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dontcallmeharry

Previa Heater Only Blowing Cold Air

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Hello,

My 1996 Previa is only blowing cold air out of the heater system.

The engine appears to be running at normal temperature according to the temperature gauge.

The vehicle has no air-conditioning system fitted.

Is the answer to change the thermostat?

Many Thanks for your help in advance!

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The thermostat has nothing to do with the heater The heater pipes come off taps before and after the thermostat housing. I fear you either

1. Best case sceanrio have an air block.

2. Worst case, have a head gasket that is on its way out.

How much mileage has your car done and have you noticed that either you are losing coolant, the car is smoking white smoke, your Oil is taking on a milky appearance, there is Oil in your coolant or all of the above ??

The roll of the thermostat is to allow the coolant to come up to operating temperature quickly and thereafter maintain an optimum temperature. If your gauge is sitting at +- 9 o'clock then it sound slike the thermostat is ok.

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The thermostat has nothing to do with the heater The heater pipes come off taps before and after the thermostat housing. I fear you either

1. Best case sceanrio have an air block.

2. Worst case, have a head gasket that is on its way out.

How much mileage has your car done and have you noticed that either you are losing coolant, the car is smoking white smoke, your oil is taking on a milky appearance, there is oil in your coolant or all of the above ??

The roll of the thermostat is to allow the coolant to come up to operating temperature quickly and thereafter maintain an optimum temperature. If your gauge is sitting at +- 9 o'clock then it sound slike the thermostat is ok.

Thanks for replying....

I have owned the car for 11 years and had it serviced regularly. It has now done 98,000 miles, still runs really well and does not appear to be using Oil or water.

Let's go for the 'best case' scenario! Do you know where I should start checking?

This has happened before with this vehicle and the garage sorted it out but charged me a fortune and I was hoping to do it myself and save some money.

Thanks.

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First thing is to check that the overflow pipe on your header tank is not blocked. It is a small pipe that exists from just under cap at the rear. Take it off and blow through it to ensure it is clear. Then with the car cold open both your heater selectors and start the car. Watch the temp gauge and once it reaches operating temp switch on your fan to the first position and raise the RPM to about 2000 rpm for 30 secs. Then replace the cap and leave it to idle for around 5 mins then take it up to 2000 rpm for 30 secs all the time feeling the air coming from fan. CAREFULLY remove the rad cap, you should feel a release of pressure and it should start to gurgle possibly with a reduction of level. Repeat this process a few times and eventually it should start to clear. If and when the water level drops use a 50/50 mix of distilled water and antifreeze or premixed antifreeze from Halfords.

Have someone watch the water bottle all time and please be careful not to scald yourself. Use a thick rag or a welders glove to open the bottle. If the water consistantly bubbles over the top then I am afraid you need to start suspecting the head gasket again.

ONE LAST THING: - Take a look at your coolant, if it is red in colour then you have Toyota red which does not mix with water or other antifreezes and so you will need to go and buy some from Toyota before you start.

Best of luck.

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Did as you suggested with the overflow pipe and noticed the coolant level was actually quite low.

I have filled it up and cleared the overflow pipe for blockages and now the heater works fine.

Many Thanks for your help.

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You are most welcome BUT again I must stress a caution here.

Water does not just disappear from an engine as it is a sealed system. There are only three ways it can do so and here they are in optimistic order.

1. A leak

2. The rad cap is worn

3. The head gasket.

If you haven't noticed a leak then pop down to your local auto factors and buy a new rad cap and monitor the level carefully

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Hello I have the same problem and reading the above can u tell me where the overflow pipe on your header tank is. I have a toyota previa gs auto on a p(19197). Thanks

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Had the same problem and although I am quite regular at monitoring fluid levels, in this case I had let the overflow reservoir run down. When it was replenished heater returned.

Isaiah

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I'v had the same problem. Make sure the heater is on. Lift the overflow pipe so its higher than the heater. Disconnect the top heater matrix pipe and put funnel in hose and fill untill water runs out of the heater. Reconnect hose. You will need to check the level in the main resevoir and drain to correct level. Take for a short drive. allow to cool before rechecking water level. I have fitted a bleed valve on my top hose.

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