This article is about most common BMW cooling system faults and how to diagnose and repair it. Well, to start we need to know what perfect temperature specs for this V8 V12engine. When car is fully warmed up and idling for 10 minutes you should see these numbers: Upper Hose temperature-103-105C note: Lower hose should be within 60-70C, this is very important because it indicates proper cooling system function. Lower hose or coolant output readings should be within 60-70C with open tstat. very common mistake when mechanic thinks he bled the system right, but he doesn't know the heater control valve is clogged and there is no way to bleed the air out and lower hose stays COLD, even auxiliary water pump fails because of this. This screenshot shows proper transmission temperatures, when cooling system is fully functional and sealed: NOTE: Some cars have cold firmware which opens up thermostat earlier therefore engine running temps are lower. ALWAYS REPLACE RADIATOR CAP EVERY 5 YEARS, IT DOESNT LAST FOREVER! If temps stay at 105-110C, it definitively means you have an airlock, which causing overheating and lower hose running cold. This engine has self bleeding system, but it only works if cooling system is in great shape! So most common problem you cannot bleed the air out is HEATER CONTROL VALVE, which always goes bad after 5-7 years or even earlier. Its very easy to replace and costs around 140$. Usually rubber valves crack and deteriorate clogging the valve so you cannot bleed the air out, moreover it clogs heater core, which is a real pain to replace. So remove the valve and at least inspect it: -it should be clean inside and valves are open without 12V applied and easy to blow air through, in other words it should not have any restriction, but word of advice-REPLACE it, don't wait, and it will also improve heat cabin. LEAKS: -Front seal aka weep hole problem can be easily diagnosed checking weep hole on the timing cover Can be easily fixed with aftermarket solutions or with simple aluminum+RTV solution, which actually works pretty good. -Valley pan gasket leak. You need to remove intake to replace it. Be careful not to damage knock sensor which is very common. -Rear cover plate. Hardest point here-you need to remove transmission for that Other leaks include lower hose sensor leak and hoses also get old and is a good idea to replace them every 5 years. Also Vent hose connected to the heads near throttle body goes bad every 5years or 80-100kmls Always pressure test your cooling system- you cannot rely on visible findings saying there is no leaks. You cannot see 30% cooling hoses located in the rear of your engine. MAKE SURE YOU ALWAYS BLEED AIR OUT FROM COOLING SYSTEM EVERY TIME YOU WORKED ON IT: -FILL COOLANT TANK TO FULL WITH BMW COOLANT, LEAVE CAP OPEN. -TURN ON IGNITION (DONT START ENGINE YET) AND SET HEATER TO 90F WITH LOW FAN SPEED. MAKE SURE AUXILLARY PUMP IS RUNNING-YOU SHOULD HEAR IT ON THE DRIVER SIDE, LET IT RUN FOR 5 MINS -START THE ENGINE AND LET IT RUN FOR 5 MINS, CLOSE THE RADIATOR CAP -DRIVE YOUR CAR FOR AT LEAST 30 MINS -NEXT MORNING CHECK THE LEVEL, ADD COOLANT IF NEEDED Always take care of any leaks and check running temps! BMW cooling system is very important not only for the engine but for transmission as well- tranny cooler is connected to the same main radiator. Poor condition cooling system will ruin your engine and transmission very quickly. Running with airlock will eventually deteriorate all rubber gaskets including valve seals and stuck piston rings.
In this article we are going to cover most common engine error codes and most common issues. So don’t be freaked out with CEL and don't rush into BMW dealer- its not that complicated to diagnose it yourself. First you need BMW software (INPA, RHEINGOLD, DIS, GT) or even simple OBD reader can be of great help. Any check engine light can be diagnosed with OBD reader, though you cannot go in details, but in most cases is enough. So you got error codes, now its time to decode them online so you know what those error codes mean. Good idea to check fuel trims and O2 sensor adaptations, it will tell you if you have any vacuum leaks, which will make your engine run very inefficiently, shaking etc. NOTE: IF YOU HAVE 0420, 0430 ERROR CODES WHICH TELL YOU THAT CATALYTIC CONVERTERS ARE NO GOOD ANYMORE, IT MEANS YOUR ENGINE IS BURNING OIL KILLING CATS, SO NEW CATS WILL NOT LAST IF YOU DON'T FIX INITIAL PROBLEM WITH VALVE SEALS!! CATALYTIC CONVERTERS CAN EASILY LAST 300-400K, AND THEIR FAILURE INDICATES INTERNAL ENGINE PROBLEMS... MOST COMMON AIR LEAKS: -CCV or crankcase breathers. Cracked old membrane will create air leak, so DME will increase fuel trim, making it running rich -VACUUM PUMP SEALS AND OIL SWITCH will create vacuum leak as well. They always leak after 5 years or so. Solution is simple- RTV or new seals from BMP DESIGN company, since bmw only sells small oring and they want you to buy 300$ vacuum pump instead. -old oil cap will also create vacuum leak -leaking valve cover gaskets will also create air leaks and more importantly leaking spark plug pipes will create misfires due to fouling ignition coils. If you remove a coil and its covered with oil, it means its leaking and VCG (valve cover gaskets) need to be replaced asap. -old rubber intake boot is very common issue on N62b48 engine or BMW 750i, BMW 750LI -intake manifold gaskets and injector o-rings also don't last forever But be aware that some error codes not necessarily mean you need to replace that or these parts. For example running lean or rich does not mean your O2 sensors or catalytic converters are bad. Always check O2 sensor adaptations, and if they adjust mixture and not stuck, it means youve got something else causing rich or lean mixture and O2 sensors have to adapt the mixture. Sometimes bad Valvetronic or VVTI sensors don't throw error codes but make engine run rough., you can always disconnect VVTI sensor and your engine will run using conventional throttle body approach, and if it runs smooth without VVTI, it means VVTI sensor is not working well or not adapted. POST YOUR COMMENTS BELOW AND I WILL TRY TO HELP, you ca also email me, but since its not my primary job, i can not reply asap. Logic7repair@gmail.com ABS, DSC, BRAKE LIGHT CHRISTMAS TREE?? NO PROBLEM!! So you got very nice Christmas tree on your dashboard?? Well dont worry it happens sooner or later to any BMW. So one of a sudden all lights are on and IDRIVE is going crazy? Don't worry it can be fixed I under 200$!! MOST COMMON CULPRIT IS YOUR ABS, DSC UNIT !!! IT DOES GO BAD VERY OFTEN DUE TO AGE AND HEAT UNDER THE HOOD!! There could be other things (abs sensors, harness issues, etc) causing those lights, but if all lights are on especially angle sensor light is on, it means module is dying, MOST COMMON DSC/ABS MODULE FAILURE SYMPTOM-NO ERRORS WHEN COLD AND AFTER ITS WARMED UP EVERYTHING IS BAD. There are 2 options about it: -Repair DSC module with warranty (best cheapest option). Don't buy used one- it might not last and can also be bad and worst part you have to code it, which is not very simple procedure. Always try to fix it or get new one, WHICH IS SELF CODING AND WILL CODE ITSELF AFTER YOU PUT IT IN. -Buy new module for 600$, self coding- will code itself after you installed it. Great option, but I think rebuilt one is better since its going to be stronger than OEM. Replacing is easy: remove the unit, send it for repair or replace it with new one. Located on passenger side, black unit. You need to remove coolant tank to get access to all bolts holding it. So it wasn't very bad, isn't it? Enjoy fully working dsc system, it will also affect transmission shifting, because its reading lots of signals form DSC unit. Bmw dealer will charge you more than 1200$ for it.