BMW thermostat problem and solution
We offer you “Cold” thermostats for petrol-engine BMW and Rolls-Royce cars with the engines: N62, N62N, N63, N63N, N73, N74, N74B, N74L, N74R, S55, S63M, S63N, S63R, M52, M54, M56, M62.
The earlier “Cold” thermostat is installed in the engine cooling system, the more there will be savings on the repair and maintenance of the engine and all the mechanisms and modules which are in direct contact with it, such as: transmission, gaskets, valve seals, pipes, sensors, plugs, coils, expansion tank, various plastic items, wiring etc.
With a decrease in the engine operating temperature:
the pressure in the cooling system reduces by approximately 1.5 times;
oil properties are retained longer, and oil consumption is reduced;
engine detonation is decreased, thereby adding the engine power;
gearbox temperature drops.
By having “Cold” thermostat installed, you will save ten times more that the cost of the thermostat itself. “Cold” thermostat is an investment that quickly pays off and generates profit due to lower maintenance costs in future.
For modernization (lowering the opening temperature to 90 ° C), we use only original BMW thermostats or high-quality BEHR and WAHLER thermostats which are not inferior to original thermostats in reliability. A slight variation in the “Cold” thermostat opening temperature is allowed within ±2°C (from 88 to 92°C). In case you need “Cold” thermostat, the number of which is not present in the table below, please contact us and we will try to find it for you.
We offer you “Cold” thermostats that are modernized in such a way that their opening temperature will remain constant over time. They have no elements that could jam, fail, or lead to a coolant leakage. Our “Cold” thermostats do not require connection to a computer to adjust their work.
Images from the thermal imager before and after replacing the standard thermostat with a “cold” one under the same conditions: engine speed, operating time, ambient temperature.
A thermostat is a valve that allows access to a full range of cooling through a radiator at a time when the small circle has already warmed up. A thermostat cannot directly reduce the temperature of the coolant. And if it is fully open, to open it wider is impossible. If the engine temperature starts to rise noticeably above 90 °C (± 2 ° C) with the thermostat completely open, this means that there is not enough antifreeze in the system. Or the electronic cooling fan of the engine and air conditioner radiators cannot cope with the cooling of the engine radiator. The fan starts to work when the air conditioner is turned on or when the temperature of the lower branch pipe of the engine radiator is 65 °C or higher. There may also be issues with the water pump and clogging of the cooling system, especially the engine radiator, both inside and outside.
7 main reasons to install a “cold” thermostat!
Reason № 1: “Сold” thermostat allows you to save on maintenance and repair of the engine, including the various elements and fluids that are in contact with it.
Since 1996, BMW has introduced a controlled thermostat with a temperature of 105 °C for petrol V8 engines, the opening temperature of which can be regulated using an electronic DME control unit. And since then, a controlled thermostat with an opening temperature of 105 °C has been a weak point of BMW engines of M and N series (BMW thermostat problem). A heating element of a controlled thermostat is in the form of a spiral. With its help, you can open a thermostat below the temperature for which it is calibrated. For example, when the spiral is heated, it may open at a temperature of 95 °C instead of 105 °C. What is it done for? First of all, the temperature should be in the range of 105-110 °C when driving in the city at low loads and speeds. This is done under the pretext of better combustion of the fuel, thereby slightly reducing the output of CO and consumption by 1-2%. But due to increased detonation, the engine starts to work incorrectly and at some point the fuel consumption may, on the contrary, slightly increase. And for this insignificant reduction in CO and a very dubious reduction in consumption by 1-2% while driving in the city you pay an incomparably high price. Reducing engine power at a temperature of 105-110 ° C is nothing compared to how much the life of the engine and all its surrounding elements is reduced, including the gearbox. Therefore, V8 and V12 engines are the most susceptible to heat stroke. First of all, all this is done by very “honest” marketers in order for you to buy a new car every 3-5 years. They also do not earn less from selling new parts to those who cannot afford to buy a new car. If you think that the engines of the M and N series produced since 1996 are designed to work at such high temperatures, then look at how the engine temperature drops on the highway (at high speeds and loads). It can be 90-98 °C, since the DME electronic control unit supplies voltage to the heating element of the controlled thermostat, causing it to open earlier in order to reduce the level of detonations and increase the engine