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Brake Issue Using Dot 5

M

Mariposa Mike

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Yesterday I noticed an "oil" slick on the floor beneath the right rear tire and found that it is brake fluid. The 66 Charger is new to me (11 months) but previous owner (deceased) had converted to Dot 5 fluid with a dual reservoir. I have never used it but considered doing so in the past for seldom driven cars. Taking the drum and cylinder off I found one of the cups leaking and one end seized with some corrosion on the bore. Thought this stuff was supposed to stop that. Maybe some moisture got in the system but now I'm wanting to know if I should just go back to Dot 3. Been planning on converting the front to disc and could drain and flush the system if that is way to do it.

Another amazing thing was that I made a rush trip to O'reillys figuring I would have to order the parts and they had two rear cylinders in stock. Got the one on before dark and have a car show to attend tomorrow but I plan to do the other rear next week and probably should do the fronts as well even though I plan to do the conversion later. I've had some issues with adjusting the rear brakes which look new and this might explain that issue. They were tightening up and overheating the drums/rims. Even after backing off the star adjusters they tightened up again. The front brakes were apparently doing the braking for the car and my blaming four wheel drum brakes for less than satisfactory braking was in error. The brake cylinder I removed was frozen so could not have been helping stop the car. Might be the same on the left rear.

Anyone with experience using Dot 5 that has some feedback it would be appreciated or advice for future conversion.

Mike
 
You probably don't know how it was converted to dot 5 and if wheel cylinders were replaced to use dot 5. I have a 05 ram PU and had a front caliper freeze up, and destroy the rotor, so I replaced both fronts rotors, calipers and pads. I noticed new calipers uses some sort of plastic piston probably to prevent it from freezing up. Also gave me a chance to drain 20 year old dot3 and replace entire system with fresh dot3 fluid.
 
Dot 5 fluid does not absorb moisture, but it doesn't prevent it from getting into the system, and causing rust if it does. How new were the cylinders etc. I would top it off with DOT 5 and investigate after the weekend.
 
Mariposa Mike said:
Yesterday I noticed an "oil" slick on the floor beneath the right rear tire and found that it is brake fluid. The 66 Charger is new to me (11 months) but previous owner (deceased) had converted to Dot 5 fluid with a dual reservoir. I have never used it but considered doing so in the past for seldom driven cars. Taking the drum and cylinder off I found one of the cups leaking and one end seized with some corrosion on the bore. Thought this stuff was supposed to stop that. Maybe some moisture got in the system but now I'm wanting to know if I should just go back to Dot 3. Been planning on converting the front to disc and could drain and flush the system if that is way to do it.

Another amazing thing was that I made a rush trip to O'reillys figuring I would have to order the parts and they had two rear cylinders in stock. Got the one on before dark and have a car show to attend tomorrow but I plan to do the other rear next week and probably should do the fronts as well even though I plan to do the conversion later. I've had some issues with adjusting the rear brakes which look new and this might explain that issue. They were tightening up and overheating the drums/rims. Even after backing off the star adjusters they tightened up again. The front brakes were apparently doing the braking for the car and my blaming four wheel drum brakes for less than satisfactory braking was in error. The brake cylinder I removed was frozen so could not have been helping stop the car. Might be the same on the left rear.

Anyone with experience using Dot 5 that has some feedback it would be appreciated or advice for future conversion.

Mike
Click to expand...
As long as the initial conversion was done with all new components I can't believe it would corrode as you say? If any DOT 3 was left in the system that may have drawn in the moisture.
Mike
 
I used Dot5 Silicone fluid in my 65 system that I converted to front disc. All brake components were new. I only had to flush the lines. Been in for 1.5 years with no problems.
Dot5 fluid does not absorb moisture, but if there is moisture in your system, it will separate out and pool in low spots. The non-silicone brake fluids do absorb moisture, so any moisture is mixed in with the fluid. Pick your poison.
I wanted to avoid spills, leaks from ruining the paint, which is why I went with Dot5.
 
Moisture will still get in the brake system, the dot 5 will not absorb the water.
Dot 5 will not prevent water in the system.
It is not a desiccant or a dehumidifier.
 
