2013 TDCi Engine Temperature Varying

[AlCan]

Hi Guys,

Just back from the cold NZ south, and have really noticed the "dreaded" overcooling problem on my 2013 TDCi. This problem is discussed in various places around the net, mainly relating to MB / DW10B engines, but doesn't seem to appear here. And I can't find the answers I need, anywhere. There is another thread here about engine temps, but it doesn't mention the oil thermostat.

Basically (as typical) the engine is slow to heat up, especially in cold weather, then varies all over the place, below normal temp.

In cool weather, the temperature struggles to get over 70 degrees - i.e the first line after the 60° line. If the engine is working hard, it will get up to normal temperature, just shy of the middle, vertical line, but as soon as it's at reduced load, the temperature drops back again. I know this is normal during a long downhill but not for ordinary highway driving. This doesn't happen on the 2011 TDCi, and sounds exactly like the oil cooler thermostat problem discussed on Talkford and elsewhere.

Do the DW10C engines even have an oil thermostat?

The 2011 is also a DW10C but has hydraulic Power Steering, whereas the 2013 is electric. Can't imagine that has anything to do with it, but as above, the 2011 engine temperature remains almost rock steady once it's warmed up. So, there's something different.

I've searched the net for oil thermostats and only found them for engines up to 2008. P/N 1128018. Looks just like a baby, old-style radiator thermostat housing, but skinnier. Can't find anything for later models. The DW10B oil thermostat appears to live on the front(?) centre of the engine, about where the 10C EGR valve is, but I can't see much else in that area.

Can anyone throw any light on this, please?

[AlCan]

I'm hoping someone has a Parts Diagram and can put this question to bed, but in the meantime, I've done a bit more research and some thinking about this.

The Engine Oil Cooler is in fact an Oil<->Water Heat Exchanger, located below the Engine Oil Filter Housing on the lower front of the engine. The Housing seems to bolt to the Heat Exchanger or vice versa, and it's very compact and hard to see what's going on. There seems to be a (coolant?) pipe coming out of the block below the intake manifold and heading down, which probably feeds the Heat Exchanger but there was no visibility on the black and grimy wrecker's yard engine I looked at.

Anyway, it's rare that things are improved by removing parts but this might be just such a case. If the coolant feed to the Heat Exchanger is continuous (no separate thermostat as on 10B engines) and comes hot from the engine BEFORE (i.e upstream, inner side of, i.e. the water pump output side of) the Main Coolant Thermostat, then it could serve a dual function.

When the oil is cold, it could actually heat the oil to near Engine Coolant Temperature (about 80°C), which is almost ideal, while when the oil is over 80°, it would pass heat to the coolant, bringing its temperature down closer to 80°. All temperature control would thus be achieved by the single Coolant Thermostat in its housing at the flywheel end of the head. This would also help explain why these engines seem to take so long to warm up, as they also have to heat up 5.5 litres of oil before the engine will get to thermostat opening temperature.

I don't know if this is how it works but it makes sense to me. Could even call it an elegant design...

If so, would mean the problem must be with the Coolant Thermostat itself, which must be not closing fully or has a faulty seal so that coolant is bypassing it. It looks like a bit of a job to change, but not that bad. Probably much easier than pulling the Oil Filter/Heat Exchanger out - if there's even a thermostat there somewhere.

So, my next question is, what coolant is recommended here, please?

[aussiblue]

This? https://www.youtube.com/watch?v=iZTadyzsrxE