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Audi A4 Coolant Expansion Tank Replacement
 
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Pelican Technical Article:

Audi A4 Coolant Expansion Tank Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$25

Talent:

*

Tools:

Pliers, Philips screwdrivers, fluid pump

Applicable Models:

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

Parts Required:

New expansion tank, coolant

Hot Tip:

Replace the tank with the engine cold

Performance Gain:

A major cooling system leak fixed

Complementary Modification:

Flush cooling system

Over time, the coolant expansion tank tends to become brittle and form micro fractures and sometimes leak. When the car warms up, both the heat and pressure of the coolant starts to attack the weakest point of the tank, eventually causing it to fail and the car starts leaking coolant. The good news is that the replacement tank is relatively inexpensive and can be changed in less than an hour.

Take a look around the coolant tank. In some instances, you can instantly see it has been leaking. In others, you may only see a faint trace of coolant weeping/staining the crack or seam. It's important to tackle this problem as soon as possible. This is also a good time to check your hoses and clamps for wear or damage and replace as needed. Please see our article on hose replacement for additional assistance.

If you are losing coolant from your engine, and you're not sure where it's going, then you can perform a few relatively simple tests to check. First, get an air pressure adapter that will allow you to hook up a shop compressor to your coolant tank cap. Then, pressurize the system to about 13-15 psi. Let it sit and see if you can hear or see any coolant escaping. If the coolant is getting past the head gasket into the crankcase, it will mix with the oil, and you will be able to see that easily when you empty the oil. If the head gasket is leaking coolant into the cylinders, then they will begin to fill up with coolant, and you can see this when you remove the spark plugs.

When the car warms up, both the heat and pressure of the coolant starts to attack the seam along the edge of the tank, eventually causing it to fail and the car starts leaking coolant. Take a look around the coolant tank. In some instances, you can easily see that it has been leaking. In others, you may only see a faint trace of coolant beginning to emerge from the molding seam. It's important to tackle this problem as soon as possible. Failure to do so could cause a complete loss of coolant and perhaps even engine damage.

You do not need to drain all the coolant from the vehicle just drain enough so that it is below the coolant reservoir.

The coolant tank is located on the left side of the engine bay between the intake manifold and the windshield reservoir (red arrow).
Figure 1

The coolant tank is located on the left side of the engine bay between the intake manifold and the windshield reservoir (red arrow).

The expansion tank is the high point in the coolant system so you only need to drain enough fluid to get below the bottom of the tank.
Figure 2

The expansion tank is the high point in the coolant system so you only need to drain enough fluid to get below the bottom of the tank. 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. Note: if reusing the fluid use a container cleaner than the one illustrates in the picture. Coolant is expensive and not very good for the environment so if the coolant in your car is good, try and save it to reuse. Use a turkey baster or fluid pump and drain as much fluid as you can from the tank.

Use a set of pliers and remove the upper hose and clamp (red arrow).
Figure 3

Use a set of pliers and remove the upper hose and clamp (red arrow).

Place a catch container below the lower hose and then remove the hose clamp and disconnect the hose (red arrow).
Figure 4

Place a catch container below the lower hose and then remove the hose clamp and disconnect the hose (red arrow). There will be some fluid left in the tank. You want to be able to properly catch and dispose of it.

Use a Philips head screwdriver and remove the single screw at the front of the tank.
Figure 5

Use a Philips head screwdriver and remove the single screw at the front of the tank.

Lift the tank up and pull it forward out of the two mounting clips on the rear (red arrow, one shown).
Figure 6

Lift the tank up and pull it forward out of the two mounting clips on the rear (red arrow, one shown).

Disconnect the wiring connection on the bottom of the tank by squeezing the clip and pulling the connection straight off (red arrow).
Figure 7

Disconnect the wiring connection on the bottom of the tank by squeezing the clip and pulling the connection straight off (red arrow).

Always check the tank and make sure to use the appropriate coolant (red arrow).
Figure 8

Always check the tank and make sure to use the appropriate coolant (red arrow).

Installation is the reverse of removal.
Figure 9

Installation is the reverse of removal. Make sure to pay attention to the level markings on the front of the tank (red arrow) when refilling the coolant.

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Comments and Suggestions:
Amadou Comments: Hi,
Just check DIY pic 7 the black connection red Arrow. That is what i need to secure my expansion tank wire.

Thanks
December 1, 2016
Amadou Comments: Hi
Thanks for this smart DIY. I am searching for the black connection of the expansion tank wire. Only the wire remains on my engine. The connection has been removed when i gave the car to the mechanic. Amadou A4 B6 1.8T
November 29, 2016
  Followup from the Pelican Staff: Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Jon Comments: Whats the part for the wiring connector that connects to the coolant level sensor? One of the wires is broken . 2003 Audi A4 1.8t quattro
August 28, 2016
  Followup from the Pelican Staff: I’m not the best with part numbers.

Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Amadou Comments: Hi, my coolant level sensor is a bit destroyed. Only the wiring harness left and is directly plugged to the tank.
I want to replace it, finding out a neaw coolant level sensor. Help me please.
February 20, 2015
  Followup from the Pelican Staff: What is the year and model of the vehicle?

Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need. - Nick at Pelican Parts
 
bless626 Comments: What do you recommend u do ?
December 22, 2014
  Followup from the Pelican Staff: Inspect the sensor, if it is leaking into the harness. Replace the sensor and vehicle wiring harness. Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 
BLESS626 Comments: Can a coolent leak electrical problems I have some kind of fluid in my radio wires please help me...dont knoe how the hack that that happen
December 19, 2014
  Followup from the Pelican Staff: If you have a faulty coolant sensor, it can wick through the wiring harnesses, maybe into the fuse panel, then to the radio. I have seen it make it's way to DMEs before, but never radios. - Nick at Pelican Parts  

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