Hi-About a month ago my Granddad's 1992 Ford F150 351 EFI experienced severe overheating and a blown head gasket. When we pulled the engine we found that the AIR check valve was broken off of the rear air pipe (or did we do this??). Could this condition cause catalytic converter meltdown and severe engine overheating? Thanks for any advice

 

I had this happen on one of my wife's older cars. It was a Mazda GLC and the air check valve failed. The hot exhaust gases bleed through and melted some smog control device that was between the check valve and the air pump. She drove the car for about a year before we had to get it fixed to pass smog. I also inspected the cats and they were fine. If your grandfather’s cats were not getting supplemental air from the air pump, then the cats really can't do their job of burning unburnt fuel (no air to mix with). They wouldn’t over heat because of this, in fact they would never get hot enough to work correctly. This could cause the cats to gum up over time causing a severe restriction in exhaust flow which in turn could blow out a head gasket. But cats can melt down too, I seen one that has and it pretty ugly. Have you inspected the cats, what to they look like on the inside?

 

No I haven't inspected the converter but my Dad said he thought the exhaust manifold was leaking (these were brand new ex. manifolds torqued down to specs-the old manifolds were too warped to use). Right now I'm just wondering if driving this thing with the air pipe-check valve disconnected will cause any further damage cause I think my Grandddad is trying to drive this thing. How would I inspect the converter? Thanks for the input