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Flush your brake fluid!

dhrivnak

Active Member
Jan 8, 2011
4,417
3,577
NE Tennessee
I too am a bit confused. I have now owned 7 cars and driven them all over 100,000 miles and never did a break flush. If I changed the caliper or cylinder I would bleed them but never did a flush. I cannot figure out what is different with a Tesla.

PS I also did 95% of all my own maintenance and have always kept the cars a minimum of 8 years.
 

hcsharp

Active Member
Jun 7, 2011
3,379
1,341
Vermont
I too am a bit confused. I have now owned 7 cars and driven them all over 100,000 miles and never did a break flush. If I changed the caliper or cylinder I would bleed them but never did a flush. I cannot figure out what is different with a Tesla.
What's different about a Tesla is that we don't use the brakes. While heat cycling draws air (with moisture) in and out of the system, The_User pointed out that tiny pockets of water molecules will also boil when hot, forcing some of the steam out of the system. I have trouble keeping the rust off my rotors much less heating them up enough to evaporate some of the water content. I suspect that's what's going on. I have never flushed my brake fluid in any car except when doing repairs without any problems like this.
 

AndrewBissell

Member
Apr 16, 2009
645
3
I spoke today with the Service Manager in the UK, Geoff Hurst. He gave me permission to post (my synopsis of) his reply on this topic:

Every time a car comes in for service they take a sample of the brake fluid and test it using a special-purpose machine. This tells them if the brake-fluid is still good or needs changing. They change the fluid only if it fails the test.

This seems good enough to me.
 

JRP3

Hyperactive Member
Aug 20, 2007
19,803
44,472
Central New York
It sounds insane to me. Honestly I've never heard of any vehicle that had this much attention given to brake fluid. I'm sure I've had vehicles that had brake fluid in them from the factory that were 20 years old and had no brake fluid issues. This is almost like being told my differential fluid gets inspected regularly and needs changing every two years. Bottom line I do not consider brake fluid as a regular maintenance issue, and one of the benefits of EV's that we claim is reduced brake maintenance. If EV's in general need regular brake fluid changes that argument is gone.
 

Doug_G

Lead Moderator
Apr 2, 2010
17,881
3,347
Ottawa, Canada
I think you guys are really overblowing this. ONE owner had contamination of his brake fluid; probably a one-off problem caused by a defect of some kind (in the Lotus-supplied hardware).

If you bought a new ICE car and take it in to the dealer for regular service they probably check the brake fluid ever so often as part of their regular service program. Unless something was wrong you probably never even bothered to notice this fact.
 

frequencydip

Sig 100 - #52
Dec 11, 2011
172
35
Los Angeles
I spoke today with the Service Manager in the UK, Geoff Hurst. He gave me permission to post (my synopsis of) his reply on this topic:

Every time a car comes in for service they take a sample of the brake fluid and test it using a special-purpose machine. This tells them if the brake-fluid is still good or needs changing. They change the fluid only if it fails the test.

My car was in for its anual service 4 weeks before I flushed my own fluid, I kinda doubt they tested my fluid unless they happend to pull it just from one front brake, both front brakes the fluid was clean and normal. Both rear brakes had the gelled fluid.
 

doug

Administrator / Head Moderator
Nov 28, 2006
16,908
1,025
SF Bay Area
There is nothing special about the Roadster brakes (except that they have to use an electric pump for the brake booster since engine vacuum isn't available). In the cars I've had, I just change the brake fluid every couple years or so, or when the clutch fluid starts getting dark (same type of fluid, similar procedure).
 

hcsharp

Active Member
Jun 7, 2011
3,379
1,341
Vermont
My car was in for its anual service 4 weeks before I flushed my own fluid, I kinda doubt they tested my fluid unless they happend to pull it just from one front brake, both front brakes the fluid was clean and normal. Both rear brakes had the gelled fluid.

Rear only? That would support the theory that never giving your brakes a good hot soak prevents the moisture from evaporating out. Doesn't prove it of course.
 

bolosky

Member
May 5, 2009
701
591
I just had my 36K mile service done. In addition to removing the entire back half of the car (I posted another thread on that), they changed the brake fluid. The Ranger mentioned to me that it was very bad.

So, maybe more than one car has had a problem.
 

smorgasbord

Active Member
Jun 3, 2011
3,194
5,059
SF Bay Area
This site has some good general brake fluid information, including this on water/moisture:

Water/moisture can be found in nearly all brake systems. Moisture enters the brake system in several ways. One of the more common ways is from using old or pre-opened fluid. Keep in mind, that brake fluid draws in moisture from the surrounding air. Tightly sealing brake fluid bottles and not storing them for long periods of time will help keep moisture out. When changing or bleeding brake fluid always replace master cylinder caps as soon as possible to prevent moisture from entering into the master cylinder. Condensation, (small moisture droplets) can form in lines and calipers. As caliper and line temperatures heat up and then cool repeatedly, condensation occurs, leaving behind an increase in moisture/water. Over time the moisture becomes trapped in the internal sections of calipers, lines, master cylinders, etc. When this water reaches 212º F the water turns to steam. Many times air in the brake system is a result of water that has turned to steam. The build up of steam will create air pressure in the system, sometimes to the point that enough pressure is created to push caliper pistons into the brake pad. This will create brake drag as the rotor and pads make contact and can also create more heat in the system. Diffusion is another way in that water/moisture may enter the system.

