Chevrolet Cruze 1.8 Z18XER oil cooler (heat exchanger) leaks, what to do

The 1.8-liter Chevrolet Cruze F18D4 engine (Z18XER) is considered quite reliable and resource-intensive. However, it also has its weaknesses, well studied by our drivers. The Chevrolet Cruze heat exchanger cooling and lubrication systems are one of the sore points of this engine.

Why do you need a Chevrolet Cruze Z18XER oil cooler (heat exchanger)


Maintaining a normal stable operating temperature of the engine in all operating modes is an important condition for efficient use of fuel, minimizing the wear of friction elements and the oil itself.

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From the point of view of the lubrication system, the Chevrolet Cruze heat exchanger partially serves as an oil cooler. The only difference is that the radiator only cools the oil, and the heat exchanger helps to stabilize (equalize) the temperature of the oil and antifreeze, which affects the uniformity of heating and cooling of all engine systems in the complex.

It is very important for the lubrication system that the engine oil is maintained at stable temperatures for as long as possible. This will provide a nominal viscosity, fluidity, reduce the intensity of burnout of oil components. In addition, overheated oil copes much worse with the formation of an oil film, and also seriously complicates the life of the cooling system.

The same can be said about cold olive oil. Thick unheated oil cannot physically enter the channels away from the oil pump, such as the cylinder head, and this impacts the lubrication quality of many elements and systems. The heat exchanger allows the oil to heat up much faster due to close contact with warm antifreeze, which heats up much faster.

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How the Chevrolet Cruze 1.8 heat exchanger works (oil cooler), structure


The Chevrolet Cruze 1.8 Z18XER heat exchanger consists of a housing and a cooler. The oil filter is attached directly to the housing, and the oil from the crankcase pan under the pressure created by the oil pump passes through the filter and enters the cooler.

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Another channel enters the cooler chamber, antifreeze through the pump and the tube with the flanges. The tightness of the fastening of a tube is reached at the expense of sealing rings. The oil chamber and the antifreeze chamber are adjacents, which allow you to heat the oil to operating temperature if necessary, or cool it if the temperature is above normal.


Oil and antifreeze chambers are in the immediate vicinity. To protect the systems from mixing coolant and oil, use a clever system of gaskets, the quality of which depends on the correct operation of the heat exchanger and the engine as a whole.

Malfunctions of the heat exchanger (oil cooler) Chevrolet Cruze 1.8 l


Theoretically, such a simple system should work smoothly. However, in practice everything is different. Chevrolet Cruise heat exchanger often throws its owners extremely unpleasant surprises. If you start the state of the node, you can easily fly to overhaul the engine.

The main signs of leaking heat exchanger Chevrolet Cruze:

  1. Leakage of antifreeze from under the exhaust manifold.течь антифриза
  2. Oil leak on the cylinder block in the area of the exhaust manifold, oil getting on the catalyst housing and the exhaust pipe.масло на блоке круз
  3. White-gray emulsion on the oil dipstick and under the oil plug, on the walls of the neck and the inner surface of the valve cover.эмульсия
  4. Oily stains on the surface of the antifreeze in the expansion tank of the cooling system.масло в антифризе

All this indicates only one thing – the heat exchanger gaskets have completely exhausted their life and require replacement. In some cases, the depressurization of the channels and chambers of the heat exchanger occurs due to thermal deformation of the plane of the housing or the cooler itself. This is due to systematic overheating of the engine, non-operating thermostat, or pump.

How to remove the oil cooler (heat exchanger) Chevrolet Cruze Z18XER


You need a manhole or hoist to replace the gaskets, repair or replace the heat exchanger. If we are convinced that there are problems with the heat exchanger, drain the antifreeze with a drain fitting in the lower right corner of the radiator, first removing the plastic protection.

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Unscrew the three nuts that attach the catalyst collector to the receiving pipe, as well as the bolts securing the thermal protection. Use a 13 mm socket wrench or head for the catalyst and a 10 mm heat shield.

