TR5/TR250 TR250 now has Silicone Brakes but no Clutch! HELP!

[angelfj1]

Last night I finished converting the 250 to silicone brake fluid. This involved replacing the master cyl., flexible hoses, rear wheel cylinders and some of the smaller brake lines. I did not remove and split the calipers. The lines which were not replaced, were left in place, but flushed with brake cleaner. I did this by using the little "straw" that come stuck to the side of the aerosol can, and squirting fluid into the lines. This was repeated until the fluid ran clear and followed by blowing shop air through the line. Re-filling the system was fairly routine, except I found one leak at a brakeline - hose junction. Bleeding was also routine, and once the lines filled, I was able to get most of the air bled out. I will now let the car sit for a few days and re-bleed. I also drained and flushed the clutch master, lines and slave cylinder. But after re-filling with silicone and bleeding, I was not able to get much slave cylinder motion. (how far should the slave cylinder linkage travel?) I repeated this several times to no avail. To complicate matters, the very small capacity of the clutch master required me to stop and refill it - a real pain. I don't understand the problem. I had a clutch before changing to silicone and now I don't. The only sympton that I noticed was that the old Dot 3 fluid was black when I flushed the lines. Help!!! :frown:

 

[Guest]

Silicone has a higher surface tension than glycol, thus micro air bubbles tend to cling to the fluid making bleeding a nightmare, sometimes... I haven't ever seen or heard of a clutch hydraulic system be trouble-free with silicone... Every last one I've EVER converted became so recalcitrant that I reverted them back to glycol... thus ending the "no-clutch" syndrome.... maybe you can prove otherwise! Good luck!

 

[Guest]

Are you talking about the Purple fluid? Is that the stuff that gels up if it comes in contact with regular brake fluid? For that reason, I would never go near it. Synthetic fluid if good enough.


.

 

[tomshobby]

Re: TR250 now has Silicone Brakes but no Clutch! H

I switched mine to silicone fluid several months and a few thousand miles ago and it has worked flawlessly.

I simply opened the bleeder and pumped as much of the old out as possible and then bled the system with the silicone fluid until I felt it was purged and only the silicone was left.

You may just have air in the system.

 

[hilsideser]

Boy, After reading this thread, I feel better. In March, I replaced the old clutch master and slave with new from the "big store in the middle of the country". refilled with silicone and have had to rebleed three times since. Air bubbles have been a real problem. Also, every time I get back into it, I have what looks like graphite dust in the silicone. Junk parts? I don know. Open to suggestion, though.I think I too am ready to go back to LMA.

 

[angelfj1]

OK So the concensus would be? I can flush out the silicone and try LMA again? I guess its worth a try.

 

[DougF]

I switched my TR3 over when I bought it in '94 and haven't had a problem.

Something that might help in the future with bleeding the clutch. KD makes a Brake Bleeder Automatic Refiller part #3711 that feeds the reservoir as the level goes down. The bottle hold approx. 16oz of fluid. It is adjustable to the level you want to maintain in the reservoir. The unit clamps to the master and has a shutoff valve to reduce spilling.

 

[angelfj1]

Hey Doug - what a great suggestion. I will definitely look into that unit! regards

 

[Marvin Gruber]

Switched my XKE over to silicone several years ago, clutch was soft for a while and has been okay since. Just did a 3000 and worked well. Plan to do the same to the 250 when I get that far with it. I have had the same trouble with TR6 clutch bleeding before. Got a pressure bleeder and haven't had any more problems.

Marv

 

[Guest]

Everyone has an opinion on this subject, and there is some diversity of viewpoints both pro and con. Why is it that nobody I'm aware of that manufactures new vehicles on a grand scale uses this "superior" product? I mean, some of the new vehicles coming from the big 3 employ cutting edge synthetic motor oil! They all certainly use cutting edge insight into electronics... blue tooth, fuzzy logic, etc. So, why is it then that these companies which collectively possess billions of dollars in research and developement capabilities glaringly exclude the use of silicone brake fluid in thesr 30K up to 100K vehicles? I posed a question some time back as to why intake manifolds are now made of plastic... one person hit it close.... several stated cost containment as a factor.... NOPE!

