Need help for '96 Jetta, 2.0L, with overheating problem.

My Jetta has developed an overheating problem. I've replaced several cooling system components: first, the expansion tank (the plastic anti-freeze overflow bottle); second, the cooling flange (the junction where two large hoses and two sensors are attached to the right side of the engine); third, the thermostat.
The expansion tank problem was obvious -- it was leaking. I drove the car for 2 - 3 weeks in that condition and refilled the tank often, until the leak got too bad, then I stopped driving until I got a new expansion tank. When I finally got the tank and installed it, a crack developed in the cooling flange, leading to a leak, as soon as I started the car. I bought a new flange and installed it. After starting the car and letting it run, it overheated.
Since the upper radiator hose was hot, but the lower radiator cool, and there was cold water dripping from somewhere in front of the car, I decided to replace the thermostat. I then started the car and it overheated again. (I'm sure I installed the thermostat facing in the right direction). The only change in the overheating problem since I installed all the parts is that it takes longer to overheat than before I started the process -- I figure this is to be expected because the expansion tank leak had gotten bad.
I checked the fuse for the cooling system and it's fine, also the radiator fan works (I ran the air conditioner to check that). It seems like the only thing left to check is the radiator. I understand that Volkswagen installed a plastic radiator as standard equipment. I don't think the one on my car has ever been changed (I bought the car used). Should I plan on purchasing a new radiator, or is there something else I should check?

Thanks for the help!

How many miles are on this car? The cooling fan should cycle on automatically without turning on the AC. If I remember correctly, there are two fans, one of which only runs with the AC, the other runs as necessary to move air across the radiator. Does this fan cycle on automatically as the car sits there and idles? It should?

I went through the same exact process as you did with replacing all the same things and it turned out the problem was the one you forgot about. It was actually the water pump which is on the left hand side of the engine and apart of the belt system. It cost about 500 but fixed the leak.

Holy Cow! $500 to replace a water pump is enough to make my remaining hair fall out. I paid around $170 for the job only because I did not have the time to do it myself. The VW water pump is a little wierd (relative to traditional Detroit steel) but certainly serviceable. :cwm27:

Check the oil....... look for a caramel color , if does , you have to replace the head gasket, because it has water in the oil.
or same process with the water. ( oil in the water ).

Whe the head gasket is blown off, the water goes to the oil or viceversa.
The oil has to be clear.
Sorry about my english..

You really can't tell much about the oil from it's color. Drain the oil into a clear container and see if you have two layers. This isn't a very good test either because water evaporates at the temperature of the oil. Sometimes the oil will get a foamy appearance, but you can't count on it. Place a cold piece of metal or mirror in front of the exhaust. Condensation is the best tell for a cracked head or leaking gasket. I've had a new pump fail because the impeller fell off inside the pump. It seemed ok, but it wasn't pumping. Check to see if there is water dripping from the seep hole in the water pump. This tells you the seal is bad and the pump will have to be replaced soon. You can pick a pump up for $60 on line with housing and $30 without. You have to take off the alternator, A/C compressor (don't disconnect hoses), and power steering pump. Then remove the metal mounting brackets for the previously mentioned items. The water pump is under the bracket and is now easily removed. You don't have to remove the timing belt cover, but it can make it easier.

Gil VW, where do you live. I have an extra 91 Jetta radiator and fan (with sensors) in my toolshed that I'd let go very cheap. You'ld have to pick it up. I'm in North Central Florida. You'll need to see if they're compatible.