Hi, has anyone used DOT 5 brake fluid in their E-Type?
A friend is using DOT 5 in his E-type and is trying to convince me to use it on mine, while I try to convince him that he should be using DOT 4.
Isn't DOT 5 silicone and isn't that supposed to be bad for the seals? My friend tells me that was a problem with the old seals (Natural rubber), the new seals he says are made of synthetic material and not affected by silicone. Any comments???
Bill.

 

I used to use silicone DOT 5 fluid but there were always things in the magazines about it and it's greater compressibility compared to the normal stuff. One thing that maybe is of importance is that any water entering the system is not absorbed by DOT5 fluid, so can accumulate in the system, because there is no way to detect it with the normal electronic devices that dip into the fluid. When I had a brake job done sometime in the late 90s on my 1980 XJ6 the mechanics flushed out the silicone stuff, and put Dot 4 back in. I had no further trouble and ceased to use DOT 5 from then on as I no longer did work on cars. Nowadays the widespread use of electronic water content devices means the once-routine brake fluid changes at 2 year intervals are no more; it is done when necessary. I remember also that owner handbooks would solemnly advise you to replace all the seals in the brake system every 5 years !!! Did anybody do this ? No, of course not.
I don't think there is any problem with seals if the brakes are relatively new replacements for the original factory items, as the seals will be of the modern material. If it were me, I'd just carry on with what you have in the system.

 

I have used DOT5 in my car for 5 years now. I have had no issues with it.

regards,
bob t

 

Hi Bob,
Thanks for your input. I am curious. You say you have been using DOT 5 brake fluid in your jag's brake system for 5 years. Is this on an E-Type? Do you know how long ago your brake seals were last changed?
Thanks,
Bill.

 

DOT5 is in my 69 E type OTS. All components are either new or rebuilt, so, new seals.

I have noticed no performance loss, sponginess, heat issues, etc.

 

OK, those are points I was curious about.
Again, thanks Bob for your input. I guess my friend was right.
Bill.

 

[QUOTE=Fraser Mitchell;2295183]I used to use silicone DOT 5 fluid but there were always things in the magazines about it and it's greater compressibility compared to the normal stuff. One thing that maybe is of importance is that any water entering the system is not absorbed by DOT5 fluid, so can accumulate in the system, because there is no way to detect it with the normal electronic devices that dip into the fluid. When I had a brake job done sometime in the late 90s on my 1980 XJ6 the mechanics flushed out the silicone stuff, and put Dot 4 back in. I had no further trouble and ceased to use DOT 5 from then on as I no longer did work on cars. Nowadays the widespread use of electronic water content devices means the once-routine brake fluid changes at 2 year intervals are no more; it is done when necessary. I remember also that owner handbooks would solemnly advise you to replace all the seals in the brake system every 5 years !!! Did anybody do this ? No, of course not.
I don't think there is any problem with seals if the brakes are relatively new replacements for the original factory items, as the seals will be of the modern material. If it were me, I'd just carry on with what you have in the

I have used silicone 5 in every vehicle I have built (59 now). and have avoided all the problems associated with hydroscopic dot 3 and 4 !

Most old British and some American cars I have restored have die cast brake cylinders and die cast pistons in them or cast iron cylinders and cast iron pistons. The two LIKE metals tend to seize together when not used often (like old cars are used), the accumulation of water attracted to dot 3 and 4
exacerbates this problem greatly...... DOT 5 will not harm seals old or new it is INERT that's why they use it in medical replacement body parts!
The new brake lines that you put on your car and new cylinders should be examined after 20 years or so of use with Dot 5 they look like new, with
Dot 3 and 4 they are always rusty. I will always choose dot 5 over any other brake or hydraulic clutch fluid.... Derek Costello