Thread: Melted Thermostat Housing Bung or Blown Head Gasket ?

Hi Spud Boy

I live in Littlehampton
Work at UniSA in the City
Wife works in Woodside and takes the Disco with her, so we found a Diesel mechanic in Woodside but I am not sure of their knowledge about LandRovers

Merlin

Personally, I would never run any engine without an operating thermostat.

Why ?

Removing the thermostat is a band-aid solution (and IMHO, a poor one at that) for a cooling system problem.

Firstly, as has been stated, the thermostat aids in quickly warming an engine up to running tamperature.

Secondly, every engine, particularly diesels, have an optimum temperature at which it is most efficient/produces optimal power/least wear. In my experience, this is in the 90-95*C coolant temperature region (this includes racing engines !). This is the temp where all the operating clearances are optimal, and combustion is at its most efficient. Remember that power is synonymous with heat. Internal combustion engines are very inefficient. The heat of the expanding gases is what powers the piston back down the bore. Far too little of this heat is used for this. The vast majority disapears into the cooling system and out the exhaust (at least the tubocharger turbine harnesses some of this)
Too low combustion chamber temperature provides insufficient burn, leading to reduced power and unburnt fuel going out the exhaust. A diesel is a compression ignition engine. This means that very hot air ignites the fuel when it is injected int the combustion chamber. Not as hot as it should/could be leads to incomplete combustion, which equates to loss of power, increased fuel consumption, higher exhaust gas temperatures and increased wear.

Thirdly, I believe that most engines need a certain amount of restriction or back pressure, generally accorded by the thermostat for optimum coolant flow through the block/head. It was fairly common years ago to see irregular bore wear in Holden sixes after extended use without a thermostat.

If an engine is overheating, please don't take the (seemingly) quick fix option of removing the thermostat. Please take a holistic approach and look at the overall system. It may be a lack of airflow, (remember that the superheted air from the radiator has to exit the engine bay for ambient air to flow through the radiator. This often isn't properly addressed) perhaps the pump lacks sufficient volume, the heat exchanger (radiator) lacks surface area, the exhaust system may have a restriction, or it may be as simple as the type of coolant used can be optimised. (e.g. OAT coolants have a heat transfer co-efficient roughly half way between conventional ethylene glycols and pure water)

A thermostat is only a temperature regulator, nothing more, nothing less, but it is an important job, and not one that should be eliminated lightly.