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

[Peter B - CV8]

All those symptoms indicate a coolant thermostat problem to me ie stuck open.

[AlCan]

Thanks Blue! Who would have guessed that? Still makes no sense to me, but I will definitely check it out / try it and let everyone know.

If it works, then I'll have to figure out why... I believe the EGR valve is open at idle (with the engine cover off you can see that the EGR pushrod position has moved), but I don't understand why it would cause the engine to cool that much if it's stuck / dirty / not opening or whatever the problem is.

Seems to me, the EGR valve is the car owner's worst enemy, the carmaker's friend and the mechanics nemesis! So many things to so many people and the cause of so many completely weird problems.

I still don't understand why Exhaust Gas Recirculation is actually beneficial. It reduces the amount of available Oxygen which supposedly reduces the amount of NOx created, but surely, it also increases the amount of incomplete combustion leading to (even more) soot and other partially burnt fuel products, which I imagine are worse for health than NOx. We need Nitrous Oxide in our bloodstream to dilate blood vessels and control Blood Pressure... Can anyone tell me why EGR is good?

I know the stink (Cooked meat in the Alan Howat video) from partially burnt fuel when there's a blown copper washer injector seal - which was bad enough to make a couple of people I know feel sick and refuse to ride in the ('11) car, but that's all sorted now. Though, a component of that unburnt fuel still lingers in the car - can smell it when you first open the door after sitting awhile. The '13 has it too, though that must have all happened before I bought it.

Anyway, the car is still down south as I flew back this trip and won't get back to it until mid-October. Will update then. Thanks again.

[AlCan]

Thanks too, Peter B,

I totally agree. It sounds exactly like a bypassing thermostat - I even went and bought a new thermostat assembly. Just haven't had the time / opportunity to fit it yet.

But then I did more reading, and am learning that with these cars, things are too often not what they seem.

(For example, even a mechanic said that the blown injector seal was due to a rocker cover gasket leak, dripping oil onto the manifold. I couldn't see / believe that, but it still took me 5,000km+ to figure out what it really was.)

From the net, it sounds like the oil thermostat can also be a hidden problem that swapping the coolant stat won't fix, so I wanted to try and see which it was first. But since there (now) doesn't appear to be an oil stat in the 10C engine, it can't be that. However, with the addition of the EGR video, I still have two possibilities.

Call me lazy, but I prefer to eliminate the possible easy fixes before I tackle the less easy! TBH, this EGR valve possibility is a nice little spanner in the works.

I still agree with you that the coolant stat is more likely, but if it's the EGR and a spray can will fix it... I'll certainly let you know!