Help me diagnose this coolant level issue

[Genes1s]

I had the cooling system re-done about 1 year ago. Ever since then I never got my coolant level right. The coolant has always gone 1" below Kalt and stayed there if I didn't open the reservoir or touched anything. As soon as I opened the reservoir cap (AFTER sitting for one day), the coolant went up all the way to the neck, never spilled though. When I opened the cap, it sounded like the reservoir was pressurized. When I went for a drive, the coolant went back exactly like before, 1" below the kalt. Car never overheated, no code, temp hovered around 200-208 in the summer traffic, might get it up to 210 and 215 if I hammered it. Car pulled like a freight train, use oil maybe about 1/5 quarts in 3000 miles, and engine felt good.

I even reflushed the coolant using Airlift cooling purge to check for leaks and remove air pocket and no luck. I bled it multiple times following the Bentley and few other DIY here with no luck either.
https://www.youtube.com/watch?v=Eouud7YLtEw

I did the engine block chemical test and came back negative. The only thing I can think off is small HG leak. So I did the leak down test, each cylinder is between 4.4%-2.2% loss. No bubble or anything came out of the reservoir.
https://www.youtube.com/watch?v=G_g365eg-Y8

Perhaps the reservoir cap is defected (brand new)?

Something is not right.

Thanks

[UsernaM3]

Have you double checked all of the hose connections?

Edit: pressure test I guess would’ve shown that. Hm

[Genes1s]

Yes, Hoses are new other than the ones go to heater core. Clamps are new and tight as well.

[UsernaM3]

Yes, Hoses are new other than the ones go to heater core. Clamps are new and tight as well.

Does the car blow hot air at temp while idling?

[Genes1s]

Does the car blow hot air at temp while idling?

Yep.....

[R Shaffner]

I've had something like that happen on my M62s. I think our cooling systems are mostly similar.

On a properly filled and bled system, if I remove the expansion tank cap and then crack open the bleed screw, the level in the expansion tank will rise to show on over-filled condition. That's because the loose bleed screw let air back into the top of the radiator, which let gravity pull coolant down from the higher level of the radiator into the lower expansion tank.

At that point, if no coolant has flowed out, then the system is still full of coolant, it just has more coolant than normal in the tank and some air in the radiator. Then, if I tighten the bleed screw, put the cap back on and drive the car, it will self-bleed to put that coolant back in the top of the radiator and the air back in the expansion tank where it belongs. When I open the expansion tank and check the cold level the next morning, it will be at the same full level that it was before.

So, your system might be basically full and cooling well. Sounds like it is. Having the level 1" below Kalt (when the engine is cold) doesn't matter. If it's properly bled then the rest of the system is full of coolant and you have just slightly less coolant in the expansion tank. Adding a little more to the tank while cold should normally take care of it.

However, it sounds like you can't just open your cap when the engine is cold and add a little more coolant, not if the coolant level immediately rises to the neck of the tank. It sounds like your system is letting air into the top of the radiator when you take the tank cap off, like mine does when I loosen the bleed screw. I've never heard of that. Wonder if your M3 system is somehow different, or if there's a problem with the bleed passages in the radiator and tank on your car.

What happens if you start the car and then open the tank while it's still cold? Does the level stay in the same place? (I'm thinking it will.) Can you then add a little coolant to bring it up to Kalt? If so I bet you can put the cap back on, drive it, and it will read full when cold the next morning.

[R Shaffner]

Here's a thread I started about these cooling systems that might help:
https://www.bimmerforums.com/forum/s...ding-Explained

Also, I should have asked what your cooling system level is when your first start the car from cold. Does it change or stay 1" below Kalt after you start it? If it drops lower still, then there might be something else going on. More on that if needed.

[jayjaya29]

This is a known issue. If the cooling system is working fine and the coolant level isn't dropping over time just leave it alone.

I've found that if you start the engine (when fully cold), you can open the reservoir cap and the fluid level won't go up.

[Genes1s]

Here's a thread I started about these cooling systems that might help:
https://www.bimmerforums.com/forum/s...ding-Explained

Also, I should have asked what your cooling system level is when your first start the car from cold. Does it change or stay 1" below Kalt after you start it? If it drops lower still, then there might be something else going on. More on that if needed.

