Mineral Oil as a brake fluid

[M/Z]

Hi all, been lurking for a while....great site. My rig, a 85 ex-mil Blazer was sold to me with mineral oil used as brake fluid. I am now experiencing comlpete brake failure. I've changed the master cylinder and bled the system, and still no brake preasure. Anyone have ideas if the mineral oil is the culprit? The PO completly flushed the system so no DOT fluid mixed with the mineral oil. Not sure as to why he decided to use mineral oil in the first place.

 

[Blazer1970]

The mineral oil probably deteriorated all of the rubber parts in the master cylinder, wheel cylinders, and calipers. You will have to pull all of it apart and replace parts as necessary. Are you sure the system is bled properly?

 

[M/Z]

That is what I was thinking might be a possibility. Looks like I will have a good multiple week-end project ahead.

 

[Eric M.]

Mineral oil?? Is this a joke ... come on, who put this guy up to this!?

If by some chance this is true, you gotta give the previous owner a call and ask him "Why?" That's just crazy .... and it's more expensive than brake fluid too!

Yo boys in Oak-Town do some crazy stuff .... but mineral oil for brake fluid?? That's a new one!

Nice to see another member from the Bay Area here, welcome


Eric M.

 

[ntsqd]

Different rubbers react to fluids in various ways. No idea how brake system rubber will react to mineral oil. You may need to replace ALL of the rubber in the system. Safest, but not cheapest, would be to just replace it all.

 

[dremu]

Hi all, been lurking for a while....great site. My rig, a 85 ex-mil Blazer was sold to me with mineral oil used as brake fluid. I am now experiencing comlpete brake failure. I've changed the master cylinder and bled the system, and still no brake preasure. Anyone have ideas if the mineral oil is the culprit? The PO completly flushed the system so no DOT fluid mixed with the mineral oil. Not sure as to why he decided to use mineral oil in the first place.

If it was a CUCV, it had silicone brake fluid originally (DOT5) which is hellishly expensive and somewhat hard to come by. Perhaps the PO decided that mineral oil was cheaper and somehow compatible.

It's still crazy. I see new brake hoses, calipers, and wheel cylinders ... and maybe a proportioning valve ... in your future.

Oh, and did you get yours from Andrew in Berzerkeley / Emeryville?

-- A

 

[diesel4me]

mineral oil???

Geesh!--I've heard of folks using Vodka instead of brake fluid in a pinch on the trail!--but mineral oil???..somebody must have worked at a drugstore!..at any rate,I doubt it did all the rubber parts in the calipers,master cyl,and wheel cylinders any justice.

.I saw a dodge dart a girl put Dextron ATF in the master cylinder once!--when I took off the cover,the gasket popped out like a jack in the box at me,and it had swelled 3 times its original size(could not put it back on!)...I had to replace everything,including the rubber brake hoses...cost her 200 bucks just for all the parts,and I charged her 100 to change everything,including blowing out and replacing a few steel lines!--a local shop wanted 300 just for labor..she wont make THAT mistake again!.

 

[2Dogs]

Hmmmm, never heard of it in vehicles but some of the new mountainbikes with full hydro brakes use mineral oil (Shimano disks for example).

Supposed to be LESS corrosive to the rubber pieces in the system.....

 

[Robert79K5]

My Massey Ferguson Backhoe uses mineral oil for the brakes. I would rather dump some DOT3 in there but im not taking any chances.

The only thing I can guess is that they specified a blend of rubber that would not deteriorate in mineral oil.... as of why they did that I have no idea...

Anyone know the specific properties of mineral oil and why it may be deemed superior?

 

[velocitiii]

before you go replacing calipers and wheel cylinders, check the prices on just new seals or "rebuild kits" sometimes its much cheaper that way. It's also not hard to do. If you have the ability to get the parts off, you can change the seals.

 

[M/Z]

Thanks for all the replies. No idea why the PO did this. Once I get the truck to my new house, I'll be replacing/rebuilding the whole system. I've done numerous brake repairs and know how to handle the work, so I'll just do it right and use DOT fluid. Any ideas on the best way to get all the oil out of the lines? I'm thinking air compressor.

 

[ntsqd]

Compressed air, followed by IPA (let it sit a bit), folllowed by air again would be my method. Might do it a couple times.

 

[M/Z]

Sorry, never heard of IPA (unless your talking about beer), please clue me in.

 

[sandawgk5]

ISOPROPYL ALCOHOL? I.E. rubbing alcohol. I think that is what it means it does wonders for degreasing and removing water and it evaporates fast once blown out.

 

[2Dogs]

Let us know what you end up replacing.

Also completely flush the system (after all the above suggestions) a few times after running awhile - maybe 1/week for 2 or 3 times....? You will have a hard time displacing ALL the mineral oil IMHO.