As mentioned in my last post, I noticed a low coolant level and subsequently a low engine operating temperature. This is a very strong indication that one or both engine thermostats are faulty and are opening too soon or not fully closing. It's a common problem on this engine and if left unchecked can result in a blocked DPF. Fortunately I noticed it in time.
The EGR thermostat only takes about 10 minutes to change so although I had already received both thermostats from Cotswold BMW, I decided to replace just the EGR one initially. Unfortunately this didn't make the slightest difference.
So this is where the 'fun' really started as I now had to replace the main engine thermostat which is buried beneath the EGR cooler and not very accessible. I had to remove the EGR 'stat again and the main radiator fan. The EGR cooler had to be disconnected from the inlet manifold and various pipes either disconnected or moved to the side to gain access.
Then I started to remove the 4 thermostat retaining bolts. The first one came off quite easily even though I was only using a short stubby 3/8" drive ratchet. Then the second one snapped right off in my hand! WTF! I couldn't believe it...
At this point the damage was done so I had to just move forward. I soaked the remaining bolts in plusgas penetrating fluid and left them while I went away and kicked things round the garage for 10 minutes. I came back and removed the remaining two bolts without any problems. The thermostat was a bit tricky to remove, mainly due to the remaining headless bolt but I got it off eventually.
At this point there was almost enough bolt (or set screw technically) sticking out of the engine block to get two nuts onto, the idea being to tighten them together and use that to remove the broken bolt. Despite several attempts this failed. I even tried cutting down a nut to allow the second one to engage further but no joy. I then spent several hours going round DIY and motor accessory shops (on a Sunday) to try to find a stud removal tool or alternatively a right angled drill chuck to allow me to drill out the broken bolt and remove with the stud extractor set I had already. Again, no joy.
As a last gasp attempt, I got an M5 halfords professional socket and hammered it onto the end of the M6 broken bolt trying to hammer it hard enough to get enough purchase but not so hard that it would split the socket open. I knew I only had one attempt to get this right...AND IT WORKED! This was about 6:30pm and it was getting dark so I got everything back together quickly and carefully and filled up with BMW approved coolant and de-ionised water and took it for a test drive. It takes a bit of running to get all the air out but after a few top-ups I enabled the hidden temperature menu again and this was what I found...
A stressful day but a satisfying ending!