Hi, all…
The Archives on this topic are quite old…and I need to flush out my systems and put in fresh fluids.
Can you tell me what you would recommend for Brake and Clutch fluids ?
I have a '65 XKE 4.2L OTS. Completing my engine refresh now…and getting all the ancillary stuff cleaned-up / refurbished as I go along.
As always, appreciate your help !
Harold
I use a high-quality DOT4 fluid in my cars, such as ATE. I will not let DOT5 silicone anywhere near my cars, having had too many ‘interesting’ braking moments in car ours back in my Healey days. Change every two years religiously.
If you did decide to fill with silicone fluid, I would still change it regularly as silicone fluid is non-hygroscopic, which means it doesn’t take in water. This means any water condensing in the system, through reservoir tanks etc., will form a separate layer which will give a ring of corrosion where that layer contacts the air. How do I know this?
Unless things have changed, switching between the two (silicone and non-s) will require replacement of all seals etc. as the fluids will cause different expansion of these components and are not compatible.
I would not use cheaper non-branded hydraulic fluid in an expensively-rebuilt braking or clutch system. I might use it to flush through, though, if there’s a lot of old black stuff in there.
Or you could go to DoT5.1 not silicon just a higher temp.
I wouldn’t presume to recommend any course of action as this topic is a minefield, but I will recount what I have done and the results I’ve seen.
After replacing the three flexible lines on the E Type I poured in DOT5 and bled the system until the fluid coming out was steadily purple.
That was six years and 37,000 miles ago. Over that time I have serviced some brake parts but have not had any problems I would attribute to the use of DOT5.
This is the same approach I used on two TRs – in those cases I have had DOT5 in use for 20 years without a problem.
Again, I am not recommending this, just saying what worked for me on three British cars.
Many here use, and are quite happy with, Castrol LMA, a DOT 4 fluid.
Just be thankful K&N doesn’t market a brake fluid. 
I have used Castrol for 20 years. For the longest time it was LMA but they discontinued that and went to a full synthetic several years back. I was nervous about it but it’s been changed a couple times since then and there have been no issues…
From what I understand, the current Castrol Dot 4 is pretty much the same stuff as the Castrol LMA they used to sell. LMA was also synthetic. Like you, I searched for LMA in stores for a while, but got over it. The name change seems to have been more of a marketing thing than anything. That said, if it says DOT4 on the bottle and you change it out every 2 years (REALLY IMPORTANT), it should be fine. Last time I replaced the BF in my Series 2, I couldn’t find any Castrol at the local FLAPS, so I used Prestone DOT 4. It’s been fine.
I haven’t seen Castrol on the shelves in any store for quite a while. I’ve just order the big bottle off Amazon the last several times.
That explains why I couldn’t find it when I did the brakes. I bought NAPA Heavy Duty DOT 4 last time. I’m about due to push all the old fluid out with new. I’ve got a bottle of the Prestone synthetic Dot 4 downstairs. I guess I just buy a quart of that.
A tip: use a 50ml or similar disposable syringe and a bit of plastic pipe that fits the end to suck all you can out of the fluid reservoirs first, without opening the bleed nipples. Get them as clean and dry as possible inside - you might be able to get paper towels in to help. Then fill with new fluid and bleed as normal. This way you are less likely to get old fluid contaminating the new.
Good tip Roger, thanks.
Helpful advice ! Thank you all.
HJK
I should have said - keep the bleed nipples closed until you have refilled the reservoir with fresh fluid. It won’t be able to mix with the old fluid still in the pipework/cylinders, but you can tell when to stop bleeding as clean fluid will appear at the jamjar. This method avoids the introduction of air pockets, as could happen if you drain the system completely before adding fresh fluid.
I’m researching this topic and came across this thread. It has been helpful. As an FYI, I found LMA being sold at Summit Racing.
It’s also on Amazon with free shipping. If you buy a case of 12 it’s about $4.50. Really not that many bottles when it can be used on most cars today, not just our Jags
