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Pelican Technical Article:

Coolant Expansion Tank Replacement

Jared Fenton

Time:

1 hour1 hr

Tab:

$40

Talent:

***

Tools:

Small fluid pump or turkey baster, hose clamp pliers, Philips head screwdriver, vacuum bleeder tool

Applicable Models:

Jetta MkIV 2.0L (1998-05)

Parts Required:

Coolant expansion tank

Hot Tip:

Try to get as much coolant out of the tank as possible

Performance Gain:

Proper function of cooling system

Complementary Modification:

Replace engine coolant

The coolant expansion tank (CET) is one of those items that tends to start failing in cars with higher mileage. The CET has a manufacturing seam that can split due to the constantly changing temperature and pressure conditions inside the cooling system. Take a look around the CET for tell-tale signs of coolant leaking from the seam. If you do find a leaking CET, replace it as soon as possible. The good news is that replacement is easy and should take no more than an hour.

Remove the cap on the CET and check the fluid level. You'll need to remove any fluid left in the CET prior to removing the tank. Otherwise it will just spill out all over the floor when removing the hoses.

The method I like to use is a simple aftermarket electric fuel pump. These are readily available at any good auto parts store for around $20. I connect the fuel pump inlet hose down to a small diameter plastic hose that allows me to slide it inside the CET and get as much coolant out as I can. The outlet of the pump simply feeds into a clean 5 gallon container. The nice thing about this method is that it allows you to simply pour the existing coolant back into the system when you are done. You can even use a turkey baster to remove the coolant. It just might take a bit longer and might be a little messy.

If your CET has been leaking badly and there is a significant amount of coolant lost from the system, a vacuum bleeder is a must have item. In these cases, air usually gets into the system and there really isn't a way to bleed it out manually. A vacuum bleeder allows you to evacuate all the air from the system using a vacuum. You then use the vacuum inside the cooling system to draw the coolant in. All things being equal, you should have just enough coolant inside the system when the pressure inside the cooling system equalizes. See our article on Coolant Flush and Replacement for more information.

Shown here is a new coolant expansion tank courtesy of Pelican Parts.
Figure 1

Shown here is a new coolant expansion tank courtesy of Pelican Parts. Often times, the new tank includes the lever sensor. You'll want to check this before ordering.

Shown here is the location of the CET on the Mk4 Jetta 2.
Figure 2

Shown here is the location of the CET on the Mk4 Jetta 2.0. Unscrew the pressure cap (green arrow) and suck out as much fluid as you can from the tank. The idea here is to prevent a big spill when disconnecting the lower hose to the CET. Use a small fluid pump or a turkey baster along with a clean container. This way, you can pour the fluid back into the CET if you aren't replacing the fluid.

Loosen and remove the two Philips head screws (green arrows) holding the CET to the frame.
Figure 3

Loosen and remove the two Philips head screws (green arrows) holding the CET to the frame. Note that one of these screws was missing form our project car. Press the tab (yellow arrow) on the coolant level sensor electrical connector and pull it off the CET. Now use a pair of hose clamp pliers and remove the hose clamp (blue arrow) holding the upper hose to the CET. Slide the clamp back and pull off the hose.

Now lift the CET up and locate the lower hose.
Figure 4

Now lift the CET up and locate the lower hose. Use the hose clamp pliers to open and slide back the hose clamp (green arrow). Pull the hose off. Be ready for a bit of coolant to spill out. Installing the new CET is the reverse of removal. Be sure to either fill the CET with the old coolant or fill with new coolant. See our article on Coolant Flush and Replacement for more information.


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Page last updated: Fri 12/9/2016 03:06:23 AM