That would be the suction jet pump, and no, it shouldn't be coming apart. The end of the suction jet pump towards the left side of the car connects to the "infamous" L-hose, which connects to the intake manifold, so it creates a vacuum leak. I call the L-hose infamous because it tends to develop a crack along it's length (it sees some fuel); you may want to replace it while you're there.
On ECS Tuning, search for "suction pump"; they don't use the word "jet." This link is for my 2001.5 AWM; I believe yours uses the same part, 058 133 753 D. The number will be molded in to the part, although the letter (D) at the end might be different, A,B, or C; for most VW parts, the letter is a revision level. Volkswagen Passat B5 FWD 1.8T Search SiteSearch Suction Pump - ECS Tuning
Here's my car, looking from the left side, with the coolant tank lifted. (Leave hoses attached; just remove 3 screws and unplug connector on bottom.)
Great info. I took off the clamp on the left, as you look at the engine from the front. With that off, I cleaned around the edge, put it back together and hit it with a few drops of Krazy Glue at the seam. It held, for now. So, I can look for the part. I'll get the L-hose also.
I suppose it's too much to hope that this will also cure the overheating when it's really hot out and I'm running the air.
I love the way the car drives, but, I've had it six months and little things like this are killing me.
These cars are rather love/hate... so many silly things break, but when you get them fixed, it's wonderful.
I can't see how this will help with overheating, but the good news is that overheating isn't a common issue. It would be appropriate to start another thread, but you'll find a lot searching. To get you started:
The A/C controls inside the car are either manual (three knobs, two buttons) or automatic "Climatronic" (LCD display). The engine cooling under the hood works the same regardless.
The AWM engine has one engine-driven fan (via a viscous clutch) and one electric fan. The electric fan should run in low speed whenever you have the A/C turned on.
The fan is further controlled by a dual temperature switch at the radiator outlet (lower connection). It runs the fan in low speed when the coolant temperature reaches 92-97°C and in high speed when coolant temperature reaches 99-105°C, whether the A/C is on or not. This dual switch is incorrectly identified in some aftermarket parts databases as a temperature sensor, i.e. an analog sensor, so someone could have installed the wrong part. Apparently it fits and the electrical connector plugs in, but it certainly won't work correctly. The correct part is two switches and will measure open circuit at room temperature. (The analog coolant temperature sensor is at the rear of the engine, just in front of the battery, rather buried.)
The fan is electrically controlled via two relays on the relay panels under the dash. The fan fuses (40A power, 5A control circuit) are also on a relay panel, not on the main fuse panel. In low speed, the fan gets power via a series resistor; in high speed, it gets 12 volts directly. There's a third relay (214) that the A/C controls energize; it in turn energizes the low speed fan relay.
The first step would be to confirm that the electric fan runs when you turn the A/C on. Happy hunting!