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Unscrew the catalyst mounting bracket with the E12 head.

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We pass into the hood space. With the E12 head, we unscrew two bolts of a heat shield, one of which by the way holds an arm of an oil probe, the second arm of a plait of wires. Disconnect the connector of the sensor wiring harness.


Before dismantling the probe, it is better to place the container under the pallet, as the probe tube goes low into the crankcase, 200-300 g of oil may leak out. Turn and remove the probe with the guide assembly.

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Remove the heat shield of the exhaust manifold and moisten the threads with penetrating oil (WD-40, for example).

Unscrew the 9 nuts securing the exhaust manifold with a head of 10 mm, starting from the middle part. Note that the nuts are thin-walled (10×8 mm), handle them carefully. Also, unscrew the head by 12 mm mounting eye.


Подайте колектор на себе та підніміть, акуратно виводячи його з моторного відсіку.

Use the E12 head to unscrew the 5 bolts securing the heat exchanger to the cylinder block and the Torx T30 head to unscrew the tube flanges from the thermostat and pump. Carefully remove the heat exchanger from the engine compartment.


Repair and replacement of gaskets for the Chevrolet Cruze Z18XER heat exchanger


After dismantling the heat exchanger assembly, thoroughly wash the housing and unscrew the oil filter flask. The used oil will leak out.


Unscrew the heat exchanger from the housing, six Torx T30 bolts, and separate it from the housing.

Remove the old gasket and thoroughly clean the sealing groove from dirt and old oil. Thoroughly wash the case and heat exchanger, purge the channels from dirt.


At this stage, it is very important to check the geometry of the plane of the heat exchanger and the housing. This can be done with a metal ruler or other perfectly flat surface, use thick glass as the last resort.

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After all the checks, carefully lay the new gaskets in place. Note that the quality of the gaskets must be very demanding. The best gasket for the Chevrolet Cruze 1.8 heat exchanger between the body and the radiator is a new type of gasket.

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They are even visually different from the old type, which after replacement and after planning the surfaces could leak after a while.

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Catalog numbers of gaskets (as in the photo):

  1. Old type GENERAL MOTORS 55354071.
  2. Old type GENERAL MOTORS 5650972.
  3. New type GENERAL MOTORS 25199750.

The rest of the gaskets are also better to buy in the original:

  1. Antifreeze rings, 2 pieces included, Opel 5650966, GM 55353328.
  2. Original sealing rings for a large tube – 24445723 та 55353331
  3. The gasket of an exhaust collector, GM 12992396. Analog – Victor Reinz 713815800, ELRING 355340.
  4. The gasket of a receiving pipe, GM 55557507/5854988, Bosal 256438, ELRING 077470.
  5. Original set of rubber gaskets, 9 pieces – GM 5650972 KIT (ELRING – 599160).
  6. Copper nuts exhaust manifold Bosal 258028 (Bosal 258038).

комплект прокладок

Assemble the Chevrolet Cruze Z18XER heat exchanger in the reverse order, strictly following the manufacturer’s instructions when tightening the bolts and nuts:

  1. Six oil radiator bolts – 8 N∙m.
  2. Five bolts of the case of the heat exchanger (fastening to the block of cylinders) – 25 N∙m.
  3. Two oil radiator intake pipe bolts and two thin exhaust pipe bolts – 8 N∙m.
  4. Three nuts of fastening of the catalyst to a receiving pipe with a corrugation – 22 N∙m.
  5. Nuts of fastening of an exhaust collector to the block of cylinders – 20 N∙m.

After the heat exchanger and exhaust system have been completely assembled, fill the full antifreeze expansion tank, and to remove air from the cooling system, remove the throttle cooling hose from the fitting. As soon as the antifreeze starts dripping from the hose, the air is released, the hose can be put in place.


Add antifreeze to the maximum level and add oil, approx. 400-500 g. Now you can start and warm up the engine to operating temperature, then carefully check the possible leaks of engine oil and antifreeze.

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