Picking out brake fluid.

[MGregoir]

Never really thought about this before, but I am due to change brake fluid in my car...long overdue, and it is to the point I can feel my brakes noticably fading in traffic so I definitely have water in the system. That combined with pads that have some but not much life left (not squealing but I will change them soon), it makes for a pretty low pedal.

My car specs DOT 3, and I know DOT 4 has a higher boiling point but absorbs water more readily. DOT 5 is out of the question for this application.

Of the little bit of information I have, two particularly interest me. One is Ford High Performance DOT 3 fluid because of its extremely high boiling point and ready availability, and another is Ate SL.6. More expensive and DOT 4, but considering how rarely brake fluid gets changed, how important it is, and that it's a lower viscosity brake fluid (it does get cold enough here for odd pedal behaviour in extreme cold) I think it may also offer some advantages. Super Blue would be overkill and it doesn't offer a viscosity advantage like the SL.6 does. I do not have ESP or require a low viscosity fluid, all the specs ask for is DOT 3. Disc front, drum rear, ABS.

How does DOT 5.1 slot into this mix? Mixes with 3 or 4, is it hygroscopic? Is it worth investigating for what most of the time could barely be considered a "severe street" application?

 

[Rabbler]

Cut and paste from another site

DOT 5.1, like DOT 3 and DOT 4, is a polyethylene glycol-based fluid (contrasted with DOT 5 which is silicone-based). Fluids such as DOT 5.1 are hygroscopic and will absorb water from the atmosphere. This degrades the fluid's performance by drastically reducing its boiling point. In a passenger car this is not much of an issue, but can be of serious concerns in racecars or motorcycles.

I think it is serious over kill on a non performance vehicle.

Can't say I've ever run into a brake fade that was caused by water absorption.

More likely the brake fade is caused by the thin brake material or worn rotor surfaces

 

[02zx9r]

what vehicle

 

[MGregoir]

I definitely need have the rotors surfaced, and when I checked the pads in December they were at what I would say is about 18% remaining. Not much life but they are not touching the tins. May be due for new rotors as well, I don't know.

The fluid is stock and nine years old, and the brakes quite noticeably go away when in traffic downhill and then stop and go traffic. It's the last three miles I have to drive that is all downhill and curving and a lot of jumping on the brakes because nobody knows how to use turn signals and there is one stretch that kills them and they are toast til I get home. Once everything has cooled down again, the pedal is not nearly as low and everything firms up again quite nicely until I go through another phase of continuous braking.


It's not spongy until it gets hot, and at its worst I basically have to push the pedal all the way to the floor to get a reasonable amount of brake force. Normally, I would just coast to save my brakes, but it is hard to do when nobody else has the same idea in traffic.

Either way, front rotors and pads, and possibly rear shoes are due to be replaced and the fluid is long overdue to be replaced. I am wondering what to use because if it's a fluid that doesn't get changed often in a system that I would say is pretty important, and might only get changed at every pad change so might as well use something that is intended to perform at the longer intervals and offer more consistent performance over that time period.

It's a 1999 Malibu. Not exactly a sports car but I do lean on my brakes pretty hard sometimes so I really notice when they are going away.

 

[PT1]

Synpower is rated in between dot3 and dot4 and should be fine.

 

[bamorris2]

The Motorcraft DOT3 does (or did) have a high dry boiling point. The weakness was in it's wet boiling point. Not nearly impressive. And, I've heard/read that Motorcraft DOT3 is now produced by a different manufacturer (and/or new forumula), and does not have the high dry boiling point anymore.

Based on my research, I chose Castrol LMA brake fluid. It had the highest dry and wet boiling points of any readily available brake fluids.

 

[Kestas]

MGregoir, your driving pattern is at the extreme end of what the brakes are designed to do. Definitely get the fluid changed. You'll do yourself and those around you a favor, and you won't find yourself in such a nervous situation.

NYSteve posted this link a week ago:
http://www.stoptech.com/tech_info/wp_brakefluidcomparison.shtml
It should help you pick out the fluid that's good for yourself.

 

[MGregoir]

A lot of it is a combination of factors, I am almost due for pads so I do have a somewhat low pedal, but it is manageable, the issue is in the old fluid compounding it once everything gets hot. New pads, new rotors, new rear shoes and new fluid and I'll probably have nothing to worry about for the next five years.

I'll try to find LMA or SynPower fluid (I don't see it on the Valvoline site), I don't know where to get SL.6 off the shelf.

What is a typical brake system capacity? I'd assume a quart is far too much and 12 ounces would be on the short side.

Rotors will probably be regular gray iron replacements and pads will be Wagner Edge or ThermoQuiets and I have no idea what for shoes, probably some other Wagner product. I'm also curious if while doing this I can shift the brake bias rearward a hair in the proportioning valve but it is not something I would likely do.

 

[mikered30]

Originally Posted By: MGregoir
A lot of it is a combination of factors, I am almost due for pads so I do have a somewhat low pedal, but it is manageable, the issue is in the old fluid compounding it once everything gets hot. New pads, new rotors, new rear shoes and new fluid and I'll probably have nothing to worry about for the next five years.

I'll try to find LMA or SynPower fluid (I don't see it on the Valvoline site), I don't know where to get SL.6 off the shelf.

What is a typical brake system capacity? I'd assume a quart is far too much and 12 ounces would be on the short side.

Rotors will probably be regular gray iron replacements and pads will be Wagner Edge or ThermoQuiets and I have no idea what for shoes, probably some other Wagner product. I'm also curious if while doing this I can shift the brake bias rearward a hair in the proportioning valve but it is not something I would likely do.


Synpower is now discontinued and it maybe hard to find. The fluid that replaced it is not as good as the synpower. I just got some last week at AZ, but it was at the back of the shelf, hopefully it is not too old.

 

[MGregoir]

Then I am down to looking for Castrol LMA as pretty much all brake fluid on the shelf here is Prestone, unless somebody knows of somewhere that carries Ate fluid.

 

[The Critic]

Wagner ThermoQuiet pads are fine, I think the EDGE pads are a gimmick. Just be sure to install them "dry," meaning no grease or disc brake quiet/anti-squeal.

Any fresh DOT3 brake fluid should be fine. Use a one-man bleeder to change the fluid, then follow-up with a manual bleed for the firmest pedal feel:

http://www.zeckhausen.com/bleeding_brakes.htm

 

[MGregoir]

I'll be working on this with my dad so we can do everything manually without too many worries.

I am being a little picky with fluid because I can be, I like the look of the Castrol LMA and the price even better, as well as it being a slightly lower viscosity fluid. First starting out some days when it is really cold here, you can get a funny pedal feel until the brakes warm up. Considering that the next fluid change will be the next pad change I want to use something with a little better wet boiling point.

I thought the Edge pads were a gimmick too and they seem to me like they offer less surface area. 25% price premium over the ThermoQuiets as well.

There are ThermoQuiet front pads on the car now and OEM shoes on the rear. The pads have lasted almost five years, and about 48,000 miles so I would say they are very good. Nothing spectacular about them but they have provided consistent braking, little or no dust (ceramic pads, OEM were ceramic as well) and been quiet.

I don't know why but I can't make myself buy anything that isn't Wagner for brake parts.

 

[Kestas]

One quart should flush the whole system.