Coolant disappears, no visual leaks, temperature seems ok.

If your 2012 BMW 535i is losing all of its water but not overheating, there could be a few possible causes:

1. Leak in the coolant system: The coolant system of your car may have a leak, which is allowing the water to escape. This could be caused by a faulty radiator, a leaking hose or a cracked engine block.
2. Evaporative loss: In some cases, the water may be evaporating due to high temperatures. This is common when driving in hot weather, and it can be caused by a malfunctioning pressure cap or a faulty radiator cap.
3. Leak in the water pump: The water pump may be leaking, causing the water to escape from the coolant system.
4. Leak in the head gasket: A leak in the head gasket can allow coolant to leak into the engine oil, causing the water to disappear.

No, check for Leaks it is working like its supposed too....

It is very possible the culprit is the radiator cap.

It can be faulty coolant temperature sensor.Its not sensing exact coolant heat temperature so its overheating then required level.

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Get the coolant pressure tested, its definitely leaking coolant. You will need to get the coolant running line.

Pressure test will help you to know from where exactly coolant/refrigerant is getting leaked.

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For complete step by step troubleshooting i suggest you to go through the help links mentioned below :----

Click the link below :-----

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http://schematicsdiagram.blogspot.com/2012/01/coolant-enters-in-transmission-on.html

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1991 Toyota Camry: Order Coolant Bypass Tube?

http://whatisbyme.blogspot.in/2012/05/1991-toyota-camry-order-coolant-bypass.html

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2002 Toyota Camry: Puff of Blue or White Smoke while Starting?

http://whatisbyme.blogspot.in/2012/05/2002-toyota-camry-puff-of-blue-or-white.html

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1994 Toyota Camry: Coolant Leak?

http://technoanswers.blogspot.in/2012/04/1994-toyota-camry-coolant-leak.html

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2006 Cadillac DTS: COOLANT LEAK AT DRIVER SIDE NEAR FIREWALL?

http://schematicsdiagram.blogspot.in/2012/04/2006-cadillac-dts-coolant-leak-at.html

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MAF, IAT, MAP and Coolant Level Sensor problem all together on Mazda MPV?

http://schematicsdiagram.blogspot.com/2011/12/maf-iat-map-and-coolant-level-sensor.html

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GMC Engine Coolant Temperature (ECT) Sensor Replacing?

http://schematicsdiagram.blogspot.com/2011/12/gmc-engine-coolant-temperature-ect.html

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Loosing Coolant?

http://whoisbyme.blogspot.in/2012/06/loosing-coolant.html

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Coolant temperature sensor dies again and again?

http://schematicsdiagram.blogspot.com/2012/01/coolant-temperature-sensor-dies-again.html

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2000 Daewoo Lanos: Where to Add Coolant?

http://repairhelpcenter.blogspot.in/2012/06/2000-daewoo-lanos-where-to-add-coolant.html

Blue Water Warning Light on Dash?

http://whatisbyme.blogspot.in/2012/07/blue-water-warning-light-on-dash.html

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Replacing Oldsmobile Engine coolant sensor?

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How to test Engine coolant temperature sensor?

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Replace Coolant Sensor Module on Oldsmobile?

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These details will help.

Thanks.

You have a small leak on the rear of engine whioch is difficult to see. Run the engine to operating temperature. Put it on a ramp and examine from underneath with engine idling.

Hello moltn, quite often people completely fill their coolant reservoir, ( the plastic bottle with the cap that says, " coolant " ), If you haven't already, make sure that the coolant level in the reservoir isn't over the FULL line. When it is overfilled, and the engine runs for a few minutes, the heat builds some pressure and forces the extra coolant out through an overfill hose. That overfill hose usually drains, on the ground, in the general area your leak is comming from.
If that is NOT the problem;

Next, we need to find out if it leaks all the time, or, if it only leaks under pressure, ( when the engine is running and warmed up ).

