Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - DOT4 Corrosion of Adapter

Disassembling the brake system for the DOT4/DOT5 switch showed some ugly effects. One of the worst was on the brake line adapters. This was the most pock-marked of the 4. Had been in place since 1995. Shown against one of the new set. Bud

Bud Krueger


That's not corrosion effects from Dot 4, that's the corrosion effect from H20 absorbed into the Dot 4.

Gene Gillam

It's almost all external, so I think it's corrosion from road salt residue and water.

Tom Lange
t lange

Gene, I'll certainly grant you that it's not caused by the DOT3/DOT4 compound. It was from the water absorbed by the fluid over time. The other three adapters showed since of corrosion, just not as striking as this one.

Tom, the corrosion above the section that goes into the banjo is obviously due to exposure to the outside world outside of the backing plate. The corrosion below that area was only in contact with brake fluid.

Until I saw this, my motivation for switching to DOT5 was one of, "why not, while I'm at it". I'm now a bit more motivated, to say the least. Those adapters are about $20/ea. Bud
Bud Krueger

Here's what all 4 looked like. Sure points out the need to bleed/change fluid periodically. Bud

Bud Krueger

Bud, If you refer to their looks as PATINA, they don't look so bad. Grin. PJ
Paul sr

I have been following and ruminating on the switch from dot 4 to dot 5, especially on my current build. Everything from pedal to shoes is new - a good time to switch.

My mind is weighing back and forth...
Dot4 absorbs water and so needs to be bled at intervals.
Dot5 absorbs air and so needs to be bled at intervals.

I'm think I'm hearing a consensus that dot4 gives a "better pedal", perhaps due to the two (overly simplistic) generalizations above.

I'm still deciding...

And those adapters in the pictures above can be cleaned up, dressed up, with some judicious application of file and emery paper to the exposed sections - just don't change them from the threaded potion down. I chucked mine in a lathe, sanded the round section, put a file to the flats... from three feet they look great. (Some evenings I have too much time on my hands.)
Most important is a new copper crush washer to prevent leaks - that is the source of the rust. When you bleed brakes filled with dot 4, you really need to clean up with brake cleaner. That fluid laying on undercarriage parts is a magnet to water and instant rust.
RwB Brown


I run DOT 5.0 in the hydraulics of the GTV8 and the Stage 6 Roadster for more than ten years by now.

Intermediate bleeding was never necessary on both cars. Brakes and clutch are working perfect without any signs of a weak pedal.
The TD will get the same change as soon as the hydraulics will need a general rebuilt.

R.S. Ralph Siebenhaar

I wouldn't hesitate in any way to convert to DOT-5! The 72 has it and the 55 has it also. Hard pedals and the B hasn't been bled in two years! It just takes patience when charging the new system, you have to go slow. I also back charge my systems through the wheel bleeders and have someone watch the master cylinder so it doesn't overflow. I made up a special temporary bleed screw for that purpose. Remember, the system must be clean and I recommend replacing all rubber components with new! That's how I do it! PJ
Paul sr

Ditto on the switch to DOT 5 - put it in in 2001 and never a problem. Have it in two TC's and an MGA and wouldn't go back to DOT 4 for anything.
Gene Gillam


That DOT-5 absorbs air so must be bled periodically is a myth propogated by a DOT-4 sales agent in an article that also claimed the absorbed air would compress on braking and cause excessive pedal travel and make the brakes feel "spongey". ( note that DOT-4 also absorbs air )

Absorbed air is no longer a gas, as in bubbles, and is dissolved in the fluid and compresses like the fluid it is dissolved in.

While it is true that DOT-5 more compressible than DOT-4, the difference in compressibility of the liquid is so small that the total effect in our braking system volume and pressure would mean a pedal travel of less than 0.008 inches over DOT-4. I am not sure I would notice this!

Using a fact...more compressible... to provide a wrong conclusion to scare the potential user. It should be noted that many of the numerous disadvantages, often quoted, to DOT- 5 sprang from the DOT-4's press release in the early days after DOT-5's introduction
Don Harmer

This thread was discussed between 21/07/2013 and 22/07/2013

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.