Vintage Mustang Forums banner

1 - 20 of 26 Posts

·
Registered
Joined
·
345 Posts
Discussion Starter #1
I've had this in our 1st generation Mustangs for many years. We have had zero problems for more than 20 years. I've not seen this discussed or I've missed the posts. We are doing a drum to disc conversion on our daughters 64.5 and am planning on continuing to use the DOT 5. Is there any downside to this product?
 

·
Registered
Joined
·
4,845 Posts
Since it will not adsorb moisture, any water that may condense out of the atmosphere can pool in low spots in the lines. Where water accumulates, it will rust if your lines are steel. Dot 5 will also compress where DOT 3 and 4 will not.
this can cause a spongy pedal. The good thing about DOT 3 and 4 is that it does adsorb moisture, and this allows the moisture to be removed during routine brake fluid flushes.
 

·
Registered
Joined
·
345 Posts
Discussion Starter #3
Since it will not adsorb moisture, any water that may condense out of the atmosphere can pool in low spots in the lines. Where water accumulates, it will rust if your lines are steel. Dot 5 will also compress where DOT 3 and 4 will not.
this can cause a spongy pedal. The good thing about DOT 3 and 4 is that it does adsorb moisture, and this allows the moisture to be removed during routine brake fluid flushes.
The only times are cars are outside is when they are in use and driving. They are stored in a mostly climate controlled garage so hopefully this should help mitigate the harmful effects of moisture.
 

·
Registered
Joined
·
8,100 Posts
You couldn’t pay me enough to use DOT5. I tried that back in 86 in a GT. Hated the spongy feel. Flushed that stuff out and went back to DOT3. Use only DOT4 now.


Mark
 

·
Registered
Joined
·
5,354 Posts
Its a waste and overkill like high octane gas and boutique engine oils in most cars. Sure $12 over $6 isnt much but the higher number and price doesn't mean better. It was originally a Euro spec and wholly un-American to use it where not specified.
Just don't mix the stuff.
 

·
Registered
Joined
·
924 Posts
My Harley came with DOT 5 fluid in it from the factory in 2005. DOT 5 will only be spongy if it contains micro bubbles of air in it. This is corrected by follow up bleeds for a few days after changing the fluid if necessary. I still have the same motorcycle and it has rock solid brakes since I know how to properly bleed them whenever I do maintenance. Because DOT 5 can form micro bubbles of air, it is not suited to anti-lock brake systems. Since our Mustangs don't have anti-lock brakes, DOT 5 would work fine if you chose to use it. But since you already have 20 years of experience with it, I'm sure you already know all of this.
 

·
Registered
Joined
·
1,733 Posts

·
Registered
Joined
·
383 Posts
When I was working on my '66 GT-350 back in 1982, all the magazines were praising Dot 5 Silicone because it was not hydroscopic. Meaning it does not attract moisture. High dollar European sports cars were using it.

Regular old Dot3 or Dot 4 brake fluid will absorb 2 to 3 percent moisture a year. That lowers the boiling point but worse is the rust it causes inside your brake system. Your brake fluid turns brown from the rusting parts. No amount of flushing will get rid of the rust. New fluid will quickly turn brown again. Since I had a brand new master cylinder from Ford,new hoses, new wheel cylinders and I rebuilt the four-piston front calipers. The system was clean of any of the old brake fluid. So I went ahead and used the Dot 5 fluid. Stuck a little sticker on the master cylinder cap to remind be there was Dot 5 in there in the event I had a brain failure. Then I never did finish the car. I got sidetracked on hot rods and house building. I can tell you that same fluid has been siting in that car since 1982. It has not moved more than 50 miles since 1982. It went around the block a couple year's ago and I terrorized that poor car, its kind hard not to. It stops great with that 38 year old fluid. The fluid looks like it did the day I put in there.

A lot of people complain about a spongy brake pedal with silicone brake fluid. My GT-350s pedal feels just like any other of the dozen mustangs I have had without power brakes, nice solid pedal. I have a lot of "projects" that sit for years as I bounce around here from car to car. The silicone brake fluid is probably the best choice for them because I'm not flushing the systems on these cars every two years. If they got driven regularly then the regular old Dot 4 would be fine. ]

I had to go to a brake training program on the new Girling brake system on the 1980s large Ford trucks with hydraulic brakes. The class was put on by genuine Ford instructors, flown out from Detroit to CA to train us because the phone company had bought so many of those trucks. The instructor said that if people would change their brake fluid every two year's the brake hydraulic systems would virtually last forever.

