We also had the front of the EGR cooler welded shut, and put block-off plates on the intake. I cleaned up as much coolant as possible with a shop-vac, and fabricated block-off plates out of stainless. We also discovered that a piece of the EGR valve had broken off and caused the death of both turbos a few months back. Removing the EGR pipes from the manifold to the cooler revealed a considerable amount of coolant in the exhaust manifold. Getting the doghouse cover off only took a few hours. Since we don't have any decent independent Navistar dealers around, we had to fix the truck ourselves. They sell cooler cores which require special pullers and installers to replace. Navistar doesn't sell complete cooler or separate coolers any more. Probably a whole lot cheaper and easier to just replace the coolers. I suppose if you completely remove the cooler assembly, it would be a little easier but would still take a lot of fabrication work if some sort of kit wasn't available. You would need to fabricate something to completely bypass both coolers before going to the thermostat housing. Trying to bypass the hot side cooler would be very challenging. The cold side cooler isn't likely the cause of the leak. The cold side cooler should be relatively easy just by fabricating some sort of bypass from the inlet to the outlet hose but there isn't a lot of room available. Trying to bypass them may be difficult depending on which cooler is leaking. It gets coolant from the low temp rad then the flow goes through the interstage cooler and back to the water pump. The rear cooler hot side gets coolant from the back of the engine and passes it beside the cold side cooler then to the thermostat housing at the front of the engine. Reputation: There are 2 separate EGR coolers and have isolated coolant passages. Can I bypass the coolant lines so that the EGR cooler will not receive coolant flow? Should I knock the cooler core out? Thanks in advance. I figure the EGR cooler is leaking into the exhaust manifold. Hey, we have a Prostar with the Maxxforce 13 engine. Welcome to world's most trustworthy automotive forum.