4.0L V6 Recurring Coolant Seal Failure

[btbrower]

Is there anything in a coolant system that could result in excess pressure, causing seals to fail?

So, I have a '93 Ranger with a 4.0L V6. In November '07 the gasket between my timing chain cover and block failed, leaving a nice trail of coolant behind me. It was a leak large enough that it wouldn't hold coolant and you couldn't drive the truck more than several miles before you're out of coolant and the temp goes through the roof. So I pulled the engine, resealed the timing chain cover and all was good... Until April 2010 (about two and a half years later).

In April 2010 the timing chain cover seal failed again and with ~250K miles on the engine, I replaced it with a rebuilt long block. Put in a new radiator, new hoses, new water pump, new rad cap, etc.

As I was driving to work this morning, I dropped coolant all over the road for the third time in less than four years. This time from somewhere near the rear of the engine. I had to get to work and haven't had a chance to find out where the leak is coming from, but it seems like there's gotta be a common denominator causing this repetitive seal failure.

Could a clogged (or partially clogged) heater core cause something like that? I would think the rad cap would blow before pressure could get high enough causing seals to fail....

Any ideas?

 

[btbrower]

Crawled under the truck tonight and found a blown freeze plug. That would explain where my coolant went...