Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Brake fluid change interval???

Ahem - it's hygroscopic - not "d"

I thought they were two different things, though very similar?

Graham's right. Something that is hygroscopic absorbs water molecules from its surroundings. The word 'hydroscopic' means pertaining to or akin to a Hydroscope, which is a device used for observing things below the surface of water.

There are people with £70,000 sports cars who will get their brakes discs skimmed down to or below the manufacturers minimum thickness, then come on to this forum to say how much they have saved from not having to fit new brake discs.

I know of no other person in my local car fixing circle who will dispose of opened brake fluid after a year or so.

To be honest, I know of very few local DIY car fixers or local garages who will change brake fluid, gearbox oil, diff oil or antifreeze as they consider it not an issue.

Local garages know if they change these item at the prescribed manufacturers service intervals on cars over three years old, that their customers will go to other local garages who charge a "proper price" for car servicing and not those "Ripoff Barstuards" who charge £50 more for that "stupid stuff".

Let’s think about it a bit.....
If a bottle of brake fluid is kept with the cap on then it will have a VERY restricted change of air (if any). The cap may not be a perfect seal but, seriously, there is no airflow. The water content of the air trapped when screwing the cap on is what would be absorbed. Leaving the cap off is a different matter though. Far more exposure to moist air.
If you want to be pedantic then decant the left over fluid in a half full bottle into a smaller one so you minimise the trapped air volume!
Every two years I buy fresh fluid for the replacement and keep the left over in case of a top up, but dispose of it when doing the change....it isn’t going to break the bank, is it?

My +4 was about 5 years old when the rear brakes seized on a Friday afternoon at about 4.30pm. I feel somewhat embarrassed to admit I had not changed the brake fluid in all that time. Luckily, I was less than 5 minute drive from Berrybrook and in the time it took to drive there I also cooked the brake shoes. I say luckily for good reason, because Bradley was still at work and spent the next 2 hours (of his own time) changing brake cylinders and shoes for me. This story has two lessons. 1. If you have to breakdown do it near Berrybrook (I still can’t thank Bradley enough for his time and skill) and 2. Change your brake fluid every 2 years, besides Dave W tells us to do it and you ignore him at your peril.

Bradley and James have been looking after my 4/4 for a long time.
This includes regular changes of brake fluid. The rear cylinders were spotted as having a slight leak 2 years ago and changed accordingly.
Top mechanics in whom I have total trust.


(Just a happy customer)

I found one rear brake cylinder leaking a few months back and chose to replace both rear cylinders and shoes at the same time. Its a fiddley job and a bit mucky too. I used to simply bleed out the dirty part of the fluid till clear flushed through but clearly that was not good enough.

How old is your Mog?
How long before the original systems deteriorate?
Rubber tubing ages so will need changing. Seals age too. Electrics...some areas are really exposed ( look under your front wings!)
When I had my 1993 4/4 I replaced all flexible fuel lines, fitted an extra filter, flushed the tank etc as a precaution as she was 20 years old.
Same with the brake system, new flexible pipes, no visible leaks from seals so no cylinder changes done.
On my Plus 8 I have had to sort out front light issues due to corroded bullet connectors. A bad design as they are hammered by spray from the tyres.
To me, changing brake fluid is a no-brainer.
I do worry a bit about the removal of MOT for older cars as it is then down to the owner’s attitude to checks/preventive maintenance on ageing or old design cars.

There is no real accurate advice on this one Graham.

June 2015, I bought a 6 year old Impreza and Subaru's in my experience can get sticky calipers.

Checked the car with an IR temperature gauge and the front and rear offside calipers were 15 to 20C hotter than the nearside after driving but not braking.

I purchased Subaru seal kits and did both the offside calipers. 18 months on and the front caliper is fine but the offside rear one that I rerubbered had the piston go rusty.

This time I replaced the offside rear caliper over Christmas 2016.

When I did both calipers I probably used 2 ltrs of fluid to make sure there was no old fluid in system. On the way down to the Lake District in February this year we were stopped at some roadworks near Pulley Bridge and with nothing to do I went round the car with the IR temperature gauge again and the nearside rear caliper was just starting to seize. It was at say 45C when the replaced offside caliper was say 25 to 30C.

I changed the nearside caliper when I got home. It appears to me that there is a local problem with metal salts from farmers fields being leached on to the roads near where we live and that appears to get through the caliper dust seals.

I have always found rear drum brake cylinders in UK supplied cars a leak just waiting to happen.