The car is a 2005 118d with the M47TU engine, other varients of this lump (such as the 120d) may differ to this!
Symptoms
The first sign that something was not quite right was fuel consumption dropping by about 20%. After I checked the tyre pressures were all OK, I began to suspect a faulty stat. To confirm this, you need to access the hidden menus with in the OBD. . Once you are in there and have unlocked the rest of the menus using step 19, you need to scroll through to step 7 which will tell you your coolant temperature. Obviously this will vary slightly as you are driving. In my case, the temp never went above 85 degrees, no matter how hard or gently I drive the car. You should see temperatures of up to about 92-93 degrees once the car is warmed up. The clue to the fault is seen in the photo below.
The thermostat is rated at 88 degrees, so it has failed open as it's designed to, which means the DDE thinks the engine is still in warm up mode all the time so pumps in more fuel. (At least that's how I understand it!)
So I decided to bite the bullet and replace both the EGR and the main thermostat. Cost for the parts was about £73 delivered, thanks to Kev and Tony @ Cotswold BMW for their excellent service again!
Parts needed
EGR stat part # 1171 7787870
Main Thermostat part # 1151 7805811
Tools and other stuff needed
Nothing too unusual, but you'll need
5mm allen key and T40 torx drive to fit onto a socket. A standard allen key or torx won't give you the leverage you need to undo various nuts.
Usual selection of sockets and extension bars, screwdrivers etc
Blue roll
At least 3L of coolant!
The Fix
Before you start, you need to take a couple of things into consideration.
1. You are going to spill coolant on the ground, so if you've just spent thousands on getting your driveway resurfaced, you might want to do it elsewhere.
2. You will have your hands in the engine bay so best to do this when the engine is cold!
3. You will have your hands in the engine bay and be dumping water and coolant into it, which leads me to the start....
1. Disconnect the -ve battery terminal, remember that you will need to get back into the boot later to reconnect it so don't shut the boot fully! Otherwise you'll be crawling in through the back seat to pull the emergency boot release!
2. Remove engine accoustic cover - 2 x 5mm allen bolts, and slide it forward towards you, also remove front air guide, 2 x T20 screws. See red dots below!
3. Unplug electric fan connector (Shown in green), 1 x T20 bold at the top L/H side of the fan as you look at it, (Shown in red) and there is a little plastic catch half way down on the R/H side you need to hold open as you slide the fan upwards (Shown in yellow).
4. Remove air feed to turbo. 2 x 5mm allen bolts at the top, the turbo end is a push fit and there is another breather pipe half way down which is also a push fit. Pipe marked yellow, allen bolts marked in red
5. Next, because BMW hide the main thermostat behind the EGR cooler, to remove the stat you first have to remove the EGR cooler. First, undo and remove the two jubilee clips that hold the ERG exhaust pipe on. Shown on the pic below in blue, EGR cooler is yellow and EGR thermostat is red.
Then remove the EGR exhaust pipe, to make this easier to remove, unplug the EGR air feed.
Here is where it starts to get wet, so to try and minimise this I packed the engine bay with blue roll and bunged up the exposed turbo air feed, as you can see above.
6. Disconnect the coolant inlet pipe that feeds the ERG thermostat and outlet pipe (jubilee clip) and remove the hoses. Let the blue stuff flow! Clips shown in yellow below. Also remove the 10mm nut that secures the coolant hose to the block, shown in green.
7. Remove 2 x T40 bolts that attach the EGR cooler above the turbo
8. Remove 3 x H5 bolts that attach the EGR cooler to the front of the engine, and remove the EGR cooler with EGR thermostat attached.
9. Once EGR cooler is removed, undo 2 bolts that attach the thermostat to it and replace the EGR thermostat for the new one, remember to fit the new 'O' ring that comes with it.
10. Release the retaining clips that hold the hoses on to either side of the thermostat and disconnect them. You will spill more coolant here for sure!
11. Remove the 4 x 10mm bolts that attach the thermostat to the waterpump, remove thermostat and install replacement item!
12. Reattach stat hoses and reassembly is the reverse of the above!
Whilst the access was good I had a feel of the turbo and checked for play, there was none, 60k and it feels fine.
13. Once the engine is rebuilt, leave the top accoustic cover off for access to bleed screws.
14. Fill and bleed the coolant system as BMW advise below.
M47TU:
Note:
When adding coolant, it is absolutely essential to adhere to the following sequence:
1) Remove cap from expansion tank (ET)
2) Open all vent plugs:
Radiator feed - ET branch piece
Coolant return pipe
EGR cooler thermostat
Heating cooler feed
3) Add coolant slowly
4) Close vent plugs on coolant return pipe and on radiator feed (ET branch piece) after coolant emerges
5) Fill ET with coolant up to edge
6) Close vent plugs on EGR cooler thermostat and on heating cooler feed (no emergence of coolant during filling procedure)
7) Start engine (idling), set heater to maximum and fan to low stage (if necessary, top up coolant to max. fill level)
8] Close ET cap, press accelerator pedal several times up to approx. 2500 rpm
9) Remove ET cap and if necessary top up coolant to max. cold fill level
10) Run engine at idle for approx. 5 minutes with open ET (until bubble-free coolant can be seen to emerge in ET); if required, top up coolant to max. cold fill level
11) Close ET cap
Took it out for a run and checked the coolant temp after a few miles.
It wasn't going past 85 previously, so hopefully that will be the fault fixed. I'll report back with an update to fuel consunption. Also, for a laugh, I'm going to phone BMW for a quote to do the above work. Place your bets now please!
