20 Most Recent 1981 Chevrolet Corvette - Page 9 Questions & Answers

The shift shaft has stuck. The modulater shifts threw all gears so if you pull the hose off and there is no fluid leak then the modulater valve may be good. You could try turning the adjusting screw inside the vachumm hose and if that does not work pull the oil pand and lube all the shift solinoids they may have rusted fron condensation. Use a screw driver to get it to move the shift levers and buy some lucas trasmisson oil and run it in there it will soften the seals. Hope this helps.

sounds like either the camber or caster is off on your alignment or possable you got your steering gear box adjustment too tight .. this will cause it to not return to center.. thanks and holler if you have more..

Replcae the head light switch and pleas rate me or I won't finish.

tell me more how much did you put in the system? and did the compressor ever kick on ? the compressor is turned on and off by a pressure switch on your dryer .. when your full or at right level with your freon the compressor will kick on .. let me know if this helps any .. you might not have quite enough in there yet to turn on the compressor.. usually empty takes about 3 cans to fill the system.. thanks Jerry

try this link
http://www.the12volt.com/installbay/stereodetail/510.html

check your grounds

Your electrical system in that car is fairly similar to the system used in most full sized chevy cars of the same year except for the need for "hard wire' grounding due to the fiberglass body. You can trace the draw down by removing fuses till the draw disappears, then checking the system that fuse operates. Your alternator may also draw down the battery if it has an internal problem. Generally this is a larger draw than any accessory problem but should be checked as well. If the alternator turns out to be the culprit, you may want to change the wiring to that used on some older Cadillacs which is basically a bypass and one wire hookup (I used to know how to do it but all I remember is that one jumper wire went to one of the plug in wires (likely not the field) and the B+ wire went straight to the battery). In any case, it's not something you should have to live with. This said, if you do not drive it often, it may be wise to hook it up to a "battery tender" that maintains the battery when not in use.

Chk the battery connections. Make sure they are clean and tight. go by your headlights, not the dome light.

Diagrams Notes

THERE IS A LOW PRESSURE SWITCH ON ACCUMULATOR.IF THE PRESSURE IS LOW THE COMPRESSOR WON'T TURN ON.CHECK THE FREON CHARGE AS WELL

surly a car that old wont have a ECM think you will be lookin for ever

That little component is a flyback diode. It is critical in preventing high voltage from damaging the relay. When you turn the current off to a large inductive load like a compressor clutch, a very strong high voltage spike is generated and it arcs across the relay contacts destroying them, also potentially jumping into the very sensitive control circuit from the ECM. That diode must be replaced and it must be installed in the right direction or it will fry. You can get them at any electronics supply store, ask for a 1N4001 diode. This system is not that hard to diagnose, but I think at this point, you would be best served to find someone with a scan tool and check to see if you're getting that request signal, and tracing it back from there. Please! replace that diode first or you will just keep melting parts. If there is anything else you need let me know.

Are you getting power to the solenoid when you press lock/unlock? If you are, because of the age I would suggest looking at the door latch asm.'s. They are known to rust up and cause malfunctions.

you will need to pull off the four retaining nuts holding seat in place. Measure the length and width of bottom support frames. Many seats are interchangable.

If the 1991 is anything like th 1969 to 1982, the ground is open under the dash at the wiper switch. Check for the ground at the wiper motor when the wipers decide not to work. Grounding is problematic on a fiberglass bodied vehicle. Hope this is of help.

The low pressure cut out switch located in the larger refrigerant line (the low pressure side) in front of the evaporator (passenger side, under the hood) may be sensing low refrigerant. Also the low pressure switch may have a bad electrical connection or the switch may be going bad.

Most of the time you will find that it's rotting rubber hoses. If these have never been replaced, they're 28 years old! Engine heat, exposure to the elements that splash up under the car, and age can rot them.

Also the actuator has a rod that comes out. This rod has a seal around it. The seal rots too. The actuator is the large vacuum cannister, that looks like two pie pans put together. It is down near the headlight. When you have the hood open, look down towards one of the headlights.
Sometimes the vacuum tank develops a hole. This can be patched. It's up on the side of the fender.

Here, let me show you the headlight mechanism,
http://www.mamotorworks.com/corvette-c3-headlight-actuator-linkage-parts-1-249-6088.html
I use this website for my parts, but this is not a link to them for advertisement. It just shows an exploded drawing, so I can explain better.

B is the Headlight Actuator. See the long rod coming out of the middle? Has threads on the end of it? Where the rod goes up into the cannister, there is a rubber seal. This dries out and cracks, and also wears through time. Corvette parts places (At least online I know they do) sell this rubber seal.

There is also a small check valve that can go bad.
You can buy the vacuum hoses in a kit. They are color coded, and have replacement instructions.

To review:
1.Check all vacuum hoses for drying and cracking. Actually squeeze them, don't just look at them. If they have a crack from your squeezing, they're shot! (You might find that some just crumble in your fingers! Oh, by the way. Dawn dishwashing soap, or GoJo takes that black rubber residue off of your fingers)

2.Start the car, let it build up vacuum. Shut the car off, and use the override switch, (Knob under the headlight switch you pull), to keep the headlights in an up position. Put your finger on that actuator rubber seal I described above, and see if you feel a vacuum leak.
If so, replace the seal.

