hi + Brake overhaul on '66 E-Type coupe
 

Hello fellow Jag enthusiasts .. this is my first post, please feel free to correct me for any lapses in forum etiquette, etc.

I am the proud owner of a 1966 E Type coupe, I live in Cincinnati, Ohio USA.
I bought the car in California in 1986 and drove her back to Ohio, not without incident, but i made it home.
Over that first winter i changed the clutch and overhauled the cylinder head. I used silicon ( dot 5 ) hydraulic fluid for the clutch.
Since then I have not driven the car as much as i would have liked ( 4000 miles in 32 years, i know shame on me )
About a month ago I braked to stop at a traffic light and was completely enveloped by a white smoke. That woke me up in a hurry !!
Thinking i had brake fluid spraying onto the exhaust somewhere i limped home using the hand brake.
The middle reservoir was about half full, but i could not find any ruptured or leaky hydraulic lines under the car.
If i depress the brake pedal ( parked with the engine idling and bonnet up ) i can hear a " gurgling noise " coming from the master cylinder area.
I guess a major brake overhaul is necessary after all this time ?
I would like to use silicon fluid for the brakes unless anyone would suggest otherwise ?
Sorry for the long post ..
Charlie R.

Do not use dot 5 in the brakes, stay with dot 4. I have been told many times that silicon will ruin the brake components. I suspect the same is true for the clutch cylinders but you added the stuff 32 years ago apparently with no harm. I assume the clutch reservoir is not down. The recommended fluid for brakes and clutch is dot 3 or 4 brake fluid and I have used that (dot 4) with no issues after rebuilding both systems several years ago.

Brake overhaul on '66 E Type coupe
 

Thanks billb44 for your reply, I will use Dot 4 brake fluid.
It's been a while since i bought any jag parts, I've used Welsh's in the past, would you recommend them or others ?

I normally use SNG Barrett because they are within driving distance plus their service, parts inventory and pricing have been good.

Go back to castrol brake fluid, BUT Imho, you have to go back and replace ALOT of things....
Sitting 30 years, the master and all IMHO, have to go, change the pistons on the calipers. That DOT5 will eat through everything.
Your locking up on the master or booster.
Good luck.
GTJOEY1314

'66 E-Type brake overhaul
 

Thank you GTJOEY1314 for your advice, much appreciated.
I may well be posting again as this job progresses !!

brake fluids ???
 

There is a lot of ill advice on brake fluids. so lets set it straight. Dot 3,4, is a mineral and glycol based fluid, it has been used for years and does a great job !

It is compatable with most seals, pistons, dics, and drum and clutch systems, in daily driven cars, BUT. it is hydroscopic !, that means it attracts water !.

When water gets in the typical system from condensation from heating and cooling the brakes the fluid becomes contaminated this lowers the boiling point of

the brake fluid ! Most drivers buy the best fluid 4. instead of 3, because it has a higher boiling point but all that changes with time because of the normal ingress

of water. So if it is so bad why does everyone still use it?? The answer is because your daily driver is driven all the time this gives the brake system time to boil off

that water (with a lot of brake applications) and thereby returning the fluid to its precontamited state and high boiling point. BUT. if you let this car sit for a while

the water in the brake system begins to rust out the lines and cylinders. Over a period of time the brakes will fail and will require rebuilding! BUT if we drain and replace

our brake fluid we won't have this problem, now most people do not drain and replace the brake fluid except during brake overhaul !

All this brings us around to DOT 5 or Silicon brake fluid, it is compatable with all brake systems, all seals, all metals all cylinders and all cars this is because

it is TOTALLY INERT ! that means it won't stick to, blend with, or be part of, any other materials, it also does not absorb water and has a higher boiling point than

Dot 3 or 4 aaannnnd it will maintain that higher boiling point for a longer time. Another great thing about Silicon it is a great lubricant, so therefore much better choice

when used in older vehicles that are left to sit more than they are driven ! Silicon brake fluid CANOT. be mixed with other brake fluids so if you decide to use it

it must be completely clean and dry system before using. Now having stated ALL the facts let us consider the people who have had problems with silicon fluids........

If it wasn't installed in a totally cleaned system then the old dot 3 or 4 fluids would contaminate the brakes and the silicon would be blamed for the failure!

For those who still like to blame silicon for thinking it's incompatable............remember It is the most widely used universal lubricant !

Brake overhaul on '66 E-Type
 

Thanks for your most comprehensive reply on the best brake fluid to use for my car.
There seems to be different opinions over mineral v. silicon hydraulic fluid.
I think for my situation, where the car will be garaged for most of the time, Silicon fluid ( Dot 5 ) would be best as it is not hygroscopic.
I did overhaul the clutch on this car 30 years ago using Dot 5 without any issues since.
Cheers and thanks for all the help.

The points presented by felinecat appear quite persuasive but go against those presented by others whose opinions I respect. Being an important factor in our cars' protection, I wonder if there are other comments from knowledgeable forum readers. Just want to make the best choice.

Most shops now have electronic water content measurement tools and only replace fluid when the limit is reached, (a fairly low limit, so don't worry too much !!). Yes, glycol-based fluid is hygroscopic, but ask yourself where does the water get in ? Well, only via the very small hole in the reservoir filler cap, the rest of the system is sealed. In the "old days", when there were no electronic water content measurement devices around, most manufacturers specified fluid changes at about 2 yearly intervals, and some even said you had to replace all seals in the system every 5 years. Well, of course, nobody did the seal replacements, yet nobody got killed by not doing so, it was a council of perfection. I well remember the regular brake fluid flushing but nowadays it doesn't seem to be part of the service anymore.

What you will find is that on the air side of a seal sitting on a cast iron caliper bore, corrosion will occur and as the piston moves, it will gradually destroy the seal. I had this with my MG Midget clutch slave cylinder that had stood 14 years. Yet the front calipers and rear pistons have been OK since 2010 except I needed a new rear brake cylinder a couple of years ago.