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MG TD TF 1500 - Switch to silicone brake fluid

I asked for advice just a few weeks ago on glycol brake fluid and wanted to post my experience for the archives.
I was convinced by the responses to consider silicone fluid. Essentially, the responses gave two recommended choices -- Castrol GTMLA and silicone. The pluses and minuses for silicone are well documented in the archives. I decided to go with silicone to reduce corrosion and followed these recommendations:

Use all new seals.
Clean out the system with acetone, denatured alcohol or Brake Clean.
Prefill the wheel cylinders.
Bench bleed the master cylinder.
Bleed the system several times after use.

In addition I had the master cylinder resleeved by Apple Hydraulics. They use brass sleeves and apparently do nothing after boring since they recommend washing the cylinder with soapy water to remove debris. The master cylinder leaked passed the secondary cup while bench bleeding. I had noticed very fine scratches in the brass, so I dismantled and used 2000 grit paper to polish the bore. It did not leak the second time I bench bled.

I also learned that Brake Clean dissolves the insides of the flexible lines and had to buy three new ones.

I replaced the brake shoes and cleaned all the wheel cylinders and polished with 2000 grit paper. I used all new copper washers.

I bled the system after connecting and filling. I left overnight and bled again. The 'feel' was softer but the brakes worked fine. There were leaks from two of the banjo bolts and I progressively tightened little by little after driving until there were no leaks. So far the master cylinder is not leaking. I rebled after a week of driving and the pedal does not travel as far as it did at first and the feel is a little softer. The brakes work fine. I am concluding that the air is out and silicone fluid is more compressible than glycol fluid, at least that decribes the performance. I like the feel fine and think it is more like modern brakes.

I am glad so far that I changed and if there are no more problems (such as the seals changing to chewing gum!) I will be very satisfied. Thanks for your input. Ron
Ron Coates

I have had Silcone fluid in my brakes for 15 years and it works fine. The best part is that if a seal does leak your paint won't come off

Chris
Chris Couper

Interesting thread, ? how would I know what fluid I have in my cars? Both purchased years ago, I was so excited to buy them it never occured to me to ask "what fluid is in in the masrer cylinder system. Can or should I assume its glyco or?
thanks for any reply
g irwin theirwins@alltel.net
gei irwin

Pop open the master cylinder and take a whiff... silicone fluid has very little smell.... the regular stuff has a distinct odour.
gordon.b.lawson '53TD

or you can just look at the fluid. If it is dark and cloudy, it is glycol. If it is clear and purple in color it is silicon. The glycol gets dark and cloudy from corrosion in the system due to the moisture that the fluid absorbs from the air and it should be flushed out and replaced every couple of years. Silicon fluid doesn't absorb moisture and therefore there is no corrosion in the system when it is used. I've had silicone fluid in our TD for almost 20 years and have never changed it. It is as clear today as the day I put it in. Great stuff. Cheers - Dave
David DuBois

I suggested to G E Love that he consider silicone brake fluid after his brake rebuild. This thread covers my experience in 2004. Since then I have had no problems at all and the fluid looks like new. I have not needed to top up the level. I am hoping for the same experience as Dave Dubois. Ron
Ron Coates

Ron,
I appreciate the fact that you let us all know how things worked out! So many times a problem is discussed on this forum, and we never hear or find out what worked or didn't work.

SPW
Steve Wincze

Thanks for reporting in Ron.

The pedal with silicone should be just as hard as the pedal with glycol. You still might have some air possibly in the front wheel cylinders.

If you use fine 400 grit paper to true out a copper washer, heat it to cherry red to re-anneal it. The sanding action will work harden the surface, what you want is smooth and soft.

Always replace the rubber lines when doing a brake job. Cheap insurance on a single cicuit system! Always replace them and any other rubber part when switching to different fluids!

I have run 7000 plus miles in the last year with silicone and love it (thanks Dave DuBois!)

Continued good wishes on your choice,
dave
Dave Braun

My experience with silicone fluid has been the same as Dave Braun's -- pedal is nice and firm. You need to make sure that you take steps to avoid any air in the fluid before you put it in the system. Don't shake the bottle, ideally let it stand undisturbed for a while before putting it in, try to pour in such a way as to minimise aeration, etc. But you should do the same things with glycol fluid as well, so silicone is no different in that regard. Maybe just a little less forgiving. But I've had no problems with it, and I've been using it since 1995....

One comment I will make in response to Dave DuBois's comment -- I had one brand of fluid (don't recall now which) that over time, the purple dye faded leaving the fluid a clear straw yellow color. So the absence of purple is not an absolute indicator of glycol.

Cheers!
Rob Edwards

For my TD, I have found the silicon absolutely great. 20 + years without any issues. No leaks, no frozen pistons like I used to get each year after storage, and a nice peddle.

But, I have it in my MGB and I don't really like the feel of it. Not sure if it is because of the different brake system or what, but have not been able to get a good hard peddle even with multiple repeat bleadings.
Bruce-C

Knowing I was going to have to replace the whole brake line system, I too put in silicon fluid (much to the dismay of my mechanic), and have been really pleased... hard pedal and no leaks and it seems as clean as when I put it in...(5 years and 25,000 miles).
gblawson(gordon)

This thread was discussed between 29/09/2004 and 21/11/2009

MG TD TF 1500 index

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