussion on this forum, found with a search for "DOT".

 

 

Edited October 1, 2017 by Spinneyhill (see edit history)

[Bloo]

DOT 5 is SILICONE fluid.

 

DOT 3, DOT4, AND DOT 5.1 are all GLYCOL-BASED fluids.

 

It is important to point this out (for US-based readers) all the glycol fluid here is labeled "SYNTHETIC" now and it is causing a lot of confusion. Apparently it is just the same old brake fluid.

 

Even the old standby Castrol GTLMA label has disappeared in favor of "synthetic"

[trini]

Sorry guys, I thought there must have been a forum on this topic before but I could not find it. I put in Lucas  DOT 4 . the label says Synthetic . But around the cover of the master cylinder there is  rust, which should not be. Also some of the labels  read DOT 4 is  equivalent to dot 5 but I cannot get DOT 5 to buy here. Supplies from the US will not ship liquids across the border. Not even an ignition coil.  The cylinders are lined with stainless steel but I am worried about the rubbers. I had a discussion with Land Rovers North on this subject about 10 years ago and he said silicone based brake fluid is better than DOT 3 but never mix them.. But technology is changing daily.  Man thanks to Keiser31, Spinneyhill,  Frank  and Bloo   who took the  time to educate me.

Cheers and have a nice day

[TerryB]

DOT 4 is what most modern motorcycle companies use too, mostly for the boiling point features.

Terry

[Frank DuVal]

Are you in Canada or or another northern country? I Googled DOT 5 in Canada and got several sources. There are restrictions on what can be shipped by Post Office (No liquids) and air (no propellants, etc.) even within a country. Truck freight can carry most anything on land with the proper permits, but the cost, ouch! Over water, more issues!

 

DOT 4 is a "better" DOT 3 (higher boiling point when new), but with the same hygroscopic nature. i.e. it does absorb water from the air and cause rust, like you see in your master cylinder cap. To prevent future damage, you must flush the DOT 4 every two to three years to remove the moisture laden brake fluid out and replenish with fresh. Even if you do not drive the vehicle. Also the more moisture the fluid absorbs, the lower the boiling point gets.

 

The rubber will be fine in DOT 3 and DOT 4 (and the new DOT 5.1, which is also the same glycol based fluid as DOT 3 & 4), it is steel parts that rust and a white crud will form inside wheel and master cylinders. Just flush routinely and all your parts will be happy for years with DOT 4.

 

I will also mention the test of steel brake lines for older cars. It is the hard HARDER test. In the safety of your driveway, step hard on the brake pedal, then pull on the steering wheel stepping HARDER on the brake pedal.  All your weight! 

 

You will not damage any good parts in your brake system, but you will make any weak parts break and not endanger you, you car and other drivers as would happen when weak parts give out on the road. 

[Spinneyhill]

55 minutes ago, Frank DuVal said:

it is steel parts that rust and a white crud will form inside wheel and master cylinders.

That white crud is aluminium oxide - the aluminium piston in the cylinder is corroding. Al is at the top of the galvanic series of course, so will corrode before the steel. Stainless (and brass) sleeves will make it corrode faster than it would have with steel. This will happen if you don't drive the vehicle regularly. I have cleaned mine out several times.

[R Walling]

15 hours ago, Frank DuVal said:

Are you in Canada or or another northern country? I Googled DOT 5 in Canada and got several sources. There are restrictions on what can be shipped by Post Office (No liquids) and air (no propellants, etc.) even within a country. Truck freight can carry most anything on land with the proper permits, but the cost, ouch! Over water, more issues!

 

DOT 4 is a "better" DOT 3 (higher boiling point when new), but with the same hygroscopic nature. i.e. it does absorb water from the air and cause rust, like you see in your master cylinder cap. To prevent future damage, you must flush the DOT 4 every two to three years to remove the moisture laden brake fluid out and replenish with fresh. Even if you do not drive the vehicle. Also the more moisture the fluid absorbs, the lower the boiling point gets.

 

The rubber will be fine in DOT 3 and DOT 4 (and the new DOT 5.1, which is also the same glycol based fluid as DOT 3 & 4), it is steel parts that rust and a white crud will form inside wheel and master cylinders. Just flush routinely and all your parts will be happy for years with DOT 4.

 

I will also mention the test of steel brake lines for older cars. It is the hard HARDER test. In the safety of your driveway, step hard on the brake pedal, then pull on the steering wheel stepping HARDER on the brake pedal.  All your weight! 

 

You will not damage any good parts in your brake system, but you will make any weak parts break and not endanger you, you car and other drivers as would happen when weak parts give out on the road. 

 

 

 Whenever I replace rusted brake lines, I always step as hard as possible in order to try and rupture any weak components. 

 Once after finishing a job I did my test and imeaditly blew another line. Had to start all over but better there than on the road.

[Frank DuVal]

Yes, the test should be done annually or more often. I am amazed at the people I heard growing up saying "Don't step so hard on the brake pedal, you might break something".  If I can break a part of the brake system by stepping on it, I want to do it in the driveway, not  approaching a red light at a busy intersection like I did 30 years ago! Panic stops will show the defects in the system RIGHT NOW!  Not good timing...

 

Now if I find a rusty line, they all get replaced (with Cunifer, but that is another discussion). After all, they were on the car the same time period and driven in the same amount of salt. Who, me, paranoid?  See above result in traffic...