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Discussion Starter #1
A reliability issue the E46 cooling system is that there are too many plastic pieces, like the thermostat. So I bought an aluminum version that stands up to heat cycles, but whose electronics were abysmal. On day 3, (why couldn't it have been immediately at install) I got stranded with no start situation, like I was fuel starved. :banghead: No CEL codes showed to diagnose the thermostat fault.

Unfortunately these Chinese sourced versions are the only aluminum versions. The Behr and Wahlers have stuck to plastic.
The result was an expensive tow and diagnosis in the shop. :censor:
The E46 uses sensors to control the thermostat opening. If the sensor malfunctions the engine simply will not start. The electrical connection is there to power a heater element in the thermostat. This enables opening of the thermostat by the engine management system. With a conventional thermostat the coolant around the cylinders would boil under hard acceleration before the water at the thermostat got hot enough to open it and cool the cylinders. With a heated (map) thermostat the engine management system can look at the power requirement and predict the heat build up, therefore it can switch on the thermostat heater and get the thermostat open in time to cool the cylinders.
My aluminum version of the E46 thermostat was not up to the job. :thumbdwn:
 

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Sorry to hear about the troubles!
I was going to buy that same thermostat from a member here on the forum. But missed the chance.
Had ask where they originally purchased it - FCPGroton, but they didn't carry it anymore. And, won't be carrying it in the future.

Any how, I didn't realize that the electronics on the OE thermostat was a "heater" element. Always thought it was a temperature sensor/switch of some sort.

It's hard to imagine that BMW authorized the use of that much plastic (the entire thermostat) when there is a heater within...

So, what are you going to do with the aluminum unit now? (May I have it? PM me.)
Guess you're going to have to go back to OEM plastic unit...
 

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Discussion Starter #3
^^ The eBay seller has a one year warranty on the part so I need to return it for a refund. My guess is that it was sourced from FCPGroton. Yes, I've gone back to a Wahler.
 

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Discussion Starter #6
Thanks, it was interesting to find out that the thermostat was pulled from the market by FPGroton. One downside of eBay an online channels is that products dropped for good reasons, like reliability can still be sold in bubble wrap on eBay and classifieds. It's bothering me that even BavAuto is not doing a good job identifying who makes certain parts they list (including this aluminum thermostat).
The German OEM suppliers get their quality control assessed pretty much every day at the BMW factory, which benefits the reliability of everything coming out of OEM suppliers.
 

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Discussion Starter #8
The car will run with the heated element unpluged, the DME will just switch to a default map, pretty much the same thing as unplugging the MAF.
I was thinking later that I might have been able to start the car by disconnecting the thermostat, but I was looking at fuel issues - lifting up my rear seat and checking the fuel pump connection and pulling fuses and checking everything fuel related. Good to know about the default map :thumbsup:
 

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Damn, I was going to get one of those..
Too bad you had to spend extra money for that crap.. :banghead:
Great thread indeed :bow:
 

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Discussion Starter #11
This is the internal build of the thermostat.


I unclipped the stem/ spring part but the stem going to the heating element area seemed solid. The plastic around the electrical connection seems to be injected into the body like in the diagram. So there was no way to remove it.
I was hoping that the manufacturer used OEM supplier electrical components but the electronics turns out to be the weak part of the product. Costly lesson for me :censor:
 

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Great post and timely for me. I'm just putting a multi-vendor order together to swat-team the cooling system and was considering hunting one of these down. There's a DIY video with a guy suggesting the metal replacement as a must have. I think it was a prior gen car but sounded like an upgrade for E46's.
 

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Discussion Starter #14
Aluminum housings do not warp from head cycles and if there is a slight leak at the mating surface you can sand the flat side of the aluminum thermostat. You were probably watching the BMP videos, but I will only go with aluminum again of Wahler or Behr sell one.

You're right the separate thermostat and housing ended with the E36. pg 4 and 5. they probably opened based on water temp instead of the heater.
http://www.pelicanparts.com/bmw/catalog/shopcart/BE36/POR_BE36_WATpmp_pg4.htm
 

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Seeing as the M54 thermostat is more likely to stick open than crack, the housing the aluminum one is overkill. The e36 thermostat was more prone to cracking and therefore an aluminum housing made sense.

With the addition of electronics, it's a pretty much done deal. No way to separate the 2.
 

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there is no need for aluminum thermostat housing on our cars. OEM Genuine BMW Plastic usually works for about 100K miles for most of our cooling systems.
 

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The car will run with the heated element unpluged, the DME will just switch to a default map, pretty much the same thing as unplugging the MAF.
Oh yah because you want to run around in limp mode all the time. :loco:
I wouldn't want to drive very far in limp. But it wouldn't have left you stranded I guess.
 

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there is no need for aluminum thermostat housing on our cars. OEM Genuine BMW Plastic usually works for about 100K miles for most of our cooling systems.
You beat me to it. I've read countless threads where a thermostat has stuck open, a couple where it was suspected that it stuck closed, and a few where the heater circuit failed. I have never heard of the plastic housing failing in any way on an E46. That aluminum one is an answer to a problem that doesn't exist, and as shown here, comes with it's own problems that the OEM one doesn't have.
 

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Discussion Starter #20
There is a BMP Design video covering plastic in the E46 cooling system.

http://www.youtube.com/watch?v=Mco77TK94GU

Resist the idea of using the aftermarket Far East aluminum thermostats - great idea, but the thermostat electronics didn't get picked up by the ECU of my car.
The OEM Wahler and Behr thermostats are far more reliable even though the case is plastic, just watch for residue like the BMP presenter talks about.
 
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