thermostat replacement/warning light

I continue to read that allot of people have luck with clearing the increased emissions light with changing out the thermostat. A couple questions. First, I would think that if you had a faulty thermostat that u would see signs like increased temperature gauge readings or noticing a smell or odor of overheating when operating the vehicle. Secondly, what does the thermostat have to do with emissions? The thermostat allows for cooling of the engine and I am confused with this having any impact on what is coming out of the exhaust. I also have the emissions light up on my 645 and was wondering should I just go ahead and change the thermostat and see if it clears. For those that have successfully changed out the thermostat and cleared the emissions light does the increased emissions light clear itself after changing the thermostat or is there a reset procedure involved in clearing the increased emissions indicator light?

Originally Posted by mfelsoci

I continue to read that allot of people have luck with clearing the increased emissions light with changing out the thermostat. A couple questions. First, I would think that if you had a faulty thermostat that u would see signs like increased temperature gauge readings or noticing a smell or odor of overheating when operating the vehicle. Secondly, what does the thermostat have to do with emissions? The thermostat allows for cooling of the engine and I am confused with this having any impact on what is coming out of the exhaust. I also have the emissions light up on my 645 and was wondering should I just go ahead and change the thermostat and see if it clears. For those that have successfully changed out the thermostat and cleared the emissions light does the increased emissions light clear itself after changing the thermostat or is there a reset procedure involved in clearing the increased emissions indicator light?

I'm not the expert here but, remember that the Temp gauge on the dash is Oil temp not coolant. Also, sometimes the error messages are more general with faults and not as descriptive as you might like so don't be fooled by the wording.

My understanding is that the thermostat fails in the open position resulting in unrestricted coolant flow from start-up and therefore a longer time for the engine to reach normal operating temperature.

It therefore probably runs a richer mixture for a longer time and has higher emissions.

Could be wrong, but that's how I reconciled it for myself.

I can only speak for the n52 engine (3.0L) but other reading I have done suggest that the thermostat does fail partially & this can cause a change in how the coolant flows to the cylinder head. I had the error 2EF5 on my car (a 630i, not sold in US, it's an e63 with a 530i engine for all intents & purposes). This error relates to the cooling flow issue, the n62 has a similar error but its a different code.
From explanations I got from a service manager (with years of BMW workshop experience that I trust) is that the code pops up when one particular circuit gets exposed inside the thermostat to coolant causing a short. This is the circuit that controls coolant flow to the head. The reason the coolant flows towards the head is to help reduce emissions apparently. He told me that there are loads on N52 engined cars driving around with this 2EF5 error & the dealer does not even mention this to the customer as it does no harm. The reason they don't mention it is that the error could also be caused by a faulty wiring harness, there's a bit of work in solving that issue.
So based on the info above it would seem that the emissions should only be a minor issue & not the primary contributory issue to an increased emissions warning light. I hope that helped more than confused!

To clear emission light I would put some injector cleaner BG44k in first and secondly consider cleaning the MAF sensor using a suitable cleaner and following the instructions......

Originally Posted by 645/333

To clear emission light I would put some injector cleaner in first and secondly consider cleaning the MAF sensor using a suitable cleaner and following the instructions......

Thanks for all of the information and suggestions.

Originally Posted by 645/333

To clear emission light I would put some injector cleaner in first and secondly consider cleaning the MAF sensor using a suitable cleaner and following the instructions......

+1 Always do the (super cheap) general maintainance that could also fix your problem first. You can do both of these in about 5 minutes.

Originally Posted by Mulchman

+1 Always do the (super cheap) general maintainance that could also fix your problem first. You can do both of these in about 5 minutes.

Hate to ask but what is the MAF sensor? Additionally, any suggestions on injector cleaner?

Was it easy to change the thermostat? Do you have the step by step DIY including draining the antifreeze? Thanks!

Originally Posted by mfelsoci

Hate to ask but what is the MAF sensor? Additionally, any suggestions on injector cleaner?

