Esprit Chargecooler Rebuild

By Edward Avila
(from Lotus email list - April 24, 1998)

Been looking to fix the chargecooler pump on my 90 Esprit SE recently:

Lotus price for the rebuild kit was $150, JAE said "several hundred dollars" and might take a few weeks, and Dave Bean had everything in stock and would send it out same day for $67. Chargecooler rebuild kit came in yesterday, and I just couldn't wait to get started.

Dealer had quoted about 3 hours worth of labor, but I decided I'd do it myself. There's nothing like the satisfaction of fixing it yourself especially if it's an easy one). The rebuild kit included a replacement impeller, two seals, a paper gasket, and an o-ring: how hard could it be? Pull out the pump, put the new parts in, and replace the pump...

The difficult part is that the pump sits under the intake manifold next to the oil filter. There's no easy way to get to it, at least from above. I sat in the boot the whole time, but perhaps it would have been easier done from below. The two ways to reach it are from the right side, across the oil filter, and from the rear, under the manifold. Access from the rear is crowded, so you need to disconnect a few electrical connectors as well as some cooling and air hoses. Even then, your arms will be jammed in there and bent in ways they weren't designed to bend.

The pump is held on by a single 10mm bolt on the top of the pump. Once this is removed, the pump will come out. However, there's about 6 inches of the pump that needs to come out, and because of the crowded spaces, it's not the easiest thing in the world (but nothing compared to putting it back in). Once you free the pump, you can disconnect the two hoses from it and remove it from the car. Just keep in mind which hose goes where.

Dismantling the pump is easy, there's three 7mm bolts holding it together. Once the cover is off, you'll see the impeller, which in my case was almost completely disintegrated (almost no fins left). I pulled the impeller off, then pulled out the driveshaft, and removed the two seals that separate the coolant chamber from the oiled drive shaft portion. These needed to be pushed out, as they are a pressure fit; both come out through the impeller side.

Cleaned up the pump, put in the new seals, replaced the drive shaft (kept the original o-ring, as it seemed of better quality than the replacement and it looked fine) and replaced the impeller. The impeller has rubber fins, and these are a TIGHT fit into the housing. I can't believe these things last more than a day in there. Another point is that the fins don't "wear" or disintegrate, they simply snap off at the base, and I found a nearly complete fin wedged in one of the output pipes. I'm fairly certain the other 20 or so fins must be jammed in the chargecooler somewhere, or perhaps in the radiator; they were obviously "broken off" rather than worn out. Anyone ever taken apart the chargecooler? I wouldn't mind looking in there...

By the way, my car has 15K miles for those who have read you need to replace impeller at around 30K. I don't see these things lasting anywhere near that long.

The replacement impeller was lighter than the original, it appears the original may have had some metal in it somewhere. With the exception of the fins the new one is all plastic. Complete "rebuild" was about 15-20 minutes.

Putting the pump back in is where most of the hassle comes in, as it's much harder to pull hoses to reach the pump, hold them there and tighten the clamps with only 2 hands. Also, it's difficult to manipulate around under the intake manifold, particularly when hoses are attached to the pump. Then you need to align it's driveshaft was well as the pump itself because they'll only go in one way when you insert it back in. Looking down on the pump, with 2 arms coming at it from different directions, for quite a while resulted in some serious bruises and scratches, and the promise that next time I'll pay someone else to do it. I like to work on my car myself, and I like the satisfaction that comes from it as well as the knowledge gained, but some tasks are best left for a qualified individual with the right equipment.

Finally I got it back in, and then reconnected everything I'd disconnected. This included 3 or 4 air hoses, 6 or 7 coolant hoses, 3 or 4 electrical connections, and a few other odd clamps/clips. Total time was about 3 hours from removing the engine cover to completion, but 3 very intensive hours. I have not really had an opportunity to test the results, but a quick drive showed I still wasn't getting a full bar of boost as some claim. Specs I've seen still seem to say .75 is the max on the SE, so I may have done all I can. At least for now. The thermostat replacement did however definitely get me above the .5 bar mark. For only about $10-$15, I'd recommend that for anyone that is not getting full boost and their coolant temperature is around 78 degrees C rather than the required 82+.

While doing the work, I swore I'd never try it again. However, looking back it doesn't seem all that bad. It is one of the more difficult fixes I've done on the car so far (purely from limited accessibility), but nowhere near what it looks like a timing belt replacement would require. Of course, that's not one I'm even going to try... And for those that are unwilling to sit in the rear boot, don't even think about it (unless you have access to a lift). It is possible that I could have had an easier time if I could have come at it from underneath, but I don't see it being much easier.