Mack problems? The Engine Facts     

Mack problems? The Engine Facts

We have many of our customers that own the Mack MP7 and MP8 engines. Some of these customers are on their third camshafts. One of them lost a head because the cam roller broke off and wedged under the rocker arm. Mack claims they have this problem resolved, but for the long time Mack owners, the E6 and E7 engines with the ceramic rollers also had cam problems. The one advantage to the MP series engines is that it is an over head cam and much easier and cheaper to change. But being easier or cheaper does not help in the independent or fleet owners and they are without their rig for three or for days just waiting on the parts, which appear to be in high demand.

There are some things an owner needs to be aware of when getting the cam replaced. Make sure it is done by a Mack dealer. Many times you can get some support through their Mack rep on these repairs. Mack realizes they have a problem and are more than happy to assist in many ways. The valve adjustments on these newer engines are more complicated and more critical than ever. Particularly if you have the PowerLeash™ engine brake. After you set the exhaust valve clearance by means of shims on the valve bridge, you will need to use a dial indicator to get the proper lift. Do not attempt this at home unless you are very familiar with the procedure. I have qualified techs that still have problems with them. And if you do not have access to the Mack specs for this, don’t worry you can use the Volvo specs, they have the same valve train.

We have also see a rash of injector cup problems. These are brass cups that are pressed into the head and house the injectors. What we are seeing is that these cups leak coolant into the combustion chamber. You can identify this problem by symptoms of hard starting and loss of coolant with no apparent external leak. If this problem is not repaired soon enough it can be very difficult to remove these cups and can lengthen down time by as much as two days.

Although these are both serious problems, I have seen the repairs take as little as one day to repair by a good technician. It is very unfortunate that I have also seen these repairs take as long as 3 days. This can be a great loss for both the driver, loosing miles on the road, and the repair shop because Mack will only reimburse them a small amount to make the repairs. But it is up to the driver to make sure these repairs are done only by qualified technicians.