power. Almost all BMW sports engines are equipped with thermostats or firmware tuned to operating temperatures not exceeding 90-100 °C. For example, Alpina N62B48 4.8is engines are often with firmware tuned to lower temperatures, so they serve much longer. In the vast majority of cases, the V8 engines (mainly N62, N63) start to have problems with the leakage of oil and coolant with low mileage. You can check it yourself, for example, by googling “BMW N62, N63 oil leakage” or “BMW N62, N63 coolant leak”. The difference from the other cars will be significant. For many owners of BMW cars with engines which worked at a temperature of 105-110 °C for a long time is more profitable to sell a car at a price below market, than to invest in repairing it. And most of this money is spent on engine and gearbox repairs. Thanks to controlled thermostats with an opening temperature of 105 °C, spare parts sellers and service workers have a steady and stable income. And you are the one who spends a lot of time, nerves and not small money on the car maintenance and repair. How else can one explain frequent failures of the BMW engine compared to the Toyota and Honda engines? Even Kia engines are much more reliable than modern BMW. And this is primarily due to the fact that they operate at temperatures of 82-87 °C without any controlled thermostats. The Mercedes engine also works at low temperatures of 90-95 °C. Although these cars have other nuances, the leakage of oil and coolant are much less common for them. And let those “specialists” (who think that BMW engineers know better what temperature to set for the engine) explain why BMW 11 53 7 836 155 thermostat (BEHR analog: THD 1 79) with an opening temperature of 79 °C is installed on BMW sport cars of M3 (E90, E90LCI, E92, E92LCI, E93, E93LCI), M5 (E60, E61 LCI ), M6 (E63, E64) series!!!
And the engines of these sport cars are very reliable and serve much longer. It only says that BMW engineers are well aware of the optimum engine operating temperature. But under the pressure of environmentalists and marketers, they are forced to raise the engine temperature under the pretext of negligible fuel economy when driving in the city and a slight decrease in harmful emissions. In reality, just after the expiration of the warranty period, your car turns into a continuous source of income for them. Below is one of the most problematic, often breaking and costly to maintain V8 N63 engine, since it has to work at a temperature of 105-110°C. But thanks to the “Cold” thermostat you can significantly extend its service life and reduce its repair and maintenance costs.
Reason №2: The “Cold” thermostat allows to reduce the operating temperature of the gearbox, as its heat exchanger has a common cooling circuit with the engine. Due to the decrease in operating temperature, the gearbox service will increase significantly.
The gearbox heat exchanger does not have a separate cooler but is included in the general cooling circuit with the engine. This means that the increased engine temperature is transmitted directly to the gearbox. The gearbox is especially affected by high temperatures. It starts to twitch and fails much faster. And if the box thermostat sticks in or the heat exchanger is clogged inside by friction discs working off, and also the box oil from high temperatures ages faster and loses its properties (but dealers say that ‘it is for the entire service life and it is not necessary to change it’), then the situation for transmissions is becoming critical. If the thermostat of the gearbox jams, or the heat exchanger is contaminated by friction discs, or the gearbox oil deteriorates from the high temperatures, then the situation for transmissions becomes critical. But dealers say that the oil does not need to be changed during the entire service life. At the same time, no warning that the gearbox is overheated is not displayed on the dashboard.
Reason №3: The service life will be longer and oil consumption will be reduced. At a lower temperature of the oil, it will not have a strong aggressive effect on the rubber gaskets leading to their destruction, followed by the flow of oil.
When the engine temperature is 105-110 °C, the oil temperature in the crankcase rises to 110-130 °C (and this is very much). At such high temperatures the oil ages much more rapidly, oxidizes, and therefore should be replaced frequently. Modern oils are chemically aggressive reagents to the rubber elements of the engine. And the higher the oil temperature, the stronger the destruction process. Despite the fact that BMW uses very high quality rubber gaskets, they still can’t stand the aggressive oil heated to high temperatures. With the “Cold” thermostat, new gaskets will serve at least 2 times longer and even after that they will not flow as strongly as at an engine temperature of 105- 110 °C. The following are the main consequences of a high oil temperature:
At an engine operating temperature of 105-110 °C, the oil burns much faster, which leads to its increased consumption and engine coking. But due to the “Cold” thermostat, oil service life will increase markedly.
