1962 Brake fluid issue

[Elwyn S.]

My car's brake system seems to have DOT 5 brake fluid in it. I figured this out by mixing the current fluid with water in a glass jar and it does separate, ( I found this test in previous/historical post), I believe this was a mistake by the previous owner. So my question is should I go back to DOT 3 and flush the system real well or should I use DOT 5 and flush with it. The current brake fluid looks to be in horrible condition... Redish/black in color. I am also having some brake issues, my pedal is spongy and I usually have to pump it twice to get good brakes, however on the second pump the car seems to stop real well. Before I go into adjusting the brakes I want to make sure the problem is not air in the brake system and a brake bleed will fix this hopefully. Thank you in advance for your assistance.

[Bruce B.]

Re: 1962 Brake fluid issue

Elwyn,
I have used both DOT3 or DOT 5 in a number of my 62 Corvettes with no issues.
Personally I only use DOT 5 in my cars now.

But it sounds like someone has mixed the 2 different fluids in your brake system.

I would throughly flush and clean the brake system and refill with DOT 5.

[Duke W.]

Re: 1962 Brake fluid issue

DOT3/4 and DOT 5 are not compatible, and the only sure fire way to convert without possible future problems is to completely disassemble the system, get every last molecule of old fluid out, then assemble the hydraulic components using the new fluid as an assembly lub.

Try flushing at least a quart of DOT 5 through the system. Your symptoms could also be a sign of an internal master cylinder leak or gunk clogging up the compensating port, or it could be that the swap to DOT 5 was not done properly as mentioned above.

Start the flush by siphoning all the fluid out of the M/C and make sure the bottom is sqeaky clean. Have plenty of Q-tips on hand.

Duke

[Elwyn S.]

Re: 1962 Brake fluid issue

Bruce,
Yes I do believe someone made a mistake in the past and mix the two together DOT 3 and DOT 5. As for as flushing the system should I use Dot 5 brake fluid as the flush? and then refill and brake bleed. I do not want to tear into the entire system and clean every thing unless I have no choice.

[Elwyn S.]

Re: 1962 Brake fluid issue

Duke,
Thank you for your response, I will flush the system with DOT 5 and then reservice and bleed the brakes. What long term effects can I expect to encounter since these two were mixed DOT 3 and DOT 5. I really do not want to tear into the system and rebuild at this time. Also at this time I should not flush with DOT 3 and go back to DOT 3. Is the reason for this is that the system has been contaminated with DOT 5 and there is no way to clean the system out unless you do a complete rebuild of the brake system?

[Bruce B.]

Re: 1962 Brake fluid issue

Elwyn,
I have to agree with Duke, the whole system needs to be super clean.
I think it can be done by flushing with DOT 5 but it will take lots of effort and expensive DOT 5 fluid.
But once it is done it will last for a long time and save the brake system components from deterioration.

[John F.]

Re: 1962 Brake fluid issue

I would flush the system with denatured alcohol first and then DOT-5. That's what I did to both of mine. The very best way is to take the whole system down and clean or rebuild if necessary.
John F

[Jim L.]

Re: 1962 Brake fluid issue

I would flush the system with denatured alcohol first and then DOT-5. That's what I did to both of mine.

I agree that this method works well. I've done it this way with excellent results and would do it again. You need compressed air to blow the alcohol out of the system.

Jim

[Jim T.]

Re: 1962 Brake fluid issue

I have used DOT 5 for over 20 years and have found that DOT 5 was a good conversion choice. The master cylinders on my 68 and 70 with the original DOT 5 installed will allow viewing through the fluid to see the bottom of the master cylinders. DOT 3/4 would not after it had been installed.

[Mike T.]

Re: 1962 Brake fluid issue

Jim Lockwood, it appears that my '61 has the same issue with 'mixed' brake fluids. When I picked up the car all the notes said the brakes had been converted to DOT 5. Got it home, checked brake fluid level which was fine and drove it. I noticed that the brakes were a little bit spongy but not that bad but did notice that it didn't stop that well and kinda blamed that on possibly the wrong pads up front but when I looked more closely at the dual master cylinder (SSBC Force 10 Front Discs with Dual MC) I found the front discs had the amber looking DOT 3 or 4 stuff while the rear drums had the DOT 5 fluid. I am going to use a Motive pressure bleeder bottle with alcohol to clear out the system but when it comes to using air afterwards, I suppose the only way to accomplish this would be to break the lines free at the master cylinder and just use the air compressor?

[Duke W.]

Re: 1962 Brake fluid issue

Try flushing a quart of DOT 5 through the system, first. If that doesn't do the job, then you're going to have to look at overhauling hydraulic components, beginning with the master cylinder.

Long term effects of mixing DOT 3/4 with DOT 5 are internal corrosion and sludge formation.

If the flush doesn't work, and you decide to overhaul the M/C, you might as well do the wheel cylinders, too. Buy new hoses and flush them and all the pipes with denatured alcohol and thoroughly dry with compressed air. Use DOT 5 as an assembly fluid. If you buy new or rebuilt master and wheel cylinders, disassemble them, clean with denatured alchohol and reassemble with DOT 5.

Duke

[Peter M.]

Re: 1962 Brake fluid issue

You can use a Motive Brake Bleeder system to flush the system with denatured alcohol and then refill it with Dot 5. However, if the brake fluids have already been mixed, you may have caused some seal damage throughout the system.

[Elwyn S.]

Re: 1962 Brake fluid issue

Thanks to all that have responded!!! After further investigating I believe I have DOT 3/4 in my system instead of DOT 5 as I thought. What I was seeing last night was the seperation of sluge/Mud/debris when I added water to my existing brake fluid. During daylight hours LOL(old eyes not good at night) I purchase DOT 5 and DOT 3 and added water to them to see the differences. I will upload the pics. My fluid is on the left and DOT 3 in the middle and DOT 5 on the right, I added water to all 3. Looking at the differences my fluid seems to look like DOT 3 it does not seperate like DOT 5 and DOT 5 floats on top of the water. Like I said earlier, the differences in my fluid where it is seperates is the debris. I plan on flushing the system out with new DOT 3 and bleeding the system with speed bleeders that I can purchase locally at Auto Zone. Once again thanks for all the help and EDUCATION on the differences of DOT 3 and DOT 5. Brake Fluid Differences.jpg Elwyn Short

[Philip P.]

Re: 1962 Brake fluid issue

Jar 1 looks identical to my master cylinder fluid that went bad about 2 years ago. I had no symptoms as when I went to move the car out for a "spring run" the pedal went to the floor. I let the gravity drain the fluid out for about a day then installed a new master cylinder and flushed it until all the fluid was clear then flushed it some more there luckily no problems with the other components. A brake job is on the horizon however.
Phil
1960/230

[Elwyn S.]

Re: 1962 Brake fluid issue

Philip, Were you using DOT 3 when you noticed your brake fluid had gone bad 2 years ago?