Checking/Removing and Installing Glow Plugs — Model 525tds (BMW 5 Series E39)

If there are difficulties when starting the engine, then first of all you should check the compression. If the engine compression is insufficient, then at low ambient temperatures the engine will not start. About checking the compression see here.

Note: The DDE control unit is equipped with a fault code memory, which stores faults that occur in the electrical part of the diesel injection system. In a BMW workshop, these faults can be read out using the diagnostic system and rectified in a targeted manner.

Checking glow plugs

Remove the engine covers and the boost air pipe above the glow plugs.



The glow plugs are located under the intake ports.



Unscrew the fastening of the glow plug connecting wire "arrow".



Connect the voltage tester to the positive (+) terminal of the intake manifold and then connect it in series to each glow plug.

If the semiconductor device's control lamp lights up, the glow plug is OK. For a more accurate check, it is necessary to measure the current consumption with an ammeter (workshop work).

If the semiconductor control lamp does not light, the glow plug is faulty and must be replaced.

Removal

Remove the intake manifold, see page 63.



Unscrew the fastening of wires "1" and "2". Unscrew the glow plugs using the HAZET 4760-1 key and inspect.

Installation

Treat the threads of the glow plugs with high-temperature copper grease CRC, available at BMW service stations. Screw in the plugs, tightening torque of the glow plugs is 25 Nm.

Caution: Do not exceed the tightening torque, otherwise the annular gap between the pin and the glow plug thread will tighten.

Connect the glow plug connecting wires and tighten the mounting nuts to a torque of 5 Nm.

Replace all seals and tighten the intake manifold to the cylinder head to 25 Nm. Also tighten the oil filter support and the exhaust gas recirculation pipe to the intake manifold to 25 Nm.



Install the engine covers and boost air duct over the glow plugs.

Glow plugs with burnt pin

Burnt glow plug pins are often the result of faulty injector nozzles. This type of damage cannot be attributed to defects inside or outside the glow plug.



If during the inspection glow plugs with a burnt pin "arrow" were found, it is not enough to simply replace such plugs. In this case, it is necessary to check the corresponding injectors for the geometry of the jet, the opening and closing of the spray needle, the injection pressure and the tightness (workshop work).