Install The Electric Water Pump on a Lotus Exige

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A comprehensive guide how to install a Davies Craig Electric Water Pump (EWP model 115) and controller in a Lotus Elise / Exige.

Why replace the mechanical water pump?

  1. Parasitic drag. Ever turn on your A/C and feel the car bog down or get sluggish? That's due to the parasitic drag it takes for the engine to turn the pulley on the A/C compressor. The same effect happens with a mechanical water pump, only it happens all the time which is why it's not felt. Removing the water pump frees up the engine from also running the water pump increasing horsepower and fuel economy.
  2. An EWP circulates water in relation to how hot the engine is versus a mechanical pump circulating based on how fast the engine (RPM) is running. After a road race / track day your engine is hottest immediately after coming off track. With an EWP it knows this and keeps maximum cooling where as a mechanical just idles in relation to engine rpm.



Lift your Exige on jack stands or with a hydraulic lift.

Follow the instructions here to learn how to safely lift your Lotus Exige / Elise.


Remove the front Clam

Follow the instructions here to learn how to remove the front clam.

Also, completely remove the bottom metal plate in step 12. This provides access to the coolant lines.

Remove impeller from water pump & thermostat


Remove the engine belt

  1. Use a 19mm 6-point socket to turn clockwise on the tensioner to pivot the pulley loosening the tension on the belt and then slide the belt off.
  2. Set the belt aside as you will reuse it or optionally replace with a new one.

Remove the water pump

There are two methods to remove the pump (1) with the pulley on and (2) with it off. #2 requires a special tool to remove it. These instructions will cover method #1.

  1. Use a 10mm socket/wrench to remove the 6 bolts starting at the top and to the right.
  2. Use a wrench to remove the remaining bolts. Patience is key as you're only going to be making partial revolutions due to the limited space.
  3. Remove the pump and seal
Image 8562 from Install the Electric Water Pump on a Lotus Exige

Remove the impeller

  1. Place the waterpump in a vise and break off the impeler in chunks with vise grips. It's a soft material and takes little to no effort.
  2. Use a chisel or sharp flathead screwdriver and hammer to break away the remaining part on the shaft.
Image 8152 from Install the Electric Water Pump on a Lotus Exige
  1. Reinstall the water pump with a new seal. Refer to the image above for the torque specs and correct bolt lengths for each location.
  2. Reinstall the engine belt

Remove the thermostat

  1. Use a 10mm socket to remove the nuts (A, B) securing the thermostat housing
  2. Be ready to catch the coolant spilling out
  3. Remove the thermostat and discard
  4. Install new water inlet gasket
  5. Replace the thermostat housing
  6. Use a 10mm wrench or socket to tighten the nuts. Don't forget the dipstick bracket

Install the EWP


Remove the OEM driver's side coolant hose

  1. Use a flat head screwdriver to loosen the hose clamp (A) securing the coolant hose to the lower hard line under the front clam.
  2. Pull the hose off the hard-line with a hose puller.
  3. Drain all coolant into a bucket. Be prepared for spillage with towels/rags.
  4. Use a flat head screwdriver to loosen the clamp (B) securing the coolant hose to the upper radiator port.
  5. Remove the hose

Resize the new 1.25" To 1.5" 90 Degree Elbow.

  1. Place the lower portion of the OEM hose just removed (your's will be rubber and black, in the picture a new silicon GRP hose is shown) on top of the 90 degree elbow, ensure the 1.25" end is sticking out (A)
  2. Use a marker to indicate where to cut the new 90 degree elbow to match the length of the original hose (B)
  3. Use a utility knife with a new sharp blade to trim the 90 degree elbow to length (approx 20-24mm)

Prep the 1.5" x 1.25" Straight Reducer hose

  1. Shorten the 1.25" hose end by cutting 20mm (~3/4") off with a utility knife
  2. Insert the 32mm (1 1/4 inch) Aluminum Hose Joiner into the 1.25" end until the middle band on the joiner is even with the end of the hose.
  3. Install and tighten a hose clamp to secure the joiner.
Image 8156 from Install the Electric Water Pump on a Lotus Exige

Prepare the EWP for install

  1. Connect the 1.5" end of the 1.5" x 1.25" Straight Reducer hose to the EWP outlet port (A). Slide it on as far as possible.
  2. Install and snug a hose clamp with a 8mm socket or flathead screwdriver
  3. Leave room for the 1.75 Inch Stainless Steel Cable Clamp fit on the outlet port (A) between the clamp and the body of the EWP. The clamp is not shown below in the picture, but you can see the space left for it.
  4. Connect the 1.5" end of the 1.25" To 1.5" 90 Degree Elbow to the EWP inlet port (B). Ensure it slides on all the way as it tends to get stuck on the lip.
  5. Install and leave loose one of the Davies Craig hose clamps included with the kit to secure the hose and fit in the hose clamp groove in the EWP.

