Category Archives: BMW V8 COOLING SYSTEM PROBLEM

BMW THERMOSTAT PROBLEM AND SOLUTION. THE MOST IMPORTANT THING ON THIS SITE!!

THIS POST AFFECTS ABSOLUTELY ALL BMW GASOLINE ENGINES AFTER 1995! M54, M62, M62TU, N62, N63, N52, N47, N63TU AND OTHERS, OR WHY IT IS A VERY GOOD IDEA TO LOWER RUNNING TEMPS!

Why I called it BMW THERMOSTAT PROBLEM? What is wrong with that simple part in BMW?? It looks like a well made thermostat and lasts for a while. Obviously nothing wrong with thermostat quality, in fact its a very good quality part made by BEHR.

So here is the thing. Since 1996 BMW introduced 105C MAP DME controlled thermostat for V8 and 97C for Inline 6 cylinders, which can be controlled by DME when needed.

So here is what it is, Nothing crazy here- just a heater, so DME can heat it up and open it earlier than thermostat is calibrated. Lets say it can open it at 95C versus 105C mechanical specs.

Sounds like a cool idea:

-Run your engine hotter in the  city or low engine loads 105-110C to get better mpg and less emissions with REDUCED POWER OUTPUT, because they think you don’t need it in the city, so to save mpg. May be a good innovative idea.

-run it cool on the highway 90-98C to get full POWER OUTPUT.

BUT HERE IS A DOWNSIDE, OR A SMART BMW MOVE??:

  1. You cannot raise the temperature to 110C without raising coolant pressure (otherwise it will start boiling), So they installed 200 (2.0 BAR) radiator cap. So imagine in the city your cooling system is under serious pressure. Compare it to Toyota 1.0-1.3 BAR max! But they run 87-90C simple conventional thermostats, without any innovations like DME controlled THERMOSTAT, and most Toyotas don’t have any serious issues at least 7-10 years, unlike BMW where you get cooling system failures all the time! Exploded, cracked coolant tanks, hoses, gaskets and other cooling system parts. Any tiny leak will lower cooling system pressure and you will get micro boiling, where OEM 105C thermostat can not open due to that micro boiling and you can experience ALWAYS COLD LOWER HOSE SYMPTOM I’M SORRY BUT IT WASN’T THE CASE FOR 1970-1995 BMW ENGINES WHERE THEY USED 85-95 TSTATS.
  2. Your engine runs at 105-115C will raise oil temperatures to up o 120-130C which is a lot, though they say synthetic oils can easily withstand it. They forgot to tell you all rubber parts don’t like this temperature at all, and rubber becomes dry or even plastic very early: VALVE SEALS, VALVE COVER GASKETS, VALVE COVERS GET WARPED VERY EARLY, ALL RUBBER GASKETS IN THE ENGINE (OIL PAN GASKETS, ALTERNATOR  BRACKET GASKETS, SPARK PLUG PIPE GASKETS, VAUUM PUMP GASKETS, VANOS SEALS AND OTHERS). There is a mechanic’s favorite joke: -IF BMW DOESN’T LEAK ANY OIL, IT MEANS THERE IS NO OIL LEFT!!!!! I’M SORRY BUT IT WASN’T THE CASE FOR 1970-1990 BMW ENGINES , WHERE ENGINES WERE THE MOST RELIABLE! NOW IN 2016 YOU CAN BUY 5YEAR OLD BMW AND START REPLACING ALL GASKETS. DO YOU KNOW HOW MUCH IT COSTS? VALVE SEALS ON V8 MIGHT COST YOU 3000-8000$ EASY! That’s why you can get 5 year old V8 BMW for “cheap”. THERE IS NO CHEAP USED BMW:) IF YOU GOT IT CHEAP, IT MEANS THEY GOT RID OF IT NOT TO DEAL WITH REPAIRS. ALSO OIL LEAKS WIL LDESTROY YOUR SUSPENSION VERY QUICK!
  3. High running temperatures 110+ will get you small detonation, but since BMW has knock sensors, you will not hear it, because DME will retard timing in milliseconds, so everything sounds ok, but engine power is reduced! Try to drive your car in the morning when cold and compare it to traffic city driving when hot. If you Have turbocharged engine you will notice a huge difference, because high temps will affect inter cooler cooling as well.
  4. High running temps can affect cylinder walls cooling unevenly, causing piston rings to lose flexibility and therefore its function, they also call it frozen piston rings (loss of compression, high oil consumption). Thus you might get high oil consumption even on low miles vehicles, but BMW will tell you it is ok  AND WITHIN SPECS to have 1QT/1000MIES! N63, M54, N52 ARE THE WINNERS HERE:) OTHERS CAN BE FIXED WITH NEW VALVE SEALS.
  5. TRANSMISSION: Since transmission has no separate cooler and connected directly to engine radiator, it also run hotter then it supposed to, and if you have always cold lower hose symptom, I can tell your tranny runs way too hot and way over 82C specs, sometimes I see 115-120C temps, running with these high temps will destroy any transmission internals pretty quick. Even 82C is somewhat high, but still okay. best temps 70-80C for this tranny.
  6. In M62B44TU, M62b44 we see lots of issues with chain rail guides broken after 100k-150k, but we do not see this problem on M62B44 E31, where they run conventional 95C thermostat, BUT THE ENGINE IS 100% the same, and this exactly the same engine lasts at least 2x times longer compared to the one with 105C MAP thermostat (E39/E38/E53/RANGE ROVER HSE), needles to say their cooling system lasts 20 years easily. You can ask e31 owners about their experience and how often they replace chain rail guides and compare it to all other running 105C tstat in all other BMW models except E31 of course. My e31 1994 with M60 running 85C tstat had original cooling system, when i bought it in 2012! All parts were original (coolant tank, tstat, water pump, hoses), it had infamous NIKASIL problem (cylinder walls cororoded), but other things were in perfect shape after 20 years and 150kmls! WHICH MEANS BMW QUALITY IS SUPERIOR TO OTHER BRANDS IN SAME CONDITIONS, BUT PHYSICALLY THEY CAN NOT WITHSTAND THESE HIGH TEMPERATURES AND PRESSURE.

