I normally drive a RAV 4, but it is getting repaired…so I was driving my husbands Toyota Previa. After the second day of driving I told him he had no heat in his car…he denied that. After a week and a half of freezing in the car, he drove it and said…hey their is no heat in the van…Hmmmmm??
After driving the van for about 3 hours all of a sudden the heat kicks in…for about 10 min. then goes off. We do not know if it is the core or the thermostat??? Help. We are broke and will do the work ourselves.
if the problem was in the heater core, it would never come on. So I think that the heater-coolant control valve is sticking. These valves used to be manual, and easy to replace, but now, because engineers need jobs, they are electronically controlled. It could indeed be the temp sender (thermostat) or the electronic on/off sw. that controls the electrically operated valve or even something a simple as the leads. Park the car, and get out your handy continuity tester to see if you have good contacts and continuity in the heater valve control circuit. (you need a wiring diagram and repair manual). You should be able to narrow down the possiblities.
The first thing to check for is air in the cooling system. Because this is a van, the heater core is positioned higher over the engine than in a car. So it’s more prone to have air trapped in it.
To remove any air from the cooling system, get the engine up to operating temperature. With the engine idling, loosen the upper radiator hose clamp. Take a small flat bladed screwdriver and slip it between the upper radiator hose and the radiator hose neck. Allow the engine to continue to idle until all that comes out of the upper radiator hose is coolant. Remove the screwdriver and retighten the hose clamp.
Tester
The fact that the heat kicked in for 10 minutes is good news. It means the heater core is intact.
First, check the coolant level. If it’s low, and it probably is, you’ll need to find the leak. You may need to do a pressure test to find it.
Once you find and fix the leak, you’ll need to replace the thermostat and refill with new coolant mix.
The thermostat’s sole function in life is to restrict coolant flow sufficiently for the engine to heat up to and maintain operating temperature. If it’s sticking open, the engine will stay cold…and you’ll have no heat. If it sticks closed, the engine will overheat.
But that burst of heat you got suggests that you’re low on coolant. And the coolant went somewhere. Typically through a leak. Hopefully the leak is not at the water pump.
Thanks…come to think of it, I have been getting something on my driveway…thought it was oil…maybe not!!
The thermostat on the cooling system for your engine allows the coolant temp to come up to operating temp, and then it opens and allows coolant to flow through the engine and the radiator and depending on the car, the heater core. But there is a valve on the heater hose that opens and closes to let hot coolant into the core. A fan blows air over the core to give you heat in the cab. If that valve is not working you get no heat in the cab. some newer and more sophisticated heaters have air temp sensor that controls both the blower fan, and the coolant flow. You may not have this, and if you dont I was wrong about my post. If you do then I still might be wrong, but maybe not. You did not mention any problem with the cooling system, such as a fluid leak or high temp or low fluid level, so forgive me if I got carried away. But good luck with this. Oil is slippery, coolant not so much.
Peggy, Do Not Continue To Operate This Vehicle Until It Is Diagnosed And / Or Repaired.
The lack of heat is inconvenient and uncomfortable to the occupants, but the lack of a normally functioning engine cooling (passenger heating) system is the kiss of death for this car’s engine.
If you’re lucky you may just have an external coolant leak. It could be a water pump, head gasket, or something more serious.
Continuing to run it will no doubt lead to very serious damage if the cooling system is indeed compromised.
At least be sure the radiator and coolant recovery tank are filled properly and stay full and consider having the cooling system pressure tested right away.
CSA