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Safe tightening on Diesel Engines

Updated: Apr 22, 2020

MAN diesel engines are used in various fields. Whether in the company’s trucks and buses, utility vehicles of third-party providers, in cogeneration units for electricity as well as in agricultural machinery, rail vehicles, vessels and special vehicles. Innovative technology and outstanding quality are the key elements for the success of the MAN engines. Prototype production and service teams, however, faced a challenge in the maintenance of the engines. More about this in the following section!


MAN-Engines is a leading company in the field of development, construction, production, distribution and service of efficient diesel and gas engines from 37 kW up to 1,397 kW (50 HP up to 1,900 HP) for the most varied applications in many industries. The MAN location Nuremberg is the international engine competence center of the MAN Truck & Bus AG.


One of the main bolting processes during the maintenance of the MAN diesel engines is the tightening of cylinder heads. A rough distinction is made between two engine programs: “New“ and “old“ MAN diesel engines. The main difference of tightening is the level of the torx screws on the cylinder heads. To carry out adequate maintenance, after the removal of the cylinder covers, first the torx screws (see picture 1 below) have to be loosened and later on tightened using the torque/angle method with pre-defined OEM values.

The old MAN engines require a torque of 60 - 75 ft-lbs.+ 90° + 90 + after 1000 km (620 miles) 90°, in several steps. The new engines require a torque of 220 ft-lbs. + 90° + 90° +90°.

Until today a traditional torque wrench had been used on these bolting connections. For the prototype construction and service teams, it was required to apply tremendous force to tighten the bolts. It was extremely time-consuming and on top of that, it was executed with less accurate repeatability and lower joint quality. This application was a significant challenge due to the limited installation space. The engineers, mechanics and alkitronic consultants were confronted with the challenge that a standard reaction arm could not be used. Therefore it was impossible to use the correct support and ensure the safe and reliable torque value without coming up with a customized solution.


To apply the required torque/angle method with the requested values the models, EFCip 10 (40 ft-lbs. – 340 ft-lbs.) and EFCip 30 (100 ft-lbs. 775 ft-lbs.) in the PLUS version were presented to the customer. These ensure a higher joint quality compared to ratchet torque tools due to the continuous rotation of the square drive. For our customers, especially the repeat accuracy of ±3 % exceeds the accuracy of a torque wrench by far.

Another advantage of the alkitronic torque multiplier, according to our contacts, is the ergonomic operation and the significant saving of effort and time which in turn contributes to the reduction of personnel workload. After selecting the suitable electric torque multipliers a solution had to be found for the challenge regarding a perfect, safe and sustainable absorption of torque. A special support arm was designed. All parties aimed to develop a support arm that offers an accurate and permanent high joint quality.

Together with the involved service staff a torque transducer, adapted to customer’s wishes and requirements, was designed based on these assumptions. After many prototypes, two special supports were made. (special sliding support (engines OLD/NEW ref. no. 11495) and special Y support (engines OLD ref. no. 11496)).


After disassembly of the cylinder heads, all required bolts are accessible at one level. Place torque multiplier on the relevant torx screw and adjust torque transducer on the next torx screw. Due to the sliding mechanism, the customer can make up for the varying bolt spacing.


The “old“ MAN engines, due to the heater plug, have an 80mm (3.15") lowered bolt. Thus, not all bolts are level. To open the bolt in front of the heater plug an additional special Y support next to the special sliding support is required. The special sliding support is used for the remaining bolts. This case has again shown that company alkitronic is a reliable, flexible and solution-oriented partner.


If you have any further questions, please contact us. Our staff will be able to design customized solutions that will let you accomplish your tasks securely, fast and reliably.

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