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Replacing your Audi A4 Radiator Hoses
 
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Pelican Technical Article:

Replacing your Audi A4 Radiator Hoses

Steve Vernon

Time:

3 hours3 hrs

Tab:

$10 to $100

Talent:

**

Tools:

Flat head screwdriver, pliers,

Applicable Models:

Audi A4 (2002-05)
Audi A4 Cabriolet (2003-06)

Parts Required:

New hoses

Hot Tip:

Work on a cool car

Performance Gain:

Proper operating temperature

Complementary Modification:

Flush the radiator

The Audi A4 uses an inline four-cylinder turbocharged engine as a power plant. The engine and turbo can develop good horsepower especially with some aftermarket accessories or tuning. One of the drawbacks to horsepower and having the engine located in a smaller car is heat. The Audi needs to be able to keep the engine in a proper temperature range even while stationary or in bumper to bumper traffic, which it does fine with its stock cooling system.

The cooling system on your vehicle is one of the most important and yet neglected parts of the car. Nothing can leave you stranded faster than not replacing a rubber hose before it goes bad. I recommend inspecting your hoses and couplings every two years or so. As they age, they have a tendency to get hard and brittle. When you gently squeeze a hose, it should be relatively soft and easy to indent with your hand. It shouldn't feel like it is brittle or crunching when you squeeze it. It should spring back to its original shape pretty quickly after being compressed. If it feels very hard, then it might be time to replace it. If there is a bulge in the hose, or any type of crack in the surface of the hose, then you should replace it as well.

The Audis cooling system uses a series of quick disconnects as well as old style hose clamps. Check for leaks around where the hoses create their connections--that is a sign that the hose should be replaced. I also recommend replacing the clamps when replacing hoses

You are going to need to safely lift and support the vehicle. Also depending on which hoses you are replacing you will need to move the lock carrier into the service position. Please see our articles on these procedures for additional assistance.

Begin by draining the coolant. Here are a couple of safety precautions/instructions you may want to observe before beginning:

If you cannot work on a cold car, allow the cooling system to cool down to a coolant temperature of less than 90°C. Open the cap of the cooling system slowly; turn a conventional coolant cap as far as the first detent and turn a screwed coolant cap approx. 1/2 turn and release the pressure. Wear protective gloves, protective clothing and eye protection. NEVER pour coolant into beverage bottles, cups, etc... Someone might accidentally pick that cup up and start to drink.

If the coolant in the car is new there is no reason to replace it as long as you drain it into a clean container. Coolant is expensive and not too great for the environment, so if the coolant in your car is good, try and save it and reuse it.

On the lower left side of the radiator is a drain spigot (red arrow).
Figure 1

On the lower left side of the radiator is a drain spigot (red arrow). This spigot is controlled by a plastic knob (yellow arrow, not shown) that is very difficult to get access to. It is much easier to drain the fluid from the coolant temperature sensor (green arrow). Pull the clip that holds the temperature sensor in place and drain the coolant through the sensor opening. Please see our article on temperature sensor replacement for additional assistance.

Upper Hose - The radiator is connected to the engine cooling system by two hoses on the front left side of the car (red arrow and yellow arrow).
Figure 2

Upper Hose - The radiator is connected to the engine cooling system by two hoses on the front left side of the car (red arrow and yellow arrow). Note: you do not need to remove the front of the vehicle to perform this work the front was removed for photographic purposes only.

Upper Hose - One of the weakest spots in the cooling system is where the coolant overflow hose (yellow arrow) meets the upper quick disconnect (red arrow).
Figure 3

Upper Hose - One of the weakest spots in the cooling system is where the coolant overflow hose (yellow arrow) meets the upper quick disconnect (red arrow). This spot is prone to breaking and was broken on our project car. The overflow hose is a hose clamp and can be removed with pliers. Use care so as not to break the connection. If you break the connection you will have to replace the upper hose.

Upper Hose - To separate the upper hose carefully pry up the quick disconnect wire from the end of the connecting piece on the hose (red arrow) and wiggle and pull the hose from the radiator (yellow arrow).
Figure 4

Upper Hose - To separate the upper hose carefully pry up the quick disconnect wire from the end of the connecting piece on the hose (red arrow) and wiggle and pull the hose from the radiator (yellow arrow). These can get stuck on and need a fair amount of force to remove. Just make sure you do not break the radiator while doing it.

Upper Hose - This photo illustrates the upper coolant hose.
Figure 5

Upper Hose - This photo illustrates the upper coolant hose. It connects the radiator via a quick disconnect and attaches to the upper metal pipe with a hose clamp (red arrows). The coolant overflow hose attaches to both the coolant reservoir and quick disconnect with hose clamps. Note: you do not need to remove the front of the vehicle to perform this work. The front was removed for photographic purposes only.

Lower Hose: If you did not drain the coolant through the coolant temperature sensor you now need to disconnect the sensor from where it meets the lower hose (red arrow).
Figure 6

Lower Hose: If you did not drain the coolant through the coolant temperature sensor you now need to disconnect the sensor from where it meets the lower hose (red arrow).

Lower Hose - To separate the lower hose, carefully pry up the quick disconnect wire from the end of the connecting piece on the hose (red arrow) and wiggle and pull the hose from the radiator (yellow arrow).
Figure 7

Lower Hose - To separate the lower hose, carefully pry up the quick disconnect wire from the end of the connecting piece on the hose (red arrow) and wiggle and pull the hose from the radiator (yellow arrow). These can get stuck on and need a fair amount of force to remove. Just make sure you do not break the radiator while doing it.

Lower Hose: This photo illustrates where the two-piece lower hose connects with the coolant reservoir (red arrows) and the thermostat (yellow arrows).
Figure 8

Lower Hose: This photo illustrates where the two-piece lower hose connects with the coolant reservoir (red arrows) and the thermostat (yellow arrows). The reservoir connection is a hose clamp, while the thermostat hose has a quick disconnect.

Thermostat - The thermostat has three lines connected to it, a hard metal line that is connected via a 10mm bolt and a gasket (green arrow), a quick disconnect to the lower radiator hose (red arrow) and the upper coolant hose connected via a hose clamp.
Figure 9

Thermostat - The thermostat has three lines connected to it, a hard metal line that is connected via a 10mm bolt and a gasket (green arrow), a quick disconnect to the lower radiator hose (red arrow) and the upper coolant hose connected via a hose clamp. Note: you will need to remove the alternator to get access to the thermostat. Please see our article on alternator removal for further assistance.

There are two coolant lines running from the turbo.
Figure 10

There are two coolant lines running from the turbo. One line connects to the upper coolant hose (red arrow), while the other is a hard line that runs to the back of the head.

There are two coolant lines connected to the oil cooler base (red arrows).
Figure 11

There are two coolant lines connected to the oil cooler base (red arrows). Both are rubber and connect with hose clamps.

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