Baby BMW Forum banner

118d main Thermostat and EGR thermostat change.

139K views 245 replies 71 participants last post by  Rocket70 
#1 ·
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!
 
See less See more
13
#227 ·
I´ve done this as well. Both of my stats were shot.
In the beginning the car was not able to hold temp above 64 degrees no matter what you´ve done.
At first I´ve done just the EGR stat - the temp was able to hover around 80 degrees.
After changing the main stat as well, the temp is around the 90 degree mark.
Success.
 
#228 ·
Thanks for a nice writeup. Changed my thermostat yesterday and at the same time threw out the whole EGR system and installed the kit from
I have been running with the EGR disabled for several years and it was good to finally clean up the engine bay by removing the parts. I have been running with the CEL lit but will now take it to a tuner to get it programmed out
 
#229 ·
Thought best to revive as it may alert others. I'm getting shocking MPG in my 123d at present, freshly serviced with no extra weight and properly inflated tyres. Dropping the run flats which I'm hoping may give a slight improvment.

I did a test this morning commute is 15 miles 95% a roads and motorway so should get up to speed fairly quickly, no matter how hard I drove I couldn't get above 85 degrees, is it worth changing the sensors based on that ?
I expect that nearly 10 degrees may help and I certainly can't think of anything else that is impacting economy as I drive like a saint on my commutes.

Cheers

LT
 
#230 ·
TALBOTL said:
Thought best to revive as it may alert others. I'm getting shocking MPG in my 123d at present, freshly serviced with no extra weight and properly inflated tyres. Dropping the run flats which I'm hoping may give a slight improvment.

I did a test this morning commute is 15 miles 95% a roads and motorway so should get up to speed fairly quickly, no matter how hard I drove I couldn't get above 85 degrees, is it worth changing the sensors based on that ?
I expect that nearly 10 degrees may help and I certainly can't think of anything else that is impacting economy as I drive like a saint on my commutes.

Cheers

LT
The target is 88° for all BMW diseasils, so 85° really isn't that bad.
 
#231 ·
marco_polo said:
TALBOTL said:
Thought best to revive as it may alert others. I'm getting shocking MPG in my 123d at present, freshly serviced with no extra weight and properly inflated tyres. Dropping the run flats which I'm hoping may give a slight improvment.

I did a test this morning commute is 15 miles 95% a roads and motorway so should get up to speed fairly quickly, no matter how hard I drove I couldn't get above 85 degrees, is it worth changing the sensors based on that ?
I expect that nearly 10 degrees may help and I certainly can't think of anything else that is impacting economy as I drive like a saint on my commutes.

Cheers

LT
The target is 88° for all BMW diseasils, so 85° really isn't that bad.
Thanks Marco, Hmm in that case not too sure, stuggling to hit 40mpg doing 65 on the motorway and a roads, back to the drawing board may still be worth doing it for 5 degrees ish the only other issue that's developed is my brake servo sensor wouldn't have thought that would make any difference.
 
#233 ·
mekon88 said:
14 mile journey in ambient temps of 10 degrees... OBD reader shows coolant temp of 52 degrees.... i think i need some stats! (and a blanket for the poor engine!)
OBDII Reader's can give erroneous results, what does the dash say?

If it concurs at 52°, I think you'll hold the record for the sickest engine, ever! :eek2: :(
 
#234 ·
I havent done the hidden menu check, I did check the ET and I am wondering if maybe there is air in the system as with a warm engine (as warm as this one gets anyway) the float was sitting around the minimum mark, I have stats on the way so will do them at weekend.... damned bonnet release decided to snap on sunday night when I wanted to add screenwash! making any sort of work..... tricky, new cable should be waiting for me at home so thats my evening plans arranged!
 
#235 ·
So I did this job after reading this excellent guide. It was very straightforward. As I was 'in there' and they're not too pricey I replaced the water pump too. The engine thermostat brought a previous 64 degree max up to 70, but the EGR thermostat brought the temp to 83 (so far - motorway run Sunday).