The rubber elements of the valve seals quickly become as hard as plastic at elevated oil temperatures. This results in increased consumption of the engine oil and smoke at sharp pressing of the gas pedal.
Increased oil temperature, especially after a long time of use, leads to the destruction of the oil sump gasket (pan), which subsequently becomes the cause of oil leakage.
Oil falls on the rubber suspension elements. As a result, the rubber begins to swell, which leads to its destruction and shortened service life. This also applies to all rubber products and nozzles that are in contact with oil flowing from the engine.
Increased oil temperature leads to rapid wear of the gaskets of the oil cup, which causes oil leakage.
Contamination of the oil filter increases due to the rapid aging of the oil under the action of elevated temperatures.
At high temperatures, the oil ages much faster, which leads to the fact that cylinder rings are coked. Also, high operating temperatures can cause uneven cooling of the piston system. Because of this, the flexibility of the piston rings and as a result their functions are lost. All this leads to increased oil consumption.
Due to the increased oil consumption, the exhaust valves (and in severe cases the intake valves) are coked up, which will require cylinder head bulkhead in the near future.
With increased oil consumption and its incomplete combustion, catalysts quickly fail, which leads to the exhaust clogging and destruction and subsequently a serious drop in power.
Increased oil consumption leads to coking of the spark plug electrodes. This will lead to misfire and unstable engine operation. In this case, the spark plug must be replaced.
Reason №4: The engine cooling system will last much longer, since the pressure in the system will drop from 2 to 1.4 bar, and the temperature will be lower by 15-20 °C.
With an increase in the coolant temperature, there is also a noticeable increase in the cooling system pressure, which has to withstand 2 bar at a temperature of 105-110 °C . Otherwise, the coolant will begin to boil. In this regard, there is an increased load on the cooling system and the constant threat of overheating. In BMW with a 105 °C thermostat, a cover which withstands 0.36 kg/sq.cm. is installed on the expansion tank. When compared to Toyota, the expansion tank lid is designed for a pressure of about 2 times lower, about 0.18 kg/sq.cm. (maximum 0.23 kg/sq.cm.). This is because thermostats in Toyota are at an opening temperature of 87-90 °C. Therefore, Toyota does not have problems for the first 7-10 years, unlike BMW in which there is a thermostat at 105 ° C and cooling system fails constantly. Also, these problems are absent in the BMW produced in 1970-1995, where thermostats with an opening temperature of 85- 95 °C are used. Thanks to the “Cold” thermostat, the engine temperature drops from 105-110 ° C to 88-92 °C. This reduces the pressure of the coolant from 2 to 1.4 bar and will consequently increase the life of the cooling system. A situation when a coolant with a “cold” thermostat at a temperature of 88-92 °C started to leak is not so critical. The consequences will be more serious if its temperature is 105-110 °C, which exceeds the boiling point. Because of this, it begins to trickle under great pressure from any microgap. The following are the negative effects caused by the increased coolant pressure at the operating temperature of 105-110 °C:
Under high pressure of 2 bars and elevated coolant temperature, there are frequent cases when the expansion tank bursts, cracks, and sometimes explodes. This leads to coolant leakage and critical engine overheating.
Increased coolant temperature affects the plastic elements of the radiator, accelerates their destruction, which will lead to leakage of coolant.
Hoses also burst and the seals in the cooling circuit are broken with prolonged exposure to high temperature and excessive pressure of the coolant. The loss of coolant due to a leak, as a rule, leads to overheating of the engine and in critical cases can lead to its failure.
A very common occurrence is damage to the gum in the stove valves due to elevated temperature and coolant pressure.
In BMW, which has an electronic pump in the cooling system, the temperature of the coolant that it has to circulate is increased. Therefore, the pump, including all electronic elements inside it, heats up. Because of this, the life of the electronic pump is reduced.