Already done BG44K, whilst more expensive it really works as many of the other injector cleaners you can buy are useless rubbish.......
MAF is the Mass Air Flow !!!
It sits between the air box and the injector intake, you cannot miss it it sticks up and is held by two screws. Check on REALOEM
This is a very important piece of kit in managing how your engine runs..... I know how it works and what it does but I am sure you can find all you need to know about it.
Every petrol engine car has one and they do fail, They can become dirty with micro dust that the air-filter allows through and as it heats up the dust builds up over time, you may only clean it once in 60k miles or more, hence the cleaner, they are the first to look at followed by the Oxy sensors in the exhaust......There is always the big debate in the use of after market air filters allowing the MAF to get dirty, I believe there is some truth in this so I always stick with OEM air filters.
The point is the extremely fine filter wire that is the sensor is incredibly delicate, so you HAVE to ensure you use the right fluid, it is readily available, nothing else will do.
Read the instructions before you start and having said all of this it is extremely easy.....lots of threads on it>>>
Basically you remove the two screws gently pull up the sensor and spray wait for it to dry, quite quick really and then replace.

Make sure to use the correct cleaner. Your auto parts store will have MAF (Mass Air Flow sensor - stateside) cleaner. Use of the wrong cleaners could harm your MAF and they are not cheap. As 645/333 said, just remove, spray, dry (compressed air or time) and replace. Do your air filter while your there if it needs it.

Once again this great forum produces great information. Thanks again for the info. I have my car stored at my dads for the winter and wont actually get to it until after the holidays so I will let u guys know in a week or so. Happy Holidays and once again thanks for the great information.

Originally Posted by mfelsoci

Once again this great forum produces great information. Thanks again for the info. I have my car stored at my dads for the winter and wont actually get to it until after the holidays so I will let u guys know in a week or so. Happy Holidays and once again thanks for the great information.

Ps if your car is stored make sure you use a battery tender at least weekly to keep it charged or you will be storing more problems for later

Originally Posted by 645/333

storing more problems for later

Too funny "I'm going to store my problems till spring"

Funny and correct. Your battery will be toast after a few weeks of storage. Do a search. Yorgi had a few recommendations that included the BMW branded charger.

Because of the type of car the 6 series is, many have stored there cars over winter, especially in those climates where it is very cold and snowy....this forum is full of people who have had issues, some never ending because they did not look after the battery during storage. They understandably (because we are using hindsight here) did not think to keep the battery in top condition and learned the hard way.
The amount of problems either caused directly or by a component associated with the power supply on these cars is amazing, so why not learn from these guys who have experienced them and consider the suggestion and save yourself a fortune in repair costs.
In fact many on here use the battery tender all through the year just to keep the batteries in top condition, and save themselves a lot of aggravation for very little inconvenience

I'm confused...it's a German made car, Germany is colder than the U.S....why so many issue during the winter!?!?!

Hi! firstly Some of the guys in the States and Canada, who are main contributors to this site do live in very cold climates during the winter months.
Secondly, whilst I have only limited knowledge of this, cars in the US and Canada are not built the same as in Europe, for example European cars including here in the UK have louvres in front of the radiator and behind the grill which are used to manage engine temperatures, They mask both the radiator and the oil cooler (?) until the engine is warm, cannot remember if they are electrically controlled once the engine has reached temp.
Without exception ( I am sure someone will prove me wrong) they do not have these fitted in the States or Canada, I believe there are other slight differences, so there's a starter.

On my 2004 645Ci convertible in the USA, on the Standard Equipment list is:

Code S823A hot-climate version

I guess this refers to the lack of "louvres in front of the radiator and behind the grill which are used to manage engine temperatures".

I am pretty sure no North American 6ers have louvers, I've only seen guys from Europe post about them.

Same goes for the folding side mirrors (wing mirrors).

I inquired about purchasing a battery tender for my 6 series while she is stored but I guess I should have provided this one small detail. My father is retired and his one duty for the winter months is to tend to my baby and drive it weekly. So far he has not objected and I believe at 74 he enjoys getting behind the wheel and driving her. The only problem I am having now is he continues to put miles on my baby while she is suppose to be resting. Everyone have a great holiday season.

One more piece of information... I just replaced my thermostat because I had the same emmissions warning. When you actually read the code with a code-reader, it will tell you if its the Thermostat or some other malfunction. I forgot what the Thermostat code is, but when you read the code you can just come back to the forums and enter the code in the search. You will immediately tell if its for the thermostat replacement or not. It was very easy to do as its right in the front of the engine and its only three bolts to replace. I got mine from the dealer for only $75... You will also need a gallon of BMW coolant as well. It should only take about 30 minutes or so.