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ChrisH · 09-19-2009, 10:23 PM

The coolant is flowing now, and everything seems fine. The solution was one or both of the following (not sure which because I didn't test one at a time).
1) I was on a trip for 5 days, and the car sat in the garage. If there was an air bubble at the water pump, then the fluid may have seeped in slowly into the pump, thus priming it and its intake with fluid.
2) I completely removed the bleed screw on the coolant header tank. Note that the Lotus manual bleeding instructions don't even tell you to loosen it. The instructions only tell you to open the two bleed screws on the hoses. I had the filler cap off the header tank, and didn't think it was necessary to open the tank bleed screw. But, the header tank does have compartments, and that may have caused air to not purge from the pump properly.

Fortunately, I didn't remove any parts before it started working.

By-the-way, I did originally follow all the bleeding procedures as per the manual instructions. This included purging air out of the bleed screws on the hoses until I consistently got only fluid (no air) coming out of them.

One note about checking if your water pump is working:
If the pump is working, you can see coolant coming out of the rear small hose that goes into the top of the coolant header tank. It is more obvious if the engine is running at 2000 to 3000 RPM. It might be more obvious if the engine is cool, because there will be a higher pressure in that hose when the thermostat is closed.

09-19-2009, 10:23 PM	#4 (permalink)
ChrisH Mountain Road Nut Join Date: Mar 2004 Location: Ramona,CA Posts: 2,337	Problem fixed. The coolant is flowing now, and everything seems fine. The solution was one or both of the following (not sure which because I didn't test one at a time). 1) I was on a trip for 5 days, and the car sat in the garage. If there was an air bubble at the water pump, then the fluid may have seeped in slowly into the pump, thus priming it and its intake with fluid. 2) I completely removed the bleed screw on the coolant header tank. Note that the Lotus manual bleeding instructions don't even tell you to loosen it. The instructions only tell you to open the two bleed screws on the hoses. I had the filler cap off the header tank, and didn't think it was necessary to open the tank bleed screw. But, the header tank does have compartments, and that may have caused air to not purge from the pump properly. Fortunately, I didn't remove any parts before it started working. By-the-way, I did originally follow all the bleeding procedures as per the manual instructions. This included purging air out of the bleed screws on the hoses until I consistently got only fluid (no air) coming out of them. One note about checking if your water pump is working: If the pump is working, you can see coolant coming out of the rear small hose that goes into the top of the coolant header tank. It is more obvious if the engine is running at 2000 to 3000 RPM. It might be more obvious if the engine is cool, because there will be a higher pressure in that hose when the thermostat is closed.