Sc400 Fading Brakes

[tippyd]

I purchased a 94 sc400 about 8 months ago. The car is incredible. It now has about 75k. I've noticed a couple of times that the brakes have faded when slowing down to a stop and the car continues to move foward as the tranmission down shifts. I actually bumped into the car in front of me at about 5 miles per hour today on the highway in bumper to bumper traffic. Is this a rotor and pad problem? Or, is there something more complex? I inspected the pads and rotors. They seem to be OK. There are no leaks in the hydraulic system. Do you think that I just need new pads and rotors. I take the car religiously for fluid inspection. I changed all the fluids after purchase but have not replaced the brake fluid.

[DomLee]

How were you able to inspect your rotors? Did you use a caliper or did you perform just a visual inspection?

Brake pads, you can tell if they are low...so this one is up to you.

For fluid, is your brake fluid boiling/bubbling after a stop?

[axis8758]

I had this problem when I had my sc300. I decided to upgrade to the bigger LS400 calipers and rotors and it made a world of difference. The stock set up felt to me like they could not handle the weight of the car.

[escee]

When my ac fan is going hard it can rob electrical power from the breaks, resulting in a lurch. For example, I'm at a light, with my foot on the break, and the ac kicks in, the car lurches forward. Dangerous yes.

[DomLee]

Upgrading brakes is not a solution to the current problem. The problem is that he has fading brakes on the stock brake system. Solving WHY he is experiencing fade would be a better and less expensive solution than having him perform an "upgrade".

My current guesses are the brake fluid is old, and the rotors are too thin/under spec.

[tippyd]

How were you able to inspect your rotors?  Did you use a caliper or did you perform just a visual inspection? 

Brake pads, you can tell if they are low...so this one is up to you.

For fluid, is your brake fluid boiling/bubbling after a stop?

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It was a visual inspection. I plan to pull the wheels off this weekend and take a closer look. After that I will take it out for some hard braking and check the fluid.

The rotors where smooth at least on the outside. I'll have someone mic them for me or pick up a micrometer.

Thx

[tippyd]

When my ac fan is going hard it can rob electrical power from the breaks, resulting in a lurch. For example, I'm at a light, with my foot on the break, and the ac kicks in, the car lurches forward. Dangerous yes.

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It's happened a couple of times. The first time in a parking lot luckily. This time is it really got my attention. Fortunately, it was in bumper to bumper traffic. I don't even want to think about it in hard high speed braking conditions. I'm going to solve this one quickly.

[tippyd]

I had this problem when I had my sc300.  I decided to upgrade to the bigger LS400 calipers and rotors and it made a world of difference. The stock set up felt to me like they could not handle the weight of the car.

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Since I've owned the car, I have never felt that the braking system was adequate. I am going to do something. Just don't know what yet.

[tippyd]

Upgrading brakes is not a solution to the current problem.  The problem is that he has fading brakes on the stock brake system.  Solving WHY he is experiencing fade would be a better and less expensive solution than having him perform an "upgrade". 

My current guesses are the brake fluid is old, and the rotors are too thin/under spec.

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Well the fluid is going to get changed immediately anyway. It's one of the systems I haven't gotten to yet.

I am looking at going to cross drilled and slotted. What do you think? I hear that the drilled "and" slotted are hard on the bake pads but very effective.

Or, should I just go with just crossed drilled? I'm looking at the Brembos but I don't particularly like the gold color. Are they really gold? I have very nice zinnitti 5 spoke 18 x 8's in crome and the discs are very visable. I don't think that I am going to like the gold in the middle.

If this doesn't solve my problem, I'll look at a set up with larger discs.

Thx.

[DomLee]

Brakes work by disappating heat. The more mass = more capacity to help disappate heat.

Therefore, the best way to eliminate fade, would be to use full face rotors.

Now, cross drilling and slotting...both methods remove mass from a rotor. In older days (say the 80s or so), brake pad materials were not as "good" as they are now. Cross drilling was a method of allowing the brake pads to release gases...thereby allowing the brake pad to remain in constant contact w/ the rotor.

Slotting also has the same effect. The reason for slotting was because cross drilling is more prone to cracking. Also, slotting is supposed to effectively scrape off a thin layer of the brake pad with each sweep...allowing for good brake pad material.

Drawbacks w/ both cross drilling and slotting is increased pad wear.

For rotors, I purchased Rotora rotors. The rear set, didn't have the proprietary "e-coating" on it. So what I did was I got a can of high temp engine spray and sprayed the rotor to help stop corrosion. It seems to have worked. You just have to clean the surface w/ brake cleaner. Just as a side note, the front rotors that did have the "e-coating", was flaking off. Luckily, I had taken the liberty of spraying the hub area w/ the high temp paint...and that has kept it down to a minimal. This is a great "cheap" way of keeping your rotors looking rust free.

[vettenut72]

I had a similar issue with a 92 Vette. Change the fluid to a Dot 4 LMA (Low Moisture Absorption) and ensure there is enough pad material. Solved my problems completely! Ford has a high temperature Dot 4 fluid that is highly recommended as well as BMW. With ABS I continue to read that they do not recommend Dot 5 Silicon Brake fluid. Now when you bleed start at the furthest caliper from the master cylinder (Right Rear) then LR, RF, and finally LF. When the fluid is clear at each you have gotten all of it including what is in the ABS module. Old school at home method of pumping the brakes three times and holding while opening the bleeder (use a tube and jar to catch the old fluid). Also I leave a little brake fluid in the jar just in case your helper lifts off the pedal before you have closed the bleeder. Hope this helps.

Joel

[TMaxxTim]

I had a similar issue with a 92 Vette.  Change the fluid to a Dot 4 LMA (Low Moisture Absorption) and ensure there is enough pad material.  Solved my problems completely!  Ford has a high temperature Dot 4 fluid that is highly recommended as well as BMW.  With ABS I continue to read that they do not recommend Dot 5 Silicon Brake fluid.  Now when you bleed start at the furthest caliper from the master cylinder (Right Rear) then LR, RF, and finally LF.  When the fluid is clear at each you have gotten all of it including what is in the ABS module.  Old school at home method of pumping the brakes three times and holding while opening the bleeder (use a tube and jar to catch the old fluid).  Also I leave a little brake fluid in the jar just in case your helper lifts off the pedal before you have closed the bleeder.  Hope this helps.

Joel

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This happens because the A/C clutch kicks in and the car jolts in power, not electrical but you're ac is belt driven so the car gives itself a little gas to keep the rpm's up in turn lurching you a little bit if you're light on the brakes. You can usually feel this on most cars.

[jbarhorst2]

I don't think you are really talking about brake fade. Brake fade is when after multiple frequent stops (usually from high speed) your brakes feel like they are working less and less.

It sounds to me like your brakes just are not holding well under certain conditions.

If your pads or fluid are low, they could cause this.

Also if your hydraulic vacuum assist system is beginning to fail you could see this.

I would try the cheapest first. Make sure your pads are in good shape and change the fluid. If that does not help then you can look elsewhere.

If, however, your problem IS after several high speed braking maneuvers, then ignore everything I said.

Tom