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I just changed the brake fluid in my truck for the first time. The truck is 26 months old with just 16,000 highway miles. The fluid was just plain ugly! Here are some pics: Brake fluid pics As you can see, the fluid is dark brown, but clean i.e. no debris. Brake fluid does absorb moisture, which turns it dark, but I believe heast does as well. I live in the desert with very little mositure (relative humidity is around 10% - 15%) but it does get hot (115F). I use the truck mainly for hauling my 10000lb 5th wheel, and it sleeps inside. I replaced the fluid, with the help of my 10 year old daughter (got to get them started young!) in around a hour. It took 44oz of new fluid to completely flush the system and refill the resorvior. I did suck out all the old fluid in the master cylinder reservior (about 18oz) before I started. I used the Valvoline DOT3/DOT4 synthetic fluid....don't know what's synthetic about it, as it has all the same warnings about removing paint if spilled, etc as 'normal' fluid. I used this fluid because it is basically a DOT4 fluid, which means it has a higher 'wet' boiling point (343F) than a DOT3 (284F). This is important if you tow or carry heavy loads as it gives you that much more margin before the fluid boils (boiling fluid = NO brakes!). They rate fluid in both 'DRY' and 'WET" boiling points. Racing fluid is typically only rated 'DRY', and very high, since the fluid is changed often and you don't usually have to worry about moisture contamination. Street fluid always has a 'WET' rating (the temps it boils at with some % of moisture in it), the 'DRY' rating is almost meaningless for street applications. Change your fluid every 2 years! |
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any advice? Did you use gravity? or the old bleed and beed method until she was running good and clean? be a good FAQ |
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Scott, I followed the procedure outlined in the Ford factory service manual....it's the normal 2 person deal.....press and hold the brake pedal while loosening the bleeder screw, close bleeder screw and then release the pedal. Do it over and over until clean fluid come out. Of course, you should remove all the old fluid from the brake reservior (18 - 20oz) before starting. I use a MityVax vacuum pump to remove mine, but a turkey baster will work; just don't get the fluid onto anything painted! Place a clear plastic tube onto the bleeder screw, the other end going into a leakproof container. You bleed the Right Rear, Left Rear, Right Front then finially the Left Front. Out of habit, I place a block of wood under the brake pedal, to limit it's downward stroke when you open the bleeder screws. On neglected brake systems, you can destroy the master cylinder seals if the pedal goes to far down, which causes the internal valving to travel down into a pitted, rough bore. I only took about a hour tops, and I used a total of 44oz of fluid (one 32oz and one 12 oz) container. |
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I for one do not get this. I have NEVER had to change the brake fluid on any of my vehicles in the 25 years I have been owning same. "Cleanliness" is not an issue with brake fluid since it is not being used to lubricate rotating parts such as motor oil. Sure, we all know that brake fluid absorbs moisture. But the heat of using the brakes dissipates the moisture. If your truck is driven regularly, this should not be a problem. The only moisture related problems I have ever had with brakes is on old trucks that sit a lot, like while they are waiting for me to restore them. I have a 1990 F150 with 220K on it and I have never changed the brake fluid and never had to replace a brake system component for moisture related failure (as a matter of fact, the master cylinder and rear wheel cylinders are original). Why is this such a big deal now? Not trying to start a war but looking for some rational reason why I need to worry about this on my new truck when it has never been an issue before? |
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I think that if you are towing heavy loads, like 5'ers, and doing it a lot, moisture in the brake fluid becomes a very real concern. The heat generated by the brakes will flash the moisture to steam if it gets hot enough. Steam compresses. This could be bad news on a long down hill. No brakes equals to stop. No stop, big boom. Dave |
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Isn't there a part of the ABS system that needs bleeding also. On my old "91" F-150, I had to bleed the the ABS valve during the process. Just want to make sure before I start. |
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jstrauss (I for one do not get this. I have NEVER had to change the brake fluid on any of my vehicles in the 25 years I have been owning same.) I thought the same as you untill: My BMW uses the same fluid and reservoir for the clutch and brakes and when the clutch started acting up I changed the fluid and it started working again. Glad it was not the brakes that went first. |
