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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 12-12-2009, 05:01 PM
stknight stknight is offline
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Thermostat gauge question...

Hi, I have a 2000 323i and have noticed that at times the temperature/thermostat gauge will move all the way over into the red but the light that indicates the engine is overheating does not come on. I won't even drive far at all so I don't believe the engine even has time to overheat. If I shut the car off then back on it seems to fix this and the temp gauge reads normal again. This has happened intermittently but it concerns me since cold weather is upon us.

Could it just be that the thermostat is stuck open? And is it okay to drive the car if the gauge moves into the red zone but the light does not come on? I feel like the problem is thermostat or a sensor but need someone that knows to possibly shed some light on the issue. The car also "seems" to burn gas more frequently and at times I believe I get a whiff of what smells like antifreeze. Even though the head gasket was replaced a few months I still have to add a little bit of antifreeze about once a month as the "low coolant" light will come on. Geez...could the mechanic not have properly fixed the head gasket?? I wouldn't be surprised as that is just my luck. Any help/advice would be much appreciated. Thanks.
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Old 12-12-2009, 05:08 PM
slyfocks slyfocks is offline
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Originally Posted by stknight View Post
Hi, I have a 2000 323i and have noticed that at times the temperature/thermostat gauge will move all the way over into the red but the light that indicates the engine is overheating does not come on. I won't even drive far at all so I don't believe the engine even has time to overheat. If I shut the car off then back on it seems to fix this and the temp gauge reads normal again. This has happened intermittently but it concerns me since cold weather is upon us.

Could it just be that the thermostat is stuck open? And is it okay to drive the car if the gauge moves into the red zone but the light does not come on? I feel like the problem is thermostat or a sensor but need someone that knows to possibly shed some light on the issue. The car also "seems" to burn gas more frequently and at times I believe I get a whiff of what smells like antifreeze. Even though the head gasket was replaced a few months I still have to add a little bit of antifreeze about once a month as the "low coolant" light will come on. Geez...could the mechanic not have properly fixed the head gasket?? I wouldn't be surprised as that is just my luck. Any help/advice would be much appreciated. Thanks.
Driving Bimmer I6's with any type of cooling system problems is never a good idea.

If your thermostat was stuck open, you would typically see your engine temp running cool, and not getting to operating temperature during cold weather.

Have you checked your engine oil to see if there is any glycol contamination from the coolant?
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Old 12-12-2009, 05:12 PM
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Originally Posted by stknight View Post
Hi, I have a 2000 323i and have noticed that at times the temperature/thermostat gauge will move all the way over into the red but the light that indicates the engine is overheating does not come on. I won't even drive far at all so I don't believe the engine even has time to overheat. If I shut the car off then back on it seems to fix this and the temp gauge reads normal again. This has happened intermittently but it concerns me since cold weather is upon us.

Could it just be that the thermostat is stuck open? And is it okay to drive the car if the gauge moves into the red zone but the light does not come on? I feel like the problem is thermostat or a sensor but need someone that knows to possibly shed some light on the issue. The car also "seems" to burn gas more frequently and at times I believe I get a whiff of what smells like antifreeze. Even though the head gasket was replaced a few months I still have to add a little bit of antifreeze about once a month as the "low coolant" light will come on. Geez...could the mechanic not have properly fixed the head gasket?? I wouldn't be surprised as that is just my luck. Any help/advice would be much appreciated. Thanks.
Few questions for you...

Do you know the service history of the car?

As in, when the water pump was last replaced...?

To your question, it IT NOT ok to drive an E46 with cooling system issues IMHO...The gauge needle is highly buffered against swings (forget the exact range of T values) but if it moves off center you have a serious problem.

As Slyfocks indicated an "open" thermostat should mean your engine will take longer to warm up...

With the fact you are topping up coolant, I would bet your water pump is on it's last legs...
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Old 12-12-2009, 05:22 PM
stknight stknight is offline
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For the most part....it does run cool and the gauge stays closer to the blue indicator. I'm just weary of the gauge moving all the way right (red zone) every once in a while. But, like I said, shutting the car off and back on seems to reset this and the gauge indicates the proper temp of the engine. Is it just a faulty sensor then?? Before the head gasket blew and it ran hot a while back, I noticed the red indicator light comes on and of course the temp would not fall back to normal until the car had time to cool back down....which in this case seems to me that it's not actually running hot just reading improperly and I am unsure if it's messing with something else and could cause an issue if I don't shut off then and there and restart the engine.

