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Old 10-28-2011, 09:00 AM   #1
Geeyore
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Low Temp Gauge Reading

OK, I've read a couple threads about low temp gauge readings on the console and have three possibilities.

Backgound: This is a 2000 323iT with less than 100K miles and decent (not perfect) maint over the last 10 years. Had a big coolant system replacement at about 70K, a few years ago, due to the notorious E46 disintegrating plastic impeller on the water pump.

Anyway, for the last week or less I've noticed temp gauge taking a long time to get past about 25 percent (normally reads dead center 50 percent of the gauge after initial warmup, just like any other E46).

This morning I drove about 12 miles of highway at 70-80MPH (oops) and it stayed around 25 percent (just above blue). Only when I got off the highway and came to a stoplight did it start a rise to the normal center position, and got to center after about 2 or 3 minutes of 25-30 MPH driving.

Also have noticed an odd smell the past day or two at stoplights, like oil burning. This morning I realized it was my car making that odor. It could also be a coolant smell. I concluded all of this on the way to work this morning and haven't yet popped the hood.

From what I've found here it could be (a) vent screw, (b) thermostat, or (c) leaky radiator cap.

Hopefully I'll be able to make 15 miles back home without problems, and take a look this evening or tomorrow AM.

Anyone have any insights or thoughts?
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Old 10-28-2011, 09:02 AM   #2
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In all likelihood, sounds like your thermostat is stuck open. Not quite sure about the smell, maybe a coincidence? Does it have a sweet smell (I believe that's coolant)? Could be oil and just happened to occur at the same time.
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Old 10-28-2011, 09:03 AM   #3
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Doesn't sound like leaking coolant, you would get air in there and then start to over heat... Sounds like thermostat stuck in option, are you getting MIL aka Service Engine Soon aka Check Engine light? Codes read on a Peake?
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Old 10-28-2011, 09:04 AM   #4
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[QUOTE=B;13745305]Doesn't sound like leaking coolant, you would get air in there and then start to over heat... Sounds like thermostat stuck in option, are you getting MIL aka Service Engine Soon aka Check Engine light? Codes read on a Peake?[/QUOTE
Option = open
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Old 10-28-2011, 09:08 AM   #5
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the smell, maybe a coincidence? Does it have a sweet smell (I believe that's coolant)? Could be oil and just happened to occur at the same time.
OK, thanks. That's a vote for thermostat, I'll poke around here for a DIY on replacement. Shouldn't be too challenging, right?

I'm not clear on the smell, whether it's oil or coolant. I've noticed it maybe 3 times in 2 days, and it's pretty faint. But whatever it is, it's from my car.
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Old 10-28-2011, 09:12 AM   #6
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\Sounds like thermostat stuck in option, are you getting MIL aka Service Engine Soon aka Check Engine light? Codes read on a Peake?
No "check engine", no console warnings, nothing. Just the gauge and the very faint odor.... of something. No code check, I don't have the gear.

One of the threads mentioned minor coolant leakage from a decaying vent screw. I guess that'll require a visual inspect, which I'll do tomorrow AM (I want to check oil and radiator cap from a cold start).
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Old 10-28-2011, 09:14 AM   #7
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Yea, the thermostat is pretty straightforward. A bit more challenging if you have an auto, only cause you have to use a 32mm wrench to get the fan off first. Otherwise pretty simple.

Check for oil, should be pretty easy. If you are smelling something, it may be oil dripping onto the exhaust manifold. When facing the car from the front bumper, look to the left side of the engine (passenger side) and look on the metal heat shield. If there is oil all over it, that may be your culprit.
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Old 10-28-2011, 09:20 AM   #8
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Yea, the thermostat is pretty straightforward.... Check for oil, should be pretty easy. If you are smelling something, it may be oil dripping onto the exhaust manifold.
Good tips, thanks, will do.
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Old 10-28-2011, 04:42 PM   #9
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The symptoms you have are EXACTLY the same problems as I am having.

Mine is a 2002 330i.

Booked it for a thermostat change on Tuesday so I will let you know the results.

Have you compared your engine temp using the hidden OBC menu?
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Old 10-28-2011, 05:23 PM   #10
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The symptoms you have are EXACTLY the same problems as I am having.

Mine is a 2002 330i.

