Attention! On engines with oil piston cooling jets, be careful not to damage the jets when cleaning the engine. The manufacturer recommends that after rebuilding the engine, adjust the position of the injectors using BMW tools 117 320 (engine M43TU) or 119 370 (N42 engine).
Cleaning
1. Remove all wiring, sensors and connectors from the engine To completely flush the engine, it is recommended to remove the process plugs from the cylinder block. To do this, drill a hole in the plug, screw a self-tapping screw into it and pull out the screw together with the plug with pliers or using an impact puller.
2. Pull out or unscrew the piston cooling oil nozzles. On 4-cylinder engines, the injectors are located in bearings No. 2 and 5, and on 6-cylinder engines - in bearings No. 2 and 7 (pic. 11.2).
3. On the 4-cylinder M43TU engine, unscrew the shut-off valve on the top side of the cylinder block. On older pet models, the check valve is screwed into the block (pic. 11.3,a). On later models, a calibrated jet with a protective sleeve can be installed (pic. 11.3,b). On the 4-cylinder N42 engine, two shut-off valves are installed on the front side of the surface under the cylinder head (pic. 11.3, in). They just need to be pulled out of the block.
4. Scrape off the remnants of the old gasket from the machined surface of the cylinder block. Be careful - the block is made of aluminum alloy and can be easily damaged.
5. Turn out plugs from all oil channels. Usually, these plugs are screwed in with a tight fit and cannot be unscrewed. In this case, they must be drilled, and a new thread should be cut in the holes. Naturally, in this case, the plugs will need to be replaced during assembly.
6. If castings are heavily soiled, they should be steam treated.
7. After such cleaning, clean all channels of the lubrication and cooling system again. Rinse the inside of the engine with warm water until the water runs clear. Wipe dry all surfaces and lubricate treated surfaces with a thin coat of rust protection oil. Grease also mirrors of cylinders. If you have access to compressed air, use it to speed up drying and to remove any debris from the channels.
Attention! Wear protective goggles when working with compressed air.
8. If the castings are not too dirty, they can be washed. Wash in very hot (how much can you endure) soapy water with a stiff brush. Take the time to do this operation and do it with the utmost care. Regardless of the cleaning method chosen, thoroughly clean all channels and cavities and dry all parts well. Lubricate surfaces to protect against rust.
9. Clean all threaded holes to ensure proper assembly torques. To clean threaded holes from dirt, rust and sealant residues, as well as to restore damaged threads, drive them with a tap of the desired size (pic. 11.9). Blow out holes with compressed air after cleaning (if there is such a possibility).
If there is no compressed air, then. alternatively, a water-absorbing aerosol can be injected into the holes.
Attention! When blowing holes in this way, wear safety goggles.
10. Dry all threaded holes.
11. Lubricate the edges of the technological plugs of the cylinder block with sealant and press them into the walls of the block. Make sure that they enter without distortion and take the proper position, otherwise leaks may occur when the block jacket is filled with coolant.
To press the plugs, you can use a socket with an outer diameter slightly smaller than the diameter of the plug.
12. Screw new plugs into the oil passage holes. Pre-lubricate the thread with sealant. Tighten the plugs securely.
13. Thoroughly clean the check valve (or jet) lubrication system and install it as follows.
14. If the engine has a valve that is screwed into the cylinder block, make sure that it is blown from the bottom up and not blown from the top down. Flush the valve thoroughly, put a new o-ring on it and screw it into the block. Tighten the valve carefully.
15. If a jet is installed on the engine, insert it into the block (calibrated hole out) and insert the protective sleeve.
Attention! If the jet is installed incorrectly, it may restrict the oil supply to the cylinder head.
16. On a 4-cylinder N42 engine, insert the shut-off valves and spacers into the cylinder block (pic. 11.16).
17. Wash the piston cooling oil jets and reinstall them (pic. 11.17).
18. On the 4-cylinder N42 engine, clean the grooves of the mating surfaces of the cylinder block and lower crankcase from the remnants of the sealant. Remove the nozzles for refilling the sealant - they must be replaced during assembly.
19. If you are not going to immediately start assembling the engine, lubricate the cylinders and engine channels to protect against rust (if it hasn't already been done) and cover the engine with a large piece of polyethylene to protect it from dust.
Status check
20. Inspect engine castings for cracks and corrosion. Check for stripped threads in the holes. If coolant leaks were noticed during engine operation, hand over the cylinder block to specialists for its check on special equipment. If a defect is found, then perhaps the specialists will be able to fix it or you will have to purchase a new unit.
21. Inspect each cylinder for scratches and burrs. Is there a belt in the upper part of the cylinder, indicating significant wear of the cylinder.
22. Pass the unit to the service station specialists. They will decide if the cylinders are too worn and need regrinding. After regrinding, it will be necessary to insert oversized pistons and rings into the cylinders.