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How to Check for Cooling System Leaks in a VW Jetta

by Contributor

The cooling system of a VW Jetta is an Integral part of the overall operation of the car. If you drive the Jetta while it is leaking coolant, it can damage the engine, sometimes irreparably. That's why the periodic checking for cooling system leaks is a must. This preventative maintenance requires no mechanical skill, just an attention to detail.

Step 1

Look on the surface where you normally park the VW Jetta for signs of leakage. This is the easiest way to check for leaks and if you make it a habit, it becomes almost second nature. It only requires a quick glance as you leave the driveway or garage.

Step 2

Open the hood and examine the hoses that connect the radiator with the engine and the engine to heater core. Look for any bulging, cracking or splitting in the hoses as well as any noticeable signs of coolant leakage. These signs come in the form of corrosion, discoloration and dripping coolant. However, there can be pinhole or pinch leaks, which surface only when there's pressure or heat exposure on the hoses.

Step 3

Use a flashlight to check the radiator for any possible leaks. Be sure to inspect the radiator from every possible angle to verify any leakage, as the radiator is made of plastic and aluminum in the VW Jetta.

Step 4

Check the water pump and shaft seal for any leakage. The water pump is behind the engine fan and connects directly to the engine. The shaft seal is what seals the connection between the water pump and engine. Verify if there is any corrosion or discoloration to confirm the source of the leakage.

Step 5

Refill the radiator to begin to pressure test the cooling system for leaks. First, twist the radiator cap one full turn, step back, wait a minute and then remove the cap completely. Next, fill the radiator to within an inch of overflowing.

Step 6

Turn on the engine of the VW Jetta and switch the heater to the high setting. Allow the VW Jetta to run like this for about 15 minutes. Shut off the engine and check the auto parts from the previous steps for any leaks.

Verify if the coolant level goes down. If it does, but there's still no visible signs of leakage, the problem may be internal. In this case, you should take the VW Jetta to cooling system specialist for further diagnostics.


  • Wear gloves and a long sleeved shirt when working with and around a radiator to protect your skin from coolant damage.
  • If the water pump is leaking, the only course of action is to replace it.


  • Be extremely careful when working with engine coolant as it is very toxic to people and pets.
  • Never open up a hot or even warm radiator as it can erupt and spew burning coolant all over anyone in the area.

Items you will need

  • Flashlight
  • Coolant
  • Gloves
  • Long-sleeved shirt

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