fixerupper
Well-known Member
Son's truck with a Cat 3406B breaks a couple exhaust manifold studs every 30,000 miles or so. It's apart now for the fourth time. The first time it happened he replaced them himself. The second and third time the studs broke he took it to a reputable truck shop to have them replace the studs. The third time the truck shop put in stainless studs and two of them just broke. We just got done drilling and torching one of them out successfully and the second one comes out tomorrow. Stainless studs are NOT going back in!!!
Do any of you guys who have worked on these engines have any ideas why the studs are breaking? Is this a known problem with this engine setup? I don't think it's in the same location every time. The manifold has not been resurfaced until today. When I took it in to have it surfaced I asked the machine shop for advice and the man who does heads and manifolds said he didn't know why Cat used 3/8 studs instead of 7/16 on that engine but other than that he didn't have any advice. The bolt holes in the manifold are oversized enough to give some wiggle room but the holes aren't way oversized.
The reason he took it apart this time is a couple of manifold gaskets were blown. He found the broken studs when he took the manifold off. So this is where we sit at the present time. The manifold is resurfaced, he has the new studs but we sure don't want to do this again.
Do any of you guys who have worked on these engines have any ideas why the studs are breaking? Is this a known problem with this engine setup? I don't think it's in the same location every time. The manifold has not been resurfaced until today. When I took it in to have it surfaced I asked the machine shop for advice and the man who does heads and manifolds said he didn't know why Cat used 3/8 studs instead of 7/16 on that engine but other than that he didn't have any advice. The bolt holes in the manifold are oversized enough to give some wiggle room but the holes aren't way oversized.
The reason he took it apart this time is a couple of manifold gaskets were blown. He found the broken studs when he took the manifold off. So this is where we sit at the present time. The manifold is resurfaced, he has the new studs but we sure don't want to do this again.