Topic: Brake Light '79 Corvette
in Forum: C3 Engines, Driveline and Handling
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Today as I warmed up the Vette I noticed the brake light (on the dash) came on for about one minute. Then it went off and stayed off. The pedal felt as firm as ever and the brake fluid level was correct. It's never done this before.
KDADDY79 2009-10-02 16:36:44
After driving it for an hour I shut it off and it sat for an hour and a half.
Upon starting it up for the ride home, the brake light came on and stayed on for around ten minutes. Pressing on the brake pedal did not seem to have any effect on the brake light. Again, the pedal was as firm as ever.
Note:
I store it in an unheated garage. Overnight it's been in the low 40"s lately.
I have not had the brakes bled in 2 or 3 years.
Much less driving time this year than previous years.
Have not used the E-Brake recently.
So, whaddya think?
Kevin
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Imma tinkin it's a short in the dash area, or possibly around the e-brake switch. Could also be a short under da hood where the brake switch is, but...the on for a minute and then off stuff makes me think it's(the problem) INSIDE the cabin somewhere. I think I would unplug both the e-brake switch and the underhood switch, and see if the light still comes on...if so, then it would be time to start tracin wires, starting from the e-brake switch...
Joel Adams
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Mounds View, MN - USA
Joined: 5/24/2007
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Vette(s): 70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe
I agree with Joel. If disconnecting the two wires does solve the problem, reconnect one of them at a time to verify which circuit. One possibility is the proportioning valve, which contains a switch that senses uneven pressure front to rear. That is where the wire under the hood connects. You might actually have unequal pressure, or the sensor might be bad.
Larry
Larry
Thanks for your ideas on this!
I would have started with bleeding the brakes and then staying confused.
Next week it's due to go in for new U-Joints on the half shafts. We'll also give both of those brake wires a look see and start where you guys said to.
I'll post the outcome when it happens.
Kevin
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Oak Creek, WI - USA
Joined: 5/21/2008
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Vette(s): 1981 Great White Shark. Red Interior, 350/190 hp. PS, PB (SS), A/C CC, T-Tops. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vettes Car Club. 175,000 Original miles!! Now own a 1998 C-5!
It is normal for the light to go on durning startup, but not to remain on for longer than about thirty seconds. Thats the problem with intermittred problems. Hard to diagnose.
So, my mechanic had what they're calling a "minor" heart attack. If all goes well he'll be back on his feet in 3 weeks or so. He's a good guy, keep him in your prayers.
My brother in law and I took a look at the brakes. He found both switches and neither seem to be the trouble.
Next, for the heck of it, we bled the brakes (RR, LR, RF, LF in that order).
The brake light is now working as it should.
Any thoughts on this?
Kevin
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Oak Creek, WI - USA
Joined: 5/21/2008
Posts: 1965
Vette(s): 1981 Great White Shark. Red Interior, 350/190 hp. PS, PB (SS), A/C CC, T-Tops. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vettes Car Club. 175,000 Original miles!! Now own a 1998 C-5!
May have been a peice of dirt or foreign matter that cause the light to come on. When you bled the brakes, you swept away the problem !! Maybe.
Dan
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Your original description seemed to point to an electrical malfunction, since using the brake pedal made no difference. Normally, if there is a problem with the P-valve switch, pumping the brakes will make a change. There might still be a problem with the switch on the p-valve(or the valve itself), since bleeding the brakes turned it off, at least for the time being.
Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Well, the darn brake light has reared its ugly head a few times more. The pedal is still firm.
KDADDY79 2009-10-24 10:34:18
Upon checking the fluid level yesterday, I had less brake fluid in the rear portion of the Master Cylinder and the front portion remained full. Off to the shop I went.
Today the mechanic told me he does not see any leaks in the calipers, lines or hoses.
He believes the Master Cylinder is going bad and is allowing brake fluid to pass in to the Power Booster. Where does the brake fluid go when this happens?
I'm inclined to agree with this but wanted to know if we're overlooking anything.
Any input is appreciated.
Kevin
in Forum: C3 Engines, Driveline and Handling
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