Start the vehicle just long enough to back it up 2 or 3 feet and then turn the engine back off. Raise the hood and visually inspect the area where you seem to leaking from. Allow about 10 minutes and then look to see if you have a new puddle under the vehicle.

If it's a non-pressure leak, you should be able to spot it right away, most likely a loose hose clamp, If so, first look closely at the condition of the hose, if it looks okay go ahead and tighten the clamp, ( you often only need about 1 full turn on the screw/nut that tightens the clamp.)
As rubber hoses age they lose some of their integrity, so clamp should be checked atleast every six months.

If you find nothing leaking, it is likely a pressure leak that is often the result of the engine and coolant reaching their operating temperature and as they do the heat builds perssure and will usually force coolant out of any weak links in the cooling system.

Let the engine run 6 to 8 minutes to allow the vehicle to get to its normal operating temperature.
Look at your temperature gauge, your needle should be about in the middle. Go back and look in the engine compartment again and visually inspect for signs of leaks. You should be able to locate any pressure leaks at this point. As before, if you locate the leak, and it is at a hose, do a good visual inspection of the hose, and the clamp.

Good luck my friend!

your water pump is starting to leak from weep hole

Chances are the coolant is leaking into the intake/cylinder head and being burned in your exhaust. An easy test for leaks involves a pressure test of the system via the radiator cap at your local garage with an ultra violet dye in the coolant .

The leak in your evap system is very small at .020. It is more than likely a small split in a hose somewhere. The cap is probably ok, we rarely find a bad one. If it is a small split in a hose it will only get larger over time. Here is the factory info on the code. We have found that alot of these leaks are from a small hose on the evap canister under the vehicle, but with out looking at your vehicle it is hard to say. If the leak goes away or is no longer large enough to be detected, your light will go out after a few days. These leaks are emmissions related and will not effect the integrity of the vehicle. I would have it checked and corrected if the light stays on at your convienience.

Symptom List:
P0442-EVAP LEAK MONITOR MEDIUM (0.040) LEAK DETECTED
P0455-EVAP LEAK MONITOR LARGE LEAK DETECTED
P0456-EVAP LEAK MONITOR SMALL (.020) LEAK DETECTED
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be P0442-EVAP LEAK MONITOR
MEDIUM (0.040) LEAK DETECTED.
When Monitored and Set Condition:
P0442-EVAP LEAK MONITOR MEDIUM (0.040) LEAK DETECTED
When Monitored: Immediately after a cold start, with battery/ambient temperature
between 40° F and 90° F and coolant temperature within 10° F of battery/ambient.
Set Condition: If there is a leak larger than 0.0409 and smaller than 0.0809 in the
evaporative system.
P0455-EVAP LEAK MONITOR LARGE LEAK DETECTED
When Monitored: Immediately after a cold start, with battery/ambient temperature
between 40° F and 90° F and coolant temperature within 10° F of battery/ambient.
Set Condition: There is a leak larger than 0.0809 in the evaporative system.
P0456-EVAP LEAK MONITOR SMALL (.020) LEAK DETECTED
When Monitored: Immediately after a cold start, with battery/ambient temperature
between 40° F and 90° F and coolant temperature within 10° F of battery/ambient.
Set Condition: There is a leak larger than 0.0209 and smaller than 0.0409 in the
evaporative system.
POSSIBLE CAUSES
LEAK AT GAS CAP
VEHICLE HISTORY AND SERVICE BULLETIN INVESTIGATION
VISUAL AND PHYSICAL INSPECTION
VERIFY EVAPORATIVE EMISSION SYSTEM LEAK
EVAP PURGE SOLENOID OPERATION
INTERMITTENT LDP MONITOR FAILURE
EVAPORATIVE EMISSION LEAK DETECTION
GAS CAP
LDP COMPONENT LEAK

This all sounds like a leaking head gasket, the fast guage swing is caused by air pockets around the temp sensor.