Hello Yall, I need help bad. My 626 is overheating at hwy speeds only. I've new themostat, prestone anti freeze, battery, spark plugs, V and serp. belts, and still at speed it wants to overheat after a couple miles. "Sometimes" I can run for miles without an overheat. I can throw it in neutral at speed and it cools back down slowly. The water pump is not leaking or making noise and seems to be working. Idleing after service, it was bulbing fluid at the rad. neck. I'm lost! And I need this car to make a major run up north for a better job very soon. Thanks Yall!!!

 

might have an air bubble in the rad fluid

 

Could be an air bubble there 6man but would suspect a restricted radiator as a little more probable. A partially resticted radiator can often dissapate the amount of heat from an engine at idle with low rpm but when you start getting higher flow volume at raised rpm the radiator can just not keep up with demand. Try running the engine at idle for 10 minutes or so or at least till the fans come on and then shut off. Unplug the fans so they don't come on while doing this and then put your hand flat on the radiator carefully from side to side and top to bottom. Wherever you can reach past fans anyway. Radiator should be a fairly even temperture across the entire surface. HOT to the touch so be carefull. If you feel any cold or cool spots or areas, then that portion of the radiator is plugged up and not allowing coolant flow.

 

baby i,m sure you're right and another check might be to see if the heater is working properly. lack of flow will produce cooler temps in the cabin even when the engine is red hot. you can also pressure flush the rad and see if it flows easily.

 

make sure your cooling fans are working. if so your rad is probably plugged

 

Same issue with my '99 Mazda Protege (100,000 miles), overheating. Runs great around town, no overheatingbut when running at freeway speeds coolant from the radiator appears to be pushedinto the overflow tank causing an overheat problem. New radiator and thermostatreplaced by reputable shop did not fix the issue. Any suggestions what could be causing this?