In my nicer car, I converted to DOT 5 just to keep from damaging the paint. I have a 4 wheel disc setup using later model Ford Mustang parts modified to fit Mopars. My project cars all still have regular DOT 3 stuff.
The cost of the DOT 5 is a punch to the gut! A one quart bottle is about 4 times the cost of DOT 3.
I'm wondering if the newer synthetic DOT 3 and 4 has the same characteristics where they don't harm paint as the DOT 5 stuff has. If so, when time comes to do a system flush, I'd go back to the cheaper stuff.
I've read from some that claim the DOT 5 does not give as hard of a pedal feel as the DOT 3 and 4 fluids. That isn't the case for me though.
 
I recently converted my 66 Satellite to DOT5. I replaced the wheel cylinders, the master cylinder, and the front rubber hoses. I flushed the lines with 99% isopropyl alcohol. You have to get all the old brake fluid out of the system or there will be problems.
 
I’ve read the horror stories for years about dot 5. I used it in the late 90s without issue, but for some reason didn’t again for awhile. Then kept hearing about problems.

Last summer I decided this car should be switched since it has show quality paint. All I did was get two pints and flush until it went purple, then flushed some more. I’d say it was equal one pint through each end of the car. I had a front wheel cylinder that was already bad, so switched that out. I used my one man bleeder kit and had zero issues. Pedal got rock hard like any other. I did both front hoses in the braided stainless line. Time was short so left the rear rubber hose dated 2016 for later.

Following what guys who had dealt with dot 5 before said, I poured slowly and did the bleeding slowly. I decided not to do any alcohol flush as dot5 is compatible with the other numbers, per Rick ehrenberg comments for years. I’ve seen comments that they don’t mix, I don’t see how you’d get anything other than fluid settling with the densest at the bottom, as long as no air is in there, it should still work. My flush was so thorough only the most trace amount of dot3 would be left. It was yellow so I know it wasn’t 5.

This spring I planned to do my normal spring flush where I take a bit out of each wheel just in case moisture had worked in and settled. I’ve been way busier than normal so that didn’t happen. Pedal still feels good and rock hard.

Dot 5 won’t fix trashed parts and it won’t trash them either.
 
The wheel cylinders were not replaced when the system was converted. There is a lot of misinformation on the web regarding how to convert to dot 5. If done properly, nothing in the system will corrode. When done properly, all components containing rubber or synthetic components must be replaced as these components absorb dot 3 and 4 fluid which is hydroscopic and does not mix with dot 5 fluid. Replace the wheel cylinders and continue to use dot 5 otherwise everything in the system has to be replaced if going back to dot 3 or 4.
 
Some Car Guy said:
I’ve read the horror stories for years about dot 5. I used it in the late 90s without issue, but for some reason didn’t again for awhile. Then kept hearing about problems.

Last summer I decided this car should be switched since it has show quality paint. All I did was get two pints and flush until it went purple, then flushed some more. I’d say it was equal one pint through each end of the car. I had a front wheel cylinder that was already bad, so switched that out. I used my one man bleeder kit and had zero issues. Pedal got rock hard like any other. I did both front hoses in the braided stainless line. Time was short so left the rear rubber hose dated 2016 for later.

Following what guys who had dealt with dot 5 before said, I poured slowly and did the bleeding slowly. I decided not to do any alcohol flush as dot5 is compatible with the other numbers, per Rick ehrenberg comments for years. I’ve seen comments that they don’t mix, I don’t see how you’d get anything other than fluid settling with the densest at the bottom, as long as no air is in there, it should still work. My flush was so thorough only the most trace amount of dot3 would be left. It was yellow so I know it wasn’t 5.

This spring I planned to do my normal spring flush where I take a bit out of each wheel just in case moisture had worked in and settled. I’ve been way busier than normal so that didn’t happen. Pedal still feels good and rock hard.

Dot 5 won’t fix trashed parts and it won’t trash them either.
Click to expand...
While I like Ehrenberg, his comments on DOT 5 compatibility don't agree with the rest of the industry.

