I noticed the upper radiator hose was collapsed when I had the intake off the 5.8L engine. With engine cold I opened the radiator cap and it "whooshed" and the hose cameback into shape. I recently had the smalloverflow tube/hose at the radiator cap split and lost about a pint of coolantand the engine temp went a little past where it stays normally but it did not overheat. I trimmed thesmall rubber overflowtube/hose back about an inch and slipped it back on the radiator cap neck nipple. The overflow jug shows about an inch of coolant above the "cold" mark on the jug when cold. Is there a connection between the overflow jug level being a little highand flowback when the engine cools? It's a little hard to see the upper hose with the intake housing in place but I'll be watching it and the temp gauge closer for sure. Thanks.

 

I think the 'woosh' you heard was air going back into the cooling system, as evidenced by the hose plumping back up. The cooling system gains pressure as it heats up (something like 15 psi) and loses pressure as it cools down. The radiator cap is more or less the regulator for that pressure. As the system heats up, the cap unseats internally and relieves pressure and thus coolant into your reservoir tank, maintaining that positive pressure. When you stop, the temps go down, and so does the pressure. The cap again, that before routed coolant into that reservoir tank, now allows a pull from it, along with the coolant thats in there (or should be). Thats how your system maintains coolant levels under varying temps / pressures. If coolant is getting into the tank (you said you levels were a little high) and not getting back in (the vacuum, or woosh you heard) I would suspect the radiator cap itself might be clogged, or the relief hose might be kinked, or some nastyness in the bottom of the tank might be preventing flow. In any case, from the nipple at the radiator to the tank, there needs to be free flow. I would check for blockage / kinking first. I would literally take the relief hose off the radiator and blow into it to see or hear bubbles in the reservoir tank. I don't recommend that cuz ethlene glycol is bad for you, but thats where I would start. HTH.