Was driving my 1999 chevy venture this morning after 12 miles had no heat & temp gauge pegged in the red. then went down & came right back up. Stopped & turned it off for 20 minutes or so. ...
You are describing a slow coolant leak and the resultant no heat and blockoverheating symptoms. The no heat is because there is insufficient coolant to cycle through the heater core, and the chuggin you describe is the engine indicating serious overheating.
With engine cold, you must add water--not anti-freeze--to the radiator itself, until it reaches the top of the radiator, then start the engine. If you do not have a radiator cap in addition to the overflow bottle (some vehicles don't), you must still add water to the radiator, even if you have to bypass the overflow bottle hose to do it. Add water until no more will go into the radiator. Start engine, let idle until operating temperature is reached. Thermostat should open and a good bit of the water will "sink" into the depth of the radiator. If you have no radiator cap, observe the temperature guage. When it reaches normal operating temp, when the thermostat opens, the temp will drop briefly at first, and you will notice warm air from the heater/defroster.
Once engine is warm and known to be full of water, seal radiator cap and/or system, and let idle for 30 minutes. Use this time to locate the "mystery leak." They can be very hard to find, and some won't leak until after the engine is turned off. During this idle period, observe the vehicle exhaust from the tailpipe as well as looking for actual water leaks: sometimes a bad head gasket can be diagnosed this way; if the exhaust is white and thick like steam, and smells like anit-freeze, you have a more serious problem. It is possible that after the repeated overheating cycles you have endured you may now have both a "mystery leak" and a blown head gasket.
Once leak is located, your next step is to let engine cool completely, drain the water, fix the leak, and then and only then add new antifreeze of the proper rating and ratio recommended by Chevy for your vehicle.
Anytime you drain a cooling system and refill it, it is necessary to check the overflow bottle at least 3 times in the first week after repair to ensure that you have the proper coolant level, and have not either missed another leak or not correctly repaired one. You MUST check it before you drive the vehicle the second time after the first repair attempt because it is normal to need to add more coolant than you added initially after the repair because of air trapped in the cooling system that will only be expelled after the first start/stop heating cycle. If after 1 week of daily normal driving you have only added a little more coolant once, and there are no more problems, you can be very comfortable that you have fixed your car.
Jan 16, 2011 |
1999 Chevrolet Venture