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Does anyone have experience of switching a TR4 (standard setup, no brake servo) from DOT 4 to silicone brake fluid? Is a thorough flush sufficient before refilling, or do all the rubber seals need to be replaced?

 

If you knew you had to lay your car up for approx. 3 years due to a secondment abroad, would you make the switch?

 

After a nasty leak in the past I'm going to have to have part of the bulkhead repainted before rust takes hold - I don't fancy doing this twice!

 

I've heard rumours that DOT 5 destroys the brake light sensor - is there any truth in this, or is it just scaremongering?

 

Thanks in advance.

 

Regards,

 

CJG

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Can't say I've heard of silicone fluid eating brake light switches, no.

 

That apart, you'll find all kinds of posts discussing the merits and demerits of silicone and traditional brake fluids, they go on almost forever . . . . try the search facility ! :D

 

You can't just switch from glycol to silicone based brake fluids, or vice versa, with a quick flush I'm afraid. It's a thorough and comprehensive flushing job, requiring careful replacement of each and every seal or rubber component of every description that touches the hydraulic fluid. Every trace of glycol must be removed. The next problem can be that brake components are designed for glycol fluids in the main, and may not like silicone based fluids - as in swelling seals, for example. OK, it's not that common, but it can and does happen, and it's no use blaming the component manufacturer. They design components to function with the vehicle manufacturer's recommended fluids, and few vehicle manufacturers specify silicone brake fluid. Certainly not Standard Triumph, BL or Austin Rover.

 

Laying up a vehicle for several years will invariably result in some water content entering the hydraulic systems. Glycol fluids absorb water, lowering the boiling point. Silicone fluids do not absorb water, it remains separate and condensation will in time find its way to the lowest point, as water droplets in calipers and wheel cylinders, for example. So they corrode.

 

Yes I know silicone fluids were designed for laid-up military vehicles - which are generally laid-up somewhere dry like the Arizona desert, where condensation and water absorption is a less significant factor than in temperate Europe.

 

Would I switch from glycol to silicone fluid ? Not in your situation or any other, thanks a bunch, been there done that - and I wouldn't touch the stuff again with someone else's bargepole.

 

Cheers,

 

Alec

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So you replace the whole brake system before you go, and then maybe again when you come back.

Or leave the Dot 4 and just replace everything when you come back. Although if it's stored in the dry you might be OK.

 

Or buy a Carcoon and a dehumidifier - is there someone who can keep an eye on it for you? - then it may survive.

 

No chance of taking the car with you then...?

 

Ivor

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So you replace the whole brake system before you go, and then maybe again when you come back.

Or leave the Dot 4 and just replace everything when you come back. Although if it's stored in the dry you might be OK.

 

Or buy a Carcoon and a dehumidifier - is there someone who can keep an eye on it for you? - then it may survive.

 

No chance of taking the car with you then...?

 

Ivor

 

 

 

Thanks for the advice.

 

I guess I'll leave the glycol stuff in then, and change the master cylinder(s) when I get back. I'll have the bulkhead repainted now (the best defence against the dreaded tinworm), but I'll make sure there is something in place to catch any fluid drips. Is I intend to use the car in the mountains when I get back, I'm not taking any chances with dodgy seals (and potential catastrophic and very downhill failure!).

 

The car will be kept in a dry storage facility in Germany. I would take it with me, but the Chinese authorities don't encourage that sort of thing (ironically, as it was first registered in Hong Kong). Shame, as there can be few more pleasant ways to cruise down the Bund on a Sunday morning...

 

Regards,

 

CJG

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If it was my car I'd drain the hydraulic system, leave the bleed nipples out and blow it through with compressed air to remove as much moisture as possible. Then change all the flexible pipes to minimise moisture diffusion through them whilst in storage. Refill with DOT 4 rather than DOT 5.1, the former absorbs moisture more slowly, bleed thoroughly to ensure solid pedal. Seal the master cylinder and reservoir in a plastic bag. Lubricate all handbrake linkages. Park with handbrake OFF, and wipe the discs lightly with PTFE spray, assuming that the brakes won't be touched in storage.

 

On return I'd clean off the discs, meths and glasspaper, relube handbrake linkages, then use the brakes with the storage fluid in - odds on they'll work, you might need to clean up the wheel cylinders. Drain, blow out with compressed air again, refill with fresh fluid. 90% chance the brakes will be fine after 3 years.

