mx5cartalk.com

Does anyone have experience, good or bad, with Motul DOT 5.1?

My clutch master cylinder failed last night. It's not something I really needed before Natmeet, but at least it's a lot better than it happening at Natmeet.

What really puzzles me is the clutch fluid. It was dark grey, almost black, with a sooty sort of look about it.

I changed the fluid only 3 months ago using Motul DOT 5.1. Motul fluid is almost clear when new. I assume the fluid has dissolved the rubbers in the clutch system. I'll replace the master and slave tonight, no problems.

What really worries me is what might be happening with the brake system. The fluid in the brake reservoir is still clear but it leaves me wondering if the Motul is attacking the rubbers there as well.

Alot of guys I know has blackish fluid in the reservoir.
When I bought my car with 85,000km, it had a very dark inky coloured fluid and the previous owner did a fluid change not more than a couple 100km's before.

I know that doesn't help much, but at least you know you are not the only one.

My clutch is fine by the way and she's done just over 134,000km

k, I think it's solved. Sorry about the drama. Spoke to David at Mania. Blackening of the fluid is a sign of failing rubbers, not a sign of fluid attacking the rubbers.

They haven't had problems with Motul over the 3 years they've been using it.

Hmmm... failing rubber will also mean leakage, sooner or later. Not a single drop has been lost on mine.

I think it may be something else. Perhaps the heat turning the liquid black?

Why the more expensive DOT 5.1 in a clutch... did the DOT 3 in the clutch ever boil?

The master lid is not 100% air tight it has a tiny hole on the top of the lid some say thats why the fluid can get dirty after only a few months. (Its odd its not 100% air tight becuase I thought the fluid was hydroscopic)

Later if you get the master and slave rebuilt ask the shop for rubber seals that can withstand 5.1

manga_blue wrote:k, I think it's solved. Sorry about the drama. Spoke to David at Mania. Blackening of the fluid is a sign of failing rubbers, not a sign of fluid attacking the rubbers.

They haven't had problems with Motul over the 3 years they've been using it.

That's right...look in the fluid closely and you'll see a fine black powder floating in suspension. But mine was like that for years.

wun911 wrote:Why the more expensive DOT 5.1 in a clutch... did the DOT 3 in the clutch ever boil?

5.1 in the clutch because I was changing the brake fluid at the same time and it was all I had. Mind you, if you look at the route the clutch piping takes ....

I've heard that different brake fluids shouldn't be mixed. Also you should be using what the manufacturer recommends

changed my clutch on the weekend phil, and yes the fluid was black.

i'm using the same motul brake fluid as you, no dramas so far with the brakes. not using it in the clutch tho, just using whatever it was that fastfreddy had lying around in his garage

1red5 wrote:Alot of guys I know has blackish fluid in the reservoir.
When I bought my car with 85,000km, it had a very dark inky coloured fluid and the previous owner did a fluid change not more than a couple 100km's before.

maybe the fluid is black

cause the fluid that was in mine was very dark green was replaced when i got the car

well from memory, when I got it, it was VERY dark green, matching the same dark green in the brake reservoir, so they used the same fluid.
But over time, the clutch reservoir became a much darker colour.