Ok, i decided to create this post because i see lots of bimmers running hot or even overheating. You would say nothing new here, right? Well believe it or not lots of mechanics or shops trying to resolve this problem with no luck and in the end as a final solution they offer head gasket repair, which won’t fix anything.

So here are the main standard problems, applies to any water cooled engine:

1. Radiator cap not sealing well or valve inside is not working anymore causing boiling in your cooling system due to pressure loss. Solution? replace radiator cap every 5 years even if its good.
2. Any coolant leak will create pressure loss and introduce air in the system. Make sure there is no leaks. Use Pressure tester.
3. Thermostat if bad, it stays open on these engines, and you usually get error code P0128 if heater inside burned or you get thermostat jammed error code. usually tstat lasts 70-100k easily.
4. Water pump impeller can slip or even fall apart or bearing might seize causing total failure. Good thing these engines head gaskets are very strong and can sustain serious overheating.
5. REPLACE TEMP SENSORS EVERY 70KMLS, THEY DO GO BAD AND SOMETIMES SHOW LOWER TEMPS THEN IT IS, ESPECIALLY WATER PUMP TEMP SENSOR, LOWER SENSOR IS KNOWN FOR  O-RING LEAK, APPLIES TO ANY BIMMER.
6.  Main engine fan (electric) is bad or fan clutch not working anymore, though even with a bad fan clutch and fully working cooling system you will not get overheating, unless you are in Dubai traffic:) AC fan is very effective even with a bad fan clutch. Since 2004 BMW uses only electric fan for both AC and engine, so if it goes bad, you  will get overheating.

So, i was not going to create simple overheating article you can find anywhere, right? Its gotta be unique on this site! Here we go:

So what to do if there is no leaks and all hoses are new, gaskets etc, pressure tester confirmed no pressure loss, but engine still runs hot overheating transmission as well??? Did you know running hot will destroy all rubber gaskets and other rubber parts? Why? Because engine temps are not consistent like it  was designed! Ok, here is something nobody cares about when trying to fix overheating issues:

NORMAL TEMPS FOR 6cyl=94-98 max

NORMAL TEMPS FOR 8cyl=103-108 max

TO CHECK RUNNING TEMPS YOU NEED TO OPEN HIDDEN MENU:

1) hold reset odometer button until you see the menu

2) go to 19 unlock menu (press button once) and enter (hold the button to enter) the sum of your last 5 vin numbers:

ex: last vin 23657, so sum=2+3+6+5+7=23

3) now go back to menu 7 and hold the button until you see running temps, if you don’t, it means you enter unlock code wrong:

here is a picture of running temps with RECALIBRATED 87C thermostat, these are actually really good temperatures for this and other V8 engines! It will keep your cooling system healthy and will prolong the life of all rubber gasket seals including valve seals. Moreover it will reduce detonation so you’ll get extra power in the city driving! Imagine lowering cooling pressure from 200 to 120??? 200 is what your tire pressure is. It is a big deal, all rubber gaskets run under serious stress and we see tons of exploded hoses, coolant tanks and other expensive leaks like:

wheep hole 2000$ if you install oem pipe

rear cover plate (Tranny needs to be removed)

valley pan (intake removal needed)

Soon we will offer these cooler temp tstats.

 

 

 

HEATER CONTROL VALVE! THIS VALVE DOES NOT LAST! RUBBER SEALS INSIDE BECOME BRITTLE, CLOGGING UP THE COOLANT CHANNELS GOING TO THE HEATER CORE! RESULT IS OBVIOUS=YOU CANNOT BLEED THE AIR OUT OF HEATER CORE=OVERHEATING! THIS ENGINE HAS SELF BLEEDING COOLANT SYSTEM, BUT IT WILL NOT WORK IF THIS VALVE IS CLOGGED.

HERE IS DISASSEMBLED HEATER VALVE FROM 2006 750LI with 98kmls. As you can see rubber seals are cracked and not flexible anymore, BUT if you have working auxillary water pump, you still get okay heat cabin, but system has air pocket, since you need very good flow when bleeding coolant system.

HERE IS THE MAIN PROBLEM: YOU SHOULD SEE A NICE RUBBER SEAL AROUND THE VALVE, BUT ITS ALL BROKEN AND THE WORST PART IT CLOGGED RIGHT CHANNEL COMPLETELY:

SO GOOD RECOMMENDATION IS TO REPLACE IT EVERY 5-7 YEARS AND START EVERY COOLANT SYSTEM PROBLEM FROM THIS VALVE REPLACEMENT. IF THIS VALVE IS GOOD YOU CAN DRIVE YOUR CAR  EVEN WITH LEAKING COOLANT (I KNOW ITS NOT A GOOD IDEA), BUT YOU WILL NOT GET OVERHEATING ISSUES IF YOU KEEP ADDING COOLANT, BECAUSE ENGINE WILL BLEED ITSELF ALL THE TIME IF HEATER CORE HAS NO AIR POCKETS.  REMEMBER COOLANT SYSTEM IS THE MOST IMPORTANT SYSTEM IN YOUR CAR!

SO UNTIL YOU SEE OIL IN THE COOLING SYSTEM, OR COOLANT IN THE OIL OR EXHAUST SMELL FROM COOLANT TANK, DO NOT BELIEVE IN THE HEAD GASKET FAILURE. WHEN HEAD GASKET IS BAD, YOU  WILL KNOW IT FOR SURE:) V8, IS VERY STRONG ENGINE AND ITS NOT EASY TO DESTROY HEAD GASKET BY JUST OVERHEATING, DOESN’T APPLY TO STRAIGHT 6 THOUGH….