How to Swap The Thermostat BMW M47 and M57 Engine

How to Swap The Thermostat BMW M47 and M57 EngineOne of the main reasons why a BMW DPF will not regenerate, and why fuel economy is below par, is because the engine’s coolant and EGR thermostats are faulty. It can also be down to the glow plugs – but it’s more likely to be the controller under the inlet manifold but we’ll cover that soon. A faulty coolant thermostat won’t allow the engine to get hotter than 70-degrees when it needs to be in the high eighties at least. When running cool the engine will be below efficiency and the heater won’t be anywhere near as good as it can be.

Diesel engines run colder than petrols which is why so many of them have vacuum or electronic shutter blinds on the radiator to reduce air flow through them until the engine is warm enough to let cooling air through. A warning though: when doing the thermostats be very careful of the hose that runs from the expansion tank/header tank to the top radiator hose where it fits the radiator on cars like the E60 520d. You would not be the first to snap the elbow where it fits on resulting in a ruined top hose…

  1. Remove the E60-type slam panel with a T15 Torx socket and with the screws out move the slam panel to one side and then remove the radiator support panel, unplug the fan wiring plug and lift the electric fan assembly out. It’s easy work and essential to gain access.
  2. On the E46 the boost hoses are secured by large Jubilee-type clips but the E60 and later 1 Series/E90 BMWs have clip fi t hoses including this intercooler to EGR boost pipe – unclip it as shown with a small flat blade screwdriver and pull it to the right out of the way
  3. This plastic MAF feed pipe comes off next and it’s easily removed with a 5mm Allen socket. The top one’s easy to access but the lower one is quite fiddly – I use an Allen socket on an extension to get at it. The two screws are staked into the plastic however so they won’t fall out
  4. Now to the EGR cooler from the exhaust manifold. These are secure with a pair of T50 Torx bolts but sizes can and do differ. These bolts aren’t magnetic so be careful when removing them as they are easy to drop into the engine bay, and good luck finding them again!
  5. Remove this regular hose clip on the EGR thermostat and catch the coolant – it’s evil stuff and incredibly toxic to wildlife. I use a big old towel under this area to catch this poisonous stuff along with clean plastic pots to catch it. Wash the area down with fresh water afterwards
  6. Now unclip the lower coolant hose on the cross coolant tube and catch as much of the coolant as you can. Please don’t just let it drain on the ground – use wishing up liquid to clean any spills. These clip-on hoses can be very tight and can put up a fight to the death – be careful!
  7. The EGR cooler can soon be removed after three 5mm allen bolts are removed – this single bolt here, and two more either side, but they’re easy enough to find. With these removed the cooler can almost be removed but the next bit is slightly tricky…
  8. This hose clip is combined with a steel pressure sealing ring mating the EGR cooler outlet stub to the side of the EGR valve. Loosen the clip fully and wriggle the whole EGR cooler off. The EGR valve itself does not need to be removed though although most need a good clean so…
  9. The EGR cooler can now come off. These are very reliable units unlike the later N47/N57 stuff. Note also the green coolant absorbing towel here – the bigger the better, you can also see the steel plate onto which the right hand EGR cooler retaining bolts fit.
  10. Now we’re needing to drain a fair bit of coolant, I used a 5-liter plastic container with the top cut off to catch as much as I could. This hose clips to the thermostat housing and it’s another steel clip to be lifted up with a screwdriver whilst you wrestle the hose off.
  11. This plastic cross coolant tube fits across the front of the engine and it’s important that it can move to avoid straining it and possibly breaking it upon thermostat removal – remove this 10mm bolt shown here – and it become a lot more cooperative when removing stuff.
  12. Here is the coolant thermostat and the four 10mm retaining bolts to be removed. These horrid press fit joints can be a bit of a pain to get apart – the trick is penetrating oil and careful yet firm persuasion. Sometimes they come apart easily, other times, not.
  13. The thermostat here was the original 2006 unit from when this car was built and it was opening at just 70 degrees. This meant it was opening far too early (or was stuck open). These engines don’t have electronically-mapped thermostats but are wax element units.
  14. Inspect the EGR cooler for cracks or black marks, signs of exhaust gas leakage. Reassemble everything ‘dry’ without exhaust sealer on the manifold flange as it could flake off end up in the turbo. Remove the two 10mm bolts and the thermostat comes off.
  15. This O ring seals the thermostat to the EGR cooler. Order a new one (BMW part number: 11532248435). Fit it dry without any kind of sealer – penetrating oil or grease will expand it, it will not fit properly and leak coolant – you only want to do this job once.
  16. A new EGR thermostat isn’t expensive – pay around £35.00 for a good make with the coolant thermostat not much more. You can buy an EGR thermostat for around £15.00 but don’t bother. I’ve used Circoli and Mahle with success. M47 and M57 coolant and EGR stats are the same.
  17. Now put it all back together but leave the fan off for now. Slowly refill the cooling system until you see coolant in the EGR themostat, fit and tighten the plastic bleed screw and fire it up. Run it for 3-minutes with the heater on full checking for leaks. All good? Refit the fan, take it for a run and revel in your new-found heat!
  18. This photo is from a LHD E90 but the hidden menu is much the same. The temp here is 90-degrees which is far better than the previous 70-degrees. The heater is now much hotter, the car is achieving an extra 5mpg and the DPF is regenerating as it should – job done!
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Engine Model Guide: M47N M57N
E87: 118d 120d
E46: 318d 320d
E90/91: 318d 320d
E39: 525d 530d
E60/61: 520d, 5256d 530d, 535d
E38: 740d (Euro)
E65/66: 730d 740d
E83 X3: 2.0d 3.0d
E53 X5 : 3.0d 3.0d

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