jwillman

The WSM manuals specifes DOT 4 for brake fluid. The owners manual for the 1979 specifies DOT 3. I have a 5 speed. Do I use DOT 3 or 4? Does it really make a difference?

Thanks

dr bob

The difference is the boiling point, with DOT4 having a higher number. Otherwise they work the same. Since DOT4 is readily available, no reason not to use it. For street cars that see spirited driving, an annual change with Castrol LMA fluid is easy, inexpensive, and the fluid is available at almost any parts place. Some folks like the slightly more expensive but harder to find locally ATE Super Blue or Gold fluids, claiming better performance in harder driving. For my road car I couldn't tell the difference honestly. I think the top of the heap for non-synthetic fluids is a Motul product right now. Brake fluid choice is somewhere just south of motor oil in the multiple-opinions race I think. Mine is bigger, mine is better, mine lasts longer, etc. Reality is that, with changes every year or maybe two, any good DOT4 fluid will do just fine in a street-only car. I use the GTX LMA because I can get it easily in a big bottle.

Mrmerlin

get ATE ( Ahh..TA) super blue racing fluid or ATE gold brake fluid,
if you know what kind of fluid you have been using then stay with it ,
as swapping to different fluid usually can cause seal swell due to different formulations .
ATE makes the brakes and so it makes it a no brainer to use their fluid

SeanR

Ditto above. We use ATE blue/gold in all of them. Switching between the two at changes so you know you've bled everything good.

dr bob

Amen! Good or bad, it took the full two liters of the almost-clear Castrol LMA to get all the blue-tinted ATE fluid flushed out last time I did it. Now I know that flushing with two full 1-liter bottles in the power flush/bleeder is adequate.

For folks playing along at home, annual flushing of the brake fluid hydraulics is one of the least-costly maintenance tasks you can do, and it pays off in spades. Keeping the moisture out of the fluid means no rust/corrosion in the system, so no crud-related hydraulic failures. Porsche recommends no more than two years between fluid replacements, and most competition groups like SCCA require no more than six months between changes. The time between changes is not mileage-related, so even if your garage queen only gets out a few times in the year, new fluid is still a good idea. This is increasingly important if you live in a humid climate.

blown 87

Changing brake fluid every other year is over rated, just like changing oil every three thousand miles is, I mean what can happen, my brakes still work, my engine still runs.

Maleficio

You're taking pictures of vomit?

Mrmerlin

thats what happens when different fluid s are mixed and then sit for a few years in a dark container

dr bob

That's what happens when you use semi-metallic brake fluid.

blown 87

That was what was in a recent brake job I did.
My guess is that it had never been changed, just topped off with DOT3 which is what it called for.
With the huge tags it had that said use only DOT3 you would really have to be a dummy to put the wrong stuff in there.

But I have seen it done before, in Jags mostly, and that gets $$$$ in a hurry.

The reason I do not think this had mineral oil in it is that the seals and rubber parts were not swelled up like they get when the wrong type get put in.

Regardless it is ugly and extra chunky.

blown 87

Does any body use the DOT 5.1 fluid?

Hayk928

I purchased right now 5.1 Pentosin (Porsche OEM) to service my PSD and I can't see any reason why not using it for the next brake-service. 5.1 is compatible with DOT 3/4.

Best

Marc

Vilhuer

DOT 3 was ok at the time when owners manual was printed. Later when WSM page was done DOT 4 was easily available and thus it's specified. Both will work, 4 is just better.

Fogey1

eewwww What part is that precisely? Did that stuff come out of the bleed ports? Or the reservoir?

blown 87

That is the bottom part of the brake accumulators filled with old DOT3 fluid, there are two of them on the older Rolls Royce's, the newer ones have spheres that you replace every 15,000 miles.

Most owners with older RR's are driving around with out a clue to how dangerous the car is with a brake light on.
They should hold pressure for at least 12 hours and 30 pumps.

We almost were not able to get them apart, even the local Bentley dealer does not service them, plus they have to be charged with nitrogen to 1300-1500 PSI.

This fluid was all through the system.
Getting it out is not a problem with a working 2,500 PSI pump though, just crack any fitting and it will come out.

Every thing seems to hand fitted and most things are rebuildable, even the brake pressure switches, which almost always need to be built as are the pressure valves.

They have a strange set up with two different circuits for the brakes, system one and two, two calipers at each wheel on the front, one for each system on each side.
The rears only have one caliper per side, but it is split into two sections.

Each system has its own engine driven pump, thus the need for working accumulators, with out them working, if the engine stops you have no brakes, the brake pedal is just a place to rest your feet till you stop by what ever means.

Feel free to ask questions if that did not explain it well.