Draining old brake fluid
04-08-2013, 01:58 PM
#31
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The typical brake system fluid capacity is less than 500 mL (16.9 oz) and you should be able to complete a full flush/fill with 1 liter of fluid. That said IMHO it's not a bad idea to 1.5 liters (3 bottles of Motul, AP Racing, Torque RT700, etc) on had just in case you need a little more than 1 liter. Much easier to have an extra bottle that doesn't get opened than to get almost done and find you're a little short.
I would suggest that spending a bit extra on fluid for the Tahoe is not at all analogous to the "Monster Cable Syndrome." There are some very real advantages to a higher performance brake fluid in terms of the lifecycle of the fluid, the additive package of the brake fluid and the overall system health and longevity. Particularly if the Tahoe is being used as a tow vehicle.
No body (or very few) questions a person spending a bit more on using a premium motor oil to increase engine life and internal component longevity but folks never to seem to have the same thought process when it comes to the brakes.
Just my $0.02
I would suggest that spending a bit extra on fluid for the Tahoe is not at all analogous to the "Monster Cable Syndrome." There are some very real advantages to a higher performance brake fluid in terms of the lifecycle of the fluid, the additive package of the brake fluid and the overall system health and longevity. Particularly if the Tahoe is being used as a tow vehicle.
No body (or very few) questions a person spending a bit more on using a premium motor oil to increase engine life and internal component longevity but folks never to seem to have the same thought process when it comes to the brakes.
Just my $0.02
04-08-2013, 02:09 PM
#32
There's a difference in how and what applications the various brake fluid manufacturer and formulas are targeted for.
I've generally found that high performance fluid like Motul and high end Castrol has excellent boiling points but sacrifice a bit of the moisture resistance found in other brake fluids. It's fine if you plan to flush it more often but the typical person will only flush it every few years or never. In this case, I'd rather have those people use a nice OTS brake fluid that will not absorb moisture as much. my $.02
I've generally found that high performance fluid like Motul and high end Castrol has excellent boiling points but sacrifice a bit of the moisture resistance found in other brake fluids. It's fine if you plan to flush it more often but the typical person will only flush it every few years or never. In this case, I'd rather have those people use a nice OTS brake fluid that will not absorb moisture as much. my $.02
04-08-2013, 02:20 PM
#33
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Just to make you guys think.....we all know that the 996 Carrera (C2) bleeds at rt rear, left rear, right front than left front. In my Porsche Work Shop Manual it says to do the C4 rt rear, left rear, left front and rt front. Now why would that be?
04-08-2013, 03:28 PM
#34
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@alpine003 there is a serious misconception about the rate moisture uptake by brake fluid with the only real difference in the uptake rate being between DOT 3 vs DOT 4 brake fluids. i.e. for a given time period a DOT 4 will uptake slightly more moisture than a DOT 3 under the exact same conditions. That said the DOT 4 fluid will still have/maintain higher performance characteristics than the DOT 3 fluid.
Although none of the major brake fluids state this, the acceptable shelf life of a DOT 4 fluid is 24 months and all the European auto mfgr's that I'm familiar with state the change interval for the is also 24 months. While I can't state that this will not happen, the possibility of a DOT 4 fluid to have enough moisture uptake to result in it denigrating in performance to that of it's stated Wet Boiling point is extremely slim. Brake fluid just doesn't absorb moisture that fast.
All that said, I would suggest the idea that you want the brake fluid to have a reduced rate of moisture uptake is completely wrong. In fact you DO want the brake fluid to uptake moisture as quickly as possible. The reality is every braking system will allow moisture in. If the brake fluid doesn't absorb the moisture (as in the case of a DOT 5 SBBF will do) the moisture would sit there, separate from the fluid, creating a potential opportunity for premature boiling. Brake fluid should uptake the moisture as quickly as possible so as maintain the highest performance of the fluid/system.
