So, while attending a small repair this week, my trusted shop advised me that my 2001 XJ8 with 165K needed new pads on the rear (OK) and then said I should have a brake fluid flush done as well. The fluid has a "green tint" to it. When I told him I've NEVER had a brake system flushed ever, since I believe the system is "closed". As such, doesn't this make fluid getting contaminated unreasonable, unless of course the system was opened for a period of time for parts, i.e. calipers, etc. He replied the tint was an indication of contamination, i.e. moisture, other non-fluid chemicals. HUH?
So, although I have trusted this shop for years to do work I couldn't, or wouldn't, do on my Jags, this has me flumixed. How about the group weighing in on this "To flush or not to flush"?

Dave in AZ

 

I bought a 2002 with 45k miles and the brakes were really dead on it. After replacing rotors and pads and still had weak pedal feel, I paid someone to do a flush. The fluid was also green, the guy had never seen that before. The difference in pedal feel was day and night. Really recommend you do it or have someone do it if it has never been serviced.

 

I bought a power bleeder and flushed and filled my brakes when I replaced the front pads and rotors. I cannot tell much difference in feel but the old fluid was very dark, so I’m glad I did it.

 

The brake system is not "closed", it has a vent on the reservoir cap. It is a well known fact that the brake fluid should be replaced (flushed) every about 2 years because it absorbs moisture which will corrode brake system parts internally. Furthermore, the fluid which has absorbed too much moisture may boil during prolonged or repeated hard braking which will result in loss of brakes. I am sure there are many articles on the net on this.

 

A definite YES on periodic flushing. Every 2-3 years on my cars.

I want to investigate the green fluid, though, so as to avoid the chance of introducing an incompatible new fluid into the system

Cheers
DD

 

+1

Although the JLR recommendation on current and recent models is for a fluid change every 3 years, I've always done this on my vehicles because brake fluid does deteriorate over time.

Brake fluid is deliquescent / hygroscopic (absorbs moisture). In addition, the movement of caliper pistons against the seals abrades tiny particles which become suspended in the brake fluid and you will often finds the first fluid out of the bleed nipple is almost black if it hasn't been changed regularly.

Take heed of Doug's warning about fluid compatability. The original specification for X308 is SUPER DOT 4 which is a non-mineral glycol based brake fluid. DOT 5 silicone based fluids have the benefit of not being hygroscopic but the two types must not be mixed. There is also evidence that seals designed for DOT 4 are not suitable for DOT 5.

Graham

 

My rule for all my cars: bleed every two years. period. paragraph. You don't want your fluid to boil on hard braking because of suspended water in the lines. It's cheap insurance.

 

Don't just bleed...but Flush the entire system. It is very important to remove
contaminates suspended in the fluid, from the system

 

Having just carried out a brake flush I have to agree with everyone with getting it done.

 

Glycol based brake fluid is hygroscopic.

Here is the maintenance checklist we performed on Jaguars back in the late 1990s ans early 2000s.

Look on the checklist for recommended vehicle maintenance.

* Replace brake fluid every 2 years: .................................................. . 2 year maint. 4 year maint. 6 year maint.

 

your brake fluid will flunk out on copper it will be easily 300ppm or more

i don’t really care about moisture but corrosion is a big no no

 

Unfortunately, it seems a lot of people have the same misconception. When I was younger and had more time and energy, I was buying wrecked cars to part out or rebuild. I always opened up the master cylinder to check if if they were worth keeping. Sometimes I could hone the bores out clean. If so I'd replace the seals and resell or reuse it. All but a couple I just threw them out with the scrap metal because they were too far gone to save. Although my experience is by no means a statistically significant sample, all the same kind of car, I have gotten the impression that 9 out of 10 cars have probably never had their brake system flushed, ever.

 

You are most likely correct. Most people don't change their brake fluid in my experience. In fact
most people do little to no maintenance (with the exception of oil changes) at all. The only time
that changes is when the car starts breaking down. Even then, if the car is very far from its prime
they look for a different newer car rather than expend time and money in what they consider to be
yesterdays' news. Jaguar owners, on the other hand are a little more particular when it comes
to recommended maintenance, Even though I am certain there are some that may not observe
the maintenance recommendations very well.

 

All for it after seeing my fluid post flush. It was absolutely horrible/compromised.

 

THX to everyone who weighed in on this issue! All good points and have convinced me to do a "brake flush", not just a bleed. Considering the old boy hasn't had a full bleed, I'm of the mind that popping for Pentosin Super Dot5 is worth the increased cost.

 

I stand corrected. I chose the wrong word. Flush is what i meant. Thanks for the terminology reminder!

 

If you're going to do this (and it's probably unnecessary, and won't provide a benefit unless you're planning on tracking the car) then make sure to use DOT 5.1, NOT DOT 5. They use a different base and won't interact well, DOT5 is silicone and 3/4/5.1 are glycol. Also the system seal material may not be compatible with silicone based fluid.

 

Thats meaningful information. Thank you.

 

Gosh! I’m embarrassed to admit I’ve never had my brake fluid flushed or changed and I’ve owned my car nine years! It has 90,000 miles. I’m definitely going to do it. So I should use SUPER DOT 4 to keep it stock?

 

Changing your brake fluid every 2 years will forestall most fluid-related issues, but there are some inexpensive tools that will help you monitor the fluid condition.


An inexpensive brake fluid hygrometer will give you a rough idea of the moisture content and they can be found for under USD $10.00:





I personally like the ones with graphic displays like this, which cost only a bit more (less than USD $30.00):





Test strips like these from Phoenix Systems make it easy to assess the copper (corrosion/mineral) content of the fluid. They're not cheap, but your friendly mechanic may be willing to sell you a few strips so you don't have to buy a full tube:




Cheers,

Don