This is for information and may assist with a similar problem and give hope...patience is the key.
Noticed that cold starting was being difficult, similar to not waiting for the Glow plug light to go out. Ignition on and the glow plug would go out after 2 seconds - no matter how cold it was.
Asked the dealer to investigate and they advised that the #5 glow plug had failed but as it would not turn at the test torque of 25 NM they advised that if it broke it would be my problem and the cylinder head would have to come off. 5 out of 6 glow plugs should be Ok for starting. Note Tier 1 warranty does not cover glow plugs.
However cold starting was poor and put the iCarsoft MB II on and in the Benz section it showed a #5 glow plug open circuit. On the OBD setting it showed Glow Plug Controller fault.
I replaced the Glow plug controller withy the newer type £99 and staring was back to normal. Now after starting the glow Plug light would go out and come back on for 1 minute. Icarsoft still showed #5 Glow plug open circuit. I confirmed this with Ohm meter showed 800 ohms. A new plug is 0.4- 0.5 Ohm.
So the Glow plug like a lightbulb had failed and due to excess current draw - burnt out the controller.
A search on line on stuck glow plugs is a scary tale of shearing off, drilling out etc and although there are tools and people that can do it, the access and clearing on the ML 320 V6 is limited.
I bought 2 new glow plugs and put one in a vice and using a 1/4 drive deep hex socket is sheared at 35nm. Dry Torque at install is 15nm.
Now that I have the old one out it is not the thread section length (10mm) that seizes in the head it is the body of the plug length (75mm) carbonised and corroded.
Again checking on line I saw that the best penetrating fluid for this job was a 50/50 mix of auto transmission fluid and acetone. Mixing it quickly into a syringe and using a straw and with the engine just warm filled the cavity where the glow plug sits. Leave the electrical plug off. Letting the engine cool overnight drawing the fluid into the threads and down the bore.
Ran the car for a week and then repeated over the next 2 weeks.
Took the car for a good run and got the Engine a hot as possible, filled the cavity again and with a straight Hex deep socket smallest extension and 1/4 drive Torque wench set at 20 Nm I tightened the Glow plug. With the same torque I then tried to remove. It turn 90 deg. Using a tee handle I spent 2hrs just turning it back and forward gaining 90 degrees each time. It felt tight again and decided to stop and let the fluid sink in again over night.
This morning went for a drive got it hot and filled the cavity gain with the 50/50 mix. Another 1 hour of 90 degrees at a time and the threaded portion was free. The glow plug came out using a gentle pull with some long nose pliers. Put some ceramic grease on the new plug threads and body and it screwed in by hand and a torque of 12nm. Fault cleared.
Although it took a lot of time soaking etc - better than it breaking off.
Noticed that cold starting was being difficult, similar to not waiting for the Glow plug light to go out. Ignition on and the glow plug would go out after 2 seconds - no matter how cold it was.
Asked the dealer to investigate and they advised that the #5 glow plug had failed but as it would not turn at the test torque of 25 NM they advised that if it broke it would be my problem and the cylinder head would have to come off. 5 out of 6 glow plugs should be Ok for starting. Note Tier 1 warranty does not cover glow plugs.
However cold starting was poor and put the iCarsoft MB II on and in the Benz section it showed a #5 glow plug open circuit. On the OBD setting it showed Glow Plug Controller fault.
I replaced the Glow plug controller withy the newer type £99 and staring was back to normal. Now after starting the glow Plug light would go out and come back on for 1 minute. Icarsoft still showed #5 Glow plug open circuit. I confirmed this with Ohm meter showed 800 ohms. A new plug is 0.4- 0.5 Ohm.
So the Glow plug like a lightbulb had failed and due to excess current draw - burnt out the controller.
A search on line on stuck glow plugs is a scary tale of shearing off, drilling out etc and although there are tools and people that can do it, the access and clearing on the ML 320 V6 is limited.
I bought 2 new glow plugs and put one in a vice and using a 1/4 drive deep hex socket is sheared at 35nm. Dry Torque at install is 15nm.
Now that I have the old one out it is not the thread section length (10mm) that seizes in the head it is the body of the plug length (75mm) carbonised and corroded.
Again checking on line I saw that the best penetrating fluid for this job was a 50/50 mix of auto transmission fluid and acetone. Mixing it quickly into a syringe and using a straw and with the engine just warm filled the cavity where the glow plug sits. Leave the electrical plug off. Letting the engine cool overnight drawing the fluid into the threads and down the bore.
Ran the car for a week and then repeated over the next 2 weeks.
Took the car for a good run and got the Engine a hot as possible, filled the cavity again and with a straight Hex deep socket smallest extension and 1/4 drive Torque wench set at 20 Nm I tightened the Glow plug. With the same torque I then tried to remove. It turn 90 deg. Using a tee handle I spent 2hrs just turning it back and forward gaining 90 degrees each time. It felt tight again and decided to stop and let the fluid sink in again over night.
This morning went for a drive got it hot and filled the cavity gain with the 50/50 mix. Another 1 hour of 90 degrees at a time and the threaded portion was free. The glow plug came out using a gentle pull with some long nose pliers. Put some ceramic grease on the new plug threads and body and it screwed in by hand and a torque of 12nm. Fault cleared.
Although it took a lot of time soaking etc - better than it breaking off.
