Apparently my coolant temp is actually too cold? Is that a thing?

of course thats a thing. your thermostat could be failing. no further understanding needed.

 

Is Failing

 

Ty guys just read a good thread by JfroJ and that was my takeaway.


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Also, when i first purchased the car and looked under the hood i noticed a low coolant level, couldn’t even see the coolant in the reservoir, so i topped it up, filling it to the rim to then start the car, wait for it to break 95, let the thermostat open and take the coolant down into the system, (i assumed it was missing alot of coolant.) only issue was it never really got to 95 to let the thermostat open.. got up to 89 after letting it idle for 30 minutes. I didn’t think much of it and capped it. Besides the risk of an expansion tank explosion, could that have something to do with my temps? That fact that i capped it when it was close to the rim? I read about a specific coolant cap that will let out excess coolant after a certain pressure threshold is reached and I can replace mine with that cap to help better protect myself from an explosion in the chance of an over fill like what i had done. Have you guys heard of this ?


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filling it to the rim to then start the car, wait for it to break 95, let the thermostat open and take the coolant down into the system, (i assumed it was missing alot of coolant.) only issue was it never really got to 95 to let the thermostat open.. got up to 89 after letting it idle for 30 minutes. I didn’t think much of it and capped it.

1. Definitely the thermostat is bad and always open.
2. If the engine runs for 30 minutes to get to 89C or 96C while tank cap is opened, this can cause local boiling in the head and can crack the head. You only can run a cold engine with removed cap for a very short time.
3. You better think much about not repeat this mistake again or it can cause big headache.

 

Therms often break 'open' rather than closed...which would be much worse. You'll be losing lots of mpgs running 'cold.' Time for a new therm, and while you're at it, not a bad idea to do things that are easy picking--if not the entire cooling system, maybe a new water pump, belts, pulley? You can replace the o-rings in hoses you open, but new hoses are much easier. O-ring sizes are here somewhere around...use silcone lube.

 

The tstat is clearly soft failing by staying open. The low coolant level is a separate issue of a leak somewhere or even a bad expansion tank cap losing coolant. Overfilling it has nothing to do with the low coolant temp.

You could rent for free a pressure tester from Autozone, and that's a good idea, but f you plan to keep the car long term this is a good opportunity to do a full cooling system refresh. Otherwise you'll be chasing one thing after another, and also risk overheating the engine if something breaks/bursts and you don't shut off in time.

Edit: just remove extra coolant with a turkey baster. Leaving it overfilled contributes to a broken plastic expansion tank, since it's already under full system pressure to begin with. Relying on the cap to vent excess fluid just puts needless stress on it. Regardless, the expansion tank is one of the main vulnerabilities and should be replaced if it is old and/or has significant mileage.

 

This is why I got an E46 again. Thanks guys, the input and direction the people in this form point you towards is always positive and helpful. I had already wishlisted* a cooling system upgrade with the Metal water pump etc on ECS waiting for a moment like this so I will take this chance to just do it all and not worry about another potential cooling system issue. I will update the thread once i've completed the change so other users can search in the future and learn.

Thanks again guys

 

This is why I got an E46 again. Thanks guys, the input and direction the people in this form point you towards is always positive and helpful. I had already wishlisted* a cooling system upgrade with the Metal water pump etc on ECS waiting for a moment like this so I will take this chance to just do it all and not worry about another potential cooling system issue. I will update the thread once i've completed the change so other users can search in the future and learn.

Thanks again guys

FWIW, the wives tales of plastic impeller pumps is a thing of the past from the E36 generation of cars. High quality pumps with hybrid nylon composite impellers from the likes of Saleri/Rein/Dolz are terrific. They all have learned, studied and have performed failure analysis, and corrected. ("He won't make the same mistake twice." Sean Connery- Hunt for red October)
Just with a very quick glance one can see there is better cavity filling with a nylon impeller over that of a metal. Owing to the easier time of molding nylon over that of metal. It's slight but there's a little advantage of the nylon impeller IMO.

