Oil mixing with brake fluid question

[scott37300]

I've read many times that NO oil should be mixed with brake fluid, don't use same funnel. Obviously you don't want anything mixing with your brake fluid but just curious for my own knowledge why oil is a big no no?

Also, I just bought a mityvac 6835 to flush my brake fluid and in the manual it says you can use some silcone grease around the bleeder screw threads to prevent air from getting sucked in around the threads. Is it OK to use silicone grease here since there is a chance of contaminating the brake fluid? Also what would be a good silicone grease for this? Is antiseize a silicone grease?

Thanks for sharing all your knowledge everyone!

 

[chubbs1]

Just imagine oil on your brakes, nuff said. Antisieze is not silicone, it is a graphite base grease. I would just go to my local auto parts store and get the silicone grease. Maybe someone can chime in differently but if it calls for silicone give it silicone...lol Oh And don't worry about the bleeder threads just leave them.

 

[Kestas]

Any petroleum product in the brake fluid will wreak havoc with the system. The elastomers used with brake fluid are incompatible with petroleum products.

I had the unfortunate experience of adding mineral spirits instead of brake fluid when servicing my brakes. The mineral spirits swelled up the elastomers and made a holy mess. My brakes locked up and I had to flush the system, and rebuild all calipers, brake cylinders, and master cylinder.

Silicone is okay to use wherever appropriate. I now butter all wheel cylinder piston surfaces with silicone before installing new calipers. This keeps the corrosive environment out of critical areas. It is inert and will not mix with brake fluid. You should find silicone grease at any auto supply house. It's sometimes called dielectric grease. Make sure you read the tube contents carefully.

Antisieze is not silicone based.

 

[Loobed]

Originally Posted By: Kestas
I had the unfortunate experience of adding mineral spirits instead of brake fluid when servicing my brakes. The mineral spirits swelled up the elastomers and made a holy mess. My brakes locked up and I had to flush the system, and rebuild all calipers, brake cylinders, and master cylinder.

Been there, done that. I was doing a brake service and decided to disassemble my calipers to clean them out. I put everything into a large coffee can and filled it with solvent (kerosene or mineral spirits?). After about an hour I pulled everything out and the seals had swelled to twice there normal size. I bought new seals and put everything back together. I kept the old seals to see what they would do. After about 3 months, they shrunk back to normal size.

 

[scott37300]

I have some dielectric grease so will use that. I just don't want air getting sucked in around the threads, I realise it won't do any harm but will be nice to see a solid stream of new brake fluid with no air.

 

[mechtech2]

Who cares if the bleeders leak while applying vacuum or pressure bleeding?
The system is purged and bled just fine.
So what if there is a tiny amount of air going by the threads out into the dump reservoir?

 

[unDummy]

It helps to troubleshoot a chronic pedal. If you see air in the bleed line, and you know its not from the threads, you definitely know you have to keep bleeding, or located the source of the air.

 

[Kestas]

The seal should be the bottom of the screw, and not the threads. There are only two reasons to treat the threads... to keep them from corroding and seizing, or to provide a seal during vacuum bleeding.

 

[unDummy]

Screw is backed off to bleed. So, your thread then becomes the seal.

 

[scott37300]

Originally Posted By: Kestas
The seal should be the bottom of the screw, and not the threads. There are only two reasons to treat the threads... to keep them from corroding and seizing, or to provide a seal during vacuum bleeding.


This was my question, when bleeding with a mityvac 6835.

I will use some dielectric grease, easier for me to tell that there is no air in the lines if I don't have to worry about air getting in around the threads while bleeding.

 

[meGrimlock]

What about cooking oil? My dad tried to help drain the brake reservoir by using a siphon used for cooking oil. Stupid idea, he ended up splashing brake fluid all over and I'm know there is grease from the cooking oil in the reservoir

 

[meGrimlock]

Well i flushed as much as i could, almost a 32oz bottle worth of brake fluid. Hoping that's enough to rid the system of cooking oil

 

[GMorg]

The issue is with the seals, not the brake fluid. I have no idea what vegetable oil will do to the seals, but I would think that fluid flush would take care of your problem.