RR 2002 p38 Overheated then corrected itself!

[RROJ]

Hello All, She overheated to the point that I had to quickly turn on the heater open the windows and pray that she would not melt before my eyes. Conditions were hot upper nineties and humid and I was idling with the A/C cranking for 20 minutes or less. Turning on the heater worked like a charm. I tried to duplicate the same when I got home, but she would not overheat. She has been fine ever since last weeks incident. With this said, is this a sign that my water pump may need replacing. I know one sign that your water pump is going is that the little hole at the base of the pump tends to warn the owner by letting a little water seep out. How long does a water pump last in mileage please? Any help on this current issue is greatly appreciated.

[Savannah Buzz]

1. It did not fix itself, you simply have not returned to the same conditions.

2. The guage is a poor way to test for problems, as it gives the same reading for a wide variety of temps.

3 A scanner that can read live data will tell you a lot more. You can see starting to overheat, etc.

4. If you have NOT been having to re-fill coolant, AND you have not had any problems at highway speed; your problems at idle are most likely one or more of these:

A. Viscous drive fan clutch - test when cold, should be stiff to spin, won't turn but just a fracton of a rotation. When warmed up, should still be stiff, not spin a whole turn, and certainly not free wheel. This controls your cooling at idle.

B. When AC is on at idle, at some point the electric fans (s) should come on to boost cooling of the AC condenser.

C. Consider doing a cooling system flush to clean out gunk in the radiator. Higher miles and you will need new radiator. Check space in front of radiator for trash. Older radiators were made of copper and brass (like a D1) and can be rodded out. Newer radiators with nylon plastic tanks are usually not good candidtaes for this, are usually treated as disposables.

D. Water pump is cheaper than radiator. But usually shows up as leaks, wobbles the pulley (final phase before fail and flail), and poor cooling at speed, squealing belts, etc. Would think your engine a bit young for a WP, just did mine and I am twice your miles.

[LRScott]

RROJ, from what I've noticed, water pumps like to go out around 80k miles or so. I replaced mine at 165k and my service records indicate it was also replaced at 81k by the previous owners. I would definitely get a scanner on the car to read the raw data like Savannah suggested. I once looked at a discovery that was overheating at around 240F, but the needle on the gauge stayed perfectly centered.

[Savannah Buzz]

Follow up - mine really needed to be done, it was wobbling, and the tolerances are such that the impeller blades were eating away aluminum at the pump and the front cover. And old skool says WP and fan clutch are usually holding hands as they jump off the cliff together.... guess that is from the clutch being out of balance and causing pump bearing stress, etc.

I refer to the upper 1/3 of the dial as the shake & bake zone - bake the engine, shake out the piggy bank.

[RROJ]

It's in the shop now and all checked fine. Mechanic is going to continue testing but all the common culprits turn out to be in working order. But it's got to be something since the AC turned itself off and the needle jumped to HOT! I will keep you all posted. Anything else you guys can think of would be a great help.
Thanks in advance.
I feel like a new father pacing in the waiting room.

[Savannah Buzz]

Kids might be cheaper... not. If you really were not overheating and had a gauge/sending unit problem or skinned wire, that might be an issue. The temp sensors drop in resistance as heat increases, so a ground on the wire could do it.