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Chargecooler Impellor Replacement
Esprit SE, S4, S4s & GT3

If you've got an SE through to a GT3, then you've got a chargecooler (read more about it here before you start), which means you'll have a chargecooler pump, which pushes the water around the system, which in turn, cools the charge from the turbo allowing the engine to produce more power.

How Do I Know If My Pump Is Broken?

Well, you don't really know. If you go out for a longish journey, the charge-cooler case will be cool to touch. A more scientific approach is to connect a scantool such as that excellent FreeScan program ;-) and check what the MAT sensor is reading during a journey.

It should read not much more than ambient, approximately 5 to 10 degC more. Mine was reading 53 degC.

The best test is to go out for a run in the car and park it with the engine off. Wait 15 minutes and the charge-cooler will heat up (because it's on top of the engine!). Connect FreeScan and you'll see a reasonably high MAT reading. Go out for a journey and after a few minutes, depending on your road speed, the MAT should start to reduce. If it does not, your charge-cooler pump is probably knackered.

The impeller, which is basically a propeller, that propels the water around, is made of a brittle plastic that lasts about 18,000 miles. In the picture above you can see what happens to it. The black circular piece on the left is the impellor and the broken black bits in the middle are what's left of the fins.


A kit can be brought from you local Independent Lotus dealer to replace the impellor and seals, which costs £48.50. Once this kit has been fitted you chargecooler system should be working, allowing you Esprit to perform as it should. See here to find out ways of how to check if your chargecooler is working. You don't want to be driving around with an under performing Esprit, all for the sake of a little impellor.

WARNING: This job requires patience. Allow minimum of 4-6 hours


You will need the following parts:

Overhaul kit for chargecooler pump
petroleum jelly
engine oil
thread locking compound

You will need the following tools:

Sockets & Spanners
Long Nose Pliers

Servicing the Charaecooler Pump

The rubber impeller of the chargecooler pump may be inspected and/or replaced as follows:

1. Drain the chargecooler system of coolant.

2 . Remove the single screw securing the chargecooler pump to the oil pump housing, and withdraw the pump with the hoses attached.

3 . Release the three screws and remove the pump end cover.

4 . If necessary, use long nose pliers to withdraw the impellor from the spindle taking care not to damage the housing inner surface or end face.


5 . Clean the mating faces of the pump body and end cover, removing ail traces of the old gasket, and ensure that the inside of the housing is thoroughly cleaned. Smear some petroleum jelly around the inside of the pump housing and on the shaft.

6 . Carefully fit the new impeller B91 OE6992F (either way round) onto the ‘D’ of the shaft and introduce into the housing whilst turning in a counterclockwise direction, so that the vanes of the impeller are trailing when the pump shaft rotates counterclockwise as viewed onto the impeller. See diagram.

CAUTION: Once the impeller has been installed, take care not ot reverse the direction of shaft rotation, or damage to the impeller vanes may occur.

7 . Apply a thread locking compound to the three end cover fixing screws, smear some petroleum jelly around the end mating face of the pump body, and using a mnew gasket A91 OE701 OF, fit the end cover, tightening the screws to 2.4 - 2.7 Nm. DO NOT OVERTIGHTEN.

8 . Smear the chargecooler pump spigot ‘0’ ring with engine oil. Ensure that the oil pump end thrust spring is fitted into the end of the auxiliary shaft before inserting the pump into the housing and engaging the offset dog drive mechanism. if necessary, align the drive dog by turning the pump shaft only in the direction of the arrow on the end cover. Retain with the single fixing screw.

9 . Refill the system with the recommended coolant mix.

CAUTION: Never run the engine when the chargecooler system is drained. The pump impeller will be damaged if run dry.

Having now completed this job, theres a couple of tips that might be helpful to other people doing this job. The article above mentions using long nose pliers to remove the impellor, well mine was well and truly stuck. By trying to extract it with the pliers all I did was scratch the inside face. So I popped down to Lakeside Engineering, and Max simply put the part in the vice and knocked the shaft through! He also mentioned that a large amount of red rubber grease should be inserted between the water and oil seal, to help prevent the two liquids mixing during operation, by introducing another barrier.


This guide has been done to give you the option of fixing your original Chargecooler pump. However LEW feels this isn't the way to go and would advise fitting an Electric pump that will last the life of your Esprit and not a few years. With the cost of £50 for the kit, you'll only need two replacement before you've covered the cost of an Electric pump, which will work better and last a life time. See here for more info on this.

LEW actually carried out this replacement in 2001 on it's SE, but at the time there was no camera available and a guide wasn't done. The parts were ordered from SJ Sportscars. On delivery, LEW wasn't impressed with the parts as it was just a few seals and a tiny impellor for £50. Fitting took all-day as access is very restricted. LEW jacked the car up and worked from underneath, but you can take the air box off and work from above. We decided to remove the oil filter for better access and did an oil change at the same time. Once the pump is out, replacing the parts isn't too difficult. Bleeding as ever is a pain!

This is something you have to do if your chargecooler isn't working. You'll notice a massive difference once everything's working again.

LEW will be fitting an Electric pump in the near future.

This guide was taken from the Workshop Manual available at your local Lotus specialist.

If you have any comments, feel free to e-mail me with at admin@lotusespritworld.com


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