Coolant Pump

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Info non-talk.png There are two pumps within the cooling system:

The coolant pump is located next to the left hand headlight pod (when sat in the car). It is a little electric pump with two wires and two hoses attached.

The electric pump operates when the engine temp is very high, but the engine is turned off. The fans and pump use the same switch (next to the thermostat).

To test the pump:

  1. Run the engine until the fans come on
  2. Turn off the engine
  3. Listen to the pump (it's quiet, so go around to the front of the car).

The pump has its own fuse, so if the fans operate but the pump does not, check the fuse first! It's located under the dash-cover (remove the two screws and lift off). It is fuse #4 in Fuse Box C.

Stuck pump

Although this theory has not been tested, it is based on a posts on a few websites where people have reported freeing them using coolant flushing compounds:

The coolant pump is likely to be turned on relatively infrequently (if at all in colder climates) unless the engine is worked hard and stopped shortly afterwards (as may occur on track). The only time the pump is necessary is if the engine stops with a high coolant temperature (just before the fans kick in) although it is possible that heat soak may also elevate the under bonnet temperature. If a car does not exercise the pump then it is possible that the pump becomes gunked up (for want of a better expression). So, the only time most people need ther pump, it is likely that it will not work!

Unlike a direct coupled pump, this motor is magnetically linked to the impeller so once the motor starts spinning, there is very little torque applied to free a stuck impeller. In this instance, a flushing compound or de-scaling liquid may help release a sticking pump. I think the best option would be to incorporate a run-on timer to run the pump for a short period every time the engine stops.



It looks like this type of pump was designed for water cooled intercoolers and similar applications.

Coolant Pump

The pump was originally fitted to Mercedes Benz 190D (1984-1989) and is a Bosch This part is an exact match, even down to the plug.

Bosch Coolant Pump

Although it is cunningly concealed, the Bosch website has technical information on the recirculating pumps and it looks like their part numbering has been updated. There are a range of pumps - PAA, PCA and PAD. Ours are type PAA so don't imagining that an RS Focus pump will fit - it won't as it's a PCA and a lot bigger! Of the 12V PAA pumps (0.392.020.024, 0.392.020.064, 0.392.020.039 & 0.392.020.034), there is only one with flying leads i.e. 0.392.020.064 which has the highest flow rate of 1200 l/hour (somewhat higher than some of the replacement types so BE AWARE if you are replacing with a none standard pump).

Bosch 0.392.020.064 Coolant Pump



During my research, Ashaman found a site which showed a very similar pump. It had been used in the past to replace a Mercedes coolant pump, which is very similar to the Lotus pump.

This pump is 12 volt and features a magnetic drive - this means that there is no way for water to ever get into the electrics. It also means that if a foreign body got into the impeller and jammed it, the motor should not burn out.

I purchased my pump in the UK from Southern Marine Supplies.

Direct Link: 59500-0012 Jabsco 59500 circulation pump

It cost me £95 inc VAT, compared to the Lotus part at £195 inc VAT.

When the pump arrived it turned out to be EXACTLY the same shape and size as the original. Even the wire colouring is the same. Only difference seems to be that they recommend a 2.5amp fuse rather than the 5amp recommended for the original pump.

Other possibilities

When researching the Bosch information, I found that a variety of V6/V8/W8 VW/Audis use a pump type 0.392.020.073 which is also a PAA type pump and available on US Motors eBay for $85. Unfortunately, I have not been able to confirm the flow rate yet. Note also that a suitable plug will be required. For reference, the VAG part numbers are 3D0 965 561 D and 1J0 965 561 A.

Bosch 0.392.020.073 Coolant Pump



  1. Make sure that the coolant is COLD!
  2. No need to drain coolant, not much spills as the pump is at the top of the system.
  3. Loosen the water pipes attached to the pump.
  4. Remove the 8mm bolt holding the pump in place.
  5. Keep the piece of rubber that is wrapped around the pump for fitting the new one.
  6. Get the new pump ready, then quickly pull the water hoses off the old pump and place onto the new one.
  7. Fit new pump in the mount with the rubber etc.
  8. Cut the power lead for the old pump and use an electrical joining block to connect the wires to the old connector (or use a new connector).

See Also