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MG TD TF 1500 - Brake lights.....

When i put on the brakes... i get brake lights...when i let up, they go off....Then about 3 seconds later, they come on again and don't go off until i apply the brakes and let off... then about 3 seconds later, they come on and stay on....
Installed a new brake switch (Moss) and wonder if it is faulty...or if somehow i have pressure building up enough to turn them on again (????). Don't notice any extra braking when they come one (as in, the car will still roll on a slight grade with them on).
I used my emergency brake on a hill in Watkins and noticed this after that?
gordon.b.lawson '53TD

Gordon;
Two things can cause this . Did you use silicone when you rebuilt the brakes. If so you may have to increase the clearance on the end of the piston as it may be blocking the small bypass hole in the master cyl. How much play do you have on your pedal when the spring pulls it back. This can cause the switch to make contact . At the same time you may want to install a brake light relay. This could also help.
Sandy Sanders
conrad sanders

Sandy - While I am not sure how silicon fluid will decrease the clearance of the main M/C seal from the bypass hole, I would agree with the possibility of insufficient clearance regardless of fluid used and insufficient pull-off provided by the return spring. I am also an advocate of a relay and arc suppression circuit on the brake light switch (see my article on same at: http://www.omgtr.ca/technical/brakelightrelay/brakelightrelay.htm),
I don't believe that it will help with the particular problem that Gordon is having. The brake lights ar coming back on because there is pressure in the system when there shouldn't be.
Gordon - a shot in the dark, is the M/C cap vent hole clear so that it is venting properly? Good luck - Dave
David DuBois

I was at the British Car Day at Bronte today and asked a couple people... my thought was somhow pressure was building up... Asked around and didn't think there was a hole in the top of the cap....two or three of us were not sure...? If there is (i didn't remember one), i will pull it off and check.
I did use silicone fluid, also have one rear cylinder with a bit of a leak... takes over a month to lose about an inch of pedal. Will have to get a new rear cylinder.
gordon.b.lawson '53TD

Gordon;
Your first problem is that an MGTD does not have an "EMERGENCY BRAKE" it has a FLY-OFF hand brake. I installed the NAPA brake light switch (Part # which was given in an earlier posting somewhere) and had also (due to lack of knowledge) purchased the Moss thing and the visual difference in quality is astounding. Hung the Moss unit on garage wall with a nail thru it (really a fake nail) but people don't know it who look at it.
Greg & Grimm
G.J. Cenzer

Has anyone contacted Moss about the inferior brake light switch they are selling and the availability of an acceptable unit from NAPA? This is really a safety issue and I am concerned about members of the TD-TF community who may not know of the discussions on this Bulletin Board. Some of Moss Motors items are repackaged commercially available products. Why shouldn't the brake light switch be one of them?

Would someone with direct experience with the Moss and NAPA products be willing to contact Moss?

Thanks.

Larry
Larry Shoer

I have used both the Moss (Inter Motor) and the NAPA (Echlin) switches and neither one held up worth a hill of beans. If one can find a NOS Lucas switch, they wil have a switch that will hold up for a reasonable amount of time. Normally the switches fail to close due to burned contacts internally, but I would guess that if the contacts has sufficient build up of carbon from the arcing and burning, they could start making contact all the time. It might be worth the time and money to try a new switch. If it works, then a relay and arc suppression circuit is in order on the new switch. Trust me Gordon, there is supposed to be a vent hole in the filler cap on the M/C. Check on the face of the flats and also on the brass baffle on the inside of the cap, there should be a hole in both places. As I said before, a colgged vent is kind of a long shot. I would suspect that a colgged vent would cause other problems than a build up of pressure keeping the brake light switch closed - however, anything is possible. Cheers - Dave
David DuBois

David
I checked the B & G Catalogue and found two brake light switches listed at different prices. The one with spade terminals is £5.50 while the screw terminal version is £11.15 which I hope means higher quality.
John
John James

It seems the price has gone up!
http://bg.mgcars.org.uk/index1.html?o=10388950663369
John James

John - The two switches are the same with different connections on them. One is for TD, TF, MGA and the one with spade lugs is for MGB. The makers are somewhat proud of the one with grub screw connections on it, thus the higher price. Both types are as good (or bad as the case may be) as the other. I have used both on our TD (just the spade lug type on our MGB) and found that with both, I needed the relay and arc suppression circuit to make them last for any longer than a couple of months (even had one fail in two weeks). Cheers - Dave
David DuBois

Oh dear David, I hope the original switch, which is still in situ, doesn't fail for quite a while. Perhaps I had better use the brakes more sparingly!
John
John James

I replaced the original one "just because"... thought it would be good to have all new... think i will put the old one back on however and give it a try... It certainly is a more solid unit then the Moss.
gordon.b.lawson '53TD

I have had the Moss switch in my car for going on 5 years and it is till doing fine. Even the third tailight has not caused a failure.
Tom

For what it is worth I am having a problem with the clutch on my S1 E Type and I suspect that the silicone brake fluid is not compatible with the clutch slave master seals( silicone fluid causing expansion of the rubber seals } I have since changed the fluid in this circuit and the result is much improved.

About a year ago when browsing at an mg spares day at Stoneleigh UK I noticed a sign next to some replacement brake seal kits which said ' these seals are not suitable for use with silicone brake fluid '!!!

I am of the opinion that silicone brake fluid does not have the same lubricity ( if there is such a word ) as conventional brake fluid and could be the cause of the problems described.

Having said all this I have no problem with using silicone fluid in my 51 TD.

Good luck

David Tinker, Wales UK

David Tinker

Silicone "should" be compatible with most rubbers i would have thought... Haven't had any trouble with stopping (other then the slight leak in the one rear cylinder). As they were all seized and had to be honed, i'm not blaming the fluid.
gordon.b.lawson '53TD

Silicon fluid that carries the statement "meets DOT 5 specs" or words to that effect is compatible with all brake materials and seals. The problem tends to crop up when it is used in a system that has previously been using DOT 3 or 4 without installing new seals. Apparently, the seals absorb a small amount of the fluids and when the silicon fluidis introduced into the system it causes a problem with the seals.

David, I too had a problem with silicon fluid in the clutch hydraulics on our MGB, in that if the pedal was pushed and released rapidly several times (like when backing in a tight spot), the clutch would not release. I believe that this was a result of bubbles were forming as a result of cavitation from the rapid use of the clutch pedal (at least that's my theroy). I changed back to DOT 4 fluidand have not had any further problems.

Gordon, if the original switch was Lucas, it is a much better switch than the replacement switches. I would still recommend installing a relay and arc suppression circuit to insure a longer life for the switch.
Cheers - Dave
David DuBois

This thread was discussed between 19/09/2004 and 21/09/2004

MG TD TF 1500 index

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