I'm not trying to offend, just provoke insight....if silicone is so superior, then why don't these billion-dollar+ companies use it? It is certainly NOT cost containment. Somewhere in the engineering aspect, silicone has been nixed for engineering reasons. THAT's good enough for me to follow the original wisdom and use DOT 3 fluif as per these folks' dictum!

 

[TR3driver]

It is certainly NOT cost containment.

How exactly did you come by that conclusion?<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Somewhere in the engineering aspect, silicone has been nixed for engineering reasons.[/QUOTE]Or that one?

I have copies of several papers presented to the SAE, describing the superiority of DOT 5 in both laboratory and real world conditions. Lots of amusing little tidbits in there, like how in one case, when they tried to find the thermal limits of DOT 5 performance in a real world test, the brake pads melted first! In another case, the tires failed first! In both cases, DOT 3 fluid would fail before the other components. The data about DOT 3 fluid absorbing not only water but <span style="font-weight: bold">SALT, right through the brake lines</span> was also quite interesting to me.

DOT 5 was specifically developed for the US military, in response to requirements that they be able to store vehicles in marginal conditions for extended periods of time, and have them instantly ready to go. Sound anything like the way many folks use their LBCs? DOT 3 brake fluid, with it's requirement that it be changed every few years <span style="font-weight: bold">whether you drive or not</span> simply could not meet the requirement.

 

[TR3driver]

(how far should the slave cylinder linkage travel?)

Full stroke is only about 1/2"-5/8".

I suggest first, letting it sit overnight. This gives any air you've managed to stir into solution time to 'breathe' and form bubbles. Then pump the pedal several times, until the clutch releases, and hold it down for 10 seconds or so. Release, wait 10 seconds, repeat. After 3 cycles, let it sit for a minute or two and see how your clutch is.

I've been running silicone in LBC clutches (and brakes, and non-LBCs) for over 15 years now, and it has worked well in every instance. However, it does have some drawbacks, and one of those drawbacks is that it is very slightly more compressible than paint-eating glycol. In effect, you lose a tiny amount of slave travel. If your clutch system was at the very edge before, converting to DOT 5 may be enough to push it over the edge. Usually, making sure the pivots (especially where the MC pushrod joins the pedal) are in good shape will solve the problem.

On both Stags, the joint at the pedal was badly worn. Although the proper solution would be to weld up the holes and redrill to size, I reamed them oversize and used a slightly larger metric pin.

 

[Guest]

Submitted to the SAE by whom? Has the DOT been informed, How about the NHTSA? I one time had a boss TELL me to dis-able the SIR on a town car. I refused and lost my job over it. Found out later what the REAL score was on safety issues. I have a call in to the lead engineer for Dodge's SVT operations... I'll get your answers from him regarding the engineering aspect of NOT putting silicone into new production cars. :hammer:

 

[TR3driver]

Submitted to the SAE by whom?

One by G.R. Browning of General Electric; the other by G.W. Holbrook of Dow Corning.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Has the DOT been informed, How about the NHTSA?[/QUOTE]Nah, they just approved silicone fluid for the market without ever having heard of it before!
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I'll get your answers from him regarding the engineering aspect of NOT putting silicone into new production cars.[/QUOTE]That's easy, they have not tested with it and therefore cannot approve it. "Only factory-tested and approved" should be used.

But that's not an engineering reason, that's marketing/legal. These are the same folk that argue you should not be able to disable that explosive charge aimed at your face, even though it's been proven to kill people (in some cases).