I know this will seem to go counter to the conventional wisdom however I would suggest the conventional wisdom is a bit mis-guided.
Even in a high humidity environment scenario the brake fluid just isn't going to absorb enough moisture and will not absorb fast enough for the rate of uptake to become a mission critical impairment
Although none of the major brake fluids state this, the acceptable shelf life of a DOT 4 fluid is 24 months and all the European auto mfgr's that I'm familiar with state the change interval for the is also 24 months. While I can't state that this will not happen, the possibility of a DOT 4 fluid to have enough moisture uptake to result in it denigrating in performance to that of it's stated Wet Boiling point is extremely slim. Brake fluid just doesn't absorb moisture that fast.
All that said, I would suggest the idea that you want the brake fluid to have a reduced rate of moisture uptake is completely wrong. In fact you DO want the brake fluid to uptake moisture as quickly as possible. The reality is every braking system will allow moisture in. If the brake fluid doesn't absorb the moisture (as in the case of a DOT 5 SBBF will do) the moisture would sit there, separate from the fluid, creating a potential opportunity for premature boiling. Brake fluid should uptake the moisture as quickly as possible so as maintain the highest performance of the fluid/system.
I know this will seem to go counter to the conventional wisdom however I would suggest the conventional wisdom is a bit mis-guided.
Even in a high humidity environment scenario the brake fluid just isn't going to absorb enough moisture and will not absorb fast enough for the rate of uptake to become a mission critical impairment
04-08-2013, 04:54 PM
#35
I see what you're saying but given the moisture is not as detrimental in making a car stop, the same thing can be said for having high boiling point fluid for normall street vehicles. Sure there might be those few times when you could maybe benefit from it. Even in towing situations, unless you are panic stopping at every stop light, I just don't see the use of exotic or high end brake fluid making much of a difference, especially since on the road your tires are likely to be the bottleneck.
Look at all those Tow Trucks/Busses/Semi's using "regular" brake fluid and they are doing just fine.
For me personally, I think it's a bit wasteful and/or unneeded to be putting exotic or boutique high end brake fluid in anything but racing or high performance cars.
Look at all those Tow Trucks/Busses/Semi's using "regular" brake fluid and they are doing just fine.
For me personally, I think it's a bit wasteful and/or unneeded to be putting exotic or boutique high end brake fluid in anything but racing or high performance cars.
04-08-2013, 06:47 PM
#36
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@alpine003 Thx for your thoughts.
I would submit this debate and your viewpoint is much akin to the non-car people out there that believe washing the car once every 3-6 months and a wax job from the drive through car-wash once a year is sufficient to keep their car looking "decent." However I would bet that most of us car-guys in the P-car community shudder at the thought of maintaining our cars' finish in such a relaxed manner. We know that 30 yr old P cars can still look great with the original paint if quality car care products are used with care, diligence and on a frequent schedule.
In the same manner the above example will play a role in the longevity and quality of the auto's appearance over time, the quality of the additive package in the brake fluid (which has a significant impact on the fluid's resistance to corrosion, resistance to the fluid going acidic [in many fluids going even more acidic] lubricity, low temperature viscosity, etc.) will determine how the lifecycle of the EPDM of the caliper's pressure seals. i.e. when do you need to rebuild the calipers or in a more dramatic fashion, when does the brake pedal go to the floor because the seals will no longer seal the pistons?
The same goes for the engine oil. I'll bet you don't use the AutoZone $3.99/qt 10W-40 for your Tahoe. And yet consider all the fleet vehicles that are maintained with the least expensive fluids available. That doesn't mean that using the cheap stuff is in the best performance and/or longevity interests of the vehicle.
Just my thoughts...
I would submit this debate and your viewpoint is much akin to the non-car people out there that believe washing the car once every 3-6 months and a wax job from the drive through car-wash once a year is sufficient to keep their car looking "decent." However I would bet that most of us car-guys in the P-car community shudder at the thought of maintaining our cars' finish in such a relaxed manner. We know that 30 yr old P cars can still look great with the original paint if quality car care products are used with care, diligence and on a frequent schedule.
