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MG TD TF 1500 - DOT5 fluid seeping

I installed all new brake components and DOT5 fluid last fall I used MOSS “Classic Gold” wheel cylinders. After no leaks all winter, noticed recently, one after another, seeping from the four wheels. I have not driven the car. Any ideas? Is DOT 5 more escape-prone than DOT 4? Should I have my original wheel cylinders rebuilt and switch to DOT 4?

Any thoughts will be most appreciated!

Tom Capehart
MG TD 16468
T Capehart

that's what i would do...the google response i got to the query, "dot5 brake fluid attack", is enough in and of itself to steer clear.
hh hoolihan

Modern rubber components are compatible with all common types of fluid - 3, 4, 5, 5.1. Silicone is a bit thinner and more slippery than 3/4/5.1 but it shouldn't be leaking from the rubber. The only area I've seen it more leak prone is around fittings where the surfaces aren't perfect. On the bright side, if it was glycol fluid (non silicone) then your paint would be eaten away by now.
Steve Simmons

I changed to DOT5 in 2019 (all new cylinders and rubber lines) and had no issues since. Leaking cylinders I hab before with DOT 4, one of the reasons I changed.
Braking feels a bit softer with DOT5, but reaches all the required levels. Brake light switch comes very late now, so I sometimes I get comments that it isn‘t working. But it is.

Rgds Mike
Mike Fritsch

I think that it was just over 10 years ago when I replaced all of my brake lines and cylinders and installed Dot5. I've barely had to touch up the system since then.

Bud Krueger
Bud Krueger

Is the leak from inside the drum- from the cylinders? Or outside banjo fitting on backplate? George
George Butz III

i switched to DOT5 after getting my TD more than 15 years ago. no issues since.
regards, Tom
tm peterson

All my older British cars, two Morris Minors, one Austin America, a Jaguar 3.8S, and the TD have been on DOT5 fluid for at least 30 years with very good results.
John Quilter (TD8986)

20 years here and have changed the brake system with my latest restoration. No leaks. If it is leaking with DOT 5, it probably would leak with any other brake fluid.

I would see if Moss has a kit for rebuild, and try that first.
Bruce Cunha

What G Butz IIII said X2 Snug up your connections. I run DOT 5 in all my cars. I replace everything including hard lines Personally speaking, if you have cylinder seals failing it is due to contamination. Not any fault of the DOT5. Wheel cylinders and a washer kit are relatively inexpensive. If you find the internal seals are the issue I would just buy new cylinders and not fool with the old pieces. If they are still under warranty contact the vender for replacement.

Bill Chasser
TD-4834
TD/c-8151
W A Chasser

DOT 5 brake fluid, a silicone-based fluid, offers a higher boiling point compared to glycol-based fluids like DOT 3 and 4. Unless you’re a racer, your MG doesn’t need DOT 5. Here are some other reasons ...

Don’t mix the DOTS - risky.

DOT 5 systems have been known to leak. DOT 5 is able to seek out the most minute path to the outside, resulting in leakage. DOT 3 & 4 also seek leak paths but significantly lesser so. DOT 3 & 4 are much more practical for our mundane T’s, MGBs and MGAs. Not unusual for DOT 3 & 4 to go several seasons W/O a leak.

If you’ want to switch to DOT 5, have a good reason. But you should first completely rebuild the entire brake system of your MG, making sure of the correct and tight fit of all parts. This includes flushing all brake lines with alcohol. Make sure your installation is surgically clean.

I can’t be bothered with this. I have over 375,000 miles on my TF with little or no brake problems. I’ve considered this option several times one the years, but in actuality, I’ve found the standard brakes, properly set up and with DOT 4 brake fluid, able to handle all of my braking needs to date.

Gord Clark
Rockburn, Qué.
Gord Clark

Knock on TD wood.

Switched over to Silicone DOT 5 10 years ago - no problems.

Secret is to make sure all brake and master cylinder is very clean and in polished condition. Then to flush out any and all silicone fluids very intensely and many times. Let the flush fluid dry out completely and flush again.

I sent out master cylinder to be SS sleeved and installed all new rubber everywhere - cleaning each rubber component before installation.

Cleanliness in converting is the major and big secret.
Michael Balahutrak

This thread was discussed between 09/05/2025 and 24/06/2025

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