1992 kawasaki vulcan 1500: engine overheats, blows steam back into reservoir, coolant in radiator is not hot enough to kick on fan. Replaced Thermostat, get air in the bleed valve at thermostat housing. Appears that the coolant in not being pumped to the housing. I inspected the water pump and everything seems fine. no broken fins and in spins when engine is turned over. At a loss.

you can be running lean gas
basically if radiator is very hot then the pump is working
squeeze the hose it should have lots of resistance
use a thermal gun it should be constant temp all over

bout all i can think of

I have heard of cases where there is enough coolant in the plastic bottle (reservoir) but, there is not enough coolant in the radiator itself. When the car is COLD (important - hot water and steam will burn you!!), remove the radiator cap and fill the radiator itself with coolant. In the COLD condition, remove the radiator cap, then start the car and while the engine is running, fill the radiator with coolant until the coolant is stagnant at the filler spout, then quickly replace the cap otherwise the engine will heat the coolant up and will start blowing out the top! If this doesn't fix the problem, replace your radiator cap and if that doesn't help either, replace the thermostat. Lastly but not likely, it might be a problem with the temperature sensor.

You have air trapped in system , change thermostat , bleed air from system , let it run hot while adding coolant with blower full blast on all front and rear heaters .

Yes it would overheat without circulation, but the coolant doesn't circulate through the overflow tank. That reservoir only gets coolant into it when the coolant gets hot and expands and pushes the radiator cap seal up to let coolant into the reservoir. When the vehicle cools down, the coolant contracts and the lower level in the radiator will siphon the coolant out of the reservoir back into the radiator. Coolant circulation is from the engine to the radiator and back into the engine...and also through the heater core.
You may have an air block in the heater core. Check by taking off the outlet hose at the firewall or at the engine and see if you have a slow steady stream of coolant, with the engine running and heater controls on high heat. If it was an air block, a steady stream should quickly start. If you get little or no flow, the core may be plugged and need flushing backward or replaced.

Remove cap from radiator and fill this way, the meaning of the word reservoir remove oir from the end and you are left with the word reserve, the mass of the coolant is located in the radiator, the resovoir holds the coolant that is exsess when the engine is hot and the water has expanded,

You have air trapped in the system. If you have cold air, warm air, cold air from your heater, then it's air entrapment. Very common these days. Go to a shop that uses vacuum method to refill cooling system & that will purge air.
Otherwise, you can try. Park uphill. cold engine - fill radiator to top with 50/50 mix of antifreeze. leave cap on but loose. fill reservior to 3/4 full. Turn heater to hot to allow coolant to flow through heater core. start engine, run at 1500 rpms until thermostat opens and upper hose is hot. tighten cap and let it cool down. after cool check level of reservoir. fill to top line on reservoir. it should **** coolant back into radiator as it cools down.
repeat if still an issue.

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Yes it can be the head gasket,one way to tell,is make sure