If you intend fitting aftermarket glow plugs to a B6 Passat, they must be made by NGK.
Passat 2.0 PD Tdi engines
B6 PD engines; BMA, BMR, BVE, BWV, BUZ, BKP, all use NGK CZ304
These are 7V glow plugs. M8 x 1.0mm thread. With an M8 hex nut body
BMP engine use NGK CZ104
These are 7V glow plugs. M10 x 1.0mm thread. With an M10 hex nut body
Passat 1.9 PD Tdi engines
BKC, BXE, BLS engines use NGK Y-607-AS
These are 5V glow plugs. M10 x 1.0mm thread. With an M10 hex nut body
Passat 2.0 CR Tdi engines
CBAA, CBAB, CBBB engines use Y-609-AS
These are 4.4V glow plugs. M10 x 1.0mm thread. With an M10 hex nut body
At the time of writing neither Bosch or Beru make glow plugs for these engines.
I can't keep everything up to date so check for yourself if you are unsure.
Fitting the wrong glow plugs can damage the wiring, the controller and even the engine.
Don’t be fooled by part numbers for other models with the same engine. Different models with the same engine do use different glow plugs. That’s because they use different wiring and different glow plug controllers.
If you fit 4.4v glow plugs from Bosch or Beru, to a B6 Passat 2.0 PD tdi , the glow plug controller will be damaged and you risk the end of the plug burning/breaking and damaging the cylinder/piston/valves etc.
The information about glow plug fitments on a number of websites is incorrect so be careful where you buy the glow plugs.
TESTING THE GLOW PLUGS ON A B6 PASSAT.
On engines with exposed glow plug wiring, the easiest test is to use a DC clamp meter. This will instantly tell you what current is flowing. If you know the glow plugs pull 10 Amps each, then 4 good glow plugs will read 40 Amps.
Because the glow plugs on the passat engines are under the cam cover with the injectors, cams and other oily bits, you can’t test the current draw easily.
The simplest test on a B6 passat is;
Remove the engine cover (Plastic bit over top of engine) and then remove the cam cover.
With the cam cover off you will see 4 thicker wires going to 4 bolts that go down into the cylinders.
The bolts are the tops of the glow plugs.
To test each glow plug, pull off the connector and measure the resistance between the top of the glow plug and the cylinder head (earth).
The resistance should be 1 Ohm.
(Make sure you know how to read the multimeter. A reading on the meter of “1” is not the same as “1 Ohm”.
A reading of “0” means the glow plug has short circuit to earth.*
A reading of “1” means the glow plug is open circuit.
(* Be extra careful taking out a glow plug that has a short circuit to earth. It is more likely to snap.)
CHANGING THE GLOW PLUGS ON A B6 PASSAT.
There are two different diesel engine designs. Single overhead cam and twin overhead cam.
The procedure is the same for both,
Take the engine cover off by pulling it up and forwards out of the fixings.
Remove cylinder head cover
Pull the connector off each glow plug.
The best tool for removing the glow plug is a deep 10mm or 8mm socket on a universal joint & extension attached to a 3/8” ratchet.
Be careful and wind out slowly. If it seems to stick, wind in a bit, add WD40 or similar and wind out. Wind in and out until it comes out without force. Excessive force may strip the thread or snap the glow plug and you don’t want that.
Before installing the new glow plug, make sure the thread in the cylinder head is clean and dry.
DO NOT oil or grease the thread in the cylinder head or the glow plug thread.
Screw the glow plug into the cylinder head by hand using the deep socket without the ratchet.
You do not want to cross-thread the glow plug.
Be careful not to tilt the glow plug at any time as it may crack.
Once the glow plug is in place, tighten to 10 Nm (M8) or 12 Nm (M10) using a torque wrench.
Before replacing the connector, check the resistance between the glow plug and the cylinder head.
If the resistance is higher than 1 Ohm, the glow plug is damaged and if it is "1" the glowplug is open circuit and won't work.
If you are happy that all glow plugs are installed correctly and have passed the resistance test.
Replace the connectors.
Wipe the cam cover clean and replace it. (You can reuse the gasket as long as it isn’t damaged.)
Start the engine. If everything seems ok, replace the engine cover.