When idling heats up normal, blows cold when driving on freeway
I'll start my van in the morning before i leave for work and it heats up normal. when i start driving it slowly returns to cold, and blows cold. what could be the problem, and what kind of price we talking, either mechanic, or do-it-myself. what's my best bet?
Re: when idling heats up normal, blows cold when driving...
Sounds like your thermostat is not functioning properly. Go on line or get a manual on your van and see if its a big job. Most thermostats are pretty easy , but there are a few out there that are bears to get to, Hopefully yours will be an easy one
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You have to make sure the thermostat is working properly and is the correct one. Idle the vehicle for about 20 minutes and then feel the upper radiator hose. It should be hot to the touch. Drive the vehicle and when the temp gauge falls to 'cold' stop and feel it again. If it is much cooler to the touch than before the thermostat is defective or wrong.
Check the base plate gasket under the throttle body, some time the gasket start to leak, and will cause a high idle, if possible with engine running get some water and pore it at the base of the throttle bode, you will hear a suction sound, that's the gasket, replace it.
Since your blower is working and it is a heat issue,thats where we'll
start,First thing is have you checked the coolant level in the radiator when
engine is cold,make sure it is filled to top,next verify you have coolant in
reserve ,Start your van and get it up to normal operation temperature,If your
heat gauge on the dash works correctly it should be 190 degrees,Now lift the
hood and locate the two heater hoses going into the heater assembly at the fire
wall,Both hoses should be hot to hold on to,if both are hot and no heat inside
your problem will be the blend air door in heater assembly. if neither hose
is that hot you need to replace the thermostat in the engine to get it up to 195
degrees. if one hose is hot and one is luke warm then the heater core is
blocked and to blame. hope this helps y
Let your engine warm up with the rad. cap off and see if the coolant level drops. and make sure your overflow is full. It blows cold air because there is no water getting to the heater core. And it shows a normal(ish) temp because the water needs to be touching the temp. sensor. I really do think there is air in the system and there is not enough coolant but hard to tell from here. Also as with overheating any time make sure to check your oil and look for any coolant as the head gasket seldomly holds together if the motor overheats.
Just finished fixing my daughters 1999 taurus heat. It would blow warm only when running down the road. At idle it blew cold. I started with replacing thermostat, and water pump because they are the easier fix. Still did not help. Then I replaced the heater core. A daunting job but not that hard to move the dash slighly out of the way to replace. There is a good write up at tarusclub.com. After that, heat was better but at idle, it would still blow cool sometimes. Researched and found answer. Park car on the steepest hill you can find with front of car up. Start car and take off reservoir cap. Let car warm up and keep rpms about 1500. After a while the fluid will come running out of the car and all over the place but it will bring air bubbles with it. Reduce rpm, add more fluid and repeat about 3 times. It will make a mess but after that, the heater works perfectly. We get heat long before the temp gage indicates any and it never blows cold unless you lower the temp.