I have removed the thermostat valve on my LPG fitted Ford Ikon due to an engine over heating issue. The mechanic says the coolant circulation is affected when the coolant is connected through the LPG kit. The mechanic says the Thermostat valve is not neeeded. The coolant needs to flow through the LPG kit to heat up the LPG. What is the solution
The cooling system doesn't know or care what kind of fuel you're using; you must have a thermostat installed. Without it there is nothing to keep the coolant in the engine long enough to warm up. You'll get cold air from the heater, increased fuel consumption from a cold engine, increased emissions, and greatly increased engine wear.
In rare instances the engine can even overheat without a thermostat because the hot coolant sails right through the radiator and doesn't stay in there long enough to give up its heat.
Look for and fix the real cause of the overheating issue. Does the electric radiator fan turn on? Are any rubber seals missing under the front or rear of the hood? Is there any modification that allows air to go around the radiator rather than through it? Has the engine been tested for a leaking head gasket?