2000 JGC Overheating (Some)

"James Nipper" wrote in news: snipped-for-privacy@corp.supernews.com:

Don't think about most likely, think about cheapest! Thermostats are very inexpensive so give that a shot first. The water pump is probably due because of the mileage on the vehicle but if it isn't leaking I'd wait until it does. It could cause your overheating but it's less likely than the radiator. It could be pretty crudded up at 120K miles.

I'd take a look at it. If it has the plastic tanks I'd replace it because the gasket that is between the tank and core will go bad sooner or later. If the tanks are metal you should be able to rod it out with good results.

BTW there's dozens of other causes of overheating that are often overlooked. Clutch or transmission slippage, very bad wheel alignment, dragging brakes, etc. all can contribute. Anything that opposes the movement of the car can cause overheating but I'd change the thermostat first and then take a look at the radiator.

How old is the coolant?

Have you added any in the last 6 months?

What kind did you add?

What does the coolant in the overflow tank look like?

Does the overflow tank look like it has a layer of 'slime' inside?

If you have the factory fill coolant is now about 7 years old and you could have corrosion in your cooling system. a can of cooling system cleaner might be of great use along with fresh coolant.

If you added coolant in the last six months and it was ANY brand other than Zerex then you probably added DexCool to the system and DexCool + DC coolant results in a reddish brown sludge which would coat and clog the system.

If you refilled the system with Prestone or Peak then you added DexCool and your water pump,thermostat, and radiator might be complete corroded and your engine seals damaged.

Anything mass produced sometimes is defective and gets part quality control, check your fan clutch again.

Depending on your answers:

You may want to add a flush-n-fill tee and chemically flush the engine, replace the thermostat and add 2 gallons of Valvoline Zerex G-05 coolant concentrate (in the gold jug) and top it off with distilled water. This will give you protection of -65 to +270.

Please note: Valvoline Zerex G-05 is the only coolant approved for the new DC vehicles. Older vehicles can use "American Green" but NONE can use Prestone or Peak (or most store brands)

: >

: > This is a V-8, 120 K miles. It usually runs around 200-210 : > degrees. During last six months or so, it will go up the 235 degrees when : > traveling over 70 mph. It will also do this when going up a medium : > incline, even at very slow speed. : >

: > It stays 100% normal at slow speeds, and at idle, such as at a traffic : > light. : >

: > Fan clutch was replaced fairly recently, that DID relate to heating some : > at idle. : >

: > I am thinking either I need radiator work or a new radiator OR that I : > may have a bad thermostat. I suppose I could also have a defective : > water pump at high speeds, but that wouldn't explain why it overheats on : > medium inclines even at slow speeds. : >

: > BTW, some folks may say 235 degrees is normal under some circumstances. I : > can assure you that this is NOT normal, as I have driven this car for six : > years and I know how it performs. : >

: > What is most likely culprit? Themostat/Water Pump/Radiator : >

: > If it is radiator, is it worth it to have it re-rodded, or is it best just : > to install a new radiator? : >

: > As a non-mechanic, are these any tests I can do to narrow it down more? : > (Water pump does not leak). : >

: >

: > Thanks for any tips !!! : >

: > --James-- : >

: >

: Sweet writed up! Kudos!