Brake fluid damage prevention

[TR6oldtimer]

... I've heard that DOT 3/4 will even eat "epoxy" paints, although not as quickly as some others.

I tried some Castrol GT LMA brake fluid on a test patch of PPG two part epoxy primer. Yep, at least with this primer, it took a couple hours to dissolve through.

I also put some on a test piece sprayed with PPG Concept DCU2042 Clear coat. After 4 hours, I wiped it off, and you could not tell it was ever covered with brake fluid. I will test this again over night. Hopefully I will remember to look at it.

 

[Geo Hahn]

...Not Wally-Mart, but the local discount parts stores used to carry it. They don't anymore...

I saw DOT 5 the other day at our local PepBoys. Just had it in the small bottle and of course, more expensive than the non-sillycone flavors.

I didn't pay much attention to the exact price as I just got a quart on sale from TRF not long ago.

 

[TR6oldtimer]

... I've heard that DOT 3/4 will even eat "epoxy" paints, although not as quickly as some others.

I tried some Castrol GT LMA brake fluid on a test patch of PPG two part epoxy primer. Yep, at least with this primer, it took a couple hours to dissolve through.

I also put some on a test piece sprayed with PPG Concept DCU2042 Clear coat. After 4 hours, I wiped it off, and you could not tell it was ever covered with brake fluid. I will test this again over night. Hopefully I will remember to look at it.

Twelve hours on the clear coat, no evidence of any damage to the finish.

 

[ichthos]

I am confused by all the information on brake fluid. This seems to be the topic I need to explore before painting. I want to use the brake fluid that is the least harsh to paint and yet not sacrifice brake performance/damage. Isn't the correct brake fluid for the TR6 DOT4? Are you saying that if I switch to a synthetic brake fluid with the same rating, or switch to a higher DOT rated brake fluid it will cause less damage to paint? If this is true, why would someone use anything else? Can't you damage rubber parts by using various DOT rated brake fluids? Isn't one drawback of using the silicon fluid that it can cause a spongy effect with the brakes?

Once I get the brake fluid question straight, my plans are to remove all rust by sanding/sand blasting, using epoxy primer, and painting. I am very interested to see the long term results of your experiment, Ray. Doesn't the ppg one step already have the clear coat in the paint itself? I have a small amount left over after painting the windsheild (I have a 69). If the clear coat works, would I need to spray an additional coat of clear?

Kevin

 

[TR6oldtimer]

... Ray. Doesn't the PPG one step already have the clear coat in the paint itself? I have a small amount left over after painting the windsheild (I have a 69). If the clear coat works, would I need to spray an additional coat of clear?

Kevin

Kevin,

The clear I am using is sprayed over Concept DCC***, which is a one step, acrylic urethane paint. It may or may not have the same resistance to brake fluid as the clear shows. If you have some DCC left over, mix up an ounce or two, shoot it, let it cure, and test with brake fluid.

I chose to use the DCU clear coat to give my paint job more UV protection and a deeper luster. The advantage for me is that I can use the single step for areas I do not necessarily need to clear coat (like in the trunk), and where I clear coat I can use the same fixer and other additives I used with the DCC.

Additional, I am not a great painter and tend to get some orange peel when putting down the color. What I have found is I can spray the color, then sand the orange peel out and shoot the clear (which flows better, less solids perhaps?).

My goal was to get a final finish that will not need sanding and buffing. The test I did on an old part (painted outside so some dust and bugs found it) has given me the confidence to go ahead and paint the car myself.

I'll put some more brake fluid on my test piece and let it set for a couple of days.





(Click on the images to enlarge)

 

[TR3driver]

Are you saying that if I switch to a synthetic brake fluid with the same rating, or switch to a higher DOT rated brake fluid it will cause less damage to paint?

DOT 5 silicone brake fluid will not damage any paint. It does have some other disadvantages, like being slightly harder to work with and slightly more compressible (especially at high temperatures); but other advantages as well.<div class="ubbcode-block"><div class="ubbcode-header">Quote:] If this is true, why would someone use anything else?[/QUOTE] For one thing, it's not what was recommended originally. Girling, Apple Hydraulics, and AFAIK all modern car makers are on record as saying it's not what the brakes were designed for, and they cannot/will not guarantee performance with it.
For another, it's much more expensive and difficult to find (although TRF sells a quart for about $25).<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Can't you damage rubber parts by using various DOT rated brake fluids?[/QUOTE]There is a problem with some older formulation seals, that some modern brake fluids will attack them. Not really a DOT rated issue, since the DOT standards only measure performance with one type of seal. Evidence would seem to suggest that "natural rubber" seals have not been made for a long time though, so it's unlikely you'll have a problem with new seals (and I wouldn't use NOS seals anyway). However, AFAIK, all DOT 5 silicone fluids are safe with the old natural rubber seals.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Isn't one drawback of using the silicon fluid that it can cause a spongy effect with the brakes?[/QUOTE]It does result in slightly more pedal travel, especially when the brakes get very hot. But Nelson Riedel calculated the additional travel to be less than 1/2" at a temperature where DOT3 would already have failed completely (boiled), which IMO is minimal enough to not be a problem. I've attached an article he wrote on the subject some time ago.

DOT 5 also has more of a tendency to get tiny bubbles of air in it, if you agitate it in air (like when adding to the MC). I've found that just waiting for a bit after adding to the MC is enough to prevent the problem; but some folks have gotten the aerated fluid into their systems where it's hard to get out.

I've run DOT 5 in all my Triumphs and most of my other cars for over 20 years now; and I simply love the stuff. My incidence of brake problems is far lower than it was running glycol (among other things, DOT 5 does not need to be changed every few years, and does not promote corrosion like glycol does), and when I do get leaks I just mop them up with no damage to paint or anything. Bought a new Chevy in 1980, converted it to DOT 5 at the first sign of brake trouble (1988), and it went to it's grave in 2003 still with all the original brake components and seals (except the one caliper that started to leak with the original DOT 4). Not bad for a car that CR rated one of the "ten worst US cars" /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

YMMV of course.

 

[TR3driver]

Good stuff, Ray. Thanks for taking time to experiment and letting us know the results.

 

[TR6oldtimer]

... I've heard that DOT 3/4 will even eat "epoxy" paints, although not as quickly as some others.

I tried some Castrol GT LMA brake fluid on a test patch of PPG two part epoxy primer. Yep, at least with this primer, it took a couple hours to dissolve through.

I also put some on a test piece sprayed with PPG Concept DCU2042 Clear coat. After 4 hours, I wiped it off, and you could not tell it was ever covered with brake fluid. I will test this again over night. Hopefully I will remember to look at it.

Twelve hours on the clear coat, no evidence of any damage to the finish.

Just wiped the brake fluid off my test piece, 48+ hours, no damage or evidence it was ever on the clear coat. Now I have to decide whether to use the silicone or stay with what I have always used... Probably will go silicone.