3.3. Check of work and replacement of the thermostat

Do not uncover a radiator, do not merge a cooler and do not replace the thermostat before the engine completely cools down.  



  1. Before coming to conclusion that the thermostat is a cause of defect in the cooling system, check the cooler level, a tension of a driving belt and serviceability of the measuring instrument (or an alarm lamp) cooler temperatures.
  2. If there are suspicions on too slow warming up of the engine (based on bad work of a heater or indications of the measuring instrument of temperature), it is possible that jammed the thermostat abroach. Replace the thermostat.
  3. If the engine overheats in operating time, feel a hand the top hose of a radiator. If the hose not hot, but the engine is overheated, then it is possible that the thermostat is jammed in the closed state that interferes with circulation of a cooler through a radiator. Replace the thermostat.

Do not allow operation of the car without thermostat. The engine will slowly get warm at cold weather that will result in uneconomical fuel consumption and bad controllability of the car. Usually new thermostat is not an expensive component.

  1. If the top hose of a radiator hot, it means that the cooler circulates through a radiator, and the thermostat is open, at least partially. Apply for information to the Section Diagnostics of Malfunctions of the Cooling System at the end of this Section for identification of the reasons of an overheat.


All models


  1. Disconnect a negative wire of the battery.

If the radio receiver of your car is equipped with system of protection against theft, make sure that you gathered the correct code before a battery detachment.

If after connection of the battery of an inscription on an instrument guard appeared not in that language, address the Section System of Protection of the Audio System from theft and language of an instrument guard where the procedure of installation of the necessary language is described.

  1. Merge the cooling system (see the Head Routine maintenance of the car). If a cooler rather new or in good shape, do not pour out it that then to use again.

M10 engines


  1. The thermostat is located in the lower hose. At first remove the cooling fan.
  1. Notice position of the thermostat, then unscrew collars of a hose and take the thermostat from connections of a hose. On M10 engines (four-cylinder) the thermostat (it is specified by an arrow) is built in a radiator hose
  1. Install the thermostat in connection of a hose and tighten hose collars.
  2. Install the cooling fan.

M20 and M30 engines


  1. Weaken a hose collar - And, then disconnect a hose (hoses) from a thermostat cover. Pay attention that the cooler temperature sensor (which is almost not visible because of the fuel pressure regulator) is located in the top part of a casing of the thermostat - Century.
  1. If the external surface of nipple connection interfaced to a hose somehow is damaged (corrosion, mechanically, etc.), its state can worsen because of removal of a hose. If this is so, then is required to you a new cover of a casing of the thermostat.
  2. Give bolts and disconnect a casing cover. If it stuck, tap it the hammer with soft brisk. Be ready that after destruction of sealant of laying a little cooler can be splashed out.
  3. Notice the correct position of the thermostat and remove it.
  1. With Zakuporte rags the formed opening in the engine, then remove all traces of material of old laying (if it paper). Otherwise remove a rubber sealing ring and remove sealant from a casing and a cover with a special scraper.
  1. Pull out rags from an opening in the engine and clear the interfaced surfaces of laying.
  2. Install the new thermostat and laying in a casing. Make sure of correctness of installation - the end of a spring has to be directed to the engine.
  3. Establish a cover and spread bolts. Tighten bolts with the required effort.

M40 engines


  1. Remove the fan of cooling and the top cover of a distributive belt.
  2. Unscrew a collar of a hose and remove the lower hose from a knee on the forward party of a head of cylinders.
  1. Otboltite a knee from a head of cylinders.
  1. Notice the correct position of the thermostat, then remove it.
  1. Remove a rubber sealing ring; for assembly it will be required new.
  2. Place the thermostat in a head of cylinders in the same situation in what it was before removal (the arrow specifies up).
  3. New sealing ring in a flute also establish to Vpressuyta a knee on a head of cylinders. Tighten bolts.
  4. Attach the lower hose to a knee and tighten a hose collar.
  5. Establish the top cover of a distributive belt and the fan of cooling.

All models


  1. Fill the cooling system (see the Head Routine maintenance of the car).
  2. Connect a negative wire of the battery.
  3. Start the engine, warm up it up to the normal working temperature, then check whether there are no leaks and whether the thermostat correctly works (as it is described in this Section earlier).