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Discussion Starter · #1 ·
Hi guys! My local mechanic just replaced my thermostat last week because my engine was running cold (car taking too long to warm up, on the freeway the needle would be about 1/4 instead at 1/2, and in stop & go traffic it would be right at 1/2 where it should be, no heating problems)... my problem is, engine is still running cold. I asked my mechanic and he says it is ok, I know he is wrong, it used to take a few minutes to reach the 1/2 mark and would stay there no matter how cold or warm it was. What else should I check/replace?
 

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im not sure... last night i took my 330ci to my uy and he changed out my thermostat with a wahler thermo and it only takes me about 4 minuets of driving for me to hit dead center now.. before my needle would slowley creep up and stop right before the center and after 20 minuets of driving it would hit center.. it was because the thermo wasent opening all the way.. try getting a quality thermo or just reinstall it and see what happens
 

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Do you have a new thermostat housing? If not, you mechanic did not change your thermostat.
This is my guess too given the symptoms you describe. I would verify if it has been changed and go from there. If they did change it, what brand did they install?

Paolo
 

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Do you have a new thermostat housing? If not, you mechanic did not change your thermostat.
This. If you do have a new housing, you got a defective thermostat; probably non-OEM. The temperature gauge in our cars is so buffered that if the needle is pointing anywhere below 12o' clock, the coolant is well below normal operating temps.
 

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This. If you do have a new housing, you got a defective thermostat; probably non-OEM. The temperature gauge in our cars is so buffered that if the needle is pointing anywhere below 12o' clock, the coolant is well below normal operating temps.
:idea: You mentioned temperature, so I was thinking if the therm was replaced and lets say it is in good working condition, would the temperature sensor at the lower hose possibly be bad causing this kind of cold engine circumstance?
 

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Discussion Starter · #7 ·
Thanks for your quick responses! Apparently he did replace the thermostat since everything around this area looks new and he even gave me the old thermostat. The brand he used is Wahler which is the same brand as the old part. Could xavi330i be right that it could be the temp sensor? Good thing is once the needle is at the middle, it stays there, but I really have to be driving in the city and not the freeway. The temperature now is around low 70's.
I also noticed my radiator fan is on even when the car is cold at startup, is this normal?
 

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:idea: You mentioned temperature, so I was thinking if the therm was replaced and lets say it is in good working condition, would the temperature sensor at the lower hose possibly be bad causing this kind of cold engine circumstance?
The temperature sensor in the lower hose is just for triggering the cooling fan. Even if the fan was running 100% of the time, a properly functioning thermostat will keep the coolant temps in the normal range.
 

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Thanks for your quick responses! Apparently he did replace the thermostat since everything around this area looks new and he even gave me the old thermostat. The brand he used is Wahler which is the same brand as the old part. Could xavi330i be right that it could be the temp sensor? Good thing is once the needle is at the middle, it stays there, but I really have to be driving in the city and not the freeway. The temperature now is around low 70's.
I also noticed my radiator fan is on even when the car is cold at startup, is this normal?
Find a thread with instructions on using the hidden OBC features to see the actual coolant temps. The gauge is so buffered that you can only count on it to tell you one of three things: Coolant temps are way cold, temps are somewhere between too cold and too hot, or your engine is about to melt.

I suspect one of two things: Your cooling system needs to be bled again (this usually results in high readings, not low though), or you got a thermostat that was bad out of the box. In any case, having your temperature gauge point below 12o' clock for more than the first few minutes after a cold start is never normal unless you're in arctic temperatures.
 

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In my experiences, that cause by bad thermostat. in too cold weather, it's stuck open. Now you had new thermostat, even though it is very rare, but may be it bad in the new box.
Other wise, the DME -coolant-temperature control system may be bad, it send power ( electrical) to thermostat, keeping it open even in the cold start beginning.
You can test by unplug the electric wire hardness on thermostart (easy, press the metal square ring and pull it up/out ) and run the car. If the car keeps cold too long & on highway it couldn't reach 12O'clock, the thermostat BAD.
If the temp gause reach 12 O'clock in 4-10 minutes, then go further , if gause keeps on 12, the system malfuntion, it could be the thermo sensor ON the ENGINE BLOCK bad/or wiring bad.
Keep an eye to the gause, if it goes over 12 O'clock, stop car immediately, plug the thermostat wiring on, (so the thermostat can open to bring temp. down,) then drive again.
In this case (DME malfuntion ) , mostly we need to scan to know where & what r bad. Myself was not in this case , so I couldn't know more.
 

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Discussion Starter · #11 ·
Thanks guys. I will try bleeing system again first; if this doesn't work I will try disconnecting hardness on thermostat and keep an eye on gauge. I guess we never expect something new out of the box to be defective, but there is always a possibility. I wll find out and let you guys know, I could also take it to a different mechanic.
 

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Discussion Starter · #12 ·
Disconnected hardness on thermostat and turned engine on. It seems that nothing happened, radiator fan was still running, left engine running for close to 10 minutes and gauge barely got to 1/4 of the way. No engine light came on or anything. Will keep posting.
 

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Did you have the A/C on by any chance? That would explain the cooling fan running... Also just to cover all bases, do you have a manual with the one electric fan, or do you have an automatic that has the clutch fan behind the radiator and the smaller electric fan in front of it? The clutch fan will always spin some when the engine is running. In any case, no matter what the fan is doing, a properly functioning thermostat will keep the coolant temps in the normal range.
 

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Disconnected hardness on thermostat and turned engine on. It seems that nothing happened, radiator fan was still running, left engine running for close to 10 minutes and gauge barely got to 1/4 of the way. No engine light came on or anything. Will keep posting.
Idling at 10 mins. might not bring engine to op temp...and you should warm up car by driving it.

It's not like a gas stove, on or off. It's a huge mass of metal getting warmed by tiny little explosions, cooled by 4 gals. of fluid. Keep rpms down a bit and just drive until warm. Then, after 10 mins, call it 3-5 miles in most circumstances and 'your' climate, it should be registering op temp.
 

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I am having the exact same problem as the poster. I have a 2002 BMW 325i and I had the thermostat and housing replaced but my car still runs around the first mark on the freeway. It runs at normal temps in city driving and the heat works.
 
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