Hi,
New to this but hope you can help.
Bought a 97 4.6 p38 hse on which the head gasket promptly failed due to the o rings on heater leaking.
Heads tested/skimmed gaskets fitted new thermostat and new o rings. Since then the cooling system is building pressure and overheating. radiator removed and flow checked by Kendal Radiators, no bubbles etc in cooling system sniff test proves clear, no cleaned pistons/ plugs, runs absolutely fine.
Only thing i have found, is the rad bottom hose to stat remains cold and does not presurise, as does the bottom part of the stat housing, where as the top does get hot. The other thing is that the expansion bottle also appears to stay cold. Have tried changing new stat with old that did work, but same problem. Compression test fine. This engine has only covered 36k.
Did think of losing the stat until i realised the amount of pipes attached to the housing and that it cannot be split.
Willing to try anything, has me beaten.