In the same manner the above example will play a role in the longevity and quality of the auto's appearance over time, the quality of the additive package in the brake fluid (which has a significant impact on the fluid's resistance to corrosion, resistance to the fluid going acidic [in many fluids going even more acidic] lubricity, low temperature viscosity, etc.) will determine how the lifecycle of the EPDM of the caliper's pressure seals. i.e. when do you need to rebuild the calipers or in a more dramatic fashion, when does the brake pedal go to the floor because the seals will no longer seal the pistons?
The same goes for the engine oil. I'll bet you don't use the AutoZone $3.99/qt 10W-40 for your Tahoe. And yet consider all the fleet vehicles that are maintained with the least expensive fluids available. That doesn't mean that using the cheap stuff is in the best performance and/or longevity interests of the vehicle.
Just my thoughts...
04-08-2013, 06:59 PM
#37
@alpine003 Thx for your thoughts.
I would submit this debate and your viewpoint is much akin to the non-car people out there that believe washing the car once every 3-6 months and a wax job from the drive through car-wash once a year is sufficient to keep their car looking "decent." However I would bet that most of us car-guys in the P-car community shudder at the thought of maintaining our cars' finish in such a relaxed manner. We know that 30 yr old P cars can still look great with the original paint if quality car care products are used with care, diligence and on a frequent schedule.
In the same manner the above example will play a role in the longevity and quality of the auto's appearance over time, the quality of the additive package in the brake fluid (which has a significant impact on the fluid's resistance to corrosion, resistance to the fluid going acidic [in many fluids going even more acidic] lubricity, low temperature viscosity, etc.) will determine how the lifecycle of the EPDM of the caliper's pressure seals. i.e. when do you need to rebuild the calipers or in a more dramatic fashion, when does the brake pedal go to the floor because the seals will no longer seal the pistons?
The same goes for the engine oil. I'll bet you don't use the AutoZone $3.99/qt 10W-40 for your Tahoe. And yet consider all the fleet vehicles that are maintained with the least expensive fluids available. That doesn't mean that using the cheap stuff is in the best performance and/or longevity interests of the vehicle.
Just my thoughts...
I would submit this debate and your viewpoint is much akin to the non-car people out there that believe washing the car once every 3-6 months and a wax job from the drive through car-wash once a year is sufficient to keep their car looking "decent." However I would bet that most of us car-guys in the P-car community shudder at the thought of maintaining our cars' finish in such a relaxed manner. We know that 30 yr old P cars can still look great with the original paint if quality car care products are used with care, diligence and on a frequent schedule.
In the same manner the above example will play a role in the longevity and quality of the auto's appearance over time, the quality of the additive package in the brake fluid (which has a significant impact on the fluid's resistance to corrosion, resistance to the fluid going acidic [in many fluids going even more acidic] lubricity, low temperature viscosity, etc.) will determine how the lifecycle of the EPDM of the caliper's pressure seals. i.e. when do you need to rebuild the calipers or in a more dramatic fashion, when does the brake pedal go to the floor because the seals will no longer seal the pistons?
The same goes for the engine oil. I'll bet you don't use the AutoZone $3.99/qt 10W-40 for your Tahoe. And yet consider all the fleet vehicles that are maintained with the least expensive fluids available. That doesn't mean that using the cheap stuff is in the best performance and/or longevity interests of the vehicle.
Just my thoughts...
I also don't mind using OTS Valvoline or Prestone brake fluid for street cars. I think they'll survive. FWIW, I'm still on original calipers without any rebuilds on my '74 BMW as well using the "regular" stuff. But this is a Porsche forum and we all like to overthink, over engineer, over use parts and such. That is the enthusiasts way.