Another little story. Back in 1977 I was swapping out a '65 8-inch rearend in a Mustang with a '66 Mustang factory 9-inch rearend. The car had a brand new paint job, maybe a week old. As we were carrying the complete old 8-inch rearend by the Mustang the brake hose flung some fluid onto the quarter panel and it swelled the paint right up. I was pissed!!! Silcone brake fluid won't hurt paint.
 

·
Registered
Joined
·
10,961 Posts
You’d be happier with Castrol SRF or Motul RBF 600. Both are DOT 4 and have the highest wet boiling points.

DOT 5 is a boutique fluid.


Mark
perhaps, but when I did it it was the mid 90's and I had a feeling the car would be sitting for extended periods of time and I had concerns about corrosion issues using DOT 3/4
 

·
Registered
Joined
·
817 Posts
Sorta on topic. Above was mentioned routine flushing of brake fluid. Maybe I'm lazy, I've never considered doing that with any car. I have a (Ewwww!) last decade 201x german car that has little blinky lights that whine when the fluid gets too old. This is the young car in the fleet. Is flushing brake fluid becoming normal service item?
 

·
Registered
Joined
·
166 Posts
DOT 5 in all the old stangs. It's been in one for 24 yrs. Clean and clear as the first day. Nobody going to talk me out of using it.
 

·
Registered
Joined
·
888 Posts
Wow! The DOT3 in my 67 has never let me down. I don't race so I see no reason for a "Better" fluid. I was also edjucated that fluids do not compress very well or at all, silicon or other. Air bubbles do!
 

·
Registered
Joined
·
383 Posts
One of the problems is when people bleed brakes you will see them pump the crap out of them a bunch of times before they open the bleeder. That breaks any large bubbles up in thousands of little ones. Don't do that! You want the big air bubbles to stay together and flow along slowly. They bubbles trapped in between fluid and have no choice but to gently flow along in the line and make their way out of the bleeders. They will gravity bleed out nicely just by opening one bleeder at a time and removing the master cylinder cap.

First I siphon the old fluid out of the master cylinder and wipe all the junk out of the bottom of it. Fill it up with clean fluid from a brand new sealed bottle, do not use fluid from an old bottle because once it has been opened it will start attracting moisture. Its better to buy the little bottles instead and pen them one at a time of so you do not end up with a half full big bottle sitting on the shelf absorbing moisture. Go to the furthest wheel from the master cylinder on which ever brakes your working on, front or rear. Perform the brake job and when your finished open the bleeder on that wheel. Then go start on the other wheel . Eventually that first wheel will have fluid trickling out of it. Once the cylinder fills up with fluid let it drain out the same amount of fluid that the line will hold between the master cylinder and the wheel cylinder, its not much that is really tiny line. That forces any air in the line to gravity flow out. Close the bleeder and spray off any brake fluid. Don't tighten the bleeders gorilla tight or they will break off. Check your master cylinder fluid level again because if it runs out you will need to bleed the air out of the master cylinder and start all over. Go open the bleeder on the second wheel and it will fill up with fluid faster than the first because the distance is shorter. Close the bleeder and your done. It is impossible for an air bubble to get trapped in the line doing that way.

The Factory Ford Engineer that trained me suggested to tap on the disc brake calipers during the gravity bleeding because little air bubbles scan cling to the sidewalls like bubbles in a glass of soda. Tapping on the caliper caused the bubbles to brake loose and float to the top and out the bleeder.

If you open a bleeder with the master cylinder cap off and fluid does not gravity bleed out the bleeder is probably plugged with rust, That's what those little rubber caps on the bleeders are suppose to prevent that nobody puts back on. Every once in awhile you get one that just does not want to gravity bleed and you have to do the old two person system of bleeding.

If you replaced the master cylinder thats a different brake bleeding lesson. That gets bled separately first.