The electronic part of the additional climate water pump often fails due to overheating. The lower the heating of the pump, the longer it will serve. The malfunction of the additional climate pump will cause the passenger compartment to warm up longer at idle in the winter and cool more slowly in the summer.
The expansion tank cap bleed valve is greatly affected by contamination of the cooling system. Therefore, it is recommended to change the expansion tank cap every 2 years after having washed out the entire cooling system. At some point, the venting excess pressure valve in the cover of the surge tank begins to wedge. Because of this, excess pressure is poorly relieved or not relieved at all. This leads to the fact that the expansion tank bursts, the branch pipes are broken, the radiator is bursting. Jamming of the bleed valve at a low temperature coolant with the “Cold” thermostat also lead to excessive pressure. But it will be much lower than with a higher coolant temperature.
Reason № 5: The “Cold” thermostat will allow to reduce the level of detonations and thereby increase the power and dynamics when driving in the city. This will be especially noticeable in hot weather.
High operating temperatures of 105-110 °C will lead to increased detonation. But thanks to knock sensors, the DME engine control unit will delay synchronization in milliseconds. In this case, the power will drop, because DME will no longer be able to save the engine from detonation, since the adjustment ranges have been exhausted. This is easily verified by comparing driving in cold and in hot weather. Since the detonation of the mixture is extremely sensitive to engine temperature, the minimum requirement for almost any modern engine is 98 petrol. Most modern engines “ring” with 95 petrol. Any BMW, for example with N63 engine, “rings” in hot weather. In this case, the engine ECU chokes, adjusting the level of detonation corresponding to the sensors. Due to good sound insulation, the driver will not hear the “ringing”. At the same time, the car will be difficult to go. At the moment when the foot is put down, the electronic control unit sends a signal to the full opening of the controlled thermostat. But the temperature can not fall sharply. And detonation manifests itself at such moments. Pistons, rings, valve, cylinder head (cylinder head) are particularly affected by increased detonation.
Reason № 6: Thanks to the “Cold” thermostat, service life of various elements that have close contact with the engine will significantly increase. And the performance of elements depending on the engine temperature will also improve.
Everything that is constantly in contact with the engine of a high temperature ages faster and eventually cracks and collapses. The crankshaft and camshaft sensors are greatly affected by close contact with the engine heated to 105-110°С. Ignition coils also heat up more. The increased temperature leads to their destruction and noticeably reduces their service life. Since they have to experience severe temperature drops due to very close contact with the engine.
Many components suffer from overheating: various vacuum tubes, gaskets for vacuum pumps, gasket for spark plugs, gaskets for spark plugs, gaskets for valve covers (valve cap itself deforms quickly), generator bracket gaskets, valve seals, vanos seals, insulation wires (cracks), electrical connectors (become brittle) etc.
If you have a turbocharged engine, then you will feel the difference for the better. While driving at lower engine temperatures, there will be more efficient cooling between the coolers. This will significantly affect the service life of the turbine.
Reason №7: Burn out of the heating element in the “Cold” thermostat will not be so critical for the engine operation as compared with severe consequences of the heating element burn out in a controlled thermostat with an opening temperature of 105 ° C.
If the coil in a controlled thermostat with an opening temperature of 105 ° C burns out, then the engine operating temperature will be 105-110 °C in all modes (even on a highway with high engine loads). And the DME engine control unit will not be able to reduce it. This primarily concerns reworked firmware for the engine ECU, which causes the thermostat to open earlier due to the fact that the DME continuously energizes the heating element. And in this case, all the negative consequences of working at elevated temperatures will be more pronounced. When a spiral burns out in a thermostat, no errors appear on the dashboard. Later an error appears in the DME engine control unit, but you will not know about it without diagnostics. In the event of a spiral burnout in the “Cold” thermostat, it will open at a temperature of 88-92 °C in any case. “Cold” thermostat will perfectly cope with their responsibilities, even with a burnt coil heating element.
3 alternatives to our “cold” thermostat!
