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100/6 BN4 Brake fluid

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L

Leew

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I have a 58 100/6 Longbridge car and the Brake master cylinder has deteriorated and is leaking so I have bought another and intend changing it
At the same time I intend flushing the old brake fluid as I have no idea what fluid the previous owner had put in the car or how long it has been in there.
One concern is that the reservoir is a dual reservoir hosting both the brake and clutch fluid so can I change just the brake fluid, which I assume is on the outside of the reservoir, without affecting the clutch fluid which I assume is in the centre of the reservoir
Also should I be using Dot3 or Dot 4 synthetic brake fluid or mineral type brake fluid
If I decide to replace the clutch fluid, where do I find the bleed screw as there is not one on the master cylinder?
 
Didn't Longbridge cars (at least the early ones) have separate brake and clutch reservoirs, as part of the master cylinders? Maybe someone added later master cylinders and the common/shared reservoir to your car. To drain this properly, you likely want to change the fluid in both systems. For the clutch system, you will find a bleeder on the clutch slave cylinder. Use Dot 4 fluid.
 
Thanks Blueskies. It definitely has a dual reservoir
Is only DOT 4 synthetic or can mineral be DOT 4
Where is the clutch slave cylinder?
Ta
 
When i rebuilt may BJ7 hydralics about 2 years ago i decided to use silicone brake fluid, my systems were completely new so I didn't have to worry about a complete flush. but a complete flush is not hard to do. I would not try to use a conventional fluid in one reservoir and a silicone in the other reservoir, they are too close together and too easy to intermingle. But to my knowledge you can intermingle DOT 3 and DOT 4. Unless my memory has gone, conventional mineral type fluid ( DOT 3) and a synthetic (DOT 4) will mix and not cause a problem. But do not mix a silicone (DOT 5) with anything else. As an example as to what can be mixed, on my out board boat motor, where I would add oil to the gas via a separate reservoir I accidentally poured in a synthetic outboard motor oil to the reservoir while I had been using conventional for years. I had no problem and then later the boat shop confirmed that there would be no problem. I also asked the dealership if I had to use just the synthetic motor oil in my C5 Vette when I bought it. The service manager said "that's what GM recommends but if you where traveling and low on oil and could not find synthetic don't hesitate to add conventional oil if necessary.
 
The clutch slave cylinder is down on the right side of the transmission bell housing and can be accessed by removing the trans cover or from under the car. It is just about impossible to bleed in place. Do a search of this forum for examples of methods to bleed it. But typically you will dismount it and attach a hose to the bleeder.

Note that the brakes and clutch on the big Healeys are kind of hard to bleed, mostly because the master cylinders are fairly small and air get trapped in the upper bends of the lines. Patience and a lot of pumping method will do it.
 
Frankly if an owner doesn't understand fundamentals like this working on brakes is not something I'd consider within their competences.

However. Use Dot4 mineral fluid. Use it both the clutch and brake whether it's a combined reservoir or not. Do not attempt to run different fluid for clutch and brakes if it is a combined reservoir. Do not mix mineral and silicon fluids or different grades of either.
The standard single circuit brake system could not be easier to bleed start on the farthest away wheel and work closer. If you keep finding air your are doing it wrong either letting air back into the system on the return pedal stoke (close the bleed nipple when the pedal is down ) or you are pushing the pedal too hard through its stroke it must be a gentle steady push then hold. Same for the clutch.
If you don't know what you are doing find someone to help who does or take it to the shop.
 
Frankly if an owner doesn't understand fundamentals like this working on brakes is not something I'd consider within their competences.

Well when he finishes he will be , don't U Think? or at least he is headed in the right direction---:emmersed:
 
Bob_Spidell said:
DoT 4 BF is not synthetic, just a better glycol:

Castrol Dot 4 is synthetic

I asked Castrol about this and their answer was all Dot 4 is synthetic
Click to expand...
 

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Thank you chaps
I will test my current fluid now I understand the difference between Dot 3 4 5 and 5.1 and mineral but I am pretty sure I will go with 4 as where the existing fluid has leaked from the master cylinder inside the car and has removed some of the paint so it is either Dot 3 or 4 given that as I understand it 5 and 5.1 does not affect paint
I really did not want to bleed the clutch so for me being able to go with the dot 4 in the combined reservoir will be an easier job
Just bleeding the four wheels is more manageable
L
 
Keoke said:
Frankly if an owner doesn't understand fundamentals like this working on brakes is not something I'd consider within their competences.

Well when he finishes he will be , don't U Think? or at least he is headed in the right direction---:emmersed:
Click to expand...

OK I take your point and the correction over synthetic/mineral . However I still find it surprising that folks consider working on safety critical systems with what looks like a very limited level of basic understanding or skill. That's why I suggested getting help to do it as the first option. Once the knowledge and skill is established no reason not to DIY next time?
 
Back in 1970 my first car was a Morris Minor 1000. One day the brakes disappeared on me coming over Putney Bridge in London. It was a bit of a shock, but I learnt very quickly and drove the car for two days just on gears and the handbrake until my dad could fix it.
I'm a lot less brave nowadays, and the traffic in London is a lot heavier, but I'm determined to make sure that I get this brake job done well as I drive my Healey a lot quicker than the Moggy.......
 
I have noted that on a couple of forums I look at the words silicon & synthetic (with regard to brake fluid) appear to have become synonymous with some folk...which causes a lot of confusion!
I'm not too sure of the widom of labeling the later glycol fluid 5.1 either.

Danny
 
DOT 5.1 I have on my car, is completely compatible with DOT 3 and 4, is a evolution of glicol brake fluid, with more working warm capacity, used on racing cars
adding DOT 4 to 5.1 reduce the resistance to the high temperature of the brakes, no others counter-indications, fluid bases are the same
however DOT 4 is the good choice for our cars -is easy to find and economic - long descents must be entrust to motor brake
 
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