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Mike S.
Mike S., Chevy Mechanic
Category: Chevy
Satisfied Customers: 6777
Experience:  ASE Certified Master Technician
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This is a extremely complex issue with a 1993 lumina braking

Customer Question

This is a extremely complex issue with a 1993 lumina braking system, good braking at low speed, poor at higher speed. I'm experienced in mechanics, every braking component has been replaced, checked and rechecked. countless hours of research, it is a issue with these cars, yet no one has a answer?
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: replaced and or went though, every single component, from booster to module to replacing every caliper and pad, sliders, I do mean everything. bleed 4x, inspect every inch of line, yes everything. Journeymen I know are baffled.
Submitted: 4 months ago.
Category: Chevy
Customer: replied 4 months ago.
In a hard stop it is like the petal hits a stop point,(no where near floor), with this much pressure normally you be thrown into the windshield yet that is not the case, only fair to moderate stopping. Please be honest if you have no answer, but it has been worked by a journeyman and he finally gave up? I've have years of experience, tried everything, research shows this is a issue with these cars, yet no one has a answer. thanks
Customer: replied 4 months ago.
Brakes feel good, good pedal, not spongy, just the stopping power is not there, when you hit the pedal hard.
Expert:  Mike S. replied 4 months ago.

How much intake manifold vacuum do you have at idle?

Expert:  Mike S. replied 4 months ago.

The reason I ask is, I had a good brake on a 1971 Chevelle, then I rebuilt the engine, put in a high lift camshaft, then the brakes were really poor and I found out by some research about the vacuum. So I hooked up a vacuum gauge and it was 14 inches at idle, supposed to be like 19 inches. I was considering installing a vacuum pump like on a diesel but I sold the car before I did.

So, if the vacuum is low, it could be the reason for the poor braking and it don't have to be because of a high performance camshaft, it could be just retarded ignition timing. If the vacuum is low, check the ignition timing and if it's retarded, advance it some, as a matter of fact advance it as far as you can go without the engine starting to run poorly, just to see how much vacuum rise you can get. Anyhow, let me know what the vacuum is for now.

Expert:  Mike S. replied 4 months ago.

Was the intake manifold vacuum low?

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