Hydralic Clutch Fluid Question

[radbrad511]

Yesterday while I was riding, the clutch lever began feeling spongy. Next time I pulled in the lever, nothing. Pulled over to find that the hose was loose at the resivoir and I had lost fluid. Was forced to add Motor Oil to continue. Planning to flush and refill Brake fluid tonight. Should I be worried that the motor oil could damage the Brake system?

Thanks Brad

 

[ace50]

Oil and fluid are very different. I'd flush entire sys with alcohol (that's what you use in a brake sys to clean) and air pressure as soon as I could.

 

[radbrad511]

Thank You!!! ::022::

 

[2daMax]

DOT4 ingredients is alcohol so it is a good solvent to wash off any motor oil. Do a paranoid flush and bleed a few times over.

 

[Don in Lodi]

Would have been safer to use water in an emergency. The rubber parts of the clutch won't do well exposed to motor oil. Hopefully you got some alcohol run through before the oil swelled up everything. Alcohol has a much lower boiling point than a lot of fluids, it will 'boil' just poured on a table top, I doubt it's a part of a high heat brake fluid. Dot 4 has a higher boiling point than Dot 3.

 

[Madhatter]

clutch system is separate from brake system ... got to wonder what caused a loose line ....

 

[EricV]

clutch system is separate from brake system ... got to wonder what caused a loose line ....

Likely he is just working with the clutch side. Since both use brake fluid, minor communication gaps in some posts.

FWIW, I used to work in the hydraulics industry. I agree, water would have been better than motor oil, in an emergency. The basic need is for a non-compressable fluid. In some applications we used grape seed oil instead of standard hydraulic oil when environmental issues required a bio compatible fluid in case of leaks or contamination, (like wetlands and saws/cutting tools). I'd probably use any high quality cooking oil as a emergency alternative for brake fluid before using a petroleum engine oil. Preferably one that is only one ingredient, rather than a mix of ingredients. Olive oil over generic cooking oil, for example.

At this point, the clutch system is thankfully smaller and less complex than the brake system, so flush it well and fix what ever was the original sin, then time will tell.

 

[2daMax]

Would have been safer to use water in an emergency. The rubber parts of the clutch won't do well exposed to motor oil. Hopefully you got some alcohol run through before the oil swelled up everything. Alcohol has a much lower boiling point than a lot of fluids, it will 'boil' just poured on a table top, I doubt it's a part of a high heat brake fluid. Dot 4 has a higher boiling point than Dot 3.

Polyethylene glycol is a main ingredient. It is a type of alcohol.

 

[Don in Lodi]

Polyethylene glycol is a main ingredient. It is a type of alcohol.

I don't find any info like that. It's soluble in methanol, a type of alcohol. But it appears to be a completely man made molecule.

 

[2daMax]

I don't find any info like that. It's soluble in methanol, a type of alcohol. But it appears to be a completely man made molecule.

https://en.m.wikipedia.org/wiki/DOT_4

Unless Wikipedia is in error.

 

[hobdayd]

Hi, sorry to say the motor oil may have severly contaminated the clutch hydraulic system and as a result the seals possibly at both ends will need changing and a complete system flush and thorough clean will be necessary. The motor oil will cause swelling of the seals which will lead to premature seal wear and possibly clutch failure. DOT 4 systems do not do well with mineral oil contamination. You might also need to change the hose.

Because of the low temperature on the clutch side water would have been the answer.

Use IPA to flush through. Change the seals and lube the master cylinder and slave cylinder bores with approved seal lube. (Sparingly).

Brake systems can generate much higher temperatures that require a fluid boiling point greater than 200 degree. C. Systems absorb water over time lowering the boiling point and as a result you can get vapour lock - a sudden gassing of the fluid resulting in a loss of brakes.

/resources/faq/dry-and-wet-boiling-points-dot-brake-fluid/

Hence, never use water in the brake side or if forced to do not generate any temperature in the calipers.

At least it wasn't on the brake side. A referb of the braking system would have been very expensive.

Sorry!

 

[hobdayd]

Oh, I forgot, all that clutch fluidthat leaked...where did it go? It will strip paint and cause corrosion and possibly damage other hoses etc. Douse the affected area with copious water to remove the clutch fluid. Sorry!

Hopefully, it's not as bad as my worst case scenario.

 

[Don in Lodi]

https://en.m.wikipedia.org/wiki/DOT_4

Unless Wikipedia is in error.

"DOT 4 is one of several designations of automotive brake fluid, denoting a particular mixture of chemicals imparting specified ranges of boiling point." That's one of the places I went. No mention of alcohol. Alcohol by definition has a very low boiling point. Glycol has a very high boiling point.

 

[2daMax]

"DOT 4 is one of several designations of automotive brake fluid, denoting a particular mixture of chemicals imparting specified ranges of boiling point." That's one of the places I went. No mention of alcohol. Alcohol by definition has a very low boiling point. Glycol has a very high boiling point.

https://global.britannica.com/science/glycol

Unless Britannica is in error. It says it belongs to the alcohol family due to the -OH molecular structure.

 

[Bigbore4]

OP
Sorry you had trouble but glad it was the clutch side. You may not have heard the last of this.

Oil is the worst choice. As others have stated brake and or clutch fluid is a chemical compound, but it is NOT petroleum based. The material selection for seals is vastly different for petroleum vs brake fluid. You can see this if you ever threw wheel cylinders or caliper seals in the petroleum based solvent in the parts washer. They swell up.

A million years ago I went to school for HD truck mechanic. When we were doing the section on "juice brakes" we actually covered this. Instructor recommended pissing in the reservoir before using oil. The colorful description has hung with me a lot of years, and I fortunately have never had to test it.

 

[WJBertrand]

In a pinch you might have been better off with the straight, undiluted antifreeze. At least antifreeze is a glycol based fluid, though of lower molecular weight. As such it would not have as much resistance to boiling as brake fluid, but that might get you by on the clutch side short term as an emergency.