Diffusion occurs when over time moisture enters through rubber brake hoses. The use of hoses made from EPDM materials (Ethlene-Propylene-Diene-Materials) will reduce the amount of diffusion OR use steel braided brake hose with a non-rubber sleeve (usually Teflon) to greatly reduce the diffusion process.

For normal driving many of us don't use the brakes enough to heat them up. What are the long term effects when this goes on for a couple of years?
 

The_User

Member
Jan 31, 2012
37
3
Seattle
Shocking this thread is still alive. I know this is my…..3rd post, so please don't hang me for having an opinion:

From what I have seen, the Tesla Roadster brake system isn't anything different than you would find on 99.9% of other sports cars. It's a pretty standard rotary ABS pump, mono-block calipers, combo of rigid and soft lines, vacuum assisted booster and reservoir that is vented to the atmosphere. I've already said this in previous posts, brake fluid is hydroscopic and will go bad just sitting in a container after it's been opened. BTW - You should never buy "bulk" amounts of fluid unless you plan to use all of it soon. Plastic containers are bad, only buy small amounts in metal containers. Sure, you can go 5+ years and not swap out brake fluid and be "okay". Why? Changing out fluid once a year is probably on the extreme side of things. Just because my ICE car oil change interval says 10k miles doesn't mean I'm not going to change it at 5k. Not changing out your fluid shortens the life of the seals, rubber lines and at times, the metal components in the system (corrosion). As I mentioned earlier, these are $100k cars, spend the $100 every couple of years and get the fluid flushed. Sheese! :)
 

JRP3

Hyperactive Member
Aug 20, 2007
19,803
44,472
Central New York
One of the reasons this thread is still alive is that some people are reporting excessive fluid gelling or problems in the rear lines only, which suggests a potential problem with EV's using regen, or a specific problem with the Roadster rear brakes. It will be interesting to see if other EV's show similar problems. Blindly changing your brake fluid at regular intervals doesn't necessarily address what is really going on here. Does the regular heating of brake fluid in normal vehicles somehow reduce moisture buildup, and if so how, where does it go?
 

Bradleybang

Member
Apr 14, 2008
391
130
Oakland, CA
My 2 year was up last September and I scheduled for service in Melo Park. Here is what they sent me in service confirmation email:

According to your service history, you are due for:

24k/24m annual service ($600)
Brake fluid flush ($110) performed every 2 years.
Firmware update (warranty)
Battery Bleed test (warranty)
 

Bradleybang

Member
Apr 14, 2008
391
130
Oakland, CA
Good question. Its a complete check of car. I don't know all stuff done. I do remeber them replacing the front shocks (warranty) as they said had too much noise.
 

speedy99

Model 3 (2018, LR)
Aug 15, 2011
56
4
Santa Cruz, California
But the fluid issues reported and the change intervals are not standard from my experience. In fact I've had a number of off road vehicles that regularly went in deep water and mud and I never saw excessive water or gelling in the brake fluid and never did yearly brake flushes. In most cases unless I had to change system components they never got a full flush and never had any issues, and this was with regular DOT3 fluid. I'm just mystified by the fluid change intervals some of you seem to think are standard. If some mechanic suggested to me a yearly brake fluid flush I'd think he was trying to rip me off and I'd never go back there again, but I've never heard of such a thing before. Maybe the DOT 4 and up fluids are more sensitive to moisture?

We seem to have two classes of Tesla owners. One class where this is their first performance car, and another where it is not. I've always changed fluid every 2-3 years as a precaution, and on cars I have taken to a track, I change it every time I am on the track. Why? Because at the limit, brake fluid is ultra sensitive to moisture and fades more easily when heated if not fresh. If you haven't experienced brake fade at 100mph surrounded by k-wall, you are probably less picky about your brake fluid.

Having said that, I see no reason why the tesla brake fluid would get warm, let alone hot. The car goes into reduced power mode if flogged, and strong regen also relieves brake pressure. They do seem to have a stronger rear wheel brake bias than most cars. I am only 6 months into ownership, but now plan to pay for the fluid change at my 1 year. Maybe some funky manufacturing or shipping contamination happened. It might explain/help the relatively poor tesla braking.

How many people have rear brake 'gel', and what are the build dates of those cars?
 

malcolm

Active Member
Nov 12, 2006
3,072
1,729
Can't see an easy/cheap permanent fix for this. Either someone needs to reformulate brake fluid (could an additive be developed, tested and licensed?) or EVs need to have some way of passing any spare heat via a heat exchanger to the existing fluid type.

But heat levels are unlikely to match those generated by pad friction, which is what seems to deal with the moisture at the point of ingress.

So for now it looks like brake fluid is the new oil change :(
 

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