Cooling system check

Here you will find useful basic information and tips relating to faults in the vehicle cooling system, e.g. engine overheating, engine not warming up, or heating not warm enough.

In most cases, irregularities in engine temperature or an insufficient heating output can be attributed to faults in the cooling system. Based on the respective symptoms, on this page we will show you which test steps to take in order to quickly identify the fault source.

Important safety note The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their work. The information provided on this website is intended for use by suitably qualified personnel only.

 

COOLING SYSTEM CHECK AND DIAGNOSTICS: BASIC PRINCIPLES

In the event of faults in the cooling system, for example insufficient heating output, engine not reaching operating temperature, or overheating, it is possible to track down the fault cause using simple means. First of all, the cooling system should be checked for a sufficient coolant level, contaminants, antifreeze, and leaks. The V-belt or V-ribbed belt should also have sufficient tension.

 

Depending on the symptoms, troubleshooting can then be continued by monitoring components or recording temperatures as follows:

ENGINE OVERHEATS: TROUBLESHOOTING

Is the displayed temperature realistic?

  • If necessary, check the coolant temperature sensor and indicating instrument ✓

 

Are the radiators or upstream components (condenser) free from contaminants to ensure an unrestricted air flow rate?

  • If necessary, clean the components ✓

 

Does the radiator fan or auxiliary fan work?

  • Check the switch-on point, fuse, thermal switch, fan control unit; check for mechanical damage ✓

 

Does the thermostat open?

  • Record the temperature before and after the thermostat, remove the thermostat and inspect in a water bath if necessary ✓

 

Is the radiator clogged?

  • Check the temperature at the input and output of the radiator, check the flow rate ✓

 

Is the coolant pump working?

  • Check whether the pump wheel sits firmly on the drive shaft ✓

 

Are the overpressure and/or underpressure valves of the radiator cover and/or expansion tank working?

  • If necessary, use the test pump and check whether the seal of the cover is present and/or damaged ✓

ENGINE DOES NOT WARM UP: TROUBLESHOOTING

Is the displayed temperature realistic?

  • If necessary, check the coolant temperature sensor and indicating instrument ✓

 

Is the thermostat constantly open?

  • Record the temperature before and after the thermostat, remove the thermostat and inspect in a water bath if necessary ✓

 

Does the radiator fan or auxiliary fan work permanently?

  • Check the switch-on point, thermal switch, fan control unit ✓

VEHICLE HEATING DOES NOT WARM UP: TROUBLESHOOTING

Does the engine reach operating temperature or does the coolant get warm?

  • If necessary, first carry out the test steps under "Engine does not warm up" ✓

 

Does the heating valve open?

  • Check the electrical control and/or Bowden cable and valve ✓

 

Is the heating radiator (heat exchanger) clogged?

  • Check the temperature at the input and output of the heat exchanger, check the flow rate ✓

 

Does the flap control work?

  • Check the flap positions and limit stops, fresh-air and recirculated-air function, air outlet nozzles ✓

 

Does the interior blower work?

  • Noise, fan levels ✓

 

Is the cabin filter soiled or air flow rate decreased?

  • Check the cabin filter, check the air ducts for false air ✓
How helpful is this article for you?

Not helpful at all

Very helpful

Please tell us what you did not like.

To get the free HELLA TECH WORLD newsletter.

Many thanks. But before you go.

Sign up for our free HELLA TECH WORLD newsletter to receive the latest technical videos, car repair advice, training course information, marketing campaign details and diagnostic tips.

Show additional information on our newsletter Hide additional information on our newsletter

Register for our free HELLA TECH WORLD newsletter to stay up-to-date with the latest technical videos, car repair advice, trainings, diagnostic tips and marketing campaigns.

Together we can get cars back on the road quickly!

Please note:
You will only be subscribed to the newsletter once you have clicked on the confirmation link in the notification e-mail you will receive shortly! Data Protection | Unsubscribe

Please note:
You will only be subscribed to the newsletter once you have clicked on the confirmation link in the notification e-mail you will receive shortly!

Data Protection | Unsubscribe

Almost there!

All you need to do is confirm your sign up!
We've sent an e-mail to your email address.

Check your inbox and click on the confirmation link to start receiving HELLA TECH WORLD updates.

Wrong e-mail or no confirmation received?
Click here to enter it again.

SIGN UP NOW!

To get the free HELLA TECH WORLD newsletter.

Show additional information on our newsletter Hide additional information on our newsletter

Register for our free HELLA TECH WORLD newsletter to stay up-to-date with the latest technical videos, car repair advice, trainings, diagnostic tips and marketing campaigns.

Together we can get cars back on the road quickly!

Please note:
You will only be subscribed to the newsletter once you have clicked on the confirmation link in the notification e-mail you will receive shortly! Data Protection | Unsubscribe

Please note:
You will only be subscribed to the newsletter once you have clicked on the confirmation link in the notification e-mail you will receive shortly!

Data Protection | Unsubscribe

Almost there!

All you need to do is confirm your sign up!
We've sent an e-mail to your email address.

Check your inbox and click on the confirmation link to start receiving HELLA TECH WORLD updates.

Wrong e-mail or no confirmation received?
Click here to enter it again.