Question on oil selection for new master & slave

[Mike]

I am going to replace the master and slave cylinder this week. The clutch doesn't want to rebound. The cylinders are the originals and I decided to get the hydraulics right. The master and slave are new, with that being said,what oil should I select? Also, a friend of my suggested pushing kerosine through the system to clean with the old cylinders before I replace, is this wise? Any additional suggestions on redoing the hydraulics would be much appreciated. This is my first go at it!

Thanks for your input. I am eager to get the Bug Eye out on the road (the title finally came in) but the hydraulics took a dump.

Mike

 

[jvandyke]

I still use DOT 3 brake fluid. I wouldn't push anything through except brake fluid, why risk new parts with chemical baths? When you bleed, bleed a lot (and you will) and you'll flush it out plenty good I'd bet. Bleed until the fluid coming out is as clear as the stuff you're putting in the MC as you bleed. I put a speed bleeder nipple on the clutch slave last time around, that made it easier, I bought two and I was going to use the second on the end of the bleeder hose a valve but I can't find it back! Ugh.

 

[nomad]

I agree with jv on system flush but even though the rubber seals you are getting are supposedly now immune to dot 3 I would use dot 4 personally. If you are working on the system alcohol is the accepted solvent. Unless you were completely evacuating the system and replacing everything new the best flush would be brake fluid. I guess it comes from systems that I remember from the 60's but I cringe at the sound of dot 3. I remember it as being blamed at least for many complete british car brake overhauls. Hopefully you have a manual that should tell you the spec's
Best regard's. KA

 

[spritenut]

I agree with nomad,
Dot 4 (Castrol LMA) and only alcohol as a flushing agent.

 

[jvandyke]

I thought DOT 3 and 4 were similar but for 4 having higher boiling point?, I just avoid DOT5 and beyond in anything not intended for it until convinced otherwise.
5 may not eat your paint if you spill it but it could wreck old seals and not compress as well. Brake Fluids

 

[JPSmit]

Whatever you choose, I'd suggest you use whatever you were using or something compatible. there are five rubber hoses plus the seals in the brakes themselves. unless you want to rebuild the whole system (as opposed to flushing it) stick with what you had.

 

[nomad]

Can't be more vindicated than having spritenuts support! Tnx. As to dot 5 I invite everyone to remember high school physics:: How compressible is a liquid? If it compresses it can't be enough to be noticeable in a brake system. I've had it in a MGB since the mid seventies and no problems. That alone has convinced me. I seem to remember that a lot of the bad press it has gotten has come from brake part manufacture's that have a vested interest in selling brake part's!!!
Just my .02 worth. Tnx,KA

 

[jvandyke]

Yeah, I don't know. But sticking with something compatible with what's in there and has worked fine for 40+ years seems like a safe route to me.

 

[WA1KWA]

Had DOT5 in my MGB since 1984, my BMW since 1990 both as regular seasonal drivers.

No problems at all.

Colin

 

[nomad]

Can't fault sticking with what has worked,jv. I hate to be reminded but I've had dot 5 in the B for over 30 years now. It does'nt absorb water like other fluids. Anyway I'm probably a little overbearing on my praise for 5. I apologise if I have stepped on toes. For Mike he will want to use dot 4 (Castrol LMA) and bleed it till it comes out clear
plus maybe a little more. Dot 5 is'nt compatible with other fluids.
Best regards KA

 

[sparkydave]

Just a tip, don't put ANYTHING petroleum based through your brake lines like kerosene or oil. It will destroy your seals!

 

[John Moore]

Just a tip, don't put ANYTHING petroleum based through your brake lines like kerosene or oil. It will destroy your seals!

I used alcohol to blow them out.

FWIW I used DOT 5 in my B and have been happy. Doesn't ruin the paint too.

 

[sparkydave]

Alcohol is OK, just nothing oil based. Agreed on the DOT 5, I put it in my Midget and no problems.

 

[jvandyke]

Can't fault sticking with what has worked,jv. I hate to be reminded but I've had dot 5 in the B for over 30 years now...snip

Has it been around that long? I don't remember when I got put off the DOT 5 stuff but I did and, old dog new trick I guess. I've never rebuilt an entire brake system at once which is probably the only time I'd dare switch to an incompatible fluid.
I've not been playing with old cars very long either so I haven't had one long enough to go through brakes twice. Seems like on both my old cars, by the time I've had the brakes where I wanted them, I'd run through gallons of DOT 4!