I had a seam leak, caused by poor solder joint when I had the 5-row core put in in Baja. I took it out and to a rad shop(15 miles away) to have it fixed. The guy suggusted that I use a 7lb cap(he gave me one free) rather than the OEM 12lb. He said that using a higher pressure cap just puts too much strain on all the system and if the engine gets soo hot as to need that much it's already too late and way past safe for engine. Pressure cap increases boiling point 1.5 deg/1lb of pressure. Water boils at 212+(12x1.5)=230. A 50/50 mix Antifreeze raises boiling point to 265 deg(way higher than I EVER want to see my coolant temp), add the (12psi times 1.5psi cap=18deg) and you're up to 283 deg
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. My engine is a 91 with a 12lb cap and had A/C until I ripped it out(Another story for another time). I'm now running with a 7lb cap. OkieGringo
This below, was posted over at TDS by "Runboy"
Well, the previous owner had installed a 16lb rad cap! I went looking through the parts books and my truck (89) called for a 7lb. 90 they went to 12lb and super duty called for 16lb if memory serves correct.
Anyways, cap has been replaced with 7lb and I am curious to see if some of the top tank seapage issues are resolved.
Mike