tr7triumph.com

I am currently stripping the entire underside of my car to enable me to repaint the chassis. As a result I have drained the brake & clutch fluids. I've heard you shouldn't mix normal fluid with silicone fluid, so how do I determine which type was in my car before I refill with fresh stuff. I don't want to mix it & cock up the seals etc.
Also, what is considered the best fluid for our cars? I have a standard TR8 set up.

Andy
1981 UK SPEC TR8

You will most certainly get a lot of opinions on this. I run DOT5 Silicone in all my cars. The system should be flushed out before a changeover. I have done them by simply blowing through the system with shop air and then bleeding through with the DOT 5. Some will claim disasterous results with DOT5 but I have never had a problem. I have it in 3 cars, 2 motorcycles and my boat trailer.

Unless someone else changed it, you would have DOT3 or the equivalant. Do you have any of the old fluid collected? If so, put some on a scrap painted surface. If it wrinkles & removes the paint after a while it's DOT3. If nothing happens, it's DOT5.

Jim Underwood
72 MGB BRG
80 TR8 Persian Aqua
If women don't find you handsome, they should at least find you handy.

Andy

Here in the USA silcone brake fluid is purple or blue in color. The DOT 3 - 4 is clear.

If you have a scrap piece of metal that is painted put some of your fluid on it. If it is DOT it will start to remove the paint.

DOT in my opinion is best for normal use, less problems with air bubbles and trying to bleed the system.

Dale
1974 TR6
1977 TR7 FHC

I have run DOT5 in the brake system of my FHC for about 5 years without problems. The system was flushed through as the two types do not mix at all, but I did not change seals, I have had no problems or leaks.

Some will argue that because DOT5 is not hygroscopic (i.e. it will not absorb moisture) then any water that does get into your brake system will tend to "pool" at the low point in the system & be a potential cause of corrosion.

On the other hand, the fact that DOT5 will not absorb moisture also means that it will not loose its effectiveness over time unlike DOT3 or 4 (moisture absorbtion decreases the boiling point of the fluid).

So, pros & cons to both. DOT5 is normally a kind of purple/blue colour as mentioned by Reddragon. The paint test is a good way to tell what you have got in there - also another plus point to DOT5 as when your clutch master decides to leak (they all do, don't they?) you will not strip all the paint off the bulkhead!

One word of warning - only DOT5 is silicone based, you may see DOT5.1 which is NOT silicone based (I think it is some fancy racing formula).

Tony

<font size="1">1981 2L FHC Cavalry Blue
1980 3.5L V8 DHC Jaguar Regency Red - sadly sold!
TR8 FHC EFI Factory development car Inca Yellow</font id="size1">

Thanks for all your replies, I've tried the paint stripping test & it didn't touch it which suggests it's silicone however my fluid is clear not purple.
I have since searched through a box file of receipts for my car & found one from '95 when the car was converted, & one from a '98 service, both for silicone fluid!
I'll be refilling with silicone. [:D]

Andy
1981 UK SPEC TR8

One tip if I may. Be careful handling the silicone DOT5. Although it won't harm painted surfaces, it will irritate your eyes. If you get it on your hands, don't put them anywhere near your face until you have washed them with hot soap & water. I think the stuff is great but it has caused my eyes to burn on more than one occasion. Not sure why but it does.

Jim Underwood
72 MGB BRG
80 TR8 Persian Aqua
If women don't find you handsome, they should at least find you handy.

A decent DOT4 or DOT5.1 for me please [:)]
Had DOT5 in 't Kreng fot a few years and I was not impressed to say the least [B)]
Gave a very spongy feel to the brakes, which went when I switched to a high quality DOT4.
Only positive thing that I remember of DOT5 is that you can polish the paintwork with it [:D]

As for the water absorbtion DOT5 doesn't absorb the water so it collects at the lowest point of the system ...
It's a good thing to change hydraulic fluids every year.

<center>
<font color="blue"><i>1980 TR7 DHC (my first car, currently being restored)
1981 TR7 FHC Sprint (better known as 't Kreng)</font id="blue">
<b>http://tr7beans.blogspot.com/</b></i></center>

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Beans</i>

A decent DOT4 or DOT5.1 for me please [:)]
As for the water absorbtion DOT5 doesn't absorb the water so it collects at the lowest point of the system ...
It's a good thing to change hydraulic fluids every year.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

If DOT5 doesn't absorb water, how can it collect at the bottom of the system, the system is sealed except for air flow access at the master cylinder cap. Dot 3 or 4 will absorb water vapour in this area and so will have to be bled periodically. The reason the US military use it is so this maintenance doesn't have to be done. No doubt DOT5 is more difficult to bleed but I suspect there is a lot of urban legend and old obsolete info circulating around on the subject.


TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra

OK, I'll add some fuel to this old debate.[}:)]
My MGB was restored in 1992-93. Complete overhaul of the hydraulic system with DOT5. Never been touched since. Both cars have seen track days. Burned the frt brakes off the TR8 the first time out. No fluid related issues though. Irregaurdless of the other so called issues, the paint removal problem is a nobrainer for me.[:D]

Jim Underwood
72 MGB BRG
80 TR8 Persian Aqua
If women don't find you handsome, they should at least find you handy.