Brake and idle problems at elevation of 6,000 ft.

[Dave McDufford]

Re: Brake and idle problems at elevation of 6,000

I agree with Mike Ward. The difference in air pressure between sea level and 6,000' is about 3 psi or 20%. Assuming the brakes function correctly at sea level, I cannot imagine this is enough to cause the pedal to go to the floor. I would think the volume of air in the system required to cause this at 6,000 would cause very spongy brakes at sea level.

Dave

[Clem Z.]

Re: Brake and idle problems at elevation of 6,000

no you can not do to the edelbrock what you can do with a holley because they use a diffent style of air bleeds.

[Michael W.]

Re: Brake and idle problems at elevation of 6,000

Bob,

If the indicating light from the distribution valve is frequently coming on, you have more problems than just changes in altitude. The amount of runout that would provoke loss of brake pedal is around .005", far less than can be seen by eye. I suggest again that you at least measure it to eliminate this as a contributing factor.

[Joe L.]

Re: Brake and idle problems at elevation of 6,000

Bob-----

If the brake pedal gets soft at higher altitude but then returns to normal at lower altitude, then the problem is NOT due to rotor runout/ "air pumping". When that condition causes a pedal to go soft, it stays soft until you bleed the air out of the system. It WILL NOT "get better" by itself when you return to lower altitude.

Sometimes you will get a mistaken indication of air in the system when you're bleeding if air is getting around the threads of the bleeder valves as you bleed. To eliminate this, apply silicone grease to the threads of the bleeder valve before you screw it into the caliper. This will seal out the air from causing an erroneous indication of "bubbles" in the bled fluid.

If the brake warning light comes on while you're driving, it indicates that there is a pressure imbalance in the system and likely, in this case, indicates that one of the systems has air in it. Unfortunately, there is no way that the warning system will tell you WHICH system has the air in it.

[Terry M.]

Re: Brake and idle problems at elevation of 6,000

Just a question out of curiosity Joe:
Have you tried a pressure bleeder?
I really hate those things. A leak, or "blow out" from the bleeder with DOT 3 or 4 can be a disaster for the paint finish, but it may be the only way to be sure all the air is out of the system. Most pressure bleeders sit around the shop with fluid in them, and the fluid deteriorates before it ever gets into the car.

[Joe L.]

Re: Brake and idle problems at elevation of 6,000

Terry-----

I've used pressure bleeding (several times), vacuum bleeding (twice), pedal bleeding (many times), and gravity bleeding (2 or 3 times). Once, I even had the car pressure bled at relatively high altitude (Susanville, CA elev. 4,148)when I was still using DOT 3. All to no avail, whatsoever, as far as curing the high altitude brake loss syndrome.

I agree with you; pressure bleeding terrifies me, too, because of the increased potential for spillage. However, I use DOT 5 silicone now (which eliminates the spilled fluid concern), and I plan to try pressure bleeding again with the Motive Products bleeder.

[Terry M.]

Re: Brake and idle problems at elevation of 6,000

Keep us posted on how the Motive Products bleeder works. This certainly is a puzzle.