I had an ASE light duty and the separate heavy duty brake certifications until I let them expire when I retired. I let 17 ASE certifications, a State Smog Test and Repair license and a Class A drivers license e all expire. No way in hell I will ever work on vehicles for a living ever again!!!!!
 

·
Registered
Joined
·
10,961 Posts
One of the problems is when people bleed brakes you will see them pump the crap out of them a bunch of times before they open the bleeder. That breaks any large bubbles up in thousands of little ones. Don't do that! You want the big air bubbles to stay together and flow along slowly. They bubbles trapped in between fluid and have no choice but to gently flow along in the line and make their way out of the bleeders. They will gravity bleed out nicely just by opening one bleeder at a time and removing the master cylinder cap.

First I siphon the old fluid out of the master cylinder and wipe all the junk out of the bottom of it. Fill it up with clean fluid from a brand new sealed bottle, do not use fluid from an old bottle because once it has been opened it will start attracting moisture. Its better to buy the little bottles instead and pen them one at a time of so you do not end up with a half full big bottle sitting on the shelf absorbing moisture. Go to the furthest wheel from the master cylinder on which ever brakes your working on, front or rear. Perform the brake job and when your finished open the bleeder on that wheel. Then go start on the other wheel . Eventually that first wheel will have fluid trickling out of it. Once the cylinder fills up with fluid let it drain out the same amount of fluid that the line will hold between the master cylinder and the wheel cylinder, its not much that is really tiny line. That forces any air in the line to gravity flow out. Close the bleeder and spray off any brake fluid. Don't tighten the bleeders gorilla tight or they will break off. Check your master cylinder fluid level again because if it runs out you will need to bleed the air out of the master cylinder and start all over. Go open the bleeder on the second wheel and it will fill up with fluid faster than the first because the distance is shorter. Close the bleeder and your done. It is impossible for an air bubble to get trapped in the line doing that way.

The Factory Ford Engineer that trained me suggested to tap on the disc brake calipers during the gravity bleeding because little air bubbles scan cling to the sidewalls like bubbles in a glass of soda. Tapping on the caliper caused the bubbles to brake loose and float to the top and out the bleeder.

If you open a bleeder with the master cylinder cap off and fluid does not gravity bleed out the bleeder is probably plugged with rust, That's what those little rubber caps on the bleeders are suppose to prevent that nobody puts back on. Every once in awhile you get one that just does not want to gravity bleed and you have to do the old two person system of bleeding.

If you replaced the master cylinder thats a different brake bleeding lesson. That gets bled separately first.

I had an ASE light duty and the separate heavy duty brake certifications until I let them expire when I retired. I let 17 ASE certifications, a State Smog Test and Repair license and a Class A drivers license e all expire. No way in hell I will ever work on vehicles for a living ever again!!!!!
I still have ASE in Brakes And Suspension and NY inspection license .but I know what ya mean I'm on the plus side of 50 now and working production rate ain't getting any easier. but retirement is only a dream
 

·
Registered
1968 Coupe, 302/T5
Joined
·
66 Posts
I’ve run dot 5 in my vintage military vehicles and vintage cars for about 6 years. Hard firm pedals and no issues, never regretted swapping them over and love that it doesn’t eat my paint if it leaks or spills.
 

·
Registered
Joined
·
2,211 Posts
After an engine bay refinish and all 100% all new brake system with stainless lines there was no way I'd ever put anything but DOT 5 in my car.
This was done many, many years ago and no regrets.
If your brakes are spongy with it you have done something wrong.
 

·
Registered
Joined
·
7,107 Posts
I'll add, there are moisture test kits that allow one to test the moisture content of brake fluid. I've used them and thought...OK. Put the MC cap back in place and keep on truck'n.....
 

·
Registered
Joined
·
35,852 Posts
DOT 4 for me. I like to flush my brake system every few years and, to me, running DOT 5 brake fluid would be like running some Hocus Pocus motor oil that's 5x more expensive than VR1 but doesn't provide any benefit for 99.9% of the driving I do and gets dumped well before it's "used up" anyway. On the other hand, human nature being what it is, when you DO spend 5x more on a product you're certainly NOT going to admit that it does the same job as "brand x".
 
1 - 20 of 26 Posts
Top