86 560 SEL Cooling system question

Noticed something the other day with car running and sitting in park for about 15 minutes. Temp went up to 110 C and aux fan kicked in bit temp continued to stay at about 110-115. Reving the motor immediately brought down the temp. Heat from climate control was warm, but not scorching hot at idle but when rpms picked up heat was hotter. After starting to drive again, temp stayed at 85 C even after I stopped with car running for about 5 minutes. Radiator, fan clutch and T-stat are new. Temp outside was about 45 F. So this problem does not always occur. What are the symptoms of a defective aux water pump and can a bad one cause engine temp to rise significantly? After reving the motor a few times the heat inside the car stayed hot. Any ideas?

It is possible that you have an air pocket in the system or that the impeller of the water pump has excessive wear and isn't allowing for good circulation. The aux. water pump is for the climate control only and shouldn't contribute to the engine running warmer

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ASE Master Technician, Lead Technician for Deutsch American Inc. Over 6 years of Import experience-specializing in German Automobiles.

If the water pump impeller is bad why wouldn't I consistently have this problem? Or why does car run properly after driving it?

[Benzmac]

I have not ever seen a bad impeller on one of these. I think that you had an air pocket, but that depends on how new the parts are. Did you check the level after cooling? I would. It may be low now.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

After the temp dropped the level in the reservoir was low and I had to put more coolant in. It's possible for the car to be running fine and then suddenly encounter an air pocket? Radiator, clutch and t-stat were installed 6/99.