"Mixing DOT 5 with glycol-based brake fluids like DOT 3 or DOT 4 can lead to system malfunctions." A quote from this site:
DOT 4 vs DOT 5 Brake Fluid: 10 Major Differences - MrOilGuy
One of many articles warning against mixing.
 
Bottom line is DOT 5 has been chosen by our Military for all vehicles. The stuff gets churned up and air bubbles
are produced by the ABS pump in a regular vehicle, so it's a No No for ABS Systems. No ABS in sevice vehicles.
As long as everything is clean, there shouldn't be a problem. The guy was probably lazy when he did the flush.
Once the DOT 5 is in there, you can fagghetabotit!
 
Photon440 said:
While I like Ehrenberg, his comments on DOT 5 compatibility don't agree with the rest of the industry.

"Mixing DOT 5 with glycol-based brake fluids like DOT 3 or DOT 4 can lead to system malfunctions." A quote from this site:
DOT 4 vs DOT 5 Brake Fluid: 10 Major Differences - MrOilGuy
One of many articles warning against mixing.
Click to expand...

I don’t think I’d take that guy seriously. I see he gives the standard line on problems, doesn’t say what, then this-

DOT 4, a glycol-based brake fluid, is more forgiving when handling and spillage. It’s less likely to cause damage to vehicle paint or surfaces in the event of a spill.

On the other hand, DOT 5, which is silicone-based, can be more challenging to handle. It tends to damage paint and surfaces, making care and precaution necessary during maintenance.



Dot 3 and 4 will strip paint right off your inner fender. I have seen guys say 5 will leave a film that is hard to get off when repainting a car.

I think people just parrot things and haven’t used the products in question.
 
If you continue using DOT 5, just don’t mix it with DOT 5.1 which is glycol bases. I use Bosch DOT 5.1 in a lot of vehicles.
 
I converted my 67 Satellite to DOT 5 during its resto in 1990. I replaced all rubber components and flushed any lines I reused with denatured alcohol as that was the guidance I got at the time. Zero issues with it and haven't had to touch the brakes in 35 yrs other than replacing the rubber hoses recently due to age.
 
Some Car Guy said:
I don’t think I’d take that guy seriously. I see he gives the standard line on problems, doesn’t say what, then this-

DOT 4, a glycol-based brake fluid, is more forgiving when handling and spillage. It’s less likely to cause damage to vehicle paint or surfaces in the event of a spill.

On the other hand, DOT 5, which is silicone-based, can be more challenging to handle. It tends to damage paint and surfaces, making care and precaution necessary during maintenance.



Dot 3 and 4 will strip paint right off your inner fender. I have seen guys say 5 will leave a film that is hard to get off when repainting a car.

I think people just parrot things and haven’t used the products in question.
Click to expand...
I don't think the NHTSA in its Federal Motor Vehicle Safety Standards is parroting when they advise:

"If your vehicle contained a brake fluid other than DOT 5 in its brake system, we recommend that the old fluid be flushed completely out of the brake system, before being replaced with DOT 5. This is necessary to ensure that the DOT 5 brake fluid does not mix with any other brake fluid type."
 
I had a instructor in college that told the class a story about having to pee in a master cylinder to keep the brakes working on a military truck they were using when he was in the army. Hey liquids do not compress!
I can agree with Rick Ehrenberg on the mixing of fluids-to get by in a emergency. The system can always be flushed and recharged with your fluid of choice when convenient.
Mike
 
When I did my 70RR resto about 15yrs ago, did the front disc conversion, with new calipers, brake lines, wheel cylinders, and NOS master cylinder, rebuilt OE T - metering - prop valves, filled with DOT5. Solid pedal and stopping performance since. As noted system must be new or rigorously flushed/cleaned.
 
I used dot5 in my 65 coronet when I changed it to dual reservoir master cylinder, front disc brakes and Dana 60, all new parts, in 2000. I just replaced both rear wheel cylinders this year. I've changed 4 cars to dot5 and have yet to have any issues.
 
In the past 30 years I have used DOT5 in a wide variety of cars without issue. That said, all of them had the entire brake system completely rebuilt. You have to pump slow and steady when bleeding, air bubbles seem to disperse more easily in silicone fluid. I like that it doesn’t harm paint, which is the primary reason I use it.
 
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