Auxiliary Heater Coolant Pump Replacement

Auxiliary Heater Coolant Pump Replacement

What is an auxiliary coolant pump?

Some Sprinters vans come equipped with auxiliary heaters, or small diesel furnaces that can be used to warm the engine block on cold days for easier starting, warm the cabin of the van independently of the engine running, and help the engine reach operating temperature more quickly.

Wait… How do I know if I have this?

Well, at least on my van there is a small control module on the dashboard for activating and scheduling the auxiliary heater.

Another way, and leading into the replacement process, is to look under the hood to see if you have a small electric coolant pump mounted to the firewall under the brake booster.

What is needed to replace this pump?

Do not attempt to replace this pump or open the radiator unless the engine is COLD!

Time: ~30 minutes

Cost: ~$50-150



  • 10mm socket and driver/ratchet
  • Medium size flat head screwdriver
  • A couple of small clamps
  • Container to catch spilled coolant
  • Mechanics mirror (optional)

I’m pumped, show me how to replace it!

As I mentioned earlier, the auxiliary heater coolant pump is located on the drivers side of the firewall under the brake booster.

If you have a mirror, you can peak underneath to find the two 10mm bolts holding the mount to the firewall.

With the pump and it’s mounting bolts identified, carefully remove the power supply plug.

Next, use the socket driver to remove the 10mm mounting bolts.

Once the pump is freed from the firewall, the hoses can be bent and the pump carefully maneuvered to a more convenient location. Furthermore, raising the pump as high as possible will help reduce the amount of coolant lost when disconnecting the hoses.

Pinch the hoses with the spring clamps to help restrict coolant flow.

Using the screwdriver, loosen the worm clamps on the hoses. They don’t need to be removed entirely, just loosed enough to remove the hoses. It’s also a good idea at this point to position the container below the ends of the hoses to catch escaping coolant.

The hoses can then be removed from the pump and the pump removed from the engine compartment.

Finally, note the orientation of the mounting bracket and slide the old pump out.

And that’s it, the installation instructions are the removal instructions in reverse.

Some final notes:

  • The coolant system is self-bleeding, so any air in the system should safely find it’s way out on it’s own.
  • Be sure to monitor the coolant levels and see if any coolant needs to be added to replace what spilled. It’s probably a good idea to replace it with new fluid rather than reuse was captured in the container.
  • Be sure to responsibly dispose of any waste coolant.


  1. Hi, thanks and nice write up. I just realized my T1N does have a Auxiliary Heater Coolant Pump, however I don’t see an Espar Heater mounted anywhere. Also, how does one test the Auxiliary Heater Coolant Pump to see if it needs repaired/replaced? Thanks

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