MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

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 - Servo vs. Silicon

As I mentioned in another thread, I'm refreshing the entire brake system of Lazarus in preparation for next year's 4,000+ mile (RT) venture to Texas. I've decided to install the Lockheed brake servo. This is the system seen in http://www.ttalk.info/TinkerServo.htm as used by David Tinker. The servo is available as a kit from Victoria British, but you can buy it from Jeff Zorn of LBCarCo for a better price. Please, no bantering about the adequacy of the TD/TF brake system. 80 year old knees can use a little help.
I'm considering converting Lazarus from Castrol GTLMA to DOT 5. However, a little snag has arisen. Turns out that the Lockheed folks are against using the servo with silicon brake fluid. Among the arguments is that a leak in the vacuum system would subject the engine to sand, a derivative of silicon. Has anyone had any experience with a brake servo system using DOT5? Bud
Bud Krueger

Bud - I think that 'sand' is a red herring and the least of the worries. The bigger issue would be air entrainment. When silicone fluid is run through very small orifices, it tends to produce bubbles of air within the fluid, which is very slow to dissipate. this is the main reason that silicone fluid is a no-no in cars with proportion control and anti lock systems. Cheers - Dave
David DuBois

I've run silicon fluid in my MGC with vacuum servo for many years. No problems whatsoever.

I've heard the same theory about the fluid solidifying into an abrasive material when burned, but I don't know how factual it really is.
Steve Simmons

David, I've got to agree with you on the 'red herring'; bit. Maybe they can turn water into OSH.

Steve, thanks for the response. I'd been hoping to hear from someone from the MGB/C community since this servo is of that design. I'm hoping that I can have the best of both worlds.

I'm probably going to go ahead with the DOT5. So far there is documentation about mounting this servo in two locations -- 1) as David Tinker did, on the tie bar behind the driver's seat (LHD), and 2) on the hoop in the passenger compartment. I'm also going to check out the possibility of locating it under the passenger's foot ramp. The negative there is the heat from the exhaust pipe. It'll be a couple of weeks before I have the parts. I don't dare begin the project until after the July 4th parade.

Anybody else? Thanks, Bud
Bud Krueger

Bud,

At one time I used silicon fluid in the Clutch circuit of my Jaguar E Type but after experiencing problems with the clutch slave cylinder sticking I switched to standard fluid and solved the problem. I think that silicon fluid does not have the lubrication properties of standard fluid.

Cheers,

David
David Tinker

Bud,

I fitted a remote servo when I rebuilt my TD, I also used silicon dot 5 fluid. The good news is that was over 5 years and 6000 miles ago. I have had no issues and the brakes have been and are still excellent. The only maintenance carried during that time is regular brake adjustment during the service. I hope that puts your mind at rest.

Regards Chris
C A Pick

Thank you, Chris. That's really good to hear. I'm still thinking about your 'on the hoop' mount. Would you do it that way again? Bud
Bud Krueger

Yep, I have just finished restoring a MGYA and also fitted a remote servo behind the glovebox on the firewall, tucked out of the way but still easily accessible.
Regards Chris
C A Pick

The main thing that you have to know when using dot5 fluid, is that ALL the rubber parts have to be new, throughout the system...No amount of flushing will get rid of Dot3/4 residue,in the rubber, and any mixing of , even small amounts, of incompatible fluids will cause the rubber to disintegrate over time, and stickiness of moving parts.
After the m/c and slaves have been removed, flushing the lines with brake cleaner is also necessary....
As far as proportional systems, with power brakes, I have been using Dot 5 in my FFR "Cobra" replica, for 11 years, without any negative problems, and have not had to change the fluid in that time.
Dot 5 was in my Honda 750 Motorcycle, without changing, for 27 years, with no negative effects, and I never changed the fluid...brakes were great.
Just my 2 cents.
Edward
Edward Wesson 52TD

Have been very busy getting rid of any presence of the old DOT3/DOT4 brake fluid. In the course of doing so I've drained the old fluid from the old master cylinder and replaced it with acetone and bled all of the hard lines. This afternoon I was doing some over-kill bleeding and ran into a problem. No pressure in the brake lines. Finally dawned on me what had happened. The master cylinder seals can't handle the ultra-low viscosity of the acetone. Looks like it's time to install the DOT5 master cylinder and purge the lines of the acteone. Bud
Bud Krueger

A lengthy job, but it's in and working. Image shows it mounted behind the rear cross brace. More details to come. Bud


Bud Krueger

Hello Bud,
may be I am misinterpreting but when I look at your last picture, it appears to me that the brakeline behind the diff is so far out that it will be scratched by the petroltank whilst the car is moving on its springs. I enlarged that picture for you but it is easier to see on the real thing of course. Greetings, Huib


Huib Bruijstens

Hi Huib. What you're seeing is where the paint on the face of the side curtain box had been scraped from an earlier orientation of that brake line. There's actually a gap of about 3/4" at its closest. That's a good observatio. I brought that up in a previous thread. Folks tend to install the side curtain box and never notice that issue. Bud
Bud Krueger

This thread was discussed between 11/06/2013 and 08/09/2013

MG TD TF 1500 index

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