dumb mistake on CAT 3208TA HE

Last year I rebuilt my HEs using brand new end caps (or "bonnets" as CAT calls them). The new caps were a different part number than the originals and have thicker flanges for the gasket surfaces. I only found out about the new caps when I tried to order the old part numbers and was informed they had been superseded. I dutifully put the HEs back together with the 3 required gaskets and one required o-ring per my parts manual and ran the boat all last season with no issues. On Sunday, I went out for a little cruise and my starboard engine started spitting coolant out the exhaust system and the exhaust system bypass raw water outlet. I am 90% sure the only way coolant could get into the exhaust system bypass raw water outlet and the exhaust system is through the HE so I concentrated on that. Well, it turns out the new HE end caps I got require two fewer gaskets and two more o-rings than the old design. I'll pick up the new parts today. Fingers crossed that I found the issue, but it sure looks like a smoking gun...



I learned to study the associated parts diagram much more intently whenever a part number has been superseded.

I'm curious why you had to replace the old bonnets? Mine are OEM bronze bonnets and show no signs of failure since 1983. It's the steel flange on the HE that is showing deep pitting. When I had them open to clean the tubing bundles this winter I put a thick layer of RTV on the steel flange and that side of the first gasket. Dry the rest of the mating surfaces. It will fun getting it apart next time.

Portage_Bay said:

I'm curious why you had to replace the old bonnets? Mine are OEM bronze bonnets and show no signs of failure since 1983. It's the steel flange on the HE that is showing deep pitting. When I had them open to clean the tubing bundles this winter I put a thick layer of RTV on the steel flange and that side of the first gasket. Dry the rest of the mating surfaces. It will fun getting it apart next time.

Click to expand...

My bonnets (old and new) are plastic and the flanges on the old ones were badly warped after 29 years of use. The new bonnets have double the flange thickness, I presume as a design improvement to prevent warp. The new bonnets also have a groove on each flange face, that's obviously for an o-ring, that I stupidly overlooked.