BMW engine coolant temperature сorrector


Coolant temperature сorrector for engine model:

BMW N20, B48, B58, N52, N55, N53, N54

BMW B38, N46, N43, N13

BMW N63, S63, N74

Installation instructions

Please note that installation of the BMW engine coolant temperature сorrector on B-series engines (eg B38, B48) will require a car-electrician skills or some experience with BMW electrics. Installation on N20, N55 engines is relatively easy.

Installation experience 1 

Installation experience 2


BMW engine overheating and solution

For several years of practice, decent usage statistics have been accumulated. Mainly concerned with BMW V8 engines as the most affected by heatstroke. The most common of which is the BMW N63.
Long time this was an effective solution for engines with an open-type mechanical thermostat: modernization of the thermostat itself, its physical replacement with a modified version.

For modern engines with the same problem, but equipped with thermostats of a different design, such a conversion is very difficult and unprofitable.

For generation B engines (ICE cooling regulation by a thermostat module), this procedure seems completely impossible.

An alternative solution, designed to eliminate all known shortcomings at once, is currently a BMW engine coolant temperature сorrector.

The work of the BMW engine coolant temperature сorrector is fundamentally an electrical correction to an electronically controlled value, forcing the car’s thermostat not to switch to ecology mode, which has a detrimental effect on the engine during daily operation in traffic jams. For which the engine with a controlled thermostat was not fundamentally calculated.

The actual temperature of the engine coolant (at an ambient temperature of about 15 degrees, without an air conditioner) – on the dashboard 105C.

Surface actual temperature measured at the hottest point of the liquid heat exchanger:

The same measured with a thermal imager:

The result of the BMW engine coolant temperature сorrector:

Comparative data on the real “urban” cycle of movement, as a comparison of data from internal and external sensors:


The car will warm up more slowly, especially in winter …

Correction circuit operates only in the area of the “hot” temperature control zone (in the range of 95-110 + degrees) and does not participate in heating in any way.


This is a duplicating, low-current (and, moreover, isolated) circuit, which is “cleverly” involved exclusively in the formation of the electrical correction of the temperature sensor signal. The worst thing that can happen is that the correction will stop working. But this is practically impossible: its reliability is equivalent to the reliability of a meter of wire and is obviously more reliable than the thermostat itself. Even if the circuit is forcibly disconnected, the computer will only stop seeing the sensor signal itself and will continue to work normally.

The controlled element of the thermostat will live less…

Yes, the problem of spiral burnout has been encountered before. By itself, without correction, on the earliest generations of controlled thermostats from the early to mid-2000’s. Perhaps it was mainly associated with their design features. Breakage of new thermostats is a very rare occurrence, and our internal statistics show at least 2 to 3 years of external control of the spiral without any problems. This is comparable to the typical lifetime of the old type thermostats. By the way, the cost of a new original thermostat is extremely low, even by BMW standards.

Is this technology planned for a diesel engine? They started using map-thermostat…

The diesel engine is not tied to the stoichiometry of the mixture and limits the actual heating of the engine by drastically reducing excess fuel emissions. It has significantly fewer overheating problems. It does not waste fuel or generate excess heat.

In short, diesel engines don’t need it. It is possible to try to install it (for “street racers”), but the real result can be almost useless.

What if the engine suddenly gets “too cold”?

The thermostat is just a valve. The achieved engine temperature is largely related to environmental factors, the capabilities of the cooling system (both to passive-constructive and active: a fan, an electric pump, for example). The guaranteed action of the correction circuit is to prevent the thermostat from forcibly increasing the temperature to too high (above 100 degrees). The correction is valid only when the engine temperature is already close to critical (then the correction is performed). This is, for example, 99% of the time when driving in a traffic jam: the motor is constantly on the verge of overheating. And an overcorrection “down” is simply impossible, since the valve will already be completely closed by the DME signal. In other words, intervention occurs only in the area of critical overheating (top), low temperature conditions are not affected at all.

It is known that some firmware versions (even for one engine) may have slightly different thermostat mappings. Therefore, it may be necessary to select the most optimal point (range) of correction …

In case of any fantastic need, it is possible to adjust the correction range for a specific engine directly on the car. Each thermostat model for each specific engine was tested on a maquette with adjustable correction (see photos of tests). The equipment receives a calculated standard correction value for a specific type of sensor, with a preset correction range of 12-15 degrees. There are no exceptions yet. The likelihood that you will need to adjust it for your car/engine/firmware is almost zero.

What if my factory settings are already “cold” and I don’t need it?