Incidentally, 88 is not a 'target' temperature. It's the point at which the engine thermostat opens to let water through to the rad to cool it before returning to the block. An engine running at 80 or above is normal taking into account outside temp and air flow.
 
#237 ·
After small increase in fuel consumption I decided to check my coolant temp and on a 25 mile drive on pretty much flat road while doing 70mph it never got past 79 degrees. Driving on a mountain pass doing 60mph in 4th gear and around 2500rpm got it to 87 degrees.

The question is which thermostat should I change, main, egr or both.
 
#239 ·
I did a few checks on the pipes, and trying to make sense out of it. Engine temp was 73 degrees after 7-8 minutes of driving

- The pipes marked with red were hot on the touch. The smaller pipe in the bottom seems to come from the egr cooler. The pipe going to the radiator looks like is coming from somewhere further in the engine.


- The pipe on the bottom was cold or slightly warm on the touch. That one looks like is connected to the main stat, but I am not sure if water is going or coming off the radiator.


- My local BMW dealer gave me a price of 85 euros for the main stat and 45 euros for the egr one.
 
#240 ·
Hi guys,

Just a quick one...

I think I need to do this on my E87 2005 120d, as I'm only getting up to around 82c after running for 30 minutes about town.

Will the two part numbers given here be correct for my engine too? Its a 2005 120d M47.

1151 7805811
11717787870

Cheers
 
#242 ·
marco_polo said:
Yup, they were the one's that went into my 2006 120d. Don't forget the demineralised water and G48 coolant.
Cheers.

How much of each of those will I need?

And does anyone have a video guide on how to do the coolant /bleeding? Or live in the Birmingham area and can help me! Haha

Also, Where's the best place to find these parts? I can see some on Ebay. But BMW Sytner want £95 for both including Vat.
 
#244 ·
Hi,

I have been having some issues with my 2008 e87 120d (N47). The car revs up on its own when ticking over, it goes from 830-850rpm up to 1200rpm, this only normally happens in the first 10-20 mins of a journey at traffic lights/junctions etc. Also, the main engine fan comes on occasionally when the engine is stone cold acting as if it is overheating.

I mentioned this very briefly to a mechanic I know and he said 'it may be the coolant temp sensor playing up'.

I've ordered one which will be here soon.

I then found this thread which contains some very useful information leading me to further investigation.

I've accessed the hidden menu and found that the temp goes from the expected figure suddenly to some random sub zero figure, i.e. It'll read 35deg then -45deg. It will flick back and forth several times and as suspected (and as the mechanic predicted) when the temp reads this super cold temperature, the engine revs more. I'm assuming that the opposite is what causes the fan to come on but I am yet to see it.
(As soon as the temp is over 40ish, is stops doing the flicking to sub zero thing).

I took the car out yesterday and eventually the temp seemed to settle in the 70s occasionally flickering into 80s then back again (took a long time to get there too, maybe 30+mins. So, reading this thread, I think I may possibly have a thermomatat issue as well.
I'll test the new temp sensor, when that is fitted, if it is faulty, it may show different temps and that the thermostat is fine, but I'm think it's likely the thermostat is not working and I am trying to research the right one so I can order it straight away if needed.

Am I correct that the fl, N47 cars don't have a thermostat in the egr? I can't seem to find the part or a definitive answer and the pictures of the N47 on this thread have been curse by Photobucket by the looks of it.

I have always been disappointed with the cars MPG (had it just over a year), which is 37 if I drive normally, or 39 if I drive to save fuel (so no point in trying). I'm hoping that sorting this temperature issue out will help with the fuel economy!
 
#245 ·
Wanted to thank the OP - as I fixed my issue:

1. Plugged my laptop in and diagnosed the error
Code:
Error: 1(11) No.: 12024  0x2EF8 Kennfeldthermostat, Ansteuerung                           frequency: 79
2. Went into the secret menu to monitor the coolant temp - was not going higher than 72C in my case
3. Got a new thermostat and replaced
4. Temps now reaching 104C or even slightly higher

Look forward to observing my mpg going forwards. Happy days :D
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top