The instructions for replacing the heat exchanger gaskets are, in principle, the same for all GM engines of the A / Z16 / 18XER / LET series.
Below is: the essence of the problem, a few photos of the process on the Zafira Z18XER, instructions with tightening torques on the Z18XER and at the end of the spare parts number.
The problem of GM engines of the XER / LET series (A16LET, Z18XER, etc.) common to Opel, Chevrolet is oil leakage through the heat exchanger gasket (aka the engine oil cooler) / or oil getting into the antifreeze through the heat exchanger.
The heat exchanger is located in a hard-to-reach place, behind the exhaust manifold, therefore, if you do not pay attention to the sweating of oil or the appearance of smudges, you may not notice it in time. But as soon as the oil starts to flow in full and falls on the exhaust manifold, this fragrant smell of burning will immediately notify you of a malfunction.
Antifreeze and oil pass through the heat exchanger. The assembly is heavily overloaded with many gaskets and tubes, the seals of which are made of rubber.
Over time, rubber loses its properties and "dubs". The seals lose their tightness and oil starts to flow through the cylinder block, or get into antifreeze, because the pressure in the lubrication system (oil pressure) is higher than the pressure in the cooling system (antifreeze).
We had a Zafira X18XER, the instructions were taken from the CRUZE Z18XER, no different. One caveat: somewhere it was written that it is necessary to remove the air conditioning compressor on the Zafira. They did nothing of the kind, they just removed the cooling fan. It is better to do it right away, because with a fan, it is problematic to even remove the exhaust manifold heat shield.
1. Remove the cooling fan, oil dipstick.
2. Drain the coolant. Radiator plug. In the direction of movement of the car from the bottom right, from the end of the radiator.
3. Disconnect the lambda block, exhaust manifold heat shield.
3. Remove the exhaust manifold spacer (6)
4. Nuts securing the catalytic converter to the flexible exhaust pipe (1)
5. Nuts securing the catalytic converter to the cylinder head (8)
6. Remove the 2 bolts (1) from the engine oil cooler outlet pipe. Remove the engine oil cooler outlet pipe (2).
7. Remove the 2 bolts from the engine oil cooler inlet pipe (4).
8. Dismantle the engine oil cooler inlet pipe (3).
9. Remove the 5 bolts (2) of the engine oil cooler housing.
10. Remove the engine oil cooler housing (1).
11. Remove the 6 engine oil cooler bolts (2) and remove the engine oil cooler (1) from the radiator housing.
12. We wash everything, change all gaskets, assemble in reverse order.
13. If desired or necessary, change the oil, filter, flush the cooling system, change the antifreeze.