3'F per PSI...then 257'F (212+3x15) is the max temp the coolant will ever reach before it boils. Once it starts to boil it is no longer water but steam. Once the coolant reaches 257'F the PSI of the cooling system is 15psi and the radiator cap will start to vent or "boil over" as it is also called. At that point melting fuel hoses is not your real problem or concern anymore. You've got bigger problems. Steam is hotter than boiling water, but is much less efficient at transfering heat.

The HIH is the only thing the car has. I run 50/50 blend in the stock tank.

The Poly hose is completely encased by the 3/4 heater hose. All the way to and including the hose clamps. There is no expose poly tubing, not even at the very end. There are no sharp bends or anything. It is possible that the poly hose might have gotten kinked while assembling.

I'll be removing the HIH after work today and see what I find.

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1987 300TDT
1981 VW MKI Caddy 1.6 diesel, waiting on engine swap
1983 D-50 Power Ram 4x4 "Mitsubishi" 2.3 turbo diesel
assorted gas powered crap and motorcycles

RIP: 1984 300TDT, 1982 300TDT, 1984 190D 2.2, 1992 300D 2.5, 1987 300TDT, 1982 Maxima LD28, 1983 Maxima LD28, Isuzu C223 P'ups X3, 1983 Holiday Rambler 6.2 Banks turbo diesel, 1984 Winnebago LeSharo 2.1 TD, 1985 Allegro 6.5