Coolant Expansion Tank Story: Vanagon

The Vanagon cooling system runs the length of the vehicle. For details about how the system functions, please check out our article, "Cooling System in Vanagons: Explained." The article you are reading now is about one specific component of the cooling system: the expansion tank. 

In the old days, coolant tanks were part of the radiator, as demonstrated on this typical American car radiator:

Normally, a radiator like this would have a separate, non-pressurized coolant overflow tank. When the coolant expanded as it got hot, it needed a place to be stored, and then it would return to the tanks on the radiator when the system cooled off between uses. The one in your parents' old Ford might have looked something like this:

All water-cooled Vanagons have an overflow tank like the one pictured below. It is located right in front of the rear license plate door. 

The difference between an overflow tank and an expansion tank is that the former does not hold pressure, while the latter does. 

In an effort to make the front area of vehicles smaller and smaller—for reasons of aerodynamics—the radiator had to shrink, too. In order to do this, the tanks were reduced in size to an absolute minimum until they were essentially nothing more than manifolds instead of radiator-mounted tanks. More volume was needed for expansion, so the "remote" expansion tank concept was born. 

The Vanagon radiator looks like this:

There are no tanks on the radiator—the expansion tank is located in the back of the vehicle next to the engine. This is not because the engineers were trying to make the front of the vehicle smaller (indeed, it is definitely not small!); rather, the remote expansion tank was employed due to the overall layout of the vehicle's cooling system: radiator way up front, engine in the back, along with an expansion tank that looks like this:

The hose that attaches to the cap at the top of the expansion tank runs to the bottom of the overflow tank. Thus, when the cooling system heats up and the coolant expands, overflow of coolant flows to the overflow tank. When the system cools off, the coolant flows back to the expansion tank—keeping it completely full of liquid and free of air. 

These expansion tanks have been the source of great disappointment over the years. This is not, however, because the original design was flawed. In fact, the original tanks were known to last well over 20 years. The disappointment began when the original VW-made tanks became obsolete, and many different manufacturers started producing an aftermarket tank—most of which are... well, junk. Some tanks would literally melt the first time the engine got a little too hot. This led to some of our competitors claiming the design was flawed, necessitating a tank made of metal instead of plastic. This is really not the case. 

One only needs to look under the hood of every modern car to see, almost without exception, a plastic expansion tank. Plastic is the best material, plain and simple. It is lightweight, transparent, and corrosion-proof. Plus, a plastic tank can be easily shaped to achieve maximum space and strength efficiency. Metal tanks offered for Vanagons, on the other hand, possess none of these benefits—and are just not cost-effective. 

Even if a metal tank were to last forever (which it most certainly won't), for the cost of a metal tank you could replace your plastic tank every five years for the next hundred years and still save money. The tricky part, of course, is making sure to get the right tank!

We have experimented with all of the plastic iterations that have appeared over the years. Truth be told, most any tank currently available will last a few years. Nevertheless, we have searched far and wide to source the best tank—we want you to be happy, and we install these in our own Vanagons. 

You can play it really safe and consider the expansion tank a "maintenance item," replacing it and the level sensor every five years. Typically, the tanks will yellow and become brittle over time, like this:

And eventually, cracks will appear, like this:

This crack was actually leaking, but the beginning signs of the crack appeared long before it started leaking. Bottom line: a high-quality plastic tank replaced regularly is by far the most reliable option—and the best bang for your buck!

Replacing the tank on any 1986-91 Vanagon is very easy and quick. If the tank is replaced in this way, it will take about 20 minutes and no air will be introduced into the system:

1. Pinch both coolant hoses on the tank with hose pinch pliers.
2. Remove clamps at tank using channel-lock pliers.
3. Remove tank (hoses remain in place in the engine compartment).
4. Install new level sensor in replacement tank. We recommend using soapy water on the O-ring. Hand tighten only!
5. Install new tank and sensor assembly.
6. Attach hoses and hose clamps—but do NOT un-pinch the cooling hoses yet!
7. Fill tank with mixture of 50/50 phosphate-free coolant/distilled water.
8. Remove pinch pliers from hoses.

You're ready for a worry-free trip! Well... you won't have to worry about your expansion tank, at least! 

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