Yes, you can find such firmware versions on some BMWs, but rarely. On the dashboard, you can display the real readings of the coolant and oil sensors. If they exceed 100 (usually 105-111) degrees – than your thermostat is set for “eco”. Please do not confuse the engine temperature with the oil temperature indicator that is displayed on the dashboard of many BMWs. Engine and coolant temperatures are different. The oil has different dependencies, although it can also get a little colder. More on this below.

I don’t want any “check engine” or other malfunctions in my engine.

The BMW engine coolant temperature сorrector is not built into the electronic part of the engine. It only corrects the electrical signal from the temperature sensor. The corrector affects its absolute value in a very limited range. (see above). Please pay special attention to my words: the DME itself does not see any abnormal changes at all, since there is only a shortening of the operating range of the thermostat by let’s call it “biting out” 10-15 degrees of its “hot” working zone.

I installed this BMW engine coolant temperature сorrector, but the coolant temperature according to the sensors (scanner or dashboard) remained the same! How so?!

Yes, I repeat: the system sees the same temperature and shows it to you. But the “plate” of the thermostat (or thermostatic device, as in the B series engines) is pushed back, and with this the real temperature of the engine also decreases. This is the whole point of the corrector – it is invisible in the system and does not interfere with other components… I will add that the oil temperature still displays correctly – as it really is.

I already have a modified “cold” MECHANICAL thermostat. Why do I need a corrector?!

If you already have a “cold” thermostat installed, this question needs to be clarified.

The fact is that a “cold” thermostat has a “dead zone” – approximately a range of 100-115 degrees, when the DME does not interfere with the active part of the cooling system (pump, fan), considering this temperature to be normal. So if you are standing in a traffic jam in summer, a mechanical cold thermostat is almost useless under these conditions: it already works as a “cold” thermostat (fully opened already). But there is simply nothing can remove heat from the engine (car hardly moves, no air flow, fans are running at normal speed). The corrector solves this problem – with this device, system will try to cool the engine in advance, as if in “critical” conditions, before the temperature actually reaches the terrible 110-115 degrees, which the system initially considers to be NORMAL.

This is the meaning and main advantage of the BMW engine coolant temperature сorrector.

I installed your BMW engine coolant temperature сorrector. In the situation described above (heat, traffic jam), the warning “engine overheating” appeared for a second!

Absolutely right! This suggests that your cooling system was working at its limit, and after making an artificial correction by 10-15 degrees, it already malfunctioned, detected overheating and warned about it. The conclusion is very simple: sometimes you need to WASH RADIATORS. Especially before the season. Remove them from the car and clean them well to remove all dirt and dust from there. Modern BMW firmware even limits the power mode for “overheated” cars. Throttling. You can’t even accelerate – the car immediately drops speed, forcibly reducing heat generation. This is verified.

I installed your BMW engine coolant temperature сorrector, but OIL temperature did not drop…

In a modern engine, oil cools the piston crown through oil nozzles. It takes heat directly from the back of the piston crown. In other words, the oil is in almost constant contact with the pistons. And the pistons themselves are located close to the oil, at a distance of the palm. Why would it get COLDER ?! Has the combustion temperature in the cylinders gone down?! The oil literally sprinkles the PISTONS, and below (where the sensor itself is installed) oil is located in a thin metal pan. Where is the thermostat and unit temperature here? Where is the connection with the ECU at all?!
The exception is engines with an oil cooling circuit (with a radiator) or with an efficient heat exchanger (BMW N20, for example) of any design. On such engines, the OIL temperature can really drop, since the oil line can have some kind of “binding” to the liquid heat exchanger. A positive side effect, although expected, is not guaranteed – it all depends on the design of the engine.

If you want to significantly influence other design parameters of the cooling system, look for custom radiators, intercoolers, heat exchangers … All this also works.

What else?!

I repeat, do not forget, that the engine temperature is physically tied to the condition of the radiators, which can become significantly contaminated in 1-2 years of operation. I also recommend not only washing the radiators, but installing a new type of thermostat (for engines older than 2-3 years). This is due not only to electrical, but also to its mechanical reliability. In this case, the efficiency and reliability of such upgrade is the highest, although it is extremely high without it.

If all of the above did not help you to understand the point (this happens to the best of us), then it is better to abandon the idea of installing a BMW engine coolant temperature corrector. Let’s assume that it does not exist 🙂

Step-by-step instruction:

  1. Find out your engine model BMW:

N20, B48, B58, N52, N55, N53, N54

B38, N46, N43, N13

N63, S63, N74

  1. Please note that installation of the BMW engine coolant temperature сorrector on B-series engines (eg B38, B48) will require a car-electrician skills or some experience with BMW electrics. Installation on N20, N55 engines is relatively easy. Instructions included.

The device has a 2-year warranty.


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