35d worsening gas mileage - solved- thermostat/fan/EGR cooler - DIY with pics

[Dr. Anthony]

I saw that post yesterday while I was reading the thread of the guy who went through 5 EGRs due to cracking. Thanks, i'll make sure to check it out.

While I'm in there, is there anything else you think I should replace? I remember on my 335, the water pump (electric) had to be replaced. Any known issues with them? (its only 3 more bolts to remove the water pump)

Originally Posted by ZetaTre

Look around for a post from ninja_zx10 on the proper tightening sequence of the EGR cooler. Make sure you follow it.

I'd also suggest you put some anti-seize on the bolts and the mating surface on the exhaust manifold side of the EGR cooler to ensure the bolts don't get stuck in the cast iron. In my case I put the anti-seize on the bolts, drove them through first and then recoat them before installing the cooler.

You don't need to disconnect any of the vacuum lines on the EGR cooler. You can simply flip it up and out of the way.



One side of the thermostat connects to a rigid line that goes towards the driver side around the head and under the throttle valve. There is bolt under the throttle valve that hold that line. It may help to release that bolt to get a bit more slack out of the rigid line.

Some of these things may not make lots of sense now, but keep them in mind as they will become clear once you're in there.

[Dr. Anthony]

For anyone else reading this thread, here are the torque specs, and the EGR Cooler installation instructions with the tightening sequence.

[Dr. Anthony]

Just an update. I just realized I was reading my cluster wrong. I'm actually getting 12L/100km (19mpg) so now I'm really looking forward to see if this helps with mileage

[jfoj]

FWIW, soft thermostats are not uncommon among the German car manufacturers. I believe the problem is with the main spring tempering or maybe lack of.

I see this exact same problem on the I6 gasoline engines as well. You cannot easily flag a soft thermostat until the ambient temps drop below 70F and get the vehicle cruising above 40 MPH constantly.

Best to baseline/benchmark the engine coolant temps and then carefully monitor the engine coolant temperature before the hard Winter temps settle in.

[Dr. Anthony]

Originally Posted by jfoj

FWIW, soft thermostats are not uncommon among the German car manufacturers. I believe the problem is with the main spring tempering or maybe lack of.

I see this exact same problem on the I6 gasoline engines as well. You cannot easily flag a soft thermostat until the ambient temps drop below 70F and get the vehicle cruising above 40 MPH constantly.

Best to baseline/benchmark the engine coolant temps and then carefully monitor the engine coolant temperature before the hard Winter temps settle in.

I'm going to replace mine. I'm waiting for the part to arrive (should have been today, hopefully tomorrow) Our winters get pretty cold (-30c plus windchill at times)

[RIHI]

Based on recommendations here, I will monitor the temps on my X5 but will already order both thermostats, just to be ready.

[jfoj]

Another point of reference that others should gather is what is the "nominal" engine temperature on these Diesels.

So if the thermostat states say 89C this does not necessarily mean the engine will run at 89C. The displayed operational engine temperature depends on where the coolant temperature sensor is located.

On many gasoline engines with the temperature sender located in the water output path of the cylinder head actually register about 15F /9C higher than the thermostat operating temperature.

So it would be helpful for anyone that installs a new thermostat to note what the "nominal" engine operating temperature is around 70F ambient or lower.

[London Lad]

Mine settled out at 95c when fully warm after new main and EGR stats were fitted

[jfoj]

Seems that most modern engines tend to run around 205F/96C except for the N62 which seems to run around 226F/108C!!!

Can you confirm if the thermostat for the Diesel is labeled with 88C like the one in the beginning of the thread? I believe even if the thermostat is labeled as 88C then this is typical that the engine temperature is actually operating about 15F/9C higher than the thermostat operating temperature.

[London Lad]

Originally Posted by jfoj

Seems that most modern engines tend to run around 205F/96C except for the N62 which seems to run around 226F/108C!!!

Can you confirm if the thermostat for the Diesel is labeled with 88C like the one in the beginning of the thread? I believe even if the thermostat is labeled as 88C then this is typical that the engine temperature is actually operating about 15F/9C higher than the thermostat operating temperature.

Yes.

Prior to the new stat i was running at a MAX of 84c and it took longer to get there. since the new stat I seem to be getting 2-3 more miles per (UK) gallon