likelihood of missing water pump blades/fins?

[dlb]

I installed the current water pump on my car within the last few years but I don't know what brand it is. Never had a problem with running hot since I installed it (the gauge always read from about 1/3-1/2) but I swapped clusters and the current cluster shows the temp 1/2-2/3 on the gauge. At first I was like "whatever, probably just the gauge" but now I'm worried that the old gauge was incorrect and the car has been running hot this whole time. The only other notable thing is that the engine cools down slightly (according to the gauge) when the engine revs are higher, ie if cruising at lower RPM it runs hotter, and cools down a bit if you drop it down a gear so the revs are a bit higher.

I remember taking a water pump off some car once and finding the metal impeller blades were all worn off, so I'm worried that this might be the case with this water pump. Or am I being a worry wart and it's probably just this gauge reading hot?

[Mark]

I'd verify temps with a laser thermometer or something like that. I've found that dash gauges can be all over the place and different from each other. I installed a separate temp gauge in my '85 van since I didn't trust the dash gauge. It was showing about 1/3 when the coolant was about 190 degrees F. When the real temp was 250 F (overheating), the dash gauge showed just under 1/2. On my Tercel wagon I noticed that the dash gauge creeps up over 1/2 when I'm using the cabin heater. I suspect the extra flow being diverted from the radiator through a smaller, less efficient heater core means less heat is being removed overall. I'm not sure how resistance changes the reading on the dash gauge, but higher electrical resistance from old corroded connectors might affect the reading as well. As far as pump vanes, I thought that was a potential issue on my van when it was having overheating problems, but when I removed the pump, the vanes were fine. I've only replaced one pump on a Tercel because it was leaking (the vanes were fine). I'd think there would have to be some serious long-term neglect like using tap water for years for vanes to corrode away.

[NWMO]

Hey fellas,

I’ve noticed the temp gage will run slightly higher (right at the middle) with the heat/defrost on and the fan running on high. I’ve always assumed it’s an electrical anomaly. I believe that running the heat in a vehicle should lower the coolant temp, as additional heat is being drawn out. After running through the heater core, the coolant follows the same path it would with no heat on (heater valve closed), so the heater core should provide additional cooling to the coolant.

Chris

[dlb]

That's a good idea about the laser thermometer. I've never had one but have run into a handful of situations over the years where I could have used one so I think it's time I finally pick one up.

But also, I remembered that my thermostat has acted up a few times over the last several months and made the car engine run cool. I ordered a new one a while ago but haven't put it in yet. I heard years ago that thermostats always fail in the open position but did some reading today and it seems like that is most common but not guaranteed, so I'll replace that soon and see if that helps at all.