Originally Posted by parmblagan' post='827458' date='Mar 26 2009, 08:33 PM

i too have just come back from doing some test just like our friend JER

got back from work today, journey is just under 5 miles, through stop and start traffic, car only got to about 76 degrees. (that's from ambient temperature -76 degrees)

came home and after about an hour went back out and started the car and went to the menu to find the cars temp was at 56 degrees, drove about 3/4 of a mile and parked up,car was at 88 degrees, but kept the engine running for about 10 minutes and again checked the temperature to find that the cars temperature had gone up to 94 depress.

drove of again and and took her for 2.5 mile run and the temperature went done to 87 degrees.

mpg for that run was 22.4 mpg.

the question is that, I understand that when the car is stationary, it will heat up faster as the air from the outside isn't cooling down the engine, but there is only 3 degrees difference from my cars 87 degrees, and what the members on the forum are saying, the optimum temperature should be 90 degrees.

so if you guys were in my situation would you still be will to spend the money to have the main thermo replaced, (already replaced the EGR thermo)

Originally Posted by jer' post='827439' date='Mar 26 2009, 08:12 PM

So we can guess that as the weather warms up the gap will close and we'll get more mpg as the higer ambient temperature and "open" thermostat leads to a closing between. I expect in Summer our 80 something degrees will hit the

I'm going to get the thermostat checked first I'm sure it worked for mini me but no so sure why the Exhast gas recirculation thermostat effects mpg and warm up time. This should also report in the case of a fault to the management computer. Does'nt EGR Exhaust Gas Recirculation Taps some of the exhaust and adds it to the normal mix at high rpm?

Lets see how quick I can get the main thermostat replaced and then so what happens.

Originally Posted by mini_me' post='827474' date='Mar 26 2009, 08:03 PM

True, with higher ambient temps the engine will go nearer to 90C.

As for the EGR thermostat; as you can see at the beginning of the thread, the EGR therm. is parallel to the main one. When the EGR them is faulty (thus open) it will let a coolant flow go into the radiator and get cooled down there as a result.
Therefore the faulty EGR them. will slow down warmup time or even prevent the engine from ever reaching operating temps. (in my case it wouldnt even let the engine reach anything higher then 70C or so).

Since the engine never reaches operating temps of 90C the engine management system will inject more fuel to compensate for the low engine temp.

Makes sense m8?

To clearify; The EGR valve lets a small amount of exhaust gasses go back into the intake manifold. This is done to lower the combustion temps (because of less oxygen in the mixture) resulting in lower NOx emissions.

The EGR gasses on their way to the intake manifold, are cooled down by the engine coolant. This EGR cooling flow is regulated by a 2nd smaller thermostat the EGR thermostat.

So basically you should not mix up the two; the EGR circuit routing exhaust gasses to the intake and the cooling circuit sooling the EGR gasses.


so do you think at 87 degrees (90-87) will make some difference to the mpg, ie do you think that the engine is still injecting more fuel at 87 degrees. maybe at 90 degress the ecu tells the car to inject less fuel, normal amount.

Originally Posted by mini_me' post='827474' date='Mar 26 2009, 08:03 PM

True, with higher ambient temps the engine will go nearer to 90C.

As for the EGR thermostat; as you can see at the beginning of the thread, the EGR therm. is parallel to the main one. When the EGR them is faulty (thus open) it will let a coolant flow go into the radiator and get cooled down there as a result.
Therefore the faulty EGR them. will slow down warmup time or even prevent the engine from ever reaching operating temps. (in my case it wouldnt even let the engine reach anything higher then 70C or so).

Since the engine never reaches operating temps of 90C the engine management system will inject more fuel to compensate for the low engine temp.

Makes sense m8?

To clearify; The EGR valve lets a small amount of exhaust gasses go back into the intake manifold. This is done to lower the combustion temps (because of less oxygen in the mixture) resulting in lower NOx emissions.

The EGR gasses on their way to the intake manifold, are cooled down by the engine coolant. This EGR cooling flow is regulated by a 2nd smaller thermostat the EGR thermostat.

So basically you should not mix up the two; the EGR circuit routing exhaust gasses to the intake and the cooling circuit sooling the EGR gasses.

Originally Posted by parmblagan' post='827512' date='Mar 26 2009, 09:57 PM

so do you think at 87 degrees (90-87) will make some difference to the mpg, ie do you think that the engine is still injecting more fuel at 87 degrees. maybe at 90 degress the ecu tells the car to inject less fuel, normal amount.

Originally Posted by E61530DAT' post='800999' date='Feb 25 2009, 07:39 AM

I`m finally reaching normal operating tempereature 90 - 93 C ! After first replacing the EGR thermostat temperature improved from 62 to 78 C. Now I have replaced the main thermostat (not as easy as EGR!) and temperature are stable at 91 C !!!

Replacing the main thermostat took me 4 hours and I had to remove two airducts and the exhaust cooler to get to it. ...

I drove to work today 100 km with both higway and rush traffic - now using average 7.1 liters /100km - before 8.3 liters /100km

Originally Posted by parmblagan' post='827538' date='Mar 26 2009, 04:28 PM

how muchis it to purchase the main thermo from the dealers? i have found this on ebay, dont now if ths is the correct part
http://cgi.ebay.co.uk/BMW-E46-E39-E60-X3-X...2|39:1|240:1318

Originally Posted by Bob525D' post='827545' date='Mar 26 2009, 09:44 PM

Not the right one, I believe that is for a petrol engine. My dealer told me that if the warranty didnt cover my replacement it would have been about ?240+ vat for them to replace it.

The design and part numbers are different when you compare it in Realoem. Sorry.

Originally Posted by parmblagan' post='827569' date='Mar 26 2009, 10:19 PM

you wouldnt happen to know the part number for the main thermo, or if you can locate on real oem and send me the link for the diagram (just dont know where to start)