Coolant level warning light dx

[Asiah119]

As I was on my merry way to work this morning I was greeted by the warm amber glow of my coolant level light. I've aborted my commute (thank you internet gods for remote access) and need to try to track this down.

What I know:
Water pump is new. Expansion tank and radiator as far as I'm aware are original to the car (92k). Coolant temp sensor is new.
Upper coolant line was firm and didn't give any sounds like there was air in the line.
Aroma of coolant from the front of the engine. No obvious moisture on the belly pan. No obvious coolant sitting on the block, no milkshake instead of oil (per dipstick), quick inspection with my phone flashlight didnt show any obvious cracks in the expansion tank. There is an anonymous patch of a wettish looking something on the accessory side of the expansion tank (didn't investigate too closely because work clothes) and there is a white film that looks like its been sprayed\flung around by the accessorys\serpentine that has been there for a short while.

Without a puddle I'm a little at a loss as to if the sensor just got wonky because of the change in temp or if its something like a small enough leak in the radiator that its just not leaving a puddle. Definitely dont want to have that yellow light go red while I'm coming home from work (65mi commute 99% of which is in farm country).

[az3579]

That whitish film is most likely dried coolant. You appear to have a leak somewhere.
I would fill the system and let it run and see if you can observe leaking with a full system.

[danewilson77]

What's the current mileage? Not sure if you told us what expansion tank level is? :dunno

"No flamesuit required"

[kayger12]

Sounds like a textbook cracked expansion tank. Conventional wisdom on exp tank longevity is 90k miles

[Johnmadd]

Possibly the cap?

[Asiah119]

Im around 92000 miles. After the car had cooled a bit I popped the cap off and the level wasnt extraordinarily low. The return hose had emptied out.

[melonz]

If you run the car do you see drops of coolant dripping?

[Asiah119]

Couldnt see any, and nothing looked wet. Just had some aroma.

[BCS_ZHP]

Here's my distance diagnosis. From your water pump replacement, there may have been a small air pocket trapped in the heater core. Now that it's gotten cooler and you're using your heater, that air pocket worked its way back to the ET to make it show a little low on coolant. The white residue on side of ET indicates you are losing some coolant there too. I would suspect if you remove the ET cap when the car is cool and look at the rubber seals inside that cap, they will show to be depressed and not as plump as the rubber rings on a new ET cap. Try replacing that cap, it costs less than $20, clean the side of your ET and look for more residue to show up. If it does, then your ET needs to be replaced. If it doesn't, then your leak was from the ET cap.
Bruce

[Asiah119]

Thanks for the tip BCS

[Asiah119]

The shop that I generally dont trust for anything complicated took a look yesterday and couldn't find any leaks. I started off for work this morning and got a light after a mile. Headlight housing and air box are soaked.

[kayger12]

Sounds like a textbook cracked expansion tank. Conventional wisdom on exp tank longevity is 90k miles
:)

[Hornung418]

The shop that I generally dont trust for anything complicated took a look yesterday and couldn't find any leaks. I started off for work this morning and got a light after a mile. Headlight housing and air box are soaked.
Hairline crack in the ET. Recommend replacing the unit and if money is available, replace the coolant hoses and thermostat housing. New o-rings seat better when the surfaces are new too. Best of luck. It's a fun job. Like going to Sea World...without the dolphins and Shamoo.

How is your oil consumption? Check for leaks on the oil filter housing. The gasket is a $6.00 part and will deform over the years. While you're in there, you might as well, right?

[Asiah119]

I completely forgot to include that t-stat has been replaced within the last year. Oilfilter housing gasket has just been replaced too.

I'm debating whether I want to do this myself and end up shifting my work hours or bend over and let bmw do it. With something like this I cant get to my usual guy.

[kayger12]

Exp tank is an easy job. Plenty of help available here if you need it

[BCS_ZHP]

And order a new ET cap too, the New ET doesn't come with one.

[Hornung418]

I completely forgot to include that t-stat has been replaced within the last year. Oilfilter housing gasket has just been replaced too.

I'm debating whether I want to do this myself and end up shifting my work hours or bend over and let bmw do it. With something like this I cant get to my usual guy.
Thats great to read. Should be an easy repair then. New hoses and ET and ET cap should do the trick.

[Asiah119]

Plot twist. I took it to a different inde shop. I know the guy w multiple defenders and several bimmer owners go there. They ran another pressure test. No leaks. Said that the water pump was flopping around though. Could get it to wobble with some leverage. Pump is new from when I had my engine swap saga.

[BCS_ZHP]

But you said the back of the headlight was wet, the water pump can't shoot the coolant that far. Water pump normally gets wobbly, loses coolant at the shaft seal. In order to get the headlight wet, if the pressure test was correct, then your ET cap is shot and shooting coolant over at the headlight. A cheap fix to add that cap in.

[Asiah119]

Yeah, they said that when they were doing the pressure test that it was doing a v slow leak at the cap. But yesterday the ET was empty after driving for 20 minutes.

Edit: I really need to find a way to do the coding fix so that my temp gauge actually shows the temp instead of a range.

[ELCID86]

Edit: I really need to find a way to do the coding fix so that my temp gauge actually shows the temp instead of a range.

I really don't think that will help with your issue though. :dunno

[LivesNearCostco]

+1
Very hard (maybe not impossible) for leaking water pump to get back of headlight wet. That suggests ET crack, ET cap, upper radiator hose, or perhaps loose/cracked bleeder screw. Could also be radiator plastic end tank cracked.


But you said the back of the headlight was wet, the water pump can't shoot the coolant that far. Water pump normally gets wobbly, loses coolant at the shaft seal. In order to get the headlight wet, if the pressure test was correct, then your ET cap is shot and shooting coolant over at the headlight. A cheap fix to add that cap in.

[danewilson77]

I've deduced that the long longitudinal cracks in the expansion tank will seal themselves when engine temp is cold, then open themselves up when engine is at NOP/NOT.

"No flamesuit required"

[Hornung418]

But you said the back of the headlight was wet, the water pump can't shoot the coolant that far. Water pump normally gets wobbly, loses coolant at the shaft seal. In order to get the headlight wet, if the pressure test was correct, then your ET cap is shot and shooting coolant over at the headlight. A cheap fix to add that cap in.
When my pump had an internal failure, the coolant dribbled out on to everything and would get flung all around the engine bay. Alternator, headlights, fans...it was a mess. But that was my case.

[LivesNearCostco]

Ah good point, didn't think about that. I will soon be replacing my E46 water pump to try to figure out A) Is that the source of my slow coolant leak, and B) Is it really an EMP Stewart Pump or not?