LB7: CP3 Freeze plug blow out

duramax hd

Member
Feb 27, 2009
664
0
16
36
CT
Ok guys, I’d like to get some opinions on this. Took my truck out for the first time this year and it was running great. Took it up to buddies and got it detailed up. Driving home, I was 'getting up to speed' on the highway and blew an intercooler boot off right after the valley charger. I fixed it on the side of the highway, and got back into traffic. I was about 3/4 throttle and my buddy noticed I was smoking pretty good. I looked down and all gauges were normal but the smoke was pure white. Pulled over and noticed a trail of fluid under my truck as I slowed down. Stopped the truck and shut it down. It was pouring diesel out the bottom. I quick glance and I noticed the CP3 lost one of its 'freeze/expansion plugs' on the side. This is my second CP3. What the hell could cause this? I did some quick searching, and came up with a few potential causes. One being not enough lift pump pressure, causing the pump to cavitate? The other, being that I have reason to believe that one of the pumps has a modded regulator and the difference in pressure could cause this? I kind of had a loppy idle at my buddies when it was warming up, but went away when it was up to temp. It smokes pretty good at idle but that could be the 100 over’s. It still has a 'rough' tune I would say, and Tony and I know we need to hook up and get the idle tunes worked out. Maybe the CP3 I got with the build motor was just garbage? That’s a possibility too. Any thoughts would be welcomed.

Thanks
 

paint94979

Beer Nazi
Sep 18, 2006
11,714
7
38
37
You are describing my exact scenario lol... Mine blew out every plug there was and sprayed metal pieces all over my valley. Mine was modded
 

duramax hd

Member
Feb 27, 2009
664
0
16
36
CT
damn mine only took one plug out, but Im gladit wasnt my valley cp3. Has anyone said what could cause it?
 

juddski88

Freedom Diesel
Jul 1, 2008
4,651
116
63
Chesterfield, Mass.
Kris,
This normally happens when the bores wear out and there is "blow by"....could be caused by failing lift pump, or other feed restriction....or just old pump that has been through a lot of abuse.

Tim