overheating / Waterpump

[Ennva]

Intersting tempratures..........I purchased a water thermometer and tested the water temp to try and compare against the temprature guage. After loosening off the fan sensor on the bellhouse i let the car get hot, the temprature guage was showing 90-95 whilst the water above thermostat was showing low 80's, increasing the revs saw the temprature guage go over 100 and conitnue to climb to 115 - 120, the actual water showed 88 rising to 89 as the thermostat opened and i got a nice funnel of hot water coming out. Would this indicate the temp sensor on bellhouse is caput or indeed temprature guage. or are the reading accurate, thoughts welcome as it may mean the water pump is okay.

many thanks

[billwill]

If the water pump pulley on the front of the engine is spinning from its drive belt it would be next to impossible for it to not pump water. What goes wrong with water pumps is that the seal breaks down and water gets into the part that should be 'dry' Normally it drips out of a tiny drain hole (which you cannot see when the outer pulley is mounted).

If the drain hole gets blocked, the water builds up in there and gets into the water pump bearing and it rusts away giving a wobbly shaft. It then leaks like mad but it still pumps the water around the system.

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So you can be pretty sure your pump is working, but what can happen to reduce water flow is that the radiator pipes get clogged up. You clear this by reverse flushing. You drain the system take out the radiator and wedge a garden hose with rags into the lower hole. Turn on the tap, slowly increasing to full flow and it back washes any clogging goo out through the top hole and the filling cap hole.

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It looks like your temperature gauge is reading high, assuming that it was a reasonable quality thermometer that you used. It is impossible for the actual temperature of the water to exceed 100 deg C if your water system is 'open' to poke a thermometer in. Because it would boil at 100 deg C.

[StressCraxx]

The Smiths' water temp gauges, particularly the mechanical ether filled type are often inaccurate, particularly the new ones from Smiths. The thermistor driven electrical gauges can also be a problem. Best is to test the gauge in boiling water to have at least a single calibration point.

[richardcox_lotus]

I tested mine in situ - rigged up a camping gas ring on a stool alongside the car. I thought mine was over-reading as well - until I noticed that the sensor was dangling in the top half of the pan of water but the test thermometer base was touching the base of the pan. So I supported it so they were in the same height in the pan. Readings were consistent up to just before 100 degrees.

Whig meant my gauge was ok & the engine was in fact running too hot.