Install the EWP and test placement

  1. Slide a hose clamp onto the 1.25" To 1.5" 90 Degree Elbow.
  2. Install the EWP by sliding the 1.25" To 1.5" 90 Degree Elbow through the hole in the crash structure and connect to the coolant hard line underneath. Snug the clamp, do not tighten.
  3. Rotate the EWP body until the 1.5" x 1.25" Straight Reducer hose on the outlet port is directly aiming at the radiator inlet port. It should resemble the picture at this point.
Image 8404 from Install the Electric Water Pump on a Lotus Exige

Connect the EWP to the Radiator

Since I can't predict exactly how your EWP was mounted and what clearances you ended up with this part requires you to take measurements and determine hose cutting on your own.

  1. Take the OEM radiator hose, or alternatively a new 90 degree 1.25" elbow, and slide it onto the radiator port.
  2. Now angle it down so it matches the angle of the EWP 1.5" to 1.25" reducer hose as if you're going to connect it.
  3. Determine how much needs cut off the end of the hose connecting to the radiator to bring it in line with the EWP hose. Cut the hose in small increments if unsure and test fit multiple times. I trimmed mine ~35mm for reference.
  4. Install the 32mm hose joiner at the end of the EWP hose
  5. Mark the OEM hose at the halfway point on the joiner and cut to length
  6. Use 2 hose clamps to secure the hose to the EWP joiner and the radiator
Image 8575 from Install the Electric Water Pump on a Lotus Exige

Install mount for EWP

  1. Place a Lokman 2" Rubber cushioned clamp around the EWP directly behind the hose clamp. Ensure the flat side is flush with the black composite crash structure.
  2. Insert a M6x25mm bolt (A) through the mounting holes in the clamp and mark on the composite crash structure where a hole is needed.
  3. Drill a hole to fit the M6 bolt through
  4. Insert the M6 bolt through the hole and place a nylon M6 locking nut and washer on the back side to secure it.


Before beginning the wiring a location must be determined for the controller. DaviesCraig states the controller must be installed in the cabin away from any moisture exposure.

I've chosen to ignore that recommendation due to the extremely limited cabin space in a Lotus and I see no need to have access to the controller while driving. Therefore, the following steps are how to seal the controller from environmental risks (e.g, dust, dirt, moisture, etc.) for installation on the firewall in the engine compartment.

Skip the following weatherproofing steps if installing in the cabin.

Weatherproofing the controller

  1. Cut out the sticker covering the single screw (A) holding the controller together on the backside
  2. Use and Phillips head screwdriver to remove the screw
  3. Separate the back cover, circuit board, and front cover
  1. Read the safety data sheet included with the Silicone modified conformal coating
  2. Don't be stupid. Wear safety gloves, a proper respiratory mask with organic filters, and ensure adequate fresh air flow.
  3. Ensure the circuit board is clean and free of debris.
  4. Coat the entire surface of the circuit board with the SMCC. Use several thin coats and don't stop until it looks like glass. Too much is not a factor here, only too little. Be careful not to get it on the single toggle switch (A) on the circuit board.
  5. Use the UV-A light to validate all surfaces are covered. The SMCC appears blue under UV-A light.
  6. Repeat this process for the backside of the circuit board.


Do not coat the leads inside the white connector where the plug connects.


Reassemble the controller

  1. Place the circuit board on the bottom (back) controller housing.
  2. Run a bead of gasket maker (or equivalent sealing product) along the edges where the controller housing seats.
  3. Press the top (Front) controller housing on to the assembly, turn over install the screw to secure it.
  4. The controller housing does not tightly close with the single screw. Run another bead of gasket maker along the seam and around the white wire connector. Ensure it's completely sealed up.
Image 8169 from Install the Electric Water Pump on a Lotus Exige

Make a mental note to mount the controller upside down so the wires point to the ground. Water doesn't run up hill :)

There is no way to weatherproof that horrible connector without replacing it with a better Autosport or Deutsch style sealed connector.

