6.7L EGR Cooler Failure and Cracked Cylinder Head

This video discusses coolant consumption in a 6.7L which seems to be a recurring problem. It is not common but we are starting to see issues at about 130K-160K miles, particularly in ambulances. Is this something to be alarmed about? Probably not, this is an ambulance and when it gets run hard, it gets run hard, otherwise it is sitting there idling. It gets a lot of severe duty that normal pick-up trucks don’t get. But when I see something that is a trend, especially in the ambulance trucks, I am going to tell you about it. That is what POWERSTROKEHELP.COM is all about.

I have worked with this particular ambulance crew for years. They are tough on their trucks. They take care of them, but they run them hard. At about 150K miles this crew started seeing their coolant levels drop in their engine coolant.

There are two separate cooling systems in a 6.7. There is an accessory cooling system for the charger cooler, the fuel heater, and the EGR cooler. People don’t know that the EGR cooler has two halves with part of the EGR cooler run by the engine coolant and part of it run by this secondary cooling system. The secondary cooling system sits on top of the valve cover on the passenger side on top of the engine. These ports are run by the secondary cooling system but it only works with half of the EGR system. The coolant which actually comes from the engine runs through half of this. The reason is to get the EGR cooler hot enough so that it won’t coke up and build up carbon. If you have a 6.7 truck that is consuming coolant and you can’t seem to find it, you need to replace the EGR cooler. It is just that simple.

However, sometimes replacing the EGR cooler simply doesn’t fix it and it is still consuming coolant. We are finding that there are heads, especially in the 2011’s and 2012’s, which have been prone to cracking.

We sent the passenger side cylinder heads to the machine shop and we found out it was cracked. At this point, we are going to install the Bigg Dogg, o-ring, completely remanufactured cylinder heads. We have installed about 50 sets of these so far and once we are done with them, they are never a problem again. ~Bill Hewitt