A few months back I replaced my master cylinder. I used dot 3 brake fluid as I thought it was what was in the car prior to replacing the MC.

Anyway, I was looking at receipts from the prior owner and there were receipts for dot 5 fluid.

I have no problem flushing the system and doing it with denatured alcohol as recommended but I don't want to do it unless I'm sure the car can use dot 5.

How do I know if my car is capable of using dot 5 fluid?

Ed

 

My '62 has had dot 5 since '86. As a matter of fact everything I have as a collector vehicle has dot 5. I would not be afraid of it If I owned you car,for me, it would have dot 5. But, to cover my tail, it is up to you to decide.

 

Can u put dot 5 in a stock setup or do you have to make any changes? I just sent a note to the last owner asking him if he had dot 5. If the car is capable of dot 5 I will flush it with denatured alcohol and put it back in.

Ed

 

dot 5 brake fluid

 

Works just fine, no changes at all. It isn't like an R-12 to R-134 A/C upgrade.

 

Thanks. After reading about it more, it might be best to just leave it alone as some suggest that this alchohol flush causes issues.

 

Well, only if you determine the car had DOT 3 before you added more DOT 3. If it had DOT 5 and you put DOT 3 in with it, expect problems.

 

I'm worried about creating bigger ones. When I put the new fluid in I used a power bleeder to flush it out.

If it was dot 5, what would u do? I just read that rinsing with alcohol as mentioned numerous times is not a good thing.

Ed

 

At a minimum I'd significantly bleed the brakes, enough to run at least a pint or two of fluid all the way through the system.

I also happen to be one who has successfully flushed with Alcohol when converting to DOT 5, with no issues. Others have alternate positions.

My 65, prior to my ownership, had DOT 3 and DOT 5 mixed by mistake. After the car sat for a while I helped my friend (owned the car at the time) pull the brake calipers and we found them full of a funky gel, which we suspect but do not know is the result of mixing the fluids.

 

Thanks. So I'll confirm the dot 5 with the prior owner. Given the receipts my guess is it was dot 5.

So if it was, which is the best option:

1) leave it alone
2) flush it more with dot 3
3) flush it with dot 5
4) flush it with denatured alchohol and then dot 5

Given your experience my guess is your vote is #4. Just trying to understand which would likely result in the least issues.

Ed

 

Anything but #1 will make someone on the forum happy. I'd do 4, because before I ever did a fluid conversion years and years ago, I read a lot of technical auto repair articles that indicated a need to flush with alcohol first. I have no reason not to trust those sources. Then I like DOT 5 in the collector cars because it doesn't eat paint, and now I've seen first hand how perfect a wheel cylinder looks after 25 years of DOT 5 use.

 

Thanks. What type of alchohol did you use?

 

Denatured alcohol from the pharmacy. I flushed with it, let the system air dry over night, and then filled and bled the system.

 

Thanks Jeff. I'll give it a shot. So just to be clear, you used the alchohol and ran the system completely dry then lit it sit over night to make sure whatever was left evaporated?

 

Both of my 62s have dot-5 with no problems. Flushed with alcohol and rebuilt all wheel cylinders and master cylinder.

 

Yes, I left the master cylinder cap off and all the bleeders open. I didn't know enough (still don't) to know what would happen if brake fluid and liquid alcohol mixed.

BTW, this was in a 1972 Skylark, which I restored in 1997. For various reasons (other car projects) this car has been driven less than 15 miles in the last 8 or 9 years. But I've driven it several times this year and the brakes are still just fine.

My restored my 62 in 1981-1983 and used DOT 5 at that time. A few years ago I replaced my wheel cylinders as part of a prophylactic measure before putting the car out on the road for the first time in years. However when I disassembled all 4 of the wheel cylinders I found them to be in brand new condition.

 

Jeff:

Assumed you used pure alcohol or at least the 91+ percent denatured alcohol to minimize water??

Since Ed just had this issue, he might be okay to just drain the DOT 3 and power flush everything with DOT 5 without the alcohol flush. There should be no "gunk" build-up in the brake system at this point yet.

He could alsways come back 3 months (or so) later and do a second DOT 5 flush and fill. That would do it.

Larry

 

I believe the sludge is formed when the Dot 5, Dot 3 and any water in the system comes together in a mixture.

Most any Dot 3 sytem will have some/a lot of water in it. If the hydraulic part of the brake system has been serviced and cleaned recently, I'd think a simple compressed air flush and pressure bleed with the Dot 5 would be sufficient. On the other hand, if that hydraulic system condition is unknown, I'd take it apart, clean it, blow the lines, put it back together and then add the Dot 5.

I don't have an opinion on the alcohol.

 

I don't recall, it's been 14 years.

 

I would concur...

When I first began using (converting to) Dot-5 brake fluid many years ago, I used isopropyl alcohol to flush the Dot-3 from the system. I would blow out the lines (with low pressure air to keep from damaging any seals) and then fill with Dot-5, bleeding the system generously. I never had an issue with any of these vehicles.

Later, realizing the difficulty of removing all of the old fluid from a system in which the bleeders are typically at the top of a wheel cylinder or caliper anyway, I stopped using this method and began to just replace calipers or wheel cylinders with new ones or to carefully disassemble and clean them to be sure and remove as much of the old fluid as possible. This also makes it much easier to blow out the lines of old fluid and flush them with Dot-5.

The DoD converted much of it's rolling stock (with hydraulic brakes) many years ago to Dot-5 fluid to reduce maintenance and increase readiness. At this time they also created a small (~1" X 2") Warning label to be affixed near the brake reservoirs that warned to use Dot-5 fluid only. I was able to get a hold of a few of these and whenever I switched a vehicle over to Dot-5, placed one in the vicinity of the reservoir where it could not be missed. If you have a friend that works in DoD vehicle maintenance, they may still have these available. It can certainly remove some of the guess work from future maintenance.

Good luck... GUSTO