And how would I know if there is any glycol contamination? Am I looking for a color or abnormal thickness in the oil? Thanks.
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Old 12-12-2009, 05:24 PM
jbanske jbanske is offline
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I will chime in with my two worth little cents.
I can confirm the open status of thermostat makes your engine run cold..my them is open ( waiting on part) and the car is burning gas pretty aggressively and the car is running so cool the needle sits just above the blue. I would not push your luck, replacing the motor would be an expensive lesson
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Old 12-12-2009, 05:26 PM
stknight stknight is offline
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The water pump was just replaced a few months ago along with a new radiator fan, belts, and reservoir tank.
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Old 12-12-2009, 05:33 PM
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The water pump was just replaced a few months ago along with a new radiator fan, belts, and reservoir tank.
How about the radiator?
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Old 12-12-2009, 05:35 PM
stknight stknight is offline
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The mechanic said the thermostat sticks open and mine does just as yours does (sits just above the blue) with the exception of that occasional swing that raises my concern. I've heard if it happens then it's better for it to be stuck open than closed b/c you supposedly can drive it until you have time to replace it. But with the cold weather fast approaching ( I live in the south, GA to be exact) the cold weather concerns me and, pardon my ignorance, but I'm unsure as to how damaging it can be to the engine if it all. From what you guys have said I feel like I need to have it replaced ASAP before it screws with anything else. Thanks for all your input.
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Old 12-12-2009, 05:36 PM
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The mechanic said the thermostat sticks open and mine does just as yours does (sits just above the blue) with the exception of that occasional swing that raises my concern. I've heard if it happens then it's better for it to be stuck open than closed b/c you supposedly can drive it until you have time to replace it. But with the cold weather fast approaching ( I live in the south, GA to be exact) the cold weather concerns me and, pardon my ignorance, but I'm unsure as to how damaging it can be to the engine if it all. From what you guys have said I feel like I need to have it replaced ASAP before it screws with anything else. Thanks for all your input.
If you are having cooling issues, and have a part that's as failure prone as the BMW cooling system is, I would certainly replace it asap.

By chance are you looking for a good used thermostat?
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Old 12-12-2009, 05:45 PM
stknight stknight is offline
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Wingspan, I have not had the radiator replaced and am unsure as to if it ever has been. The mechanic I took the car to AFTER I had someone else replace the head gasket is highly knowledgeable...I wish I had found him when the head gasket blew b/c he could have saved me a couple thousand dollars. The idiot that replaced the head gasket assured me he knew what he was doing but when he went to put it back together he misplaced the cam shafts and burnt them up. The new mechanic said he checked back over the head gasket the other guy did and said everything seems to be fine. I'm still kicking myself trusting that idiot that f**k'd it up to begin with and the costly subsequent repairs on the cam shafts.
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Old 12-12-2009, 05:50 PM
stknight stknight is offline
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And, yeah, it looks like I will be looking for thermostat. If you don't mind me asking...how do you know it's still "good" and won't flake out on me??
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Old 12-12-2009, 05:50 PM
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Wingspan, I have not had the radiator replaced and am unsure as to if it ever has been. The mechanic I took the car to AFTER I had someone else replace the head gasket is highly knowledgeable...I wish I had found him when the head gasket blew b/c he could have saved me a couple thousand dollars. The idiot that replaced the head gasket assured me he knew what he was doing but when he went to put it back together he misplaced the cam shafts and burnt them up. The new mechanic said he checked back over the head gasket the other guy did and said everything seems to be fine. I'm still kicking myself trusting that idiot that f**k'd it up to begin with and the costly subsequent repairs on the cam shafts.
Gotcha.

Well, running through the data, you have nine year old car that overheats with a radiator that is unknown.

Perhaps 9 years of gunk has built up and it's not functioning properly?

Might be an idea to get your mechanic to sort out a radiator and thermostat change.

It's not a huge deal to swap these components out. He can also run a hose through the radiator to check if it's plugged up...

The reason I asked about the thermostat is when I did my cooling service (http://www.bimmerfest.com/forums/sho...1&postcount=72) this past February I had a slight leak in the lower hose to thermostat area...I replaced the thermostat (which was new, from www.autohausaz.com) after a month with another one. I still have it. It's probably going to go into the for sale hopper along with a bunch of other misc E46 parts I have kicking around, at some point.
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  #13  
Old 12-12-2009, 06:47 PM
stknight stknight is offline
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Well...I do wanna get it swapped out. How much are looking to sell it for? I plan to do a search later on and see if I have to purchase the thermostat only or does it have to come with a housing or other parts & what have you. I believe the mechanic did a radiator flush when he put the new reservoir tank on a few months back so hopefully I'm good there.
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Old 12-12-2009, 06:51 PM
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Well...I do wanna get it swapped out. How much are looking to sell it for? I plan to do a search later on and see if I have to purchase the thermostat only or does it have to come with a housing or other parts & what have you. I believe the mechanic did a radiator flush when he put the new reservoir tank on a few months back so hopefully I'm good there.
To be honest, you probaby just want to buy a new one from a reliable parts house (e.g. www. pelicanparts.com). They really aren't that expensive ($65 IIRC) and then you know you have a new part going on.

Yes, they come (at least, my Wahler one did) with the gasket etc.