 

Cheers,

 

Alec

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Alec, very thorough but how do you stop the clutch sticking to the flywheel? PTFE spray again!! :rolleyes:

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Hi Ian,

 

PTFE spray would be a bugger - to get on and off again . . . . how many times do you want to remove the box ?!! B)

 

One option is to wedge the clutch, as in piece of wood between pedal and seat, leaving the clutch disengaged and hoping the hydraulics hold.

 

Then there's the old trick of frying the clutch immediately before laying-up - sorry if I'm teaching you to suck eggs.

 

Get the engine good and hot, then slip the clutch until you can smell it - that has burnt off all the minor cr*p deposits on the friction plate and the flywheel, polished nicely. Engine off, hold the clutch pedal down for a few minutes to allow the mating surfaces to cool. Later, once the engine is cold, pedal down and turn the engine slightly so the clutch is in a different place from that at which it cooled off. You've eliminated 90% of the 'stiction' factor, it shouldn't be much of a job to unstick the clutch 3 years down the line in the usual way. As ever, when recommissioning get the engine hot before trying to free off the clutch.

 

Yes it'a bit of a performance before laying up, but it's a darn sight less work than extended recommissioning. :D

 

Cheers,

 

Alec

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As for the hydraulic switch for the brakes on my 1958 TR3A, I have had some failures and replacements. On one that lasted 5 years, I turned it in the lathe to find out how it is designed and to study what I found inside. It did not fail because of silicone fluid which I have been using for 21 years. The fluid pushes on a sealed rubber boot which advances a small disc towards the two contacts. I found that the copper disc had oxidised on the face that makes contact with the two points. The disc was black. Copper is a good conductor but black copper will fail.

 

Five years earlier when I bought that brake switch, I ordered two of them so I could have a spare at all times. I put this "new" 5-year old switch into the TR after it sat in the box in my boot and it wouldn't work. So I turned this one on the lathe and the copper was black too. Both were in blue and white boxes indicating they were made by in Birmingham.

 

So don't buy one 5 years before you need to.

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A propos of nothing at all, I think Intermotor actually began operations in Hucknall, Nottinghamshire - SWMBO's birthplace. Their parts are definitely designed down to a price in my opinion.

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There is confusion over Silicone Dot 5 Brake fluid in that I've known people use in Rolls-Royce and had the seals swell up and stop the brakes working altogether. This includes the Governor General of Australia's P6! From what I gather modern seals are not compatible. Therefore my advice is to contact the manufacturers to establish whether it's feasible in TRs.

 

In my opinion Dot 4 is fine and just needs changing annually to keep it clean, which is no more than BMW recommend for their cars and bikes.

 

Ash

Edited by Ashley James
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Does anyone have experience of switching a TR4 (standard setup, no brake servo) from DOT 4 to silicone brake fluid? Is a thorough flush sufficient before refilling, or do all the rubber seals need to be replaced?

 

If you knew you had to lay your car up for approx. 3 years due to a secondment abroad, would you make the switch?

 

After a nasty leak in the past I'm going to have to have part of the bulkhead repainted before rust takes hold - I don't fancy doing this twice!

 

I've heard rumours that DOT 5 destroys the brake light sensor - is there any truth in this, or is it just scaremongering?

 

Thanks in advance.

 

Regards,

 

CJG

 

 

CJG: No, but when we restored the '250' in 1985, we went with DOT 5. I hadn't even given this a though until my beautiful bulkhead paint was efficiently removed by the Dot 3 fluid. I was quite angry and decided I just could not deal with that again. So we went with silicone. That's 25 years and let's just say that I have been pleased ever since.

The majority of LBC enthusiasts here have done the same and it appears that experience has been positive. That said, there is anecdotal edivence that some of the original rubber components went all gooey in the presence of silicone, but modern rubber should not mind. As a minimum, I would suggest you flush your system with ethanol, blow it out with air and then fill with Dot 5. A better approach would be to replace all of the rubber components in the master and wheel cylinders. After you fill the system with Dot 5, air will continue to come out at the master, so its best to wait at least a day or so before bleeding them. Don't be alarmed if you have a soft pedal after the first bleeding. Wait several hours and repeat and you should have a firm pedal. When you say brake light, you mean the shuttle valve sensor? I didn't think a TR4/4A had a PDWA. But, I can't imagine those components being attacked by silicone. If you have a PDWA and you're concerned , you can replace the internal rubber seal. Details here:Overhauling MC & PDWA

For the 250, I pressure bleed the brakes every spring and replace the fluid every third.

good luck06030004.jpg

Edited by angelfj
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Hi Ash,

 

this discussion has gone on for decades. Silicone fluid manufacturers can't tell you if their product is suitable for a particular car, model or marque, not unless the vehicle manufacturer specified silicone fluid in the first place, which applies to precious few vehicles . . . . and even then, years later who knows what variety of after market components might be in there, and not specified for silicone ?

