The check coolant light that will never go away

[fratrickbateman]

Hi Gents,

I recently replaced my thermostat waterpump and upgraded to the aluminum radiator last year. The coolant light stayed off for about 6 months, but of course it is back again. Unreal. No leaks in the car either as confirmed by two different mechanics. The computer is throwing a faulty waterpump signal. Every now and then it will dodge to the right, only happens once every couple of weeks. Oh and I replaced the fan clutch as well. I'm all out of ideas. I just drove the car on a 700 mile trip last week and it lost no coolant.

[RIboater2]

It may be the coolant level sensor in the expansion tank. With a cold engine, when you remove the cap, does the red stick pop up? Should come up level with the top of the tank opening. If it doesn't, and you can see coolant is surely in the tank, bang the side of the tank to see if it loosens the stick to float up. If it's staying down that will trip the low coolant message. Finally, check the electric connection plugged into the bottom of the tank. If that's lose or not clipped on correctly that would also trigger the message. You can buy those sensors separately on Ebay.
The occasional needle going to the right is possibly an air bubble passing by the temp sensor in the water pump.

[fratrickbateman]

Yeah I also forgot to mention. Brand new expansion tank and sensor installed a few months ago. That didnt' fix it either.

[georgebest]

What's the exact error code?

[fratrickbateman]

What's the exact error code?

The code I'm getting is 0045 auxillary water pump

[georgebest]

The code I'm getting is 0045 auxillary water pump

Sorry, not finding anything with that code.

[racer2086]

I have that same code. What is that for? Is that part of the heater control valve?

[Timm]

That error shouldn't bung up the check coolant level message - quite a few E38's are happily driving around with dead auxiliary water pumps - the pump is used for the REST (restorative) heating and increases heater coolant flow at idle - you won't really notice it being dead - I took mine out 5 years ago with no loss of function!

The errant message will be from dodgy wiring to the level sensor or a failing connector pair at a guess.........

[racer2086]

Well it's interesting because I've been getting the coolant message ding up at times and I have that code too. Don't think they are related, but it is coincidental.

[fratrickbateman]

Yeah I'm done. The whole cooling system has been rehauled and there is no valley pan gasket leak either. I'm not ripping apart the harness etc. just to get rid of a stupid error code/chime and risk damaging anything. I'll just live with it for now.

[georgebest]

Oh wait, now I remember that, I had that code for a while back.
First solution was to deoxit the connector that worked for a approx 3 months, then code came back. At that point I bit the bullet and bought a new pump/valve combo for $400+. No codes since, and also no difference in anything either, hoping for some super fast heating in the winter or something. Need something to justify the spending... you can buy a whole car for that!

[georgebest]

Also, it has a fuse in the e-box, check that one as well.

[racer2086]

Yeah I'm done. The whole cooling system has been rehauled and there is no valley pan gasket leak either. I'm not ripping apart the harness etc. just to get rid of a stupid error code/chime and risk damaging anything. I'll just live with it for now.

Chances are you don't have a coolant leak. Did you replace the expansion tank? That's the thing I notice that when they age, causes weird coolant messages. They can be changed in 20 minutes without disassembling anything more than the air ducting. Otherwise, I'd just replace the sensor. It twists out the bottom of the expansion tank and costs like $13.

Oh wait, now I remember that, I had that code for a while back.
First solution was to deoxit the connector that worked for a approx 3 months, then code came back. At that point I bit the bullet and bought a new pump/valve combo for $400+. No codes since, and also no difference in anything either, hoping for some super fast heating in the winter or something. Need something to justify the spending... you can buy a whole car for that!

Yeah, not going to replace it. In Florida, I don't need heat. Plus my heat works anyway. I'll clean the connector just in case, but that's it. I know the units can be rebuilt, but the hoses have been on there so long, it'll take me longer to get them off than to rebuild the thing.

[georgebest]

Yeah, not going to replace it. In Florida, I don't need heat. Plus my heat works anyway. I'll clean the connector just in case, but that's it. I know the units can be rebuilt, but the hoses have been on there so long, it'll take me longer to get them off than to rebuild the thing.

Probably doesnt make much sense to replace it even here. But I'm kind of in a contest with myself to try to fix as many error codes as possible and this was one
Additionally, when you bleed the cooling system it makes it easier to have the pump running. Probably the reason why I never have coolant issues.

[SpeedyE38]

So, on the day of the polar vortex yours truly decides to go out and start and warm up the car. The end result being that I now get the Low Coolant code on the dash. But what was interesting is that when I cranked the car, it sounded like all the parts had frozen together and were scraping and such to work. After about 3 seconds the car went to normal quiet and I chalked it all up to frozen condensation (though still not clear how that could be since I hadn't driven the car in a few days.)

Anyway, I am about to go out and check it all out. It might be worth mentioning that I had the water pump, thermostat and expansion tank all replaced less than 6 months ago from the dealer (I broke down 4 hours from home.)