Alternative №1: To make a “cold” thermostat on your own. There are many articles on the Internet about how various handy-man try to make a “cold” thermostat experimentally by means of a standard thermostat. Here are the main ways of thermostat alterations which we found.
Method №1. Paraffin injection
To begin with it should be understood that various paraffins may have quite different properties (viscosity, density, melting temperature, coefficient of expansion), which under the influence of temperature and pressure may change over time. These properties may differ even in different batches from the same paraffin manufacturer. To experimentally select the correct amount of paraffin, you need to repeatedly disassemble and assemble a thermostat and adjust the amount in small portions. But frequent disassembly increases the chance of damaging a thermostat. The required amount of paraffin, depending sometimes on its non-permanent properties, can differ by more than 2 times. Therefore, in some forums they claim that one paraffin ball is enough, while on others they prove that 3 balls are required. It is possible that over time, paraffin can partially leak and flow. Some types of paraffin can also change their properties due to excess impurities. And a thermostat can start to open at a temperature of 85 °C, which will certainly lead to an error in the engine and will be reflected on the dashboard and in the engine control unit.
Method №2. With metal washers, balls, etc.
You can adjust the thermostat temperature with the help of various metal washers, balls etc. experimentally by multiple disassembly. Again, frequent disassembly increases the likelihood of damaging the thermostat. But there are a lot of pitfalls here. For example, foreign objects may accidentally jam. And we have seen quite a few such cases. This will cause a thermostat to malfunction. There may be an error in the engine that will be reflected on the dashboard and in the engine control unit.
Method №3. Spring elasticity change
You can try to change the spring elasticity so that the thermostat opens at a temperature of 90 °C. But this is a rather difficult and painful process. You will have to disassemble a thermostat dozens of times to find the right spring elasticity. An addition to this, frequent disassembly increases the chance of damaging a thermostat. Spring quality can be diminished due to improper exposure. And over time, the spring will try to return to its original state. All the attempts to adjust the temperature by changing the spring elasticity will be in vain.
We deliberately emphasized for all the alternatives that there is a high probability of damaging a thermostat when disassembling it. No matter how simple its construction may seem at first glance. If the thermostat is not properly disassembled, then it will constantly wedge in spite of the fact that during visual inspection no damage or abnormalities will be noticed. This will be accompanied by errors in the engine ECU such as: thermostat jamming, wrong temperature, etc. We know from our personal experience that after this a thermostat can be thrown away. If an option is suitable for one type of thermostat, as a rule, it does not work for another type or possibly for one of another manufacturer. It is not uncommon when people eventually bought a thermostat from us after several unsuccessful attempts to alter it on their own. There are those who managed to make a “cold” thermostat on their own. But after a few months, it started to wedge, to opene prematurely, which led to an error on the dashboard. Finally, they also bought our thermostat.
Alternative № 2: Buy Chinese or Turkish “Cold” thermostat of the shelf. Avoid low-grade Chinese and Turkish fakes, which are sold as “Cold” thermostats with an opening temperature of 90 °C. Chinese and Turkish “Cold” thermostats have proven to be of very poor quality. They may be of not exactly the right size, which can make it difficult to fit and install them, especially in hard to reach places. They can begin to flow after a couple of months of work. The plastic electrical connector often cracks due to a high temperature, moisture starts to get into the cracks. This leads to corrosion of both the connector on the thermostat and the connector from the car to the thermostat. Also, Chinese and Turkish “Cold” thermostats can have a large difference in opening temperature. For example, a thermostat may start to open at a temperature of 85 °C. This will certainly lead to an error in the engine, which will also be reflected on the dashboard and in the engine control unit.
Alternative №3: Reprogram the engine ECU with specialized firmware. There are specialized firmware for the electronic control unit (ECU) of the engine, which makes it necessary to constantly apply voltage to the electronic heating element (coil) of the thermostat so that it opens earlier. These firmware are much more expensive than our “cold” thermostat. But this option will lead to a rapid burnout of the spiral inside the thermostat, as it will heat up almost constantly. The level of detonations in a thermostat with a burnt coil will increase during the transition process. The working temperature will be constantly high. This further reduces the engine life. And such a thermostat must be replaced.