I've just totally rebuilt my brake system using the original booster _ all seals (as far as I know) are of modern materials.

I am now running silicone fluid with no problems, it's in my Bentley as well.

The brakes worked right out of the gate, even tested them today with a pesky Dear with a death wish out on the highway today _ pedal feels good and solid _ nice response !
I'll never use alcohol base fluid again, too much maintenance.

Take note that I totally dismantled the entire system which allowed me to wash out every last spec of old fluid.
I siphoned wood alcohols through the lines, then silicon brake fluid and then discarded that.
There was no trace of the fluid left and all was spotless.

I also rebuilt my power steering box many years ago and I have this in mine.
And does it really matter what ATF goes in it, all the seals are neoprene O-rings ?

Pennzoil Dex/Merc ATF | SCL

 

You will get the best operating life out of your PS using Type F or G fluids. (Meeting Ford spec M2C-33 F or G). They have superior anti-wear protection. Other fluids will work. They just don't offer the same level of protection.

Regarding brakes I have commented here.

https://www.jaguarforums.com/forum/m...ne+brake+fluid

Note: The Polyglycols are hygroscopic & will require the minor inconvenience of replacement every 2 to 3 years.

 

Jeff R1

“I am now running silicone fluid with no problems; it's in my Bentley as well”

Interesting, what model and year is that Bentley?

Certainly I don’t know any insurance company in Europe that would cover such a vehicle, if it should have DOT4 or Castrol 363

 

It's a 1951 Mark VI, so a pretty antiquated braking system compared to the new ones.
All it has is just one master cylinder and two front wheel cylinders for the front drum brakes, the rears are mechanical.

Why would putting in different brake fluid void any insurance ?
My insurance doesn't cover anything like that, nor is there any insurance for that, AFAIK.
It's up to the owner to put in the correct fluid and if he/she doesn't, then it's the owners fault.

As I have collector plates, I'm expected to look after the exterior/interior of the vehicle and maintain it to factory standards from that era.
We are allowed upgrades to improve safety and reliability like electronic ignition, seat belts, modern headlights etc, but if we damage the engine or braking system by not maintaining that, there is no insurance for that.

I could easily see voiding a factory warranty on a new car by adding incorrect fluids, but that's a warranty issue, not an insurance issue.

 

I've been using silicone fluid for for the last thirty five years in my S Type and listed it on insurance forms with various companies under modifications and not one of them has ever questioned it or given me hassle over it.

 

If the exotic brake fluids offered any real benefit major global OEM's such as Benz/AMG, that fit extremely advanced & sophisticated braking systems to their cars, would be using them. They don't. They use the premium DOT 4 fluids.

 

One thing our cars don't have is a sophisticated braking system with a single circuit system. I grant you that silicone fluid is not suitable for modern ABS systems due aeration, that's one reason it's not used. It's far from exotic as the US military and NATO have been using it for years. I can only speak from experience but I've never had a problem with it in my S Type, I get no corrosion in the components and it doesn't trash the paint and has always passed the brake roller test at MOT time.

 

Plenty of people suffer elastomer compatibility issues & especially in boosters. You have been lucky that all your "rubbers" have been happy. Many find they aren't when it's too late. Hence I will never recommend them.

 

I had all my bores re-sleeved and then used it to lubricate and assemble them.
I got the seals from XKS.com and they were on contact with it for many months, or even more then a year before I finally got the whole system back together.
Upon assembly, the caliper seals were not sticky or swollen or had become hard.

I suppose if someone would have used new old stock, then there may have been something to worry about, but stock that old would not have been able to be used no matter what type of fluid one would be using.
I think one has to do their research and decide if it's right for their needs, but just saying that it's bad all across the board and will cause problems for sure, is not the right way to think either.

Here's an article supporting the stuff.

Conventional vs Silicone Brake Fluid ? Moss Motoring

 

Yes I know that article JeffR1 ~ I also accept that we oilco folk get far greater exposure to issues than the man in the street regarding, jammed boosters, air entrainment, elastomer issues, failed brake light switches etc.etc. ad nauseam. There are most definitely potential issues. It depends on how much they bother you. The average man in the street has no way of evaluating elastomer compatibility over typical conditions that seals are exposed to. They have to accept things on good faith. I simply raise the issue. People must do as they wish with their own cars.

That article also contains this report below.

quote:

"When I restored my 1966 Triumph TR4A Daytona 24HR race car in 1992, I put silicone in a completely new system. Everything was new down to the steel lines. The brake master cylinder has failed 2 times since then. The rubber seals were like jelly and came apart in my hands. This car is rarely driven and in my garage in Florida. My other 2 Triumphs, a 1966 TR4A and a 1972 TR6 are driven regularly and have had the same master cylinder break down regarding the seals. Not sure what is happening here but now there is a warning on the box saying ” use of silicone fluid voids the warranty”. No more silicone for me. Currently, Castrol GTLMA is my preferred brand."

unquote

 

I certainly didn't intend to spark such heated debate. Though it has to do with lubricants so I should have known...... in any case thank you for your input. I will be using type F for the PS and standard DOT 3/4 brake fluid....

 

He He... heated debate, I thought it was quite civil.
Some of the other forums I belong too can get really out of hand, one is about home theatre projectors.

 

[[color=#000000]JeffR1

I think you are correct; it is not heated debate but an exchange of ideas that are tempered by ones experience.

Glyn covered it all from a Tribologists view point when he said ……

“I also accept that we oilco folk get far greater exposure to issues than the man in the street regarding, jammed boosters, air entrainment, elastomer issues, failed brake light switches etc.etc. ad nauseam. There are most definitely potential issues. It depends on how much they bother you. The average man in the street has no way of evaluating elastomer compatibility over typical conditions that seals are exposed to. They have to accept things on good faith. I simply raise the issue. People must do as they wish with their own cars”…………………..