Mount Controller


Figure out where to mount the controller.

  1. Place the controller housing where it should be mounted on the firewall and mark the hole locations. Pictured below is my chosen location, you're free to place it anywhere away from heat.
  2. Drill each hole on the firewall out with a drill bit. Keep in mind there is stuff on the other side so drill carefully. If you ram the drill bit through more than an inch you'll most likely hit the rear speaker.
  3. Install M5 Jack Nuts.

Do not use Rivnuts, they simply won't stand the test of time with that soft firewall material.

Reference below for my chosen mounting location. Note the bolts are M6 as I had M6 jack nuts laying around, I don't recommend using this size although it's doable. M5 are a better choice.

Image 8186 from Install the Electric Water Pump on a Lotus Exige
Image 8187 from Install the Electric Water Pump on a Lotus Exige

Note the bottom right hole does not have a jack nut and bolt installed. When attempting to install I found out the hard way that location is directly behind the magnet on the rear speakers. As a result, there isn't room to install the jack nut without pulling the speaker and replacing after install. I chose to just skip that bolt.

Install temp sensor

The stock temp sensor in the block cannot be used with the DaviesCraig controller. The ohms (electrical signal) generated by the OEM temperature sensor is too far off from the DaviesCraig sensor for it to work with the DaviesCraig Controller.

Plus there is the issue with taping into an RTD style sensor (resistance).

Drilling and tapping the thermostat housing is an option. I felt it was too thin to trust it, so the solution below was developed.


The solution

  1. Use the 34mm Dewhel Aluminum adapter and drill the top port out with a 29/64 drill bit. Before doing so verify your drill press is setup correct and the top of the Dewhel part is perpendicular to the drill bit and the bit rotates without any wobble.
  2. Place the adapter in a vise and ensure the top surface is level.
  3. Use a 1/2-20 Tap to thread the hole.
  4. Wrap the threads of the DaviesCraig temperature sensor with PTFE tape and install.
Image 8730 from Install the Electric Water Pump on a Lotus Exige

Some of the DaviesCraig sensors come with a rubber o-ring seal and others do not. If your's came with a seal and you really want to use it then follow the instructions below. Otherwise just relying on the PTFE tape and the NPT threads is perfectly fine.

The following 3 steps are OPTIONAL

  1. Overbore the hole in the Dewhel adapter to allow the seal to fully seat. If you don't the NPT threads will stop well before the seal mates to the adapter.
  2. Use a 9/16" drill bit to bore NO MORE than 9mm down the hole from the top of the adapter. I highly recommend drilling to 6mm and test fitting then slowing going deeper. The trick is to get it just right so the seal mates to the top of the adapter and the NPT threads seal.
  3. Install the temperature sensor with PTFE tape on the threads
Image 8731 from Install the Electric Water Pump on a Lotus Exige

Prepare the main coolant line for the adapter

  1. Locate the hose tension clamps securing the 32mm (1.25") hose joiner from where the engine coolant return line meets the chassis line below the ECU.
  2. Use pliers to release and slide the constant tension clamps backwards off the hose joiner inside the hose
  3. Wiggle the two hoses apart and remove the hose joiner. Depending how long that joiner has been installed this may require some real muscle and patience. Mine was a total bear to remove.

Install the Dehwill adapter and sensor

  1. Slide a hose clamp on to the chassis hose (use a hose clamp or reuse the constant tension clamp)
  2. Insert the Dewhill adapter into the chassis hose and ensure the sensor is pointing up toward the ECU
  3. Secure the adapter and hose with the clamp
  4. Slide a hose clamp onto the coolant hose
  5. Attach the engine coolant hose to the Dewhil Adapter and secure with a hose clamp
  6. Plugin the black wiring harness connector from the DaviesCraig to the temp sensor
Image 8734 from Install the Electric Water Pump on a Lotus Exige


Obtaining Ignition and Fan relay trigger control

The DaviesCraig Controller needs the ability to control a radiator cooling fan (or both). If the controller is mounted in the engine compartment the easiest way to achieve this is to tap the ECU wiring harness as outlined in detail below.

If installed in cabin follow the guidance below. You will need to figure out some of this (mainly running the wire) for yourself as I didn't implement this method.