So as you can see BMW  innovative thermostat design might sound innovative, but personally I believe it is done to SHORTEN ENGINE AND TRANSMISSION LIFE, SO YOU BUY A NEW CAR EVERY 3-5 YEARS. THATS THE REASON 10 YEAR OLD BMW V8 COSTS LESS THAN TOYOTA CAMRY SAME YEARS AND MILES!

SO TO SOLVE THIS PROBLEM WE CAME OUT WITH INNOVATIVE SOLUTION TO RECALIBRATE ORIGINAL THERMOSTATS AND LET IT OPEN AT 87-90C, VS 105-110C, ITS ALMOST 20C DIFFERENCE AND IT IS HUGE DIFFERENCE, BECAUSE THIS WAY WE CAN REDUCE COOLING PRESSURE TO 1.0-1.3 MAX JUST LIKE ALL NORMAL JAPANESE CARS. ALL RUBBER GASKETS WILL LAST AT LEAST 2X LONGER, BECAUSE AT 110 RUBBER DRIES OUT VERY QUICK. ABSOLUTELY NO ERRORS AND YOU WILL FEEL THAT YOUR CAR RUNS STRONGER IN THE CITY, AND GAS MILEAGE IS ALMOST THE SAME OR EVEN BETTER VS OEM TSTAT. AFTER TESTING IT FOR 4 YEARS I CAN TELL, IT DOES NOT CAUSE ANY PROBLEMS TO THE ENGINE, BECAUSE EVEN WITH OEM TSTAT YOUR CAR RUNS 90-93 ON THE HIGHWAY! WE HAVE 85-95C THERMOSTATS FOR ALMOST ALL BMW ENGINES STARTING FROM 1995.

I UNDERSTAND, LOTS OF YOU WILL SAY BMW ENGINEERS DESIGNED IT, AND WHO ARE YOU TO SAY THAT? WELL, I HAVE MECHANICAL ENGINEER DEGREE AND OUR PROFESSOR ALWAYS TOLD US, THAT 90-95C IS THE BEST RUNNING TEMPS FOR THE ENGINES, EVERYTHING HIGHER GETS YOU DETONATION RISKS AND NOT MAKE MUCH SENSE TO GET A LITTLE BETTER MPG…

HOW ELSE TO EXPLAIN HIGH ENGINE RATE FAILURE IN BMW COMPARED TO SIMPLE TOYOTAS AND HONDAS?? EVEN KIA IS WAY MORE RELIABLE THAN MODERN BMW, THEY ALL RUN 82-87C TSTATS WITHOUT ANY INNOVATIONS. MERCEDES ALSO RUNS IT COOL 90-95 MAX, THEY HAVE OTHER ISSUES, BUT COOLING SYSTEM IS RELIABLE AND NOBODY REPLACES VALVE SEAL GUIDES AFTER 40-60K MILES ON THEM, NORMAL ENGINE CAN EASILY LAST 200KMLS ON ORIGINAL VALVE SEALS, AND SAME PARTS SUPPLIERS USED FOR BOTH BRANDS BY THE WAY.

ALL BMW M ENGINES RUN LOWER TEMP 79C THERMOSTATS, AND THESE ENGINES ARE INNOVATIVE FOR SURE AND THEY LAST MUCH LONGER AND KEEP THEIR VALUE :

  • S54 RUNS 79C
  • S62 RUNS 79C
  • S85 RUNS 79C P/N:1153783615
  • ALL DIESEL ENGINES BMW RUNS AT 88C AND THEY EASILY LAST UP TO 500k MILES WITHOUT ANY LEAKS OR FROZEN PISTON RINGS (THEY HAVE EGR PROBLEM (which can be deleted) BUT ITS NOT RELATED TO OUR TOPIC)

SO APPARENTLY THERE IS NOTHING WRONG TO RUN THESE ENGINES COOLER, JUST LIKE ALL OTHER NORMAL CARS DO. AS YOU UNDERSTAND BMW EVOLVED A LOT SINCE 1995 AND USED BMW CARS DEPRECIATED CRAZY SINCE THEN, ONLY BECAUSE OF RELIABILITY ISSUES. COULD BE COINCIDENCE??? I DON’T THINK SO, I KNOW TONS OF PEOPLE WHO DUMPED THEIR CARS FOR NOTHING, BECAUSE OF THE REPAIRS. IMAGINE NEW 7″ COSTS 100K AND 10 YEARS LATER YOU CAN GET IT FOR 10K OR LESS ALMOST CAMRY PRICE! SOMEONE SAID BECAUSE BMW USES LOW QUALITY RUBBER GASKETS, IT NOT TRUE, THEY USE TOP NOTCH QUALITY CONTROL.

