My 2001 durango overheated after the upper radiator hose broke. I replace the hose and refill the system. I had a hard time to get it to run and when it run it missfire a lot. I took the valve covers off and I found that 2 lifters came off their place in the driver side and one in the passanger side. I had test the compression in the cylinders and it check ok. Any idea why the filters came out?