Guidance on in Cabin wiring install

  1. Under the front clam, locate the Air Conditioning switch relay box on the passenger side above the control arms. It is a black box with two wiring harnesses/plugs attached.
  2. Find the wiring diagram in the manual and locate the relay that controls the fans. Tap into the trigger wire that is blue with a green stripe. This is the high-speed fan relay trigger when grounded it will engage both fans at full speed, the same as turning on the Air Conditioner.
  3. Find an ignition on trigger wire, 12v power constant, and ground under the dash. This is where you're on your own, there are plenty of ways to do this. Consult the manual or forums to find the best easiest source.

Engine compartment wiring for ignition and fan control

Fan Control

  1. Disconnect the ECU Connector on the right-hand side (closest to the engine)
  2. Split open and peel back the wiring cover to gain access to the wires. Leave yourself plenty of working room, get access to the wires at least 6 inches back from the connector.
  3. Locate the ECU high-speed fan signal wire (Blue w/ Yellow stripe, circuit 364) and choose option 1 or 2 below to connect the controller Fan Relay wire (Green w/ Black stripe)

Option 1: Cut the ECU wire. Cons ECU cannot engage high-speed fans, The DaviesCraig Controller will now do that. Pros - The ECU will NOT throw a Pxxxx code every time the DC controller kicks the fans on.
Option 2: Splice the wire. Pros - ECU and controller can engage high-speed fans. Cons - see Option 1 regarding a code. This code doesn't hurt anything, but if you're watching with ODB2 you'll see the code frequently.

Ignition trigger

  1. Locate the fused ignition wire (solid green, circuit 367) in the ECU harness and splice in the green controller wire labeled "ignition"
  2. Seal up the splices with your preferred method (e.g., liquid electrical tape) and route the wires to ensure a stress-free life.
  3. Seal up the harness and reconnect the harness connector to the ECU.

Power and Earth (Ground)

  1. Locate the main power distribution point mounted to the firewall directly below the ECU. It has a black box with a latched door on it (that door is a pain to open) and a bunch of RED wires running to it. Open the door.
  2. Locate the ground distribution point below the ECU. It will be a stud and nut with a bunch of blacks and bare wires running to it.
  3. With the DaviesCraig controller mounted cut the power (Red) and earth (Brown) wire to a reasonable length to ensure they can easily reach the main power and ground distribution points.
  4. Install a weatherproof 5/16" ring terminal on the power wire (Red) and earth (Brown) wires.
  5. Use a 13mm socket to remove the nut on the studs, slip the respective ring terminal on and replace the nuts tighten to hand tight.
Image 8171 from Install the Electric Water Pump on a Lotus Exige

These connections are both spliced, soldered, covered with liquid electrical tape, and then wrapped with electrical tape. I found this the easiest method; however, you're free to go with what you're comfortable with. Just make sure the exposed wire is covered to prevent shorts and corrosion and run everything to alleviate stress on the splices.


Running power to the EWP from the Controller

  1. Pull two 16ga wires (ideally red and black) through the driver's side sill to connect the EWP to the Controller. Alternatively, you can run the wires through the firewall, up through the shifter center column, and out the front firewall. It's way more work, but an option.
  2. Install a Deutsch connector on the end of the wires at the EWP.
  3. Remove the existing connector on the EWP and install the female/male Deutsch connector and plugin the wires.
  4. Back at the Controller, cut the existing power wires on the Controller leaving ~12" or your desired length. Use weatherproof butt connectors, solder, or Deutsch connectors (it's your choice) to join the 16ga wires you pulled through the driver's side sill to the power and ground wires on the controller connector.

Refill Coolant & Test


Congrats the hard work is over. Take a minute to re-read these instructions and verify everything is hooked up and connected.

  1. Refill the coolant system with your desired coolant mix.
  2. I highly recommend using a vacuum tester and refill tool for this. Since some of the coolant hoses are custom a leak test is a wise idea. Refer to OEMTools 24444 for a reasonably priced tool that just works (you need an air compressor, pancake ones work fine).
  3. Once a leak test is complete and the system is refilled you need to test the EWP.
  4. Turn the car on and follow the DaviesCraig instructions on how to program the controller for activation points.
  5. Let the car run to temp and verify the controller is activating the EWP (it should surge during warm-up) and turning the EWP and fans on full blast once at the programmed temp.

DISCLAIMER Last updated August 28, 2021

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