Do you change the brake fluid on your Subie? My understanding is that this service is not really essential, unless the fluid gets contaminated. I use test strips once a year when I change my oil to check the brake and coolant fluid.
Brake fluid change
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A440
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Contaminated and bad are two different things. You never want contamination. That will swell any and all rubber in the system.
As the others have mentioned, brake fluid is hygroscopic. It sucks up water. Pour some on the back of your hand. You'll feel it get hot as it sucks the water out of you skin cells. If you fill a shot glass with brake fluid to the rim, it will continue to overflow as it sucks water from the air. As you get water in the system, it settles in the low spots being the calipers. Most caliper bores are chrome lined, most pistons are not. Water gets on the piston, you get rust. Rust ceases stuff up. Water can boil and you get air in the system.
Test strips are going to test for acidity and the presence of copper. Both of which you will see little in the reservoir. Copper from the lines will settle in the calipers, and acerbate the rust build up. Acidity will be the lowest in the resivor as the cap is vented to atmosphere, an this is where the moisture starts.
Follow the maintenance manual for flush. If in doubt, every fluid in the car should have been flushed somewhere between 60-75k miles.
As the others have mentioned, brake fluid is hygroscopic. It sucks up water. Pour some on the back of your hand. You'll feel it get hot as it sucks the water out of you skin cells. If you fill a shot glass with brake fluid to the rim, it will continue to overflow as it sucks water from the air. As you get water in the system, it settles in the low spots being the calipers. Most caliper bores are chrome lined, most pistons are not. Water gets on the piston, you get rust. Rust ceases stuff up. Water can boil and you get air in the system.
Test strips are going to test for acidity and the presence of copper. Both of which you will see little in the reservoir. Copper from the lines will settle in the calipers, and acerbate the rust build up. Acidity will be the lowest in the resivor as the cap is vented to atmosphere, an this is where the moisture starts.
Follow the maintenance manual for flush. If in doubt, every fluid in the car should have been flushed somewhere between 60-75k miles.
I don't think there's any water solubility limit for DOT 3 or 4 (glycol ether-based) brake fluids, so it's not possible for water to separate out of them and collect in low spots, it should diffuse relatively evenly throughout the entire system (that doesn't mean they don't become more corrosive as they absorb water however). That's why you can use a conductivity meter at the reservoir to get a reasonable estimate of the water content. I had my fluid changed at around 5 years of age and it was still well under the maximum allowable water content. Those meters do tend to be cheaply built however, so their accuracy sometimes comes into question (since I work in a lab I was able to confirm that my meter was correctly calibrated).
However, phase-separation of water is a problem with DOT 5 (silicone-based) fluids, as they have basically zero miscibility with water (very low to zero solubility).
However, phase-separation of water is a problem with DOT 5 (silicone-based) fluids, as they have basically zero miscibility with water (very low to zero solubility).
DOT 5 fluid is also totally incompatible with DOT 3 or 4 brake fluids. DO NOT MIX THEM.
For completeness, most aircraft brake fluids are petroleum based and thus are incompatible with any DOT-spec fluid. DO NOT MIX THEM.
(To confuse things further, there is a DOT 5A fluid that is an acceptable replacement for DOT 3/4, but it's not recommended.)
Are you sure those aren't two types of beer?
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05 GT wagon(sold), 09 Spec B(sold), 18 3.6R Outback, 2024XT
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You are reading it wrong.
You have brake fluid, it should be flushed every 5 years. For those Outbacks with manual tranny's they also should flush the clutch fluid at the same time.
That's what that means.
You have brake fluid, it should be flushed every 5 years. For those Outbacks with manual tranny's they also should flush the clutch fluid at the same time.
That's what that means.
Thanks for the explanations!
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where did you find that info.. the difference in boiling point is between DOT3 and 4.. have not seen anything showing motorcraft has higher BP than normal DOT3 or 4.. DOT4 has higher BP so better for brake system in the south where the humidity is higher year around.. most likely make no difference in AZ other than the air and road temps in summer are higher a dot 4 would be better for that.. overall dot4 is the best for non race brakes.
Gearhead and tuner magazine builds.
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Just bleed my lines last week. 3 years/32.7k miles. Used (2) 12 oz bottles of the Subaru branded stuff so this is probably lightened by 1/4 of new fluid. Maybe someone in Arizona could go 5 years, but here in NYC that's what 3 years looks like. I already picked up some Bosch LV fluid for the newer cars. That should last an extra year compared to Dot 3/4.
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mine was done 12,000 miles ago BUT it was 3 years ago. im easy on the pedal usually.
BUT maint book says 3 yrs/ 30 K. ( i have the gold plus 10 yr 100k) - trying to keep that valid.
was thinking of doing it this nov. it was 120.00 to do it in 2021.
garaged all the time. / hot in summer tho and cold in winter .
what would you do.?
BUT maint book says 3 yrs/ 30 K. ( i have the gold plus 10 yr 100k) - trying to keep that valid.
was thinking of doing it this nov. it was 120.00 to do it in 2021.
garaged all the time. / hot in summer tho and cold in winter .
what would you do.?
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