Being having this problem for a while now my car overheats! I replace thermista,water pump,pump for the fan, radiator,cap to radiator,temp sensor,did a coolant flush, replace fan steals, just about everything but fan motor! Can anyone tell me why this is happening I can drive it couple miles then it will start overheatin and its does it when it wants too! Couldn tell u when it will do it whenevr like it has its own mind! I ve bleed the thermista and the system for air so isn’t not that! I put the heater on to keep car at normal temp but its still gets hot’ I see the fan goin but always the same speed sence I ve had the car! Can anyone help me out here plz!

Im no expert but did you give the cooling system a good Flushing?..

Yes, I can help, but I need more information. Believe it or not, not all LSes are the same. I need to know what year yours is, and if it is the V8 or the V6.
There are some common causes of overheating, but they vary by the year of the car (2000-2002 have one set of problems, 2003-2006 have another set).

I am going to assume for now that you have something from the 2000-2002 range due to the comment about the fan pump.

  1. The hydraulic engine cooling fan system is known to have lots of problems. If your fan does not go to nearly max speed when you turn the AC on, then you have a problem. It is common for the solenoid valve (on the pump body) to gum up and stick in the low speed position. Replacement is the cure for this. It is also possible that you will have to replace both the fan pump and the fan motor if someone added water to the fan reservoir by mistake.

  2. The degas bottle (the pressurized reservoir with the radiator cap at the base of the windshield on the driver’s side) is known to develop tiny cracks that you can’t see all over it. You may not lose much water, but it will stop the system from pressurizing and that will cause overheating.

  3. The plastic cooling system parts at the front of the engine are known to crack. This has the same results as the cracked degas bottle.

  4. The LS is very picky about the need to follow the factory bleeding procedure for the cooling system to the letter. Have you done this? Did you get a steady stream of coolant out of the heater bleed screw at the end of the procedure?

check for leaks and see if the is clogged lines and make sure the lines are tight

it could also be a bad radiator

You are giving reasonable generic advice. Mine is based on much experience with this particular car model. Radiators almost never fail on these cars, but the other items mentioned are common.

here are some tips

  • Cooling system leaks – Loss of coolant because of a coolant leak is probably the most common cause of engine overheating. Possible leak points include hoses, the radiator, heater core, water pump, thermostat housing, head gasket, freeze plugs, automatic transmission oil cooler, cylinder head(s) and block.
    Make a careful visual inspection of the entire cooling system, and then PRESSURE TEST the cooling system and radiator cap. A pressure test will reveal internal leaks such as seepage past the head gasket as well as cracks in the head or block. A good system should hold 12 to 15 psi for 15 minutes or more with no loss in pressure. If it leaks pressure, there is an internal coolant leak (most likely a bad head gasket but possibly also a cracked cylinder or engine block).
    It is important to pressure test the radiator cap, too, because a weak cap (or one with too low a pressure rating for the application) will lower the coolant’s boiling point and can allow coolant to escape from the radiator.
  • Leaky Head Gasket – Bad news because repairs are expensive. A leaky head gasket can allow coolant to seep into the engine’s cylinders or crankcase. Symptoms include a loss of coolant with no visible external leaks, and white steam in the exhaust, especially after restarting the engine when it has sit for awhile. A leaky head gasket can be diagnosed by pressure testing the cooling system, or by using a “block checker” that pulls air from the cooling system into a cylinder that contains a special blue colored leak detection liquid. If there are any combustion gases in the coolant, the color of the liquid inside the detector will change from blue to green. A leaky head gasket can often be temporarily sealed by adding a sealer product to the cooling system. But for bad leaks or ones that cannot be stopped with sealer, the head gasket has to be replaced.
  • Fan Not Working – With mechanical fans, most engine overheating problems are caused by a faulty fan clutch, though a missing fan shroud can reduce the fan’s cooling effectiveness by as much as 50% (depending on the fan’s distance from the radiator) which may be enough to cause the engine to overheat in hot weather or when working hard.
    Defective fan clutches are a common and often overlooked cause of engine overheating. The shear characteristics of the clutch fluid gradually deteriorates over time, with an average loss in drive efficiency of about 200 rpm per year. Eventually slippage reaches the point where effective cooling is no longer possible and overheating results. (On average, the life of a fan clutch is about the same as a water pump. If one needs to be replaced, the other usually does too.)
    If the fan clutch shows signs of fluid leakage (oily streaks radiating outward from the hub of the clutch), spins freely with little or no resistance when the engine is off, or wobbles when the fan is pushed in or out, it needs to be replaced.
    With an electric cooling fan, check to see that the fan cycles on when the engine gets hot and when the air conditioner is on. If the fan fails to come on, check the fan motor wiring connections, fan relay and temperature sensor. Try jumping the fan directly to the battery. If it runs, the problem is in the wiring, relay or sensor. If it fails to run, the fan motor is bad and needs to be replaced.
    With a hydraulic cooling fan, the fan must be turning fast enough to provide adequate cooling at idle and low speed.
  • Leaky Water pump – Any wobble in the pump shaft or seepage would call for replacement. In some instances, a pump can cause an engine to overheat if the impeller vanes are badly eroded due to corrosion or if the impeller has come loose from the shaft. The wrong pump may also cause an engine to overheat. Some engines with serpentine drive belts require a special water pump that turns in the opposite direction of those used on the same engine with ordinary V-belts.

It does not happen very often, but sometimes the water pump impeller can loosen up on the pump shaft and not turn, although the water pump pulley appears to be turning normally. If the impeller does not spin, there will be little or no circulation of coolant through the engine. The only way to know if this is the problem is to remove the water pump and check the impeller to see that is is tight on the shaft. Also, some plastic impellers can become severely eroded over time. So can the water pump housing. The loss of blade area or an increase in clearance between the housing and impeller will reduce the flow of coolant and can lead to engine overheating.

  • Slipping Belt – Check belt tension and condition. A loose belt that slips may prevent the water pump from circulating coolant fast enough and/or the fan from turning fast for proper cooling.
  • Lower Radiator Hose Collapsing – A pinched hose (upper or lower) or a lower radiator hose that is collapsing and blocking the flow of coolant when the engine is running can cause engine overheating. The lower hose usually has a metal reinforcing wire inside that looks like a large spring. It s purpose is to prevent the hose from collapsing when the water pump is pulling water through the hose. If this wire is missing or has failed due to corrosion, the hose may collapse.
    *Plugged or Dirty Radiator – Dirt, dead bugs and debris can block air flow through the radiator and reduce its ability to dissipate heat. Internal corrosion and an accumulation of deposits can also block the flow of coolant. A good way to find internal clogs is to use an infrared thermometer to “scan” the surface of the radiator for cold spots. If clogged, the radiator should be removed for cleaning or replaced. Backflushing the cooling system and/or using chemical cleaners can remove rust and hard water scale, but may do little to open up a clogged radiator.
    When refilling the cooling system, be sure you get it completely full. Air pockets in the head(s), heater core and below the thermostat can interfere with proper coolant circulation and cooling. If the cooling system has no bleeder valves to vent air, you may have to temporarily loosen a heater hose to get all the air out of the system.
    *Excessive exhaust backpressure – A clogged catalytic converter will restrict the flow of exhaust and cause heat to back up in the engine. Other causes include a crushed exhaust pipe or a collapsed double wall pipe. Check intake vacuum at idle. If intake vacuum reads low and continues to drop, inspect the exhaust system

selina: it’s you, not u!

automechanic: that big block of text is unreadable!

dag nab whippersnappers…