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I too was in the "what brake fluid?" school until my brakes failed completely, twice, on my F250. Once was on that last downhill stretch of road leading to the Crater Lake campground. Downshifting and trailer brakes did the job. (Whew) Next day, the brakes were perfect. The second time was just south of LA on I-5 at 5:30PM w/o the trailer. An "E" ride in anybody's book. By the time the tow truck arrived, the brakes were fine. Each time I took the truck to a shop and they could not find anything wrong. I replaced the master cylinder between the first and second times. Turns out that somewhere along the line, a shop had replaced the factory phenolic pistons with metal ones. These were allowing enough heat to be transferred to the fluid that the water in the fluid boiled and, shazam, no brakes. Once the fluid was flushed on a bi-early basis, it never did it again. The rear brakes faded on an ATV that I bought used. I changed the fluid and things are fine. I now flush all my brake systems bi-yearly. Clutches too. The moisture in the brake fluid is what causes rust and corrosion in the wheel cylinders. For the ~$30 it costs to have it done, it's cheap insurance. |
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Unfortunately, not many people realize that in some cases a phenolic piston is selected in OE use for its thermal insulation properties. Parts should be replaced with "like" parts. |
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Martin #6, On my previous truck, there was a special procedure to deal with bleeding the ABS pump. However, according to the Ford factory service manual there is no mention of having to seperatly bleeding or activating the ABS system. In fact, under the ABS section of the service manual, on bleeding the ABS system, they refer you to the "Brake Bleeding - System" section, which I have posted below: 1.Clean all dirt from and remove the brake master cylinder filler cap and fill the brake master cylinder reservoir with the specified brake fluid. 2.Place a box end wrench on the RH rear bleeder screw. Attach a rubber drain tube to the RH rear bleeder screw and submerge the free end of the tube in a container partially filled with clean brake fluid. 3.Have an assistant pump the brake pedal and then hold firm pressure on the brake pedal. 4.Loosen the RH rear bleeder screw until a stream of brake fluid comes out. While the assistant maintains pressure on the brake pedal, tighten the RH rear bleeder screw. Repeat until clear, bubble-free fluid comes out. Refill the brake master cylinder reservoir as necessary. 5.Tighten the RH rear bleeder screw. 6.Repeat Steps 2, 3, 4 and 5 for the LH rear bleeder screw. 7.Place a box end wrench on the RH front disc brake caliper bleeder screw. Attach a rubber drain tube to the RH front disc brake caliper bleeder screw, and submerge the free end of the tube in a container partially filled with clean brake fluid. 8.Have an assistant pump the brake pedal and then hold firm pressure on the brake pedal. 9.Loosen the RH front disc brake caliper bleeder screw until a stream of brake fluid comes out. While the assistant maintains pressure on the brake pedal, tighten the RH front disc brake caliper bleeder screw. Repeat until clear, bubble-free fluid comes out. Refill the brake master cylinder reservoir as necessary. 10.Tighten the RH front disc brake caliper bleeder screw; refer to Specifications in this section. 11.Repeat Steps 7, 8, 9 and 10 for the LH front disc brake caliper bleeder screw. Here is a portion of the ABS system overview from the factory service manual, it appears that the ABS pump is in a 'normally open' mode, allowing brake fluid to flow thru it during normal operation, so bleeding the brake system will also cause new fluid to be introduced into the ABS pump. The only place where 'old' fluid might be retained in the the Hydraulic Control Unit (HCU) accumulator. However Ford does not think that this needs special attention when changing out fluid. Here is the description of the ABS system: When the brakes are applied, brake fluid is forced from the brake master cylinder outlet ports to the HCU inlet ports. The fluid pressure is transmitted through three normally open solenoid valves inside the HCU, through the outlet ports of the HCU to the brakes. One circuit of the brake master cylinder feeds the front brakes while the other circuit feeds the rear brakes. If the anti-lock brake control module senses that a wheel (1007) is about to lock, based on wheel speed sensor data, the solenoid valve will pulse closed, preventing more fluid from entering that circuit. The anti-lock brake control module then reads the sensor signal from the affected wheel again. If the wheel is still decelerating, the normally closed solenoid valve for that circuit is opened. A controlled amount of hydraulic pressure between the normally open valve and the brake is relieved into the HCU accumulator. Once the affected wheel returns to vehicle speed, the anti-lock brake control module returns the solenoid valves to their normal condition, allowing fluid flow to the affected brake. Hope this helps. |
