Is any coolant loss tolerable?

[m3f_BAM3]

I had my coolant flushed about a year ago.



This morning, when I started the car, the "low coolant level" indication came up on the OBC. I came home for lunch and got the car in the air. As far as I can tell all hoses going into and out of the radiator are in good shape. I couldn't find any other evidence of a coolant leak anywhere. Pulled the dipstick and the oil looked good also.



When i opened the radiator cap, the level looked really low but to my surprise it didn't take much water at all to get it back up to the correct level.



So my question.....is there a tolerable amount of coolant loss or do I have a larger problem?



FYI - the car has 52,xxx miles on it and has the original radiator and water pump. All other maintenance is up to date.

[m3f_roarE36M3]

When you did the flush a year ago... did you replace any components?


I had a slow leak coming from underneath the t-stat housing. Was barely noticeable unless u looked really careful. It was an aluminum housing and I replaced it with OEM and have been fine ever since. Not saying that is your issue, but look around really good. 52k is not a lot of mileage, but that doesn't mean the cooling system doesn't need to be replaced. I'd try to pinpoint where exactly the loss is before you throw parts at it.

[m3f_cscat87]

Check to make sure you're actually losing coolant. Occasionally I'll get a low coolant warning on the OBC when I start the car, and its just a fluke in the sensor. Restart the car and there's no warning. Happens to me maybe 2-3 times a year. Of course if its happening often, you may have an issue, but could be as simple as a bad sensor.

[m3f_M3n00b]

I usually have to add a little coolant each year.

[m3f_aeronaut]

Checks the basics; leaks, air pockets, etc. If nothing found, either watch very closely (check daily for a while), or as sensitive these cars are to cooling problems, I'd get an oil analysis done. $25 or so, and peace of mind. (I've tried a few places, and really like Blackstone Labs...but any will detect coolant in the oil.)

[m3f_fiveightandten]

2 things:


-Coolant will contract and take up less space when it's cold, especially in the winter. It will expand when hotter.


-Turn your car off, let it cool. With a cold motor, crack the bleed screw open and watch what happens. The coolant will go rushing into the expansion tank and the level will raise a good deal higher than it was. I'm not 100% certain why this happens, but it does. A buddy of mine was worried he was consuming coolant and noticed this. We confirmed it with my car as well, and a 3rd E36 M3. They all seem to do it.


Add those 2 things together, and i'm sure the car is fine. Double check that behavior to be sure though.

[m3f_zoti]

If the expansion tank is at normal level then your level sensor is probably all gummy. I would pull the expansion tank out and wash it really good and also the sensor.

[m3f_antik]

Given a perfectly functional cooling system, I'd find myself adding a little (the volume in the expansion tank) once or twice a year.



Ultimately, the direct answer to your question is: so long as you're willing to tolerate it and the engine is staying cool, yes. If you pouring a cup a day on the ground, you'd be annoyed and get it fixed. If the engine was overheating, you'd be concerned about the longevity of the vehicle and you'd get it fixed. Otherwise, do your due diligence to check for leaks, monitor the system, and if all seems well don't stress it.



Some problems can wait until they get worse before you take action. Sometimes, they need to get worse to be visible enough to create an accurate repair diagnosis.

[m3f_WICSTA]

If the expansion tank is at normal level then your level sensor is probably all gummy. I would pull the expansion tank out and wash it really good and also the sensor.

I did this, and it worked. All is well

[m3f_scoobiedoo2029]

i have 165k miles and recently did a complete coolant over haul last winter, the only thing thats old is the heater core and the two hoses going to it and like one or two other random hoses to like the throttle body or something.



i loose about a cup of coolant every 6 months, i blame the heatercore/head gasket/expansion tank cap. mostly the expansion tank cap. there is sometimes a slight discoloration under the cap that i think is from a small amount of coolant seeping out sometimes.

[m3f_iPhantom]

2 things:



-Coolant will contract and take up less space when it's cold, especially in the winter. It will expand when hotter.



-Turn your car off, let it cool. With a cold motor, crack the bleed screw open and watch what happens. The coolant will go rushing into the expansion tank and the level will raise a good deal higher than it was. I'm not 100% certain why this happens, but it does. A buddy of mine was worried he was consuming coolant and noticed this. We confirmed it with my car as well, and a 3rd E36 M3. They all seem to do it.





Add those 2 things together, and i'm sure the car is fine. Double check that behavior to be sure though.

I've been experiencing this every time I start the car in this unusually cold weather around here. Pretty much if I start the car, cold, and it's below say like 40F, the coolant indicator will turn on for a few minutes until she's warmed up. Never seen the light until this winter came around. No leaks from what I can tell. Car is '02 with 75k.



So am I correct in saying these cars should never need a flush of the factory coolant unless there are leaks/contamination or someone flushed with and mixed with tap water?

[m3f_M3n00b]

I've been experiencing this every time I start the car in this unusually cold weather around here. Pretty much if I start the car, cold, and it's below say like 40F, the coolant indicator will turn on for a few minutes until she's warmed up. Never seen the light until this winter came around. No leaks from what I can tell. Car is '02 with 75k.



So am I correct in saying these cars should never need a flush of the factory coolant unless there are leaks/contamination or someone flushed with and mixed with tap water?

You should flush every two years.

[m3f_badgtho]

I've been experiencing this every time I start the car in this unusually cold weather around here. Pretty much if I start the car, cold, and it's below say like 40F, the coolant indicator will turn on for a few minutes until she's warmed up. Never seen the light until this winter came around. No leaks from what I can tell. Car is '02 with 75k.


So am I correct in saying these cars should never need a flush of the factory coolant unless there are leaks/contamination or someone flushed with and mixed with tap water?

You are entirely 100% and completely incorrect. EVERY fluid in the vehicle must be flushed periodically. Coolant is one of the most important.


Being that your car is an 02 it's not an e36. Let's start there. What car are we speaking about and are you the original owner.

[m3f_englishtom1596q]

As said coolant should be replaced every 60,000miles usually. The coolant breaks down and the boiling point will lower/freeze point increase. Also the additives break down and will begin to turn acidic, eating away at the inside of the motor, hoses, radiators etc.


Coolants usually 60K

Trans is usually 50K for a manual

Diff on these cars like 50K


Or if you really want to take care of it and keep it happy

Coolant every year

trans every 2 years

diff every year.


Thats just me.

[m3f_scoobiedoo2029]

As said coolant should be replaced every 60,000miles usually. The coolant breaks down and the boiling point will lower/freeze point increase. Also the additives break down and will begin to turn acidic, eating away at the inside of the motor, hoses, radiators etc.



Coolants usually 60K

Trans is usually 50K for a manual

Diff on these cars like 50K



Or if you really want to take care of it and keep it happy

Coolant every year

trans every 2 years

diff every year.



Thats just me.

coolant does something weird as well, has something to do with electrolysis or something, it either gets conductive or less conductive or something, i cant remember but its an important issue regarding an engines electrical system.



i saw my post on the previous page, i still blame my minor coolant consumption on the expansion tank and cap. i seem to need about a coffee cup full of coolant every year, and usually in the summer,, think im going with that zionville shroud setup mostly because shiny not plastic.