DOT 5 going away?

[tahoe healey]

At the Rendezvous last month one of the tech speakers indicated that DOT 5 would be going away sighting that the military was switching away from it. Thus the major source of revenue. He stated other reason which I so not recall. There was some issues about oxygen bubbles when shaken or heated. If this is in fact the case, STOCK UP. Apparently, if you change back, you need to change everything because you can never get rid of all silicon. Others who were at the meeting can jump in and fill in the things I didn't get. I wasn't listening too much since I use DOT 4. Don't shoot the messenger.

 

[BenZ]

My wife's Harley V-ROD owner's manual specifies DOT 5 for the brakes, clutch, etc. Not sure if that's the factory fluid for a Harley's or not. I don't know anything about what you're saying, but expect HD will keep the supply for at least a while.

 

[Keoke]

Yes I think you are right BenZ. Similarly, most current high performance race cars also use it. The Military application was to meet low temperature requirements and to avert the hygroscopic effects of most alcohol based products.---Fwiw--Keoke

 

[big6]

Early in my career I was a field service representative for Harley Davidson Motor Company. In 1977 if memory is correct, a safety recall was issued by Harley Davidson for the Kelsey-Hays rear brake used on FLH and FXE models. The problem was as the rear brake being applied the heat from the rotor transferred from the rotor to the pad and to the caliper piston. The heat caused expansion of the hot fluid would cause the caliper piston to push out as if applying the brake. The result was brake drag and either locked-up the rear wheel or in severe conditions the dot 3 fluid would leak out of the brake caliper hitting the hot caliper, pad, and rotor and exceeding the dot3 flash point would catch fire.

The safety recall required removal of dot 3 fluid, cleaning the brake lines with denatured alcohol, replacing the brake caliper “O” ring, replacing the master cylinder piston assembly and installing dot 5 fluid. The change of brake fluid is because the flash point for dot 5 is much higher than dot 3. The first issue experienced was the dealership repair technicians did not realize that the dot 5 fluid requires setting on the shelf after shipment allowing suspended air to rise to the top as the result of being shaken during shipment. If the dot 5 fluid is not allowed to stabilize the brake would feel spongy because of the air suspended in the fluid. If dot 5 brake fluid is installed with suspended air in the fluid the mechanic would never get the brake to bleed and work properly. Using improper dot5 handling procedures resulted in false rumors about not being able to get a firm brake pedal and poor brake performance after the completing the safety recall.

Harley Davidson no longer uses this type of Kelsey-Hays brakes but with the experiences in the seventies it would be surprising if dot 3 was ever used again. If dot 5 were no longer available I would expect Harley Davidson R & D would definitely test using a substitute fluid with a flash point much higher than dot 3.

 

[Randy Forbes]

An overview of brake fluid: https://www.afcoracing.com/tech_pages/fluid.shtml

Personally, I purge/refill my brake fluid about once a year (all cars, not just the Healey); never longer than two (2) years, and I don't like silicone based fluid.

I'm still using Castrol GT/LMA in the Healey, but I'm tempted to try ATE Amber the next time I purge the system, as I always have fresh cans from all the customer BMWs I work on; we'll see if I do that...

 

[Michael Oritt]

ATE makes fluid in both clear (amber) and blue which is great when you want to completely flush out the system.

 

[Randy Forbes]

ATE makes fluid in both clear (amber) and blue which is great when you want to completely flush out the system.

I agree, however, the blue fluid stains the BMW reservoirs, so I don't use it on customer's cars, unless the customer supplied it (as in the case of the most recent ///M Coupe I've worked on).

Generally, by the time someone has me purge their brake fluid, there's little doubt when the fresh stuff starts flowing out; significant difference between the old black sludge and the fresh amber fluid :wink:

Have you been using the ATE fluid in your British cars without any trouble from the rubber seals? Historically, it seemed that only the Castrol GT/LMA guaranteed to not damage the seals.

 

[Michael Oritt]

"Have you been using the ATE fluid in your British cars without any trouble from the rubber seals? Historically, it seemed that only the Castrol GT/LMA guaranteed to not damage the seals"
----------------------------
Randy--

I still use LMA in the Healeys because I do not change the fluid in them that often--perhaps annually. On the Elva I change every few races and have used the ATE for a few years with no problems. Of course very little on that car is original--I think the wheel cylinders are Lockheed but the masters (twin) and clutch are Tilton so I am not sure that answers your question fully.

 

[why]

At the risk of starting this one up again, I never change brake fluid, except when I rebuild a wheel cylinder or caliper. '67 Etype had an ooze in rear caliper after owning for 20 years (who knows how long been in there). '95 Caterham after 15 years not a drop of fluid lost then a rear wheel cylinder oozed and was replaced. '65 Healey had a front caliper start to ooze after 17 years (again who knows how long been in). Pedal firm in all cars, Healey caliper just mild tarnish, no pitting, so rebuilt, Caterham a weird ridge in wheel cylinder bore but little tarnish so replaced wheel cylinder. Etype also just mild tarnish, but thought it would be cool so put in the all stainless calipers.
Early in professional career heard saying "a difference that makes no difference is no difference." I understand all the theoretical reaons why it should be replaced but they do contain anticorrosion compounds as I expect my only slightly discolored bores after 15-20 years supports. I know I am not alone with same fluid for twenty years and everything works just fine. '02 Outback 70,000mi not a drop fluid replaced, brakes great; '06STi not a drop replaced etc. RACING WHOLE DIFFERENT STORY