 

Brake system component aftermarket manufacturers usually design their products to be compatible with glycol-based fluids when it comes to components for classic cars, ie DOT 3 and DOT 4; or for a minority of cars, LHM fluids. Why should they design for additional compatibility with silicone fluids, DOT 5 or any other spec ? Even DOT 5.1 can be dubious in older cars designed for DOT 3 or 4 fluids, being principally borate esters rather than glycol-based, and similarly competition spec fluids are not necessarily going to be compatible with ordinary road car seals.

 

It beats me why classic car owners will spend megabucks on restoration, then cheerfully pour whatever into their hydraulic systems with little or no understanding of the potential implications. If it was an informed decision that might be a different matter, but usually it is not so. How many users of silicone fluids could offer comment on the potentially adverse characteristics of silicone fluids as compared to glycol/borate fluids, eg ambient viscosity, air absorption, compressibility, lubricity, immiscibility with water ?

 

Opinion is not a substitute for factual data, but the average classic owner tends to be big on the former and woefully ignorant of the latter. A tendency perhaps not helped by the influence of advertisers upon journalists ?

 

Cheers,

 

Alec

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  • 10 years later...
13 minutes ago, RogerH said:

Hi Dp,

welcome to the forum.

That is interesting - what anti-freeze is this?

 

Roger

Jumping in on this... the issue is that ethylene glycol based antifreezes are highly toxic and (according to RSPCA and others) many cats die every year after ingesting it. Apparently it is sweet tasting but for whatever reason they will lap up small spills on a garage floor or driveway and it only takes a few ml to be potentially fatal.

Some antifreeze brands are marketed as non- or low-toxic. Propylene glycol is one 'safe' chemical and I think that has been around for some years (used in aircraft de-icing?) but is less effective and more expensive than EG.

I think some EG-based products including Halfords include bitrex to make the antifreeze unpalatable to cats.

That's my understanding anyway.

Nigel

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2 hours ago, Bleednipple said:

Jumping in on this... the issue is that ethylene glycol based antifreezes are highly toxic and (according to RSPCA and others) many cats die every year after ingesting it. Apparently it is sweet tasting but for whatever reason they will lap up small spills on a garage floor or driveway and it only takes a few ml to be potentially fatal.

Sames true for humans...

But there's a long way to go before cars are safe to eat..

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I switched over to silicon fluid after I rebuilt my entire brake system a few years ago. Because of our nasty winters, my car sits for several months each year, and I was concerned the DOT4 fluid was getting moisture contamination. I’ve had no issues with the silicon fluid, (soft pedal, weeping joints, etc).

Jim

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  • 2 weeks later...

Just seen this. I built my car up with Silicon fluid and have kept on using it for over 20 years now and its excellent IMHO especially now with Mintex pads! I have a servo on the shelf but never felt the urge to fit it, IF I slam the brakes on it will dive into the road faster that Tom Daley!

Pedal seems firm enough to me, never drove this car with anything else so I have no comparison BUT I am old enough to have driven cars with NO central locking/heated seats/electric windows/sat nav/parking assist (FFS) and did all my own maintenance from my first car (11 years old :lol:)

The only word of caution I would say is carry a litre with you as its not always obtainable (8pm on a rainy night, bank holiday, corner shop etc) and I like to use the same brand too.

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Also just seen this.

On 11/13/2020 at 9:16 AM, Bleednipple said:

Propylene glycol is one 'safe' chemical and I think that has been around for some years (used in aircraft de-icing?) but is less effective and more expensive than EG.

Also used in my 6-pot Spit. Propylene glycol has a lower specific heat capacity than ethylene glycol so will reduce the ability to move heat more so than EG for the same % dilution of the water. Even so, ethylene glycol is BANNED from household heating systems for just the reason you state Nigel (add children to list), so antifreeze for your domestic boiler etc. is propylene glycol. It has anti-corrosion agents that last 20- to 25-years, not 2 or 3. That means perhaps it's not so expensive.

Cheers, Richard

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  • 1 month later...

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