IF I didn’t open the reservoir cap, the coolant level is always at 1” below the kalt line, whether it is cold , hot , and in between. The coolant only rises when I open the cap. Now, I have not checked the coolant level once I start the car per your suggestion.

I’m deleting the mechanical fan and installing electric fan with lower T-Stat. I’ll be once again flushing the coolant and start this process all over.

I’ve read your post about this issue above, it was very good explanation and you had the same issue as I have basically. It just odd that BMW do this for packaging exercise. There is still room to put the tank above the radiator level next to washer fluid, instead of next to the radiator. Looking at your diagram, those passages between the top of radiator to the tank got so convoluted and small, perhaps it makes it harder for the system to “self bleed” correctly as it was intended.

[DrftKingIII]

I had a similar scenario with my car, turned out to be a small breach in the head gasket.

I'd set the coolant level cold, close the cap. Drive the car, leave it overnight. Next day at full cold, the level would be down slightly and opening the cap would reveal a hiss (pressurized) and the coolant level would raise again.

Obviously as the system heats up it pressurized but as it cooled it returned to the original coolant level as the pressure decreased to it's original level. The small breach was adding additional pressure to the system, resulting in a lower level in the overflow (compressed) and a hiss from the cap after a full cold/hot/cold cycle.

[Genes1s]

I had a similar scenario with my car, turned out to be a small breach in the head gasket.

I'd set the coolant level cold, close the cap. Drive the car, leave it overnight. Next day at full cold, the level would be down slightly and opening the cap would reveal a hiss (pressurized) and the coolant level would raise again.

Obviously as the system heats up it pressurized but as it cooled it returned to the original coolant level as the pressure decreased to it's original level. The small breach was adding additional pressure to the system, resulting in a lower level in the overflow (compressed) and a hiss from the cap after a full cold/hot/cold cycle.

How did you diagnose it was the HG?

[DrftKingIII]

How did you diagnose it was the HG?

Combination of the added pressure to the cooling system that would increase with driving and the oil sample test showing elevated levels of potassium and other things found in coolant.

[M3C]

Had similar issue years ago with coolant level drop when engine is running...it was the reservoir (inside pipe cracked/broken), after replacing with new one problem gone.

[Genes1s]

Update: 10/1/20

Started the car after its been sitting for few days and with the reservoir cap opened, I saw the coolant inside dropped right away. Did about 25 miles highway commute and see the coolant stays where it was at. Let the car sit for few hours, opened the reservoir cap and the coolant was rising slowly to where it was when cold (before I started the car when it was cold).

I'll do oil analysis next time i do oil change too.

Side topic here, I'm installing Spal Fan. Questions for you experts.

1. Do you replace your radiator cooling temp switch (that controls the aux fan) to lower temp 80/88 and use this to trigger the Spal or do you use a seperate switch/probe to trigger the Spal?
2. If you use dedicated switch to trigger the SPAL, where do you do it? Lower rad hose that circulate the coolant FROM radiator to Engine block? or do you use the probe and stick it to the radiator?


I'm leaning toward doing dedicated switch to trigger the SPAL and leave the aux fan switch alone as is.

Thanks

- - - Updated - - -

Had similar issue years ago with coolant level drop when engine is running...it was the reservoir (inside pipe cracked/broken), after replacing with new one problem gone.

Perhaps my brand new one isn't so brand new??

[DrftKingIII]

Update: 10/1/20

Started the car after its been sitting for few days and with the reservoir cap opened, I saw the coolant inside dropped right away. Did about 25 miles highway commute and see the coolant stays where it was at. Let the car sit for few hours, opened the reservoir cap and the coolant was rising slowly to where it was when cold (before I started the car when it was cold).

I'll do oil analysis next time i do oil change too.

Side topic here, I'm installing Spal Fan. Questions for you experts.

1. Do you replace your radiator cooling temp switch (that controls the aux fan) to lower temp 80/88 and use this to trigger the Spal or do you use a seperate switch/probe to trigger the Spal?
2. If you use dedicated switch to trigger the SPAL, where do you do it? Lower rad hose that circulate the coolant FROM radiator to Engine block? or do you use the probe and stick it to the radiator?


I'm leaning toward doing dedicated switch to trigger the SPAL and leave the aux fan switch alone as is.

