over heating on 2001 Toyota 4Runner

my truck run out of cloolant the other day becouse of a broken hose replace the cloolant but my truck now over heat the the temp is ok when is idle but when driving it go up to the red and start to go in the over flow i change the therms and it still do the same thing i love to get a answer please

Asked by for the 2001 Toyota 4Runner
Unfortunately, running out of coolant on vehicles that have aluminum heads is bad. You may have blown a head gasket or cracked a head. That will cause over heating at speeds and not at an idle. Here is what I thought was a very good summary of possible cooling problems at speeds (not at an idle). Hope this helps. 1-Low coolant level.

2-Restricted airflow to the radiator as from leaves or plastic bags in fron of it, or the plastic under-skirting being broken away (as from running up onto curb-stops.)

3-Restricted flow of within the radiator or hoses. Restricted flow in hoses is rarer, but rev the engine to 2000 to 2500 RPM for several seconds after the engine is fully warmed and look for either radiator hose to collapse. To check for restricted radiator, you can take the temperature of the radiator with a non-contact thermometer in several places or you can open the cap (if so equipped) and look for white deposits. White deposits mean you need a radiator. If your radiator has no cap, remove the upper hose and look in through that opening.

4-Poor heat transfer. Poor heat transfer can be radiator to air (look for missing or greenish radiator fins) or internal due to a high ratio of anti-freeze to water (use a hydrometer) or internal due to scale deposits (with an iron engine your coolant will be brownish, aluminum engines can be checked by removing the thermostat or water pump and looking inside for whitish deposits).

5-Insufficient coolant pumping. Metal water pump impellers can erode over time, especially with excessively old coolant. Plastic water pump impellers can break randomly, and are prone to break if the engine is a Ford Duratec or Volkswagen or if the water pump hasn't been replaced after an overheat. Cheap substandard $5 replacement water pumps have often have a poorly designed impeller that can become dislodged. To check, remove the thermostat(s) and fill the system with coolant or water. Remove the radiator cap (if so equipped, otherwise surge tank cap) and observe the coolant level while rapidly snapping the throttle from closed to wide open. The coolant level should change drastically (more than 1/4 inch) if the pump is good.

6-Exhaust gases leaking into radiator. This is usually caused by a leaky head gasket, but can also be caused by a cracked or eroded engine. Note that GM Quad-4 engines are particularly prone to cracking, and four cylinder Chrysler engines and cars owned by youthful males or Jewish women are prone to head gasket leakage. An electroneic gas analyzer can be used to check this condition, but for the do-it-yourselfer, check with the local parts store or tool dealer for a disposable chemical based detection kit.

7-Boiling. Boiling can be caused by too much water in the coolant, insufficient pressure due to a leak or a bad cap, Partially restricted water jackets, or overheating due to another cause. Presumably, any other overheating has already been ruled out so you might as well check for leaks, then replace the coolant with a correct mix and put a new cap on it. If you have a restricted water jacket, you're going to need the engine rebuilt.

***Fan related problems will _not_ cause overheating at highway speed.***
1 more answer
Unfortunately I suspect a blown head gasket . The most accurate way to test for a blown head gasket on a gasoline engine is to test for the presence of carbon monoxide in the cooling system. Snap-On, Matco (part # CO 2000), and Napa sell a tool to check to carry out this test. Another link to a supplier of this tool is http://www.etoolcart.com/combustion-leak-detector-lis75500.aspx. Carbon Monoxide is only present if there is a blown head gasket or cracked cylinder head. http://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm I think the napa part number 700-1006. http://www.blockchek.com/instructions.htm . Signs of a blown head gasket are coolant loss (frequently have to top up the coolant level of the engine without seeing an obvious leak), experiencing over heating or rough engine running or the presence of white sweet smelling steam from the exhaust. A badly blown head gasket may allow engine coolant and oil to mix.