2000 C4 cooling problem

[abacusnw]

Car - 2000 C4 cabriolet, 6 spd manual transmission with 80,000 miles - all maintenance always completed on time - car in excellent condition

Symptom - water pump began to leak

Solution - had water pump replaced along with thermostat, both roller pulleys and new belt tensioner plus new Vbelt and changeover from green anti-freeze to new pink variety. We also replaced the short hose coming from the left side of the water pump.

Problem - Since I had this car, it always ran a shade over the 180F mark on the temp gauge. This corresponded with the 83C thermostat (181.3F). Rarely did the temp go higher even when I drove aggressively at high RPM's. With the new water pump and the replacements made the car temp has changed dramatically.

1). Normal running temp is now about 15 - 20F higher than before
2). When car gets hot (still well within operating range - never near the red line for temp) the ability to cool down seems impaired.

We checked all of the part numbers for everything and they were all correct. We replaced the thermostat and no change. We replaced the water pump still no change. We replaced the water pump again with the turbo version of the water pump (pulley 5mm smaller - faster rotation - impeller and all other specs the same) no change.

We did not use a vacuum system to fill the anti-freeze because shop has had problems with damage to the radiators, but we filled system, raised rear on lift, ran engine, refilled until all air seemed out of the system. Over the next 3 days what air was left worked its way out of the system and we added perhaps another pint. All was stable with the coolant level after that.

Left & right air inlets are clear as are the faces of both radiators - no debris.

Car has been driven for about 200 miles with no problems except now has a operating temp noticeably higher than before and mechanic is concerned and baffled.

Can you shed any light on this situation?

[B.A.M.]

Keep bleeding/purging the system. Also check for front fan operation on both radiators. Don't recommend changing from factory coolant to "green" coolant. Hope system was drained and flushed, they don't like mixing with each other.
Tom
Bamsport