E46 320d - coolant temp and low MPG issue

[msport123]

Hi guys,

It’s seems my trusty 320d after 192k has developed an issue! The car is a 2005 model, has full service history and drives fine.

1. The coolant temp needle is not going past the quarter mark on the gauge. From memory the needle normally sits at the half way point after 5-10 miles. 300 mile trip yesterday and the needle didn’t go past the quarter mark.

2. Yesterday’s trip would have usually seen in the region of 48-50+ MPG. yesterday I achieved 39 MPG.

3. I think I’m getting noticeably more smoke under accerlation, more so than what I thought was usual. I think I had this issue prior to the MPG drop off and coolant temp issue above.

Any thoughts chaps?

Thanks in advance..

[padhinbed]

Could be a stuck thermostat so the car thinks it's cold and is overfueliing like it would when cold to warm the engine up quicker.

Don't know if it would show an error code on the computer but from memory not an expensive fix.

[helix402]

You need a new main thermostat and egr thermostat. Re smoke, check air filter is clean and also crankcase breather valve is clean. Check all boost hoses, hard pipes and intercooler for leaks. Also check for soft boost hoses with very small cracks in them.

[msport123]

Thanks chaps. Good advice.

Air filter was changed not so long ago as part of the inspection 2 service so that should be ok. The crankcase breather or oil breather I don’t believe is a service item so it’s likely it’s never been changed, I’ll get this checked.

Do you think the ERG valve is related to any of these issues? It’s never been cleaned and don’t believe it will do any harm in taking it off and giving it a good clean, but don’t want to make things worse accidentally by fiddling with things which are ok.

[helix402]

Egr valve could be dirty, can be cleaned in situ. They do not fail very often on these. Do not remove it or bypass it, you will lose power and use more fuel.