Help - Cooling system problem

[ChrisH]

Before I start removing parts, I wanted to ask for help with this problem just in case I am missing something.

My Elise is overheating. After the engine is hot (over 215 F) and the radiator fans have activated, the radiator is cool to the touch (room temperature) and the interior heater is cold. This would indicate to me that the water pump is bad. A stuck closed thermostat could cause the radiator to be cool, but not the heater. Could it be anything else?

The odd thing is that I don't seem to get any significant heat to the heater even after turning off the engine. The little electric recirculation pump should have at least moved hot coolant to the heater. The input pipe to the heater matrix is a little warm to the touch (even after running and stopping the engine multiple times over an hour), but no heat at all out of the blower.

This all started after I changed the coolant. I followed the service manual instructions, and used the multiple bleed points to remove air. However, it did take a very long time to bleed the system (hours), whereas other people have reported here that it didn't take nearly that long for them. I put in about 9 quarts of new coolant after draining.

I am wondering if an air bubble was at the water pump, and somehow caused it to go bad when I started the engine. Or, if there could be a blockage somewhere (I can't think how).

[TheViper]

The Heat Soak Pump is switched on at 230'F
Michael

[407Driver]

I think the problem is trapped air. I would try the bleeding process several more times before removing parts. It took two days bleeding before all the air was out when I changed coolant all the horizontal parts seem to trap an unusual amount of air. The thermostat will not open in the presence of air.

[ChrisH]

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.

[ZJChaser]

another trick is using compressed air and applying some pressure to the reservoir while al lthe bleeders are open, it forces the water(and air bubbles) though the system. I've had that help.

[xxxotic]

One side of the tank should be full, and the other side should be between the minimum and maximum mark.

I lost the washer that goes under the bleed screw and it took me a while to find where the coolant was leaking. After that, I had to bleed the system a few times.

Do not undo the bleeder valve on the tank unless you are bleeding the system, or else it will let air into the system.