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I started changing my brake fluid in my vehicles years ago after I had to change out some calipers and wheel cylinders due to corrosion and sticking. I try to do it every 2 years in my vehicles, but I must admit I have not done it in my 99 PSD yet with 68,000 miles. One of the nice things I have noticed after each fluid change is a MUCH firmer brake pedal and more consistent braking, e.g., no lockup on one side (I've got a few pre-ABS vehicles). Another thing that makes bleeding the brakes nice is the Speedbleeder valves. I just ordered mine mailorder from them $7.00 each, part number SB3824, for both F/R. You just loosen 1/4 - 1/2 turn, put a hose on the valve, get in, and pump the brakes. No air gets back in due to a special valve inside. I've used them before and they are great. Website is http://www.speedbleeder.com. I've also used the MityVac with good success, but I do understand the desire to pump the fluid out rather than suck it out, hence the Speedbleeders. Bleeding my brakes in on my spring list, while I am swapping my mud (huntin') tires for the highway tires (original Steelies). |
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Big veternary syringe (w/o needle) works great for sucking break fluid. Even clamp plasic tubing on them for maintaining vacuum at the the bleeder or pushing fluid up from the bleeder. Get them at any good farm supply store. Never changed brake fluid on my 4 wheel vehicles, but yearly on my motorcycle. I know, does not make sense. Good Luck |
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jstrauss, Not looking to argue, but to answer your question about "why worry" and using your 1990 F150 as an example, it has been my experience that such "newer" vehicles usually don't have problems that show up YET with brake cylinders, calipers, and master cylinders. I've run into problems a few years AFTER I bought a 10 yr old or older vehicle. Let's face it, most people don't keep their cars for 15-20 years, so many people never experience the problems that old brake fluid can lead to. Since I am one of those exceptions to the norm, with vehicles from 78, 81, 85, 86, 90, 95, and 99, and I keep them until I just can't stand them anymore, I tend to see more of the old car issues than most. I'm just speaking from my personal experience and research here. Admittedly, changing brake fluid can be considered a bit hyper-enthusiast maintenance, but I plead guilty to that. Keep in mind that it's not the mileage, but the AGE of the vehicle that usually is deterministic of braking system corrosion. As for the braking heat dissipating moisture, it would seem so, since your brakes are definitely going to get above the 212F deg water boiling point to get rid of the moisture, but keep in mind that this is only at the caliper, not in the master cylinder, the ABS valving, lines, etc. Also, I don't think the heat completely gets rid of the moisture, explained by the concept of DOT 3 and DOT 4 brake fluid temp ratings. I mean, DOT 3 and DOT 4 brake fluids USUALLY have a similar dry boiling point, which is when the fluid is fresh out of the bottle. The wet boiling points are both less than the dry, even thought the DOT 4 wet is about 30F deg higher than the DOT 3. The wet boiling point is when the fluid has been exposed enough (meaning "been in your braking system") to absorb moisture lowering the boiling point. Therefore, this would imply that the moisture is not totally eliminated from the system with usage. And like others have already said, if you are towing, you really should consider the capability of your braking system by keeping fresh fluid in the system, besides the corrosion issue. I didn't mean to go into a brake fluid dissertation, but just hoped to enlighten the masses based on some very valid questions. |
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Yup, jstrauss, I was definitely with you until a few years ago. Two master cylinders and two calipers later (both "older" vehicles), I've changed my ways and now maintain the brake fluid regularly. There are a lot of variables that may be working for you: climate, frequency of use, quality of the vehicle system (reservoir, hoses, caliper seals), but sooner or later, that fluid is going to collect enough moisture to raise havok. (I'm not starting a war either, just some friendly advice.) Check your tire pressure, check your oil & water, look at that battery once in a while, change that brake fluid! |
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Make sure you change your brake fluid!
