Skip the auto shop - Our mechanics make house calls

Q: Over heating but water is flowing through radiator

asked by on

My car is over heating, I can drive about 20 mins before it starts to over heat. There's no water leakage the radiator seems to be having water flow through, my water resovior seems to be sucking and pushing water into it. I just done see what else it could be. Not sure is its the temp gauage or switch or just need a new radiator

My car has 279000 miles.
My car has a manual transmission.

Hi there, there are a number of things that can cause a vehicle to overheat. The water flowing through the radiator can be a little misleading. Here is a list of possible causes:

These can cause overheating and as you pointed out, the gauge or the temperature sensor could be reading incorrect. An infrared temperature gun is the best way to determine if your car is actually overheating. These can be purchased at your local auto parts store. An infrared gun is often around $50 and isn’t always necessary, but it can help clarify if your motor is actually overheating.

Checking the coolant level should be done with the car cold by removing the radiator cap and making sure the radiator is completely full. Then top of the coolant jug if it is low.

Testing the thermostat is fairly simple. Begin with a cold motor, start the car and wait for the upper radiator hose to become hot to the touch. If your temperature gauge is showing your car is overheating but the upper radiator hose isn’t to hot to touch, you need a thermostat.

Radiators can clog internally and externally. External clogged radiators will have road debris stuck in their cooling fins. This you can see by simply visually inspecting the radiator from the front of the car. You can clean it with a water hose usually. Sometimes you will need to use a soft brush. Be sure not to bend the cooling fins. This will also result in overheating. Internal clogging requires the car to be completely warm with the thermostat open. Drive the car around the block and come to a stop in your driveway, turn the car off, open the hood and feel the radiator with your hand. The top should be to hot to touch and the bottom should be cooler. You are checking for cold spots that will be cold to the touch. If you find cold spots, you need a new radiator.

The best way to check for coolant flow is to remove a heater hose, then start the car. If the water pump is working, coolant should shoot out of the hose. Often choosing what hose to remove for this test can be challenging. So if the first one you remove doesn’t yield any flow, try another, but don’t remove the radiator hoses. If you don’t get flow, I would suspect the water pump impeller has problems.

Checking for a blown head gasket can be a challenge if you have never done it. The ideal method is using a tool called five gas analyzer. The next method is what is called a block tester system. The gas analyzer is a very expensive machine. The block tester can be purchased at your local auto parts store. Simply follow the instructions. The challenge of testing for a blown head gasket is because it happens in degrees. It can be really bad, it can happen only at certain times and it can happen randomly and inconsistently. This is where experience comes into play.

If you should need help with determining if you have a head gasket problem, I recommend the having a certified technician from YourMechanic assist with diagnosis of the overheating issue in order to have this properly corrected.

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!
  1. Home
  2. Questions
  3. Over heating but water is flowing through radiator

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: What circuit should I tie my new gauges into.

Hi there. If you are adding a new set of stand alone gauges then you need to be particular as to where you are splicing the wiring into. The power supply should be on its own circuit and should not...

Q: Spark plug threads

Hi There, It sounds like the threads in the spark plug chamber may be damaged beyond repair by the use of a heli-coil. In some cases, a heli-coil may not be sufficient to restore the threads in the cylinder head...

Q: Oil leaking out and I keep replacing gaskets

The valve cover gasket is a rubber type seal that keeps oil from coming out of the engine. When the mechanic replaces the seal, they must clean the head surface thoroughly, wipe it down with brake cleaner, and dry the...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.