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Best fluid to use in a clutch master cylinder

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TravelGuy Avatar
TravelGuy Kelly B
Morrow, GA, USA   USA
What is the best fluid I should use in my clutch master cylinder for my '74 MG Midget? It's been awhile since I have had to put any in and my memory is in senior mode right now...lol


Thanks,
Kelly

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topdoc56 Gold Member Charles F
Covington, LA - Louisiana, USA   USA
1956 MG MGA
1964 MG MGB
It is usually the same brake fluid that you have in your brake master cylinder.

Gary E Avatar
Gary E Silver Member Gary Edwards
Kernersville, ,N.C., USA   USA
Don't mix and match...



Gary

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ghnl Avatar
ghnl Eric Russell
Mebane, North Carolina, USA   USA
1961 MG MGA "Calvin"
Generally, DOT 3 or DOT 4. First make sure there is not DOT 5 in there. DOT 5 is silicone based - it usually has a purplish hue (you can dip a strip of white paper into the reservoir to see to check that possibility). DOT 3 & DOT 4 are usually clear or slightly amber. When any of these fluids get old they'll become 'dirty' looking*. DOT 3 & DOT 4 are compatible with each other but neither is compatible with DOT 5.

Note that DOT 4 has a higher boiling point than DOT 3 (but adding DOT 4 to DOT won't raise the boiling point much). And, also note that the labels on DOT 3 & DOT 4 will likely say 'synthetic' but that does NOT mean they are silicone based.

And, to make it even more confusing, there is a DOT 5.1 which is NOT silicone based. It is also not very common so you may not see that on the shelf at the auto parts store.

* If you don't know what is in the system or how long it has been in there I'd suggest a full system flush. DOT 3 & DOT 4 are hygroscopic - they will absorb moisture (right out of the atmosphere). Over time this absorbed water degrades the brake fluid & lowers the boiling point. A full flush with fresh fluid every 2-3 years helps keep the system in good condition.



Eric Russell ~ Mebane, NC
1961 MGA #61, 1981 Alfa Romeo GTV6, 1984 Alfa Romeo Spider, 1991 Honda ST1100

Zur Avatar
Zur Silver Member Dave H.
Amarillo, Texas, USA   USA
Especially worrisome in wet, humid climates.

* If you don't know what is in the system or how long it has been in there I'd suggest a full system flush. DOT 3 & DOT 4 are hygroscopic - they will absorb moisture (right out of the atmosphere). Over time this absorbed water degrades the brake fluid & lowers the boiling point. A full flush with fresh fluid every 2-3 years helps keep the system in good condition.



Dave

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