Thanks

- - - Updated - - -



Perhaps my brand new one isn't so brand new??

I have the SPAL wired to kick on at 80* on the 80/88 switch.

I see it kick on at about 95* cylinder head temperature (205ish* F). Obviously there's a big difference between cold side of radiator temperature and cylinder head but personal opinion is that I wouldn't want my cylinder head to be getting beyond 215-220 and wouldn't want it kicking on any later than where it's at currently.

[AHS]

As long as it's not using coolant, and there's no sign of coolant in the oil, let it be. If the cooling system holds pressure overnight, let it be. Remove the cap when the engine is cold. Start the engine. If the coolant begins to rise in a minute or so, then you most likely have a leaking head gasket. If you have had times when the engine turns over like the battery is low, and then stumbles when it first starts, then you most likely have a leaking head gasket that is allowing coolant into one of the cylinders as it sits. ( hydro lock ).
I can explain how I know this, but haven't the time right now.

Strange motors that will run for a long time with this condition before the gasket fails to the point where it becomes obvious.

[Cos270]

As long as it's not using coolant, and there's no sign of coolant in the oil, let it be. If the cooling system holds pressure overnight, let it be. Remove the cap when the engine is cold. Start the engine. If the coolant begins to rise in a minute or so, then you most likely have a leaking head gasket. If you have had times when the engine turns over like the battery is low, and then stumbles when it first starts, then you most likely have a leaking head gasket that is allowing coolant into one of the cylinders as it sits. ( hydro lock ).
I can explain how I know this, but haven't the time right now.

Strange motors that will run for a long time with this condition before the gasket fails to the point where it becomes obvious.

In the last scenario (hard start, stumbling, etc.) did you see any white smoke from the exhaust? I've been having similar symptoms but thought it was my starter or possibly a small vacuum leak since I just replaced my battery a few months ago. Got a blackstone oil report on the last oil change (1K miles ago) and passed with flying colors. Not using any coolant either. Just hit 145K miles.

[Genes1s]

Update 10/16/20.

coolant level have been stable at kalt when cold and about 1/2” higher when hot. Coolant still rises up about 1/2” when I open the cap when cold but comes back as soon as I start the engine.

what I did different this time:
I’m not sure if there is any harm of doing this, but I felt like this would force all the air out.
I installed a tube to the bleeder screw and connect it to the opened reservoir. Parked my car on a steep driveway and let the engine run till the thermostat opened. I reved it to 2500 to circulate the water pump and I could see bubbles showing up thru the tube. I did this with hot heater and slow fan as well. Basically the same procedure as normal bleeding process other than connecting the tube from the bleeder screw to the reservoir cap. Once I didn’t see any more bubbles, all coolant, flowing thru the tube, I stopped. This was roughly about 15 minutes from cold start. My heater was so much hotter now than before. I wish I have taken down the temperature for hot air before.

So moral of the story, I think when I bled it first time or second time around, there were still air in engine block. Car has been about 100 miles since I did this last bleeding process and coolant level has been stable. My engine temp is also a couple degree lower too.

[UsernaM3]

Update 10/16/20.

coolant level have been stable at kalt when cold and about 1/2” higher when hot. Coolant still rises up about 1/2” when I open the cap when cold but comes back as soon as I start the engine.

what I did different this time:
I’m not sure if there is any harm of doing this, but I felt like this would force all the air out.
I installed a tube to the bleeder screw and connect it to the opened reservoir. Parked my car on a steep driveway and let the engine run till the thermostat opened. I reved it to 2500 to circulate the water pump and I could see bubbles showing up thru the tube. I did this with hot heater and slow fan as well. Basically the same procedure as normal bleeding process other than connecting the tube from the bleeder screw to the reservoir cap. Once I didn’t see any more bubbles, all coolant, flowing thru the tube, I stopped. This was roughly about 15 minutes from cold start. My heater was so much hotter now than before. I wish I have taken down the temperature for hot air before.

So moral of the story, I think when I bled it first time or second time around, there were still air in engine block. Car has been about 100 miles since I did this last bleeding process and coolant level has been stable. My engine temp is also a couple degree lower too.

My saying for this is “I need the air coming out to be spicy hot, not just hot.”

Lol glad it’s on the up and up.