View single post by Mark Rosenbaum
 Posted: 07-29-2006 03:08 pm
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Mark Rosenbaum

Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
Your oil pressure at cold start is a bit lower than normal but seems better than average when hot.  If your oil gauge is accurate, you might wish to address the oil pressure relief valve if you ever have need to open up the oil pump, but other than that, I wouldn't be concerned.

For the temperature issue, you might wish to consider the possibility that your dash gauge is less than absolutely accurate.  Before spending lots of money to fix a problem that may not exist, it would be prudent to actually measure the coolant temperature with a real thermometer.  If your cooling system is in good shape it will keep the coolant at the thermostat's rated temperature, or 100°F above the local air temperature, whichever is greater, under normal street driving conditions.  For more aggressive driving, this temperature difference will increase significantly, but that isn't a problem unless the coolant starts to boil.  If the antifreeze mix and radiator cap pressure are correct, boiling won't occur until the coolant temp exceeds 238°F or thereabouts.

That said, if the cooling system is not performing as expected, you may wish to check the following areas (some of which have been mentioned by others on this thread):
  • Corrosion in the engine block.
  • Sediment or corrosion in the radiator.
  • Mechanical blockage due to debris in system.
  • Lower radiator hose collapsing during operation.
  • Insufficient coolant flow.
  • Radiator cap opens at too low a pressure.
  • Poor airflow through radiator or oil cooler.
  • Partially blocked radiator or oil cooler.
  • Slipping water pump drive belt.
  • Incorrectly assembled or internally corroded water pump.
  • Using wrong coolant (needs to be about 30-60% antifreeze).  Using water alone will cause your cylinder liners and water pump impeller to rust, and eventual cooling problems are all but guaranteed.
  • Head gasket leak allowing combustion gas to vent into cooling system.
  • Exhaust or intake manifold leak.
  • Excessively lean fuel/air mixture.
  • Retarded ignition timing.  The factory vacuum retard system is known to raise engine operating temperature by about 20°F when enabled.
To improve a cooling system that is known to be in good working order, there are a number of things that can be done.  These are:
  • Using a 'water wetter'.  This stuff increases heat transfer to and from the coolant and is probably advisable in any engine with sediment or internal corrosion issues.  Such engines frequently have problems with coolant flow or heat transfer that result in localized boiling that gives the impression of an overheated engine.
  • Installing a late-design Lotus water pump.  These are known to have significantly improved coolant flow compared to the JH pump, and seem to help at all speeds above idle.  My data is scanty but probably a pump with casting revision E or later would be advisable.
  • Adding a radiator shroud (fan shroud).  This increases air flow through the radiator at all speeds, and is particularly effective at idle.  Some care must be used during installation so as to avoid clearance problems and masking of the radiator core.  Installation can be a bit tricky because, in a JH, the engine sits at an angle with respect to the radiator.
  • Adding a radiator with increased heat transfer capacity.  This includes larger and/or thicker radiators, those with additional core tubes, etc.  Note that a radiator with a larger coolant capacity but the same heat transfer capacity as the stock radiator will not prevent overheating, but will increase the time it takes for the engine to overheat.  This may be adequate for street cars that see exuberant use only rarely.
  • Adding a spoiler.  This increases air flow through the radiator if the car is moving but has no effect at all when the car is sitting still.  Even a fairly small home-built sheet metal spoiler can provide some improvement.  Spoilers can be subject to enormous aerodynamic stresses, and to damage from impacts, so considerable attention to mounting is essential.
In conclusion, there's no black art to solving cooling problems, merely attention to detail and a slight acquaintance with basic physics.