• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Brake versus clutch fluid

Share this page

tr6web

tr6web

Jedi Trainee
Country flag
Offline
Is there a difference between these two? I've just rebuilt both master cylinders and now I'm getting ready to put them back in the car (72' TR6). For the brakes, I'm just going to stick with DOT 3 which the car has had forever. Also, should I put something like Teflon tape on the connectors? Any help would be appreciated.
 
So far as I know there is no difference, use the same dot approved fluid in both master cylinders. Regarding the teflon tape on the pipe fittings, that is a bad idea. The fittings are flared to seal properly and do not rely upon the threads to accomplish this.
 
Same fluid for both... in fact, on many cars (including TR3) it's the same reservoir for both.

I would not use teflon on the connections as there is a risk of getting a bit of the tape into the system. In any case, I don't think it is really the threads that make the seal in the connection.

I do use a narrow strip of teflon on the bleed screws but not all agree that is a good idea. Reason I do this is to keep air from being drawn in around the threads when I do the bleeding.
 
That's exactly what I needed to know. I've always used brake fluid for the clutch MC, but just wanted to check. I also read about the teflon tape for the bleeders. I'll use the same for both.

Another question...even though both systems have used DOT 3, since I've rebuilt them, can I change it to DOT 5? I suspect there may be remnants of DOT 3 in the brake lines, but if I add DOT 5 and then bleed, would that be ok?
 
Geo is right about the threads not having anything to do with sealing the connections. The connections are sealed by the pressure between the flanges and the nipples, the threaded fittings only provide the pressure.
 
[ QUOTE ]

Another question...even though both systems have used DOT 3, since I've rebuilt them, can I change it to DOT 5? I suspect there may be remnants of DOT 3 in the brake lines, but if I add DOT 5 and then bleed, would that be ok?

[/ QUOTE ]
This would not be advisable. DOT 3-4, fluids are not at all compatible with DOT 5. The only way that I would switch to DOT 5 is if the entire system was overhauled & cleaned first. You didn't ask, but, I think that DOT 5 is not particularly good for any brake system, for several reasons. It's one advantage is that it doesn't harm paint.
D
 
Thanks Dave. I've seen other people on here using Castrol GT-LMA. Would that be ok?
 
[quote I think that DOT 5 is not particularly good for any brake system, for several reasons. It's one advantage is that it doesn't harm paint.
D

[/ QUOTE ]
I agree that DOT 5 is not what we should use, but an other "advantage" is that it is not hydrophilic, that is to say it does not have an affinity for water, or so I thought. I think this means it will also not mix with any water that may get in the system and as such any water would "pool" at the lowest point in the system and do what water does best. This is why I put quotes around the word advantage.

Again this is what I remember and would welcome correction or confirmation.
 
I was a believer in the DOT 5 option long ago but have since altered my opinion. Seems its only advantage is it does not harm paint, that being said if you just exercise care in the engine compartment then the advantage is lost. Regarding its not absorbing water; this sounds advantageous but if DOT 5 does not emulsify (absorb) water then the water will deposit itself somewhere in the system. DOT 3 and 5 on the other hand absorb moisture thus creating a barrier between your brake components and the water molecules. Finally the price! Good grief why pay all that extra dough when the less expensive alternatives perform equally.
 
What originally came equipped in the vehicle? I see that both Moss and TRF push Castrol LMA, but is their anything wrong with DOT 3. I had my front calipers rebuilt, and I waiting for hose to come in from TRF, so my system will get a complete flush soon...
 
Hi all,

I like ATE Super Blue... for one, possibly silly reason... the blue is easy to see in semi-transparent fluid reservoirs. It also changes color when it needs to be replaced.

I'll use it in my TR4's solid aluminum reservoirs, too, simply because I have it in everything else. It's a DOT3 or 4 with a high boiling point.

It's a little more expensive, probably because the bikers and hot rodders think it looks cool.

Alan Myers
San Jose, Calif.
'62 TR4 CT17602L
 
[ QUOTE ]
Thanks Dave. I've seen other people on here using Castrol GT-LMA. Would that be ok?

[/ QUOTE ]
LMA is a DOT 4 fluid that absorbs "less" water than some fluids but still absorbs enough to prevent water pockets from forming. The more water a fluid absorbs, the lower the boiling point. I personally think that LMA is a good compromise for all around use.
D
 
I remember being told once that the G in GT-LMA is for Girling because it was usable for Girling brake systems with natural rubber seals which DOT3 fluids may destroy. Don't know if there's any truth in that, but this site says:

[ QUOTE ]
Castrol GT LMA was originally "Girling Amber", the highest performance of three brake fluids made by Castrol for Girling, one of the largest brake manufacturer in Europe. When the US Dept of Transportation put out the DOT 4 specification, the LMA met it with flying colors, and became the basic fluid for most Girling systems.

[/ QUOTE ]
 
That quote sounds right to me. I'm almost hesitant to admit that I remember the other two fluids: Girling Green, and the ever-popular Girling Crimson.

I'm also somewhat hesitant to admit just how long I've had the same Castrol GT-LMA fluid in some hydraulic systems without problem, as I do not recommend ignoring a periodic flushing/refilling schedule.

It's good stuff, though, that GT-LMA. Getting harder to find locally, but a couple of area Pep Boys stores still have the quart bottles for around $6.00 or so. Not bad compared to what it'll cost you for a 12oz. bottle mail order from the usual suspects!
 
Since I have hydraulic brakes on both my trailers (boat and car) I found out the hard way that DOT 5 is not as wonderful as I was originally led to believe. I lost a wheel cylinder to corrosion, locked one wheel up and was a real pain to get the wheel to break free at night with few tools on the side of an Interstate highway.
Needless for me to say that I will not use that stuff again!

It is possible that I could be wrong about this, but I think I read somewhere that some people have had a bad experience with the rubber bits in their brake system using DOT 5. Anyone else heard/read that? Could this could be related to an improperly cleaned system?
 
Back
Top