Gearbox oil in brake reservoir - WTF???

gobsmax · Postby **gobsmax** » Fri Oct 01, 2010 6:44 pm

To cut a long story short (it was dark, I was tired, it was late), I accidental filled my friends NA6 brake reservoir with gearbox oil.

Can anyone predict any foreseeable problems?

She has been driving around since, and hasn't had any problems. Fingers crossed

Steampunk · Postby **Steampunk** » Fri Oct 01, 2010 7:33 pm

- brake fluid is designed to withstand temperatures constantly exceeding 200 deg Celcius, even in normal daily driving, gearbox oil will rarely see over 120 deg C, and will break down.
- brake fluid will not perish the brake lines, oil will perish brake lines.
- brake fluid has special properties to withstand compressive forces, gearbox oil does not.
- brake fluid is ALOT less viscous and is ALOT more pure, gearbox oil will clog up.

That's all that I can think of, I'm sure there are a dozen more reasons.

Flush it THOROUGHLY. I'd say pump at least 2 litres cheap brake fluid to clean the system, then put in good stuff.

Immediately.

hamx5ter · Postby **hamx5ter** » Sat Oct 02, 2010 9:29 am

^+1

honestly gobsmax... you should've at least told her not to drive it around ... no brakes??? :evil:

93_Clubman · Postby **93_Clubman** » Sat Oct 02, 2010 10:51 am

^+2

Then seek specialist advice as flushing/ replacement may need to be done again.

RG.net · Postby **RG.net** » Sun Oct 03, 2010 2:33 am

I did that on my old micra, I ended up needing to replace the brake master cylinder and flush the system out alot!

Get that oil out of there ASAP!

russs · Postby **russs** » Sun Oct 03, 2010 11:03 am

See if the oil sits above the brake fluid... pour a bit of both into a glass to check. If so, slowly top up the reservoir with brake fluid which should cause the gear oil to overflow. This would be better than draining it down through the entire system. Even better, get a pump and syphon it out.

deviant · Postby **deviant** » Mon Oct 04, 2010 10:41 am

Did you just top it up or did you bleed the brakes and use the gear oil?

Even if it has just been topped up I suspect it will have made it's way in to the system as the car has been dríven. How long has she been driving the car?

First things first...act NOW and get the car off the road!!!

bruce · Postby **bruce** » Mon Oct 04, 2010 11:16 am

As said, get the car off the road immediately.

Gearbox oil is just a narrow/single grade oil for lubrication. Brake fluid is completely different (I don't think it's an oil) and will strip paint.

Guran · Postby **Guran** » Mon Oct 04, 2010 4:17 pm

bruce wrote:As said, get the car off the road immediately.

Gearbox oil is just a narrow/single grade oil for lubrication. Brake fluid is completely different (I don't think it's an oil) and will strip paint.

Bruce is 99.9% correct. Most brake fluids are glycol ester based or silicone based (DOT5), and neither are "oils". The only exception was pioneered in the Citroen DS which had a special mineral oil called liquide hydraulique minéral (LHM) for the hydraulic system, including the brakes.