Symptoms
The first sign that something was not quite right was fuel consumption dropping by about 20%. After I checked the tyre pressures were all OK, I began to suspect a faulty stat. To confirm this, you need to access the hidden menus with in the OBD. . Once you are in there and have unlocked the rest of the menus using step 19, you need to scroll through to step 7 which will tell you your coolant temperature. Obviously this will vary slightly as you are driving. In my case, the temp never went above 85 degrees, no matter how hard or gently I drive the car. You should see temperatures of up to about 92-93 degrees once the car is warmed up. The clue to the fault is seen in the photo below.
The thermostat is rated at 88 degrees, so it has failed open as it's designed to, which means the DDE thinks the engine is still in warm up mode all the time so pumps in more fuel. (At least that's how I understand it!)
So I decided to bite the bullet and replace both the EGR and the main thermostat. Cost for the parts was about £73 delivered, thanks to Kev and Tony @ Cotswold BMW for their excellent service again!
Parts needed
EGR stat part # 1171 7787870
Main Thermostat part # 1151 7805811
Tools and other stuff needed
Nothing too unusual, but you'll need
5mm allen key and T40 torx drive to fit onto a socket. A standard allen key or torx won't give you the leverage you need to undo various nuts.
Usual selection of sockets and extension bars, screwdrivers etc
Blue roll
At least 3L of coolant!
The Fix
Before you start, you need to take a couple of things into consideration.
1. You are going to spill coolant on the ground, so if you've just spent thousands on getting your driveway resurfaced, you might want to do it elsewhere.
2. You will have your hands in the engine bay so best to do this when the engine is cold!
3. You will have your hands in the engine bay and be dumping water and coolant into it, which leads me to the start....
1. Disconnect the -ve battery terminal, remember that you will need to get back into the boot later to reconnect it so don't shut the boot fully! Otherwise you'll be crawling in through the back seat to pull the emergency boot release!
2. Remove engine accoustic cover - 2 x 5mm allen bolts, and slide it forward towards you, also remove front air guide, 2 x T20 screws. See red dots below!
3. Unplug electric fan connector (Shown in green), 1 x T20 bold at the top L/H side of the fan as you look at it, (Shown in red) and there is a little plastic catch half way down on the R/H side you need to hold open as you slide the fan upwards (Shown in yellow).
4. Remove air feed to turbo. 2 x 5mm allen bolts at the top, the turbo end is a push fit and there is another breather pipe half way down which is also a push fit. Pipe marked yellow, allen bolts marked in red
5. Next, because BMW hide the main thermostat behind the EGR cooler, to remove the stat you first have to remove the EGR cooler. First, undo and remove the two jubilee clips that hold the ERG exhaust pipe on. Shown on the pic below in blue, EGR cooler is yellow and EGR thermostat is red.
Then remove the EGR exhaust pipe, to make this easier to remove, unplug the EGR air feed.
Here is where it starts to get wet, so to try and minimise this I packed the engine bay with blue roll and bunged up the exposed turbo air feed, as you can see above.
6. Disconnect the coolant inlet pipe that feeds the ERG thermostat and outlet pipe (jubilee clip) and remove the hoses. Let the blue stuff flow! Clips shown in yellow below. Also remove the 10mm nut that secures the coolant hose to the block, shown in green.
7. Remove 2 x T40 bolts that attach the EGR cooler above the turbo
8. Remove 3 x H5 bolts that attach the EGR cooler to the front of the engine, and remove the EGR cooler with EGR thermostat attached.
9. Once EGR cooler is removed, undo 2 bolts that attach the thermostat to it and replace the EGR thermostat for the new one, remember to fit the new 'O' ring that comes with it.
10. Release the retaining clips that hold the hoses on to either side of the thermostat and disconnect them. You will spill more coolant here for sure!
11. Remove the 4 x 10mm bolts that attach the thermostat to the waterpump, remove thermostat and install replacement item!
12. Reattach stat hoses and reassembly is the reverse of the above!
Whilst the access was good I had a feel of the turbo and checked for play, there was none, 60k and it feels fine.
13. Once the engine is rebuilt, leave the top accoustic cover off for access to bleed screws.
14. Fill and bleed the coolant system as BMW advise below.
M47TU:
Note:
When adding coolant, it is absolutely essential to adhere to the following sequence:
1) Remove cap from expansion tank (ET)
2) Open all vent plugs:
Radiator feed - ET branch piece
Coolant return pipe
EGR cooler thermostat
Heating cooler feed
3) Add coolant slowly
4) Close vent plugs on coolant return pipe and on radiator feed (ET branch piece) after coolant emerges
5) Fill ET with coolant up to edge
6) Close vent plugs on EGR cooler thermostat and on heating cooler feed (no emergence of coolant during filling procedure)
7) Start engine (idling), set heater to maximum and fan to low stage (if necessary, top up coolant to max. fill level)
8] Close ET cap, press accelerator pedal several times up to approx. 2500 rpm
9) Remove ET cap and if necessary top up coolant to max. cold fill level
10) Run engine at idle for approx. 5 minutes with open ET (until bubble-free coolant can be seen to emerge in ET); if required, top up coolant to max. cold fill level
11) Close ET cap
Took it out for a run and checked the coolant temp after a few miles.
It wasn't going past 85 previously, so hopefully that will be the fault fixed. I'll report back with an update to fuel consunption. Also, for a laugh, I'm going to phone BMW for a quote to do the above work. Place your bets now please!