And……….”Plenty of people suffer elastomer compatibility issues & especially in boosters. You have been lucky that all your "rubbers" have been happy. Many find they aren't when it's too late. Hence I will never recommend them”……..

I agree completely with Glyn, now from an Automotive Engineering view point……….

Firstly, there is enough evidence Worldwide to show potential incompatibly between brake seals and certain fluids. In practice a vehicle may be converted to Dot 5 and fitted with compatible seals operating without trouble, except for say long pedal travel issues. At some point along comes the mechanic, or the next owner and some brake hydraulic parts get replaced and/or Dot 4 added to the system. The scenario is that the original source of many of the parts and particularly rubber type seals cannot be traced and the rest is history. One very well-known case in various circles was when this happened to the R-R car previously used by the prime minister of Australia when Dot 5 was in the system and the rubbers swelled up.

If an injury or fatality occurs through brake failure with a car using incompatible brake fluid, no insurance company I know will fully cover that event. Incompatible here means also when any rebuilder’s instructions have been ignored. In my experience rebuilders of brake parts are very wary of Dot 5 fluid and nearly always state a case of void warranty if it is used. On a more personal note, a Coroner would not be too impressed neither.

You confirmed your Bentley being a 1951 Mark VI a vehicle I know fairly well, I have worked around those in some 44 countries and I have flown out to the USA many times to correct brake faults caused through use of Dot 5. If you are not to kill yourself, then replace the master cylinder breather cap if you use Dot 5 on that car. I am already aware that the mechanical transmission servo on that car does not like the compressibility of Dot 5.

Next, Nigel W mentioned…. “as the US military and NATO have been using it for years”

I am afraid that is incorrect…..my experience with armed forces tells me that the US Army, although initially supported development of Dot 5, very, very, quickly back pedalled on that issue. They did not take well to having some 4000 to 5000 trucks disabled at one hit. (Tip….when you are in that deep you put them all down a reversed strip and rebuild line to change the affected parts).

Having worked as a consultant and engineer, not only on USA equipment but also in Russia I can tell you their Armies and Air forces all use Dot 4, with good reason. If you doubt that then consider that one hour ago I spoke to maintenance at USAF deliberately and they confirmed my data….they use Dot4!!

I have witnessed a Dunlop 22 inch diameter disk brake (you think you have big Dunlop discs!) used on a Chieftain tank slewing brake lock up when the calliper jammed (same calliper as Jaguar) on a Dot 5 test. No good for any Army, let alone NATO.

It boils down to the fact that if you are 100% happy with compatibility issues you might use Dot 5. If on the other hand you know and have seen first-hand the problems you will not be going anywhere near Dot5.

Your mileage may vary……



Norman

 

Thanks for mentioning your US-Mil experience Norman. You are correct. We US oilcos are encouraged not to speak about our experiences with supply to the US Military so I tend not to. Habit!

 

OK Norman and Glyn, you've got me rattled about the silicone fluid. Can you recommend a way of changing back to DOT4 without dumping the entire braking system? I don't fancy taking the IRS out again and stripping it down to get the callipers out. Most of the braking system has been renewed over the last three years. BTW it looked like my US military info was well out of date.

 

If you are already running DOT5 (silicone) fluid and things are working, then why change it out ?

If it's been three years and you're not experiencing any braking issues from dissolved seals, then what's the problem ?

 

Nigel ~ you are between a rock & a hard place but fortunately fettle your own car. I would let sleeping dogs lie. It seems you got lucky with a compatible set of rubbers. Just monitor all points for any sign of fluid weeping & react immediately if you see it. Something we should all be doing with cars that have single circuit brakes with no backup. Ensure your handbrake is in good fettle.

The alternative is to rebuild the braking system with new rubbers at all locations, clean & dry pipework etc & revert to DOT4. A major exercise.

EDIT ~ if you ever have to repair a braking component try to ensure that rubbers provided are DOT 5 compatible. Sometimes very difficult to ensure/ascertain.

 

Thanks for your response Glyn, the only component I've had a problem with was the master cylinder that was about twenty five years old and started leaking. When I replaced it I stripped it down to see if the rubber seals had swollen but they were no signs any problems they were just worn out. In light of the work and expense to change everything I'm going to leave alone for now and as you say keep an eye on everything. BTW I use DOT 4 in my XJ6 and change it every two years.

 

I purchased a front crossmember from a 3.8S to use on my MK2. Apparently this was a popular upgrade before 3.8S donor cars became scarce. I also added XJ6 front calipes a bolt on proposition. (used XJ6 rear calipers with original P/brake. Also bolt on.)The crossmember uses the Marles Variomatic. I had the box rebuilt in the UK. Alosng with the pump. On the MK2 the pump mounts to the rear of the generator. I upgraded that to an alternator with provision for the pump.

A photo of the rebuilt crossmember. I bought the adjustable tie rods. Not happy with them. I would prefer new fixed length tie rods. Difficult to find as power steering cars use different tie rods than non assist.

I encounters some stress cracking in the metal. This was fixed and the bare crossmember blasted and refinished.

 

Just a tip. The Varamatic, as it requires absolutely accurate centering ~ has to have adjustable (side) tie rods & a fixed length centre link rod. The reverse of the Types 1 & 2 Burman recirculating ball PS boxes where toe is set by manipulating the centre link rod.

With Varamatic you center the steering box, drop link, centre rod & idler. You then dial in toe individually with left & right tie rods. Remember the Varamatic is variable ratio from centre to left & right lock. Most modern alignment shops do not know this.