3.It's a good idea to replace the check valve,
http://www.volvette.com/HE76.html

4.It's also a good idea to replace the vacuuum filter,
(Vacuum reserve check valve air filter) http://www.volvette.com/HE75.html

See if you get power from the gray wire. Use a 12 volt bulb, or a multimeter.

you will have to remove the master cyl no need to dissconnect the lines and dissconnect the vacuume line and from inside the car under the dash dissconnect the brake pedal from the shaft running to the booster. and remove the 4 mounting bolts that hold the booster to the firewall and pull foward in the engine compartment.
as long as you dont dissconect the brake lines you wont need to bleed the brakes.
good luck
paul

I believe, the best way to track down a headlight vacuum problem with a Corvette, is to make yourself a checklist, and go through it one by one.

Start at the vacuum source.

1.Is the main hose coming out of the intake manifold getting vacuum?
Pull the hose loose from the Vacuum Filter. (White round plastic object with a molded fitting on each side) Is there vacuum present?
No? Remove the hose from the intake manifold fitting, remove the fitting. Take a stiff piece of wire, (Open wire clothes hangar?), and see if the opening is blocked. Perhaps the carbon has built up here.
Vacuum present? Go on.

2.Remove the hose from the other side of the Vacuum filter. See if you can blow through the filter. This filter is to prevent particles from going down into the engine. The filter may fill up, and be blocked over time.
You can blow through it? Go on. No? Replace it. (Replace items that you have disconnected, and checked to be good, as you go forward in your checklist)

3.Is the Vacuum Check Valve working correctly? The check valve has two ports on one side, and one port on the other. You should be able to blow air through either of the two ports, but not be able to blow air through the single port.
Checks okay? Go on. It's bad? Replace it.

4.All devices connected and hoses. Set the parking brake. Start the car. Disconnect the vacuum supply hose under the dash, to the headlight switch. This hose connects at the back of the headlight switch.
Is there vacuum present? Should be. If not, it's the hose coming up to it. If so, disconnect the hose that is at the back of the 'Pull Down' switch.
(Manual Override Pull Down Switch)
Vacuum coming out of the fitting on the 'Pull Down' switch? Is the knob pushed up, or pulled down? Pull it down to open it. Vacuum coming through? Yes? Go on. No? Replace it. (Should be in the Up position to keep the headlight doors open. You are just testing the switch itself)

5.Car off, not running. Things get a little tougher here. You now need to access all of the front vacuum components, and hoses. The best way to do this, is to remove the hood. I would mark around where the hinges attach to the hood, so that realigning it will be easier. If you have a concours show car, I leave the method of marking it up to. Or, you just may want to remove it, and reset it without marks on your baby. I Fully understand! ('70 and '76 'Vette owner)

You should still have vacuum built up. The hose from the 'Pull Down' switch comes from under the dash, through the firewall, down the left fender well, and ends in a 'T' fitting in the Front/Middle, of the car. Remove the hose from the 'T' fitting. Use care, as the fitting may be plastic. (Or you may have replaced it with a metal one. Smart person you, if you did!)

There should be a residual amount of vacuum. If not, reattach the hose, fire the car up. Disconnect this hose again. You should be well away from the fan, and your parking brake should be set.
(I realize that the radiator, and radiator shroud, blocks you from the fan, but I just had to say that)

Vacuum coming from the hose? Okay, reattach it.

6.Your Actuators have a rod coming out of the middle of them. This rod operates the headlight mechanisms. Down where the rod first comes out of the Actuator, there is a Rod Dust Shield. Under this dust shield is a Rod Seal. The seal goes around the rod, and is attached to the middle of the Actuator. Press your finger/thumb against this seal. Hear a vacuum leak? Time to replace that seal.
Go to the other side. Is it leaking? Time to replace that seal. New Actuators are about a $100 bucks a piece. Seals are a WHOLE lot cheaper!

The Green hose opens the headlight door. The Red hose closes it.
If the headlight switch is in the On position, and the 'Pull Down' switch is in the Up position, go from underneath the car, and push up on the front of the headlight door. The headlight should come up.
No? Go to the door mechanism. There is a L shaped link. Push down on it. Now the door should come up. Suspect a bad Actuator.
Depends on if those seals are bad. If they leak enough it may not be the Actuator.

7.Your Vacuum Reservoir is up on the fender well. If it's the original one it's steel. Check it for holes. These tanks rust through.

8.Check the Vacuum Relays. There are two. The middle fitting on the body of the relay, is where the hose from the Vacuum Reservoir attaches to. If memory serves there is a single hose coming from the Vacuum Reservoir, and comes to a 'T' fitting, then splits off to those Vacuum Relays, for the '69 'Vette.

There is a diaphragm at the end of each relay. The diaphragm enclosure, looks like two pie pans put together. These enclosures can rust over time, and develop a hole for a vacuum leak. The hoses from the 'T' fitting, that goes up to the 'Pull Down' switch, comes to this diaphragm. If this diaphragm is bad, the headlight doors won't go up, or come down.