I'm wondering how quickly an L-jet 1.8 (1974) heats up. I drive mine for about 10 or 15 minutes and the needle on the temperature guage gets a little bit past halfway and just keeps going up. The temperature guage is one in the central console. Is there somethin wrong with the cooling system? How does the cooling system work exactly. Does the fan simply blow air over the heads? The defroster and heating elements in the interior work and blow hot air when they're on.

Thanks for any help.

The temp gauge in the center console shows oil temperature. That is only half the story--and it's not a very complete half, either. Since there are no numbers on the stock gauge, and at least a couple of different senders that could go in there, you don't really know anything about the oil temperature except "hotter" or "colder". Than what? Well, you have to drive the car for a while and get to know what the gauge "usually" reads.

Cylinder head temperature is the other half of the "how hot is it" question.

How it all works:
The oil gets hot running all over the moving bits of the engine, especially those that get really warm (cylinders, valves, yadda yadda). The oil gets pushed through an oil cooler that has air blown through it by the fan. This cools the oil, at least to some extent.

The fan not only pushes some air through the cooler, but it also pushes air through the fins on the cylinders and the cylinder heads, which removes heat from them directly. The heads get the hottest of those bits. The fan shroud and engine tin are designed to get about the right proportion of air to each place--oil cooler, heads, cylinders. It is also designed to keep the air moving through the fins rather than just flying off somewhere.

Warm air is dumped underneath the car, cooler air is drawn in from the top, through the grille on the engine lid.

It is very important to have all of the pieces of engine tin in place. Otherwise, the air will not go where it is supposed to go, and some parts of the engine can run too hot while others run too cool. Some people think that you cool better by throwing away the thermostatically-controlled moving flaps inside the engine tin, but that is completely false. With no flaps, air does not get ducted to the oil cooler so the oil temps actually increase! The flaps may also serve to guide air down under the engine tin as well. And, as long as the flaps are hooked up, why not hook up the thermostat so that they work correctly--a quick warm-up will reduce engine wear by getting the engine to the proper operating temperature quickly...

It is important that the fan not be blocked by rags, leaves, grocery bags, etc. It is also important that the fins on the oil cooler, the cylinder heads, and the cylinders be at least fairly clean. Caked-on oil does not transfer heat very well...

I hope this is of some help.

--DD

That helps a bunch. Next question: The thermostatically-controlled moving flaps...I think I see them (they're the flaps with the bar in between in the cooling manifold?), but how do I know they're working?

Thanks a ton

When the engine is cold the wire from the thermostat to the bar between the flaps should be tight as the engine gets hot and the thermostat expands the wire should become loose and allow the spring loaded flaps to open.