I HIGHLY DOUBT BMW CAME UP WITH THIS 105c TSTAT JUST TO SAVE MAY BE 1-2% MPG, HOW COME OTHER CARS DON’ T DO IT???? IT IS MUCH EASIER TO SELL LOWER MPG CAR, RIGHT??

ANYWAYS, IT IS UP TO YOU TO BELIEVE IT OR NOT, BUT SIMPLY TYPE “BMW LEAKING OIL OR COOLANT N62, N63” IN GOOGLE AND THINGS WILL LOOK VERY DIFFERENT FROM OTHER CARS MAINTENANCE.

 INTERESTING STORY:

One friend of mine bought 750li 2007 with 103k in okay condition with ONLY check engine light on, so when i inspected it, i was pleasantly surprised:

  • engine had zero leaks from valve covers and valve seals were in okay shape!!!! at these miles it is almost 100% valve seals are gone and valve covers leak along with upper timing covers and other things!! so no oil leaks
  • cooling system had ZERO new parts installed, everything was in okay shape, all hoses original and no issues at all. even coolant tank had no cracks, which is very rare. so all components lasted 100k!!! and still lasting
  • THE ONLY CHECK ENGINE LIGHT INDICATED JAMMED THERMOSTAT, WHICH IS NORMAL BECAUSE THEY DON’T LAST FOREVER. SO PREVIOUS OWNER WAS CHEAP AND NEVER TOOK IT TO BMW AFTER WARRANTY EXPIRED!!! BUT THIS JAMMED OPEN THERMOSTAT (FIRST OCCURRED AT 50KMLS) LET HIS CAR RUN AT 80-90c MAX, BECAUSE IT WAS NEVER 100% CLOSED DUE TO WEAR AND TEAR, SO THIS IS WHAT SAVED HIS CAR FROM EXPENSIVE REPAIRS. ABSOLUTELY ZERO NEW PARTS WERE INSTALLED ON THIS ENGINE AND ZERO LEAKS ANYWHERE! CAR RAN PERFECT!

SO HE REPLACED THERMOSTAT AND NO MORE ERRORS, BUT IN 3 MONTHS HIS VALVE COVERS STARTED LEAKING BADLY….. 5 MORE MONTHS LATER HE GOT INFAMOUS ALTERNATOR BRACKET LEAK (800$+)

THAT’S WHY WE DESIGNED THE WAY TO RE CALIBRATE ORIGINAL THERMOSTATS TO RUN AT 90-95C. NO ERRORS WERE THROWN, ENGINE RUNS PERFECT SINCE 2013 AND NO NEW LEAKS.

WE CAN RE CALIBRATE ANY BMW AND OTHER BRANDS THERMOSTATS, YOU CAN EMAIL US WITH YOUR QUESTIONS.

NEW ORIGINAL RE CALIBRATED THERMOSTAT FOR N62, N63 WILL COST YOU ONLY 120$ (FAST&FREE SHIPPING INCLUDED), WHICH IS THE BEST UPDATE FOR YOUR HOT RUNNING ENGINE. SOON IT WILL BE POSTED ON EBAY, SO IF YOU FELL MORE COMFORTABLE YOU CAN BUY IT FROM THERE, BUT ITS A LITTLE EXTRA DUE TO EBAY FEES. ALSO WE RECOMMEND INSTALLING NEW HEATER VALVE EVERY 5-7 YEARS (standard symptom-no cabin heat or one side is hot and another is barely hot, also it might cause overheating as well, because you cannot bleed the air if tat heater is partially clogged). If everything is good and no leaks i recommend replacing: thermostat, heater valve, radiator cap. With this 90C thermostat you can easily install 140 (1,4 BAR) cap from diesel engines, because pressure is reduced due to reduced boiling point, which is a good idea, since you do not need to build high pressure anymore, though with 90C thermostat it will rarely get to that point even with stock 200 cap. All bmw diesel engines run 140 (1,4 BAR) caps, same thing with old M20 engines, they run similar temp 75-80C TSTATS or even lower. As you know those old engines could last 500kmls easy, isn’t it interesting coincidence: the lower tstat is, the more reliable engine is? You can try our thermostat, and if you are not happy you can return it for a full refund. In most cases people respond with better torque and throttle response after installing our thermostats. Obviously you noticed your BMW runs better before 100C and becomes weaker after 100C.


Choose N62/63 or M62B44TU, if you need another tstat pls email



EBAY LINK TO 90C THERMOSTAT N62/63