Originally Posted By: sciphi
I have a lower radiator hose heater in the Buick. It works well. The coolant is usually around 90-100*F after being on for 3 hours before firing it up in the mornings. The coolant temperature doesn't drop after startup, which likely means the block is also at that temperature.
In my application, the heat not transferred into the coolant goes up past the ignition coils and battery, so cold-morning startups are very fast.
The heater is located near the top of the lower hose, right before it bends to head into the water pump. It's still fairly low relative to the engine and on the opposite end of the system from the thermostat, so it seems to do good job convecting the warmed coolant throughout the block.
+1
Phillips and Temro are a big manufacturer of these. They work well, provided all your coolant lines stay open cold. I originally installed a Calix heater in my Golf TDI. That heater barely warmed things up, like most block heaters, but sufficient for decent starting. Then it blew electrically (shorted out) and I found out these things were prone to that. I looked up an alternative, and these were the Phillips and Temro heaters. About $50 versus $200, and available in 1,000W or 1,500W (versus only 200W - 300W). Worked amazing! Almost instant cabin heat in a diesel in -20C and colder temperatures. A thermostat inside these prevent things from getting too hot (they never get anywhere near full operating temperature for engine coolant). Most of these are installed in the lower rad hose, but may vary by application. The VW TDI's had them installed in a smaller coolant line (might have been one of the heater lines, but I forget now).
Add a battery blanket while you're at it, so that your battery can put out as close to full power as possible to assist with starting.