So I found my truck leaking antifreeze saturday. Long story short it looked to be coming from the stat. I replaced both O-rings and it still leaked. So I removed again and checked for a damaged O-ring but nothing. I then reset it and its still leaking, so did some searching online and didnt really find much other than a guy saying only use cummins seals? Well there seems to be plenty of material to make a good seal but I am now irritated. The only other thing is possibly the head gasket but cant really tell cause the t-stat housing and the head gasket are so close together. Anyone ever have any issues with a brand new fel-pro not sealing? Its a 95' 12valve with 407,000 on it.

 

I have the same problem with a '99 24-valve. It's leaking in the same place. Prior posts suggest a known head sealing issue in that area, and that replacement head gaskets address the problem, It probably weeps when the engine's cold, then seals up. If it's like my 24-valve, you'll see dried coolant rather than wet. I've also noticed that my temp's rising with a load or at higher speeds. I'm going to replace the head gasket in the next week or so.

 

i have had the same problem on my dads 95 and that was even after we changed the head gasket cause it was leaking out the head. I think that is the common spot for that year range (2nd gen) motor to leak, and the first gen leaks out the rear corner...But i do agree on using cummins seals, they work better..