 

My 2005 E46 325Ci did that twice. I went back to the gas station, filled the car, and put the cap back on. Problem solved, both times! If it does it again, I'll buy a new gas cap.

 

P0128 Coolant Temperature Below Thermostat Regulating Temperature

How to quickly diagnose, repair, and info on symptoms and causes of a P0128 code which generally indicates a failed thermostat.

www.obd-codes.com

 

Thanks Bali, i bookmarked that website. Very useful


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Update, check engine light went away on its own. Came on while I was cruising on the highway at 80. Been watching my Temps while I drive and it wont go over 89. Once i get on the highway it drops to 77-80. Definitely not normal, MPG has been worse recently as well.


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Update, check engine light went away on its own. Came on while I was cruising on the highway at 80. Been watching my Temps while I drive and it wont go over 89. Once i get on the highway it drops to 77-80. Definitely not normal, MPG has been worse recently as well.

Yes ... shows how the error code/check engine light is beside the point. When I got my car at 95k miles the coolant temps were running around 174F/79C (city and highway) and it never had a check engine light or error code for that.

 

The tstat is definitely contributing to that low mpg. Cruising at that speed & rpm with light throttle (on flat ground) should be closer to 30 mpg. 19mpg sounds low unless you are only doing short trips and city type driving.

However, you should also check the fuel trims at a warm idle and a warm steady cruise. It's very likely that a vacuum leak somewhere could also be reducing the fuel economy and low end power/response.

Fix things one at a time to see any incremental changes.

 

Regardless of Tstat condition, do not run engine longer than 10 minutes with cap removed.

 

WHAT?

 

Lets explore this:

Does/is the cooling system designed to run with the expansion tank cap on, well naturally.
However while diagnosing issues we often have run the car for some time with the expansion tank cap off.
There are some caveats:
Since the cap is off the rate of expansion of the coolant will be greater, therefore expect some spill out as the cooling system self levels, if you will.
If the fan(s) be it electric, mechanical and/or both are operating properly the temperatures will stay within parameters.
The coolant temperature sensor for the DME to make decisions about opening up the thermostat is located (not by accident) in the cylinder head, when the temperature rises above XX°C the DME will send a PWM signal to the thermostat to "drive it open".

Having the cap on or off in no way changes the flow and/or path of the coolant.

Would I drive a car with the cap off? No way. Albeit at idle engine speeds once the level stabilizes (pressure is absent) one can run a car for diagnosis at idle, provided you started with a cold/warm engine.

All of the above becomes pernicious and not recommended for the layperson. Should there be an issue (poor pump flow, bad fans/fan clutch, bad thermostat going too hot) one can easily get scalded and a trip to the hospital is in order.
However the cap on/or off has no effect on flow capability, as long as the engine itself remains full.

 

Thank you man, was looking for an explanation as to how that could negatively effect temps within the block.


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Quick update guys! Took some advice and purchased a few maintenance items since I will be down in that area working on the Tstat. In the week that I discovered the tstat issue i also noticed a whine coming from the Air intake/Alternator area. Is directly linked to RPM. After some research i've narrowed it down to to the Idler Pulley or lower Air intake boot tear. Either way my boots are original and so are the pulleys so figured id do them both, and maybe a little performance mod while im there too

Forgot to order a new Expansion tank since mine is OEM and my car just hit 83K.... I think im right at that dangerous mileage to be driving on an oem one lol

 

Plastic, such as that used in the expansion tank, ages because of repeated heating/cooling cycles, and time. If the tank is original with 83k miles, yes it’s due for replacement but I wouldn’t worry about it too much.

The only brand of expansion tank to buy is Modine. The installation of aftermarket cooling system parts is strictly verboten!

 

Plastic, such as that used in the expansion tank, ages because of repeated heating/cooling cycles, and time.

Mostly, because of rectangular shape. Hoses and other elements of cooling system made of same plastic rarely fail.

The installation of aftermarket cooling system parts is strictly verboten!

You should put it in your signature))