The real question is "Why wasn't it tested?" and the answer is because they see no reason to pay for such testing. Filling with cheap fluid (and make no mistake, DOT 3/4 is lots cheaper than DOT 5 at the wholesale level) that will last as long (in a modern sealed system) as most people keep their new car (average about 4 years) makes a lot more marketing sense than filling with more expensive "forever" fluid.

And there might be just a slight difference between "new production" brakes and 30-50 year old ones ... for example, using DOT 5 in an ABS system not designed for it is probably a mistake. If you have a Triumph with ABS, I'll agree you probably shouldn't use DOT 5.

 

[Guest]

All my life, my late grandfather would say "If it ain't broken, don't fix it!" Perhaps that wisdom should have been heeded here! :thumbsup:

 

[hilsideser]

I picked up a set of springs for the Spit today from Bennet French at Standard Performance in Hendersonville, NC. We talked a bit and I told him about the problems I had been having with the silicone in my new clutch master & slave. He told me that the masters he gets from British Parts Northwest that come from Italy state on the box "do not use silicone brake fluid in the this unit". The units I installed didn't come in a box, but rarther in a plastic bags with nothing save the part numbers on white labels.

 

[RobT]

One thought - I am sure you have not done this BUT if the clutch slave is mounted upside down it will trap the air and not bleed properly. Guess how I know....

I have been running silicone in brakes and clutch for 3+ years without issue. You do have to re-bleed after a couple of days/miles to get the best results though.

Hope that helps.

Rob.

 

[Don Elliott]

A few weeks ago, I bled the clutch line on my 1958 TR3A. I had changed the seal kit inside the master cylinder. I filled the reservoir and went below and all I did was open the bleed valve of the slave cylinder and let the silicone fluid drain down till it had no more bubbles. Grav ity did it all. Then I shut the bleed valve. I cut an old hockey stick handle to the correct length, pumped the clutch pedal, braced the hochey stick between the pedal and the rear of the seat cushion, went below and bled it. There were no bubbles, so I concluded it was OK. Since then I've had no issues during 525 miles.

BTW, in about another 200 miles, I will have driven my TR3A 100,000 miles since I finished my body-off restoration in 1990.

And always with silicone fluid for the brakes and clutch.

Don Elliott, Original Owner.

 

[tomshobby]

Don, thanks for qualifying your post with your mileage to back it up. There seems to be a lot of good advice given on theory with little if any mileage for back up or upon a recent part replacement where there is no long term result. I much appreciate hearing from those that have been maintaining their car and been putting on the miles that show what they did actually works.
BTW - Congrats on the coming event, a testament to the TLC of your TR3A.
Thanks again.

 

[Rich_M]

The original poster's problem may be related to pedal and cylinder linkage adjustments. Here's my story:

I had a LBC specialty shop put in DOT 5 2 years ago when they changed the following parts: clutch slave and master cylinders; brake master and rear wheel cylinders; rebuild both front calipers with new seals and pistons. When I got the car back I found that after I let the car sit for more than a few minutes I needed to pump the clutch pedal in order to disengage the clutch and that I needed to pump the brakes before I applied them or else the pedal would go right to the floor.

The shop blamed the problem on the DOT 5 and blamed me for specifying it (they also charged me $1100 for labor despite giving me an estimate of $300 and telling me they'd call me if they exceeded $300).

I had little faith in them fixing things, so I tried fixing it myself.

First I flushed 48 ounces of DOT 5 through both the clutch and brake systems. Lots of ugly black fluid came out of the brake system (clearly the shop had screwed up the flushing job). When I flushed and bled I was super careful about doing things slowly (even slowly pouring the fluid into the reservoir) so as not to introduce air bubbles.

This did absolutley nothing to fix the problems.

Next, with the shop manual in hand, I checked the clearance at every linkage point in the pedal linkage / master cylinder system and the clutch slave. Everything was out of spec. Once I adjusted everything to spec the clutch and brakes worked perfectly. (I also shimmed the brake calipers to center them with respect to the rotors but I don't think this contributed to the brake problem).

Hope this helps.