Question about Chevrolet Corvette

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My 69 Vette with a base engine has a vacuum problem. I have replaced the check valve and relay valve. With the engine warm and running at speeds of 40 mph or more the wiper door will rise and then the head lamps. They do not go down until I start the engine when cold the next morning. The vaccum tests low at idle around 10 lbs. Any Ideas???

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Ignition timing, cam grind of a performance cam shaft, can lower engine vacuum at idle, also check for a bad diaphragm or vacuum storage container in the system, some of the old vettes had a vacuum storage container to store vacuum because of the solid lifter motors and the cam grind they were noted for having low vacuum , so GM would use often a container that almost looked just like a 1 lb. coffee can painted black and put in in-line in the vacuum system to store vacuum so when you suddenly accelerated the headlight doors would not slam shut, it would provide enough lag time in the vacuum loss, that the storage would recover.... hope this helps...

Posted on Sep 05, 2009

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We replaced the thermostat in ford f150 but heater still blows cold air


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First, if the engine seems to take forever to warm up, you may have a stuck (open) thermostat. Replacing the thermostat would help get your engine to warm up quickly and maintain the proper running temperature of about 180 deg F. This would solve your heater woes.

However, if the engine warms up normally but the heater just doesn't seem to put out, check the heater inlet valve. This valve is usually next to the firewall on the engine side and is activated by cable(s) or vacuum lines. It is common to find that the valve cables have frozen, the cable ends have broken off, or the vacuum lines are disconnected or broken. Another common problem on vacuum run valves is that the vacuum diaphragm that operates the valve has failed. The diaphragm won't "hold a vacuum" meaning that it leaks and won't operate the heater valve.

If all that seems to work okay. The heater core could be getting warm coolant through it but the underdash heater air handler box has a movable door inside that is not in the requested position. These doors are operated by cables or vacuum lines---so same checkout as above.

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