So my temp gauge stopped working. I thought it was the gauge itself but when swapped with a known to be good one, I had the same result. And then I checked the other end and found the wire was broken just at the sending unit connector.

I spliced a new end -- I checked and my splice was measuring below .5Ohm at the bench -- but it still does not work. So I need to check the wiring next. According to the book I looked up, there are *two* wires -- yellow/white and yellow/black -- going from gauge to sending unit, but I only see one connector at the sensor. Is the other one a ground? Also, is the harness on the engine side male or female for the connectors?

Of course, as soon as the gauge stops working something in the cooling system happens. I noticed after I stop the car and let it sit some, I will find coolant as if it is peeing off the passage from the waterpump to the head. I do not see much coolant being lost at the reservoir but I have not been driving it much since. Should I be worried about overheating?

There is a rubber mushroom gasket (donut gasket) on top of the water pump that seals to the head. Over time these can become a bit mushy (oil from leaky valve cover gaskets and spillage when adding oil doesn't help). After you shut down the engine and the cooling fan stops, the cooling system pressure momentarily rises a bit before the engine gets a chance to cool, so that's why it's weeping just after you turn the engine off. You can buy a relatively inexpensive water pump seal kit with all the gaskets and usually nuts/washers/bolt. IMO, the cheaper aftermarket ones are usually quite adequate, but if you're a purist about rubber quality then go Genuine Volvo. If you don't know when the pump was last replaced, like at the last t-belt change, then consider a new pump.

If you have not done water pumps before, check the FAQ. Tilt the pump so you can thread on the top right (driver side) bolt first, then you swing the other side up (bolt is in a slot) against the head. Lift it straight up as hard as you can by hand is all that's needed to compress the mushroom gasket against the head and tighten. You can use a pry bar if you want, just don't get carried away and do something stupid like I once did and put a jack under it which cracked the cheap pump I'd bought. Many people put a smear of RTV gasket sealer on the top of the mushroom gasket (non-drying hypalon sealer is even better, which is what I use if I've got it handy), but all you really need is something like a wipe of petroleum jelly as lubrication so the gasket doesn't get bent out of shape as you swing the pump up. Be sure to clean the mating surface under the head. Some people put gasket sealer on both sides of the paper gasket, but if the surfaces are clean then it generally isn't needed (I generally don't use anything, but again a non-drying sealent is preferable in case you ever need to re-adjust the pump). Don't forget there's a flange with a small bolt on the heater return pipe that compresses the rubber collar gasket on the end of the pipe into the back of the pump. When re-filling, open the heater valve wide and squish the upper and lower rad hoses gently to get as much air out of the system by hand as you can before starting the engine to help prevent air locks. Monitor fluid level for the next week as any residual air works it way out of the system.

As for the block temp sensor, don't forget there are two circuits, one is for the ECU and one is for the dash temp gauge. The ECU uses the signal to control the fan as well as fuel trim.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

I second Dave.

Mine did the same after cooldown. A little wet in between drives when cooled off and pressure subsides.
Keep an eye on level and replace gaskets or pump too if bearing is not in great shape at next opportunity.

Good luck with the wires.

Yan