Skip the auto shop - Our mechanics make house calls

Q: Heat

asked by on

Replaced radiator and thermostat due to over heating.fixed that problem but now the heat blows luke warm.used 50/50 antifreeze when filling it

My car has 165000 miles.
My car has an automatic transmission.

The most common reason for this after a repair is an air bubble in the system. Most of the time, if you completely warm the car, which means you have confirmed the thermostat is open by feeling the upper radiator hose it hot to the touch. If it is and the car isn’t overheating, take it for a test drive on the highway. Air bubbles can create overheating conditions, so do go to far. You only need to go about 45 mph for a few minutes. Once you get home, let the car cool for about an hour. Remove the radiator cap and see if coolant is all the way to the top of the radiator fill. If not, top it off and take a drive again.

This will often take a few tries to get the system to completely bleed. Sometimes I have had to run motors multiple times to get them to bleed the air bubbles from the system. The best test for a completely full cooling system is to check it first thing in the morning. This is when the cooling system will contract the most making room for more coolant.

If you determine the cooling system is full, but you still have luke warm air coming from the vents, the next thing to do is feel the heater hoses coming from the heater core at the fire wall. One should be really hot and the other should be cooler, but not significantly colder. If it is, you have a clogged heater. The easiest, thing to do at this point is flush the heater core. There are multiple ways to do this. Whatever way you choose, be sure to flush it both directions. If flushing doesn’t work, you will need to replace the heater core.

My information system doesn’t show there to be a heater control valve on your car, but I would still keep my eyes out for one. If it has one, make sure the valve is opening and closing.

I recommend the following inspection to help you should you need further assistance; Heater is not working replacement. Be sure to send the technician a note explaining your symptoms so he or she can come prepared.

Good luck!

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Hatchback needs sway bar replaced

Hello. There is only one front sway bar on the vehicle. The sway bar is connected on both ends with link pins. There are two of those so that may be what he is talking about. They should always be...

Q: Heater core malfunction

When the vehicle begins to overheat after cooling system repairs were done, it is usually due to air stuck in the cooling system. Normally after cooling system repairs, the coolant system is bled of all air, or "Burped". This is...

Q: Check Engine Light on again after thermostat replacement.

If the check engine light is coming on and a code like P1217 is in the computer then the computer is seeing an overheat conditions from the coolant sensor telling it your engine is overheating. This can be caused by...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.