I looked at the Fernco website and all their standard couplings seem to be rated at 4.3 psi max and 140 deg F. There may be high pressure couplings but none were obvious and I admit I didn't browse a lot. I've only seen these used on sewer lines. Radiator hose has a reinforcing fabric moulded into the hose and the hose is designed to withstand pressures well over 15 psi, the typical automotive cooling system pressure, and temperatures upwards of 250F plus the harsh underhood environment. The gap in my 1.5" pipes is maybe 4-5" and that leaves plenty of wiggle room.
Al