In fact it's dead easy to put one on, are you a DIY-type at all?
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Old 12-13-2009, 03:42 PM
stknight stknight is offline
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I am a DIY type with most everything except "cars" to be quite honest. I was able to locate the thermostat and it does seem pretty straight-forward to replace and not that complicated. I took it to my dad and let him look as well...now he is one that can do most anything when it comes to things on cars so it looks like we will be doing this one our own. When I had my Honda we changed out most everything and it was much simpler than a BMW. This shouldn't be a problem and thanks for everyone's assistance and advice on this matter.
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Old 12-13-2009, 04:56 PM
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smolck smolck is offline
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When I had my Honda we changed out most everything and it was much simpler than a BMW. .
I doubt that your Honda thermostat is much simpler than the BMW unit. Takes about 10 minutes to change it out, 20 more for the water pump. But for the thermostat you don't even have to pop your belts off. REAL easy!
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Old 12-13-2009, 05:03 PM
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I am a DIY type with most everything except "cars" to be quite honest. I was able to locate the thermostat and it does seem pretty straight-forward to replace and not that complicated. I took it to my dad and let him look as well...now he is one that can do most anything when it comes to things on cars so it looks like we will be doing this one our own. When I had my Honda we changed out most everything and it was much simpler than a BMW. This shouldn't be a problem and thanks for everyone's assistance and advice on this matter.
Ya, it's fairly straightforward.

BMW uses these cool radiator hoses, with a simple push-on connection with a wire securing bail that slips over the fitting.

The upper two hoses are fairly easy, the one at the bottom i.e. radiator end is a major PITA to remove.

I think the therm is literally one electrical connection, three bolts, the two rad hoses and bingo.

Remember (you might already know this) to refill only with BMW OEM blue coolant and distilled water mixed 50 50.
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Old 12-14-2009, 10:12 AM
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Remember (you might already know this) to refill only with BMW OEM blue coolant and distilled water mixed 50 50.
I love ya wingy, but I have disproved this theory of "magical" BMW coolant on my car. I have well over 90k miles using only Prestone and almost 200k miles total on the car.
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Old 12-14-2009, 11:27 AM
jcourcoul jcourcoul is offline
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While the longer than usual time it remains in the blue zone on the thermostat gauge may indicate a sluggish or stuck-open thermostat, wouldn't the occasional spikes in temp be caused by an air bubble trapped in the system due to inadequate purging?
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Old 12-14-2009, 11:37 AM
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I love ya wingy, but I have disproved this theory of "magical" BMW coolant on my car. I have well over 90k miles using only Prestone and almost 200k miles total on the car.
Yeah, I here ya bro, and I totally respect that, but it works for me. Way I figure it, I don't have to wonder when I buy coolant whether it's the right stuff of not...and the incremental cost ($20 / gallon) vs. how often I use it is not too worrisome. YMMV, of course.
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Old 12-14-2009, 12:30 PM
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Yeah, I here ya bro, and I totally respect that, but it works for me. Way I figure it, I don't have to wonder when I buy coolant whether it's the right stuff of not...and the incremental cost ($20 / gallon) vs. how often I use it is not too worrisome. YMMV, of course.
I hear ya too, if my budget wasn't so tight, I'd splurge for the "good stuff" too. I guess when it comes to coolant, I have become a non-conformist based on my economic situation!
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Old 01-07-2010, 12:19 PM
hopeitsapar2 hopeitsapar2 is offline
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Does anyone know the part number for the temp sensor that goes on the lower radiator hose?
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Old 01-07-2010, 01:22 PM
Melquin Melquin is offline
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Does anyone know the part number for the temp sensor that goes on the lower radiator hose?

Most likely 13621433077, it is used on most everything. What build date and model do you have to be sure?

All parts can be located on realoem.com or http://bmwfans.info/parts/catalog/E46
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Old 03-20-2011, 11:22 AM
BMWer14 BMWer14 is offline
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Originally Posted by stknight View Post
Hi, I have a 2000 323i and have noticed that at times the temperature/thermostat gauge will move all the way over into the red but the light that indicates the engine is overheating does not come on. I won't even drive far at all so I don't believe the engine even has time to overheat. If I shut the car off then back on it seems to fix this and the temp gauge reads normal again. This has happened intermittently but it concerns me since cold weather is upon us.

Could it just be that the thermostat is stuck open? And is it okay to drive the car if the gauge moves into the red zone but the light does not come on? I feel like the problem is thermostat or a sensor but need someone that knows to possibly shed some light on the issue.
I am having the exact same problem as 'stknight' did above...to the tee. Same vehicle 2000 323i. It seems to occour only with extremely cold weather...temps at or below 0'F (-18'C). Same resolution also...if I shut down the car and restart...the guage goes back to a real reading. Also like stknight, the hot engine light does not come on when the needle goes into the read...and the engine does not throw any codes...no check engine light. I know the thermostat is in the stuck open position...the car runs cold unless the outside temp warms up to near freezing..and I am waiting for some warm weather to do the DIY on the change. The coolant temp is in the normal range if outside temps are above 32'F. Just wondering if I should change the temperature sensor also..or will the thermostat change solve the problem? Or any other suggestions.
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Old 03-21-2011, 01:01 PM
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