As intimated yesterday, work on the car today was dictated by the weather. After a rather dull start and online meetings with work, I was finally able to grab the tools and head outside at lunchtime. Overcast with air temperature around 14 centigrade.
I have a new favourite tool combination to access the lower thermostat bolt assuming that this isn't corroded in place or already worn down : a Draper 55687 Expert Hi-Torq Deep Offset Ring Spanner, 10mm x 11mm that I bought off Amazon overnight (8 quid), combined with a Wera shallow 10mm socket (purchased from Amazon overnight for under a fiver).
Wera 8790 FA Zyklop Shallow Socket (for Zyklop Mini 2 Ratchet) 1/4"drive x 10mm, 05003690001
This fits perfectly into the 11mm ring retained on both sides with a small ring of bluetack squeezed into the gap (thanks for the recommendation Paul
@depronman!) - and with care you can get this oriented perfectly so that it is slightly offset from the angle of the true 10mm ring at the far end which makes tightening the lower bolt much easier given the limited access simply by turning the spanner round and being able to torque the bolt a wee bit further before hitting the thermostat housing with the spanner, then reverse ends and repeat.
I had already ordered a coolant temperature switch from Amazon overnight (Febi 35210 inclusive of o-ring (useful) and C-clip (which is too thin and a bit rubbish, so make sure you keep the original)) that I replaced on Sunday, and a Febi 17976 (87 degree) thermostat with large o-ring that arrived yesterday.
Having removed the engine cover and intercooler return pipe, I was able to loosen and remove the upper thermostat bolt within a couple of turns of the spanner and then whip this out by hand. The lower bolt was then loosened a couple of turns and then removed by fingertips likewise. Then I released the housing and lifted the pipe from the radiator upwards and hooked it out of the way.
This revealed the o-ring and the 3-year old thermostat. Past experience replacing thermostats told me to position the new thermostat and o-ring on top of the alternator within a few inches of the required position. I used a flat-bladed screwdriver to coax the old o-ring out of the housing while pushing against the installed thermostat to prevent it falling out unexpectedly, and then removed the o-ring, holding the old thermostat home by right hand. Picked up new thermostat with left hand and orientated it to match the old one. Finally, removed the old thermostat, and immediately having moved this out of the way with my right hand, inserted the new one just as the second "glug" of coolant started to make its exit (there is always a momentary pause after removing the first thermostat while the first glug forms but as soon as flow starts it will gush properly and build up speed to rapidly drain everything above this point). If I lost 150mL of coolant this time I would be surprised (I lost a lot more 2 days ago replacing the temp sensor through the original o-ring remaining stuck in place). Then, holding the new thermostat in position I fitted the o-ring and ensured it was located all around the circumference of the thermostat, then the housing with the lower bolt already in position.
(Nb. The thermostat housing lost the thermostat locating fingers 3 years ago, so the thermostat can be installed to the block with o-ring and housing on top, rather than stat into the housing with o-ring and then all bolted to block as instructed in the workshop manual).
Then followed the most precarious part of the process - holding the lower bolt (without dropping it into the nether parts of the engine bay!) through the housing against the engine block, trying to get the end to locate in the hole and catch the thread using two fingertips moving in opposite directions on the bolt head (thumb can't get access!!) while holding and adjusting the housing with right hand. Fitted, threaded and near-tightened the upper bolt by right hand to try to secure the housing in a more stable position, and eventually managed to get the lower bolt to thread and gradually work it in, 1/6 turn at a time. This took a lot longer than the entire removal and exchange process and is the one step that really would benefit from a similar tool equipped with a ratchet. Finally tightened it all up at both ends, reinstalled the removed parts apart from the engine cover and topped up the coolant.
Then the test drive - out of the village and onto country roads with cabin heater switched to "Lo" the temperatures rose as expected, but then tailed off when into the 80s. I then tried to provoke matters by climbing the local hill (about a mile in 2nd-3rd gear at 40mph) with Climatronic system switched off 4 times in a row - highish power with no fan operation over the radiator at all, and the temperature reached 87-88 degrees and wouldn't go any hotter (attachment from colour DIS on the previous post after the 4th climb in the space of a few minutes).
I'm not going to tempt fate, but the A2oc brains trust have solved this one - and I would like to thank each and every one of you in this thread who have contributed your time, skills, knowledge and goodwill to this thread over the past few days - I needed literally everyone's help to get to the resolution by a process of elimination and discussion.
Special mention to
@Ami for sending me the fuse overnight from his personal collection to cover all eventualities.
Fingers crossed I can go back to being a bit less prominent for the next few weeks!!