Booked it for a thermostat change on Tuesday so I will let you know the results.

Have you compared your engine temp using the hidden OBC menu?
Definitely stuck open therm; you can drive safely with it for a while...you'll just burn more gas than needed.

When mine occurred someone here suggested I block part of the radiator, like trucks do in the winter...make sure it's not anything that will dissolve from water and clog up the condenser grid (what you might think is the radiator).

Also, it's an easy diy...just doing the therm, very little coolant leaks out, it's a few bolts and a couple of hoses. Not bad at all, though assembly would be easier with new hose(s).

If you're doing it yourself, read/watch our DIYs until you're convulsing...then you'll be ready!
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Old 10-28-2011, 10:04 PM   #11
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Mine was doing the exact same thing when I bought it. The low temperature IS the thermostat stuck open. Like someone said, it's a cake walk in this car if it is a 5 speed. You also have a burning oil smell which is the Valve Cover Gasket (VCG). It is originally a rubber piece(s) and the heat turns it into a plastic and I had to break it off of the valve cover in pieces. Obviously, plastic doesn't seal as well as rubber and if you look on the passenger side of the motor you will see oil leaking from around at least one of the valve cover bolts. Do a search on VCG and you will get an idea of what you are in for. No big deal at all.
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Old 03-24-2013, 02:45 PM   #12
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temp guage replaced

Hello, new member, e45, 320d 2004, and just changed the thermostat yesterday. Same problem as above, the temp gauge was running low, about 30% and the heater in the car was blowing warm. using a bit more fuel too.

After changing the thermo the temp guage went back to normal at 12oclock and the heater blew hot.

Unfortunately this only lasted for an hour then the temp gauge returned to around 25% and the heater is again blowing warm air,

Any ideas?

Getting worried now

Last edited by daithi1; 03-24-2013 at 02:46 PM. Reason: spelling, oops
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Old 03-24-2013, 03:05 PM   #13
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Originally Posted by daithi1 View Post
Hello, new member, e45, 320d 2004, and just changed the thermostat yesterday. Same problem as above, the temp gauge was running low, about 30% and the heater in the car was blowing warm. using a bit more fuel too.

After changing the thermo the temp guage went back to normal at 12oclock and the heater blew hot.

Unfortunately this only lasted for an hour then the temp gauge returned to around 25% and the heater is again blowing warm air,

Any ideas?

Getting worried now
Could be your thermostat or then again maybe something else. Under full throttle, the thermostat is electrically heated to open up. Could some kind of defect be causing the stat to open? Haven't heard of that one before. Use the OBC to see what your temps are. Attached is a pdf file (thanks to jofj). Menu item #7. Temps should be in the low to mid 90s (Celsius).
Attached Files
File Type: pdf OBC hidden functions.pdf (37.1 KB, 121 views)
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Old 03-24-2013, 07:13 PM   #14
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Leak has nothing to do with that. You will get low coolant level warning light first, not such symptom like this.
Remove your thermostat and see if it's stuck wide open. It's unusual, but does happen..

To check coolant temp sensor, get a glass of hot/warm water and put the temp sensor in it. (Don't disconnect the wire, I'm sure you know that already) If temperature gauge responses, your temp sensor is golden.
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Old 03-24-2013, 08:01 PM   #15
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Sounds a lot like an open thermostat. We had the same problem. New Whaler [OEM] thermostat fixed it.
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Old 03-25-2013, 03:10 AM   #16
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thanks for all the replies guys. just read coolant temp according to the OBC pdf supplied. it reads 65. what's the chances I replaced thermostat with a dodgy, cheap one. hmmm

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Old 04-05-2013, 04:23 PM   #17
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a question

Hello, I replaced the thermo with an oem, seems I have the same problem, Can I ask is it normal for the temp gauge to drop when the heater is on? The temp guage now reads at 12 o clock but when I put the heater on it drops about 25% less.

I am not sure if this is the normal as I dont remember noticing it in my previous e46.

Thanks
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Old 04-21-2013, 03:11 AM   #18
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sorted!

For the benefit of the thread, I replaced the temp sensor, a cheap part, and presto, the temp gauge now sits at 12 o clock,as it is supposed to on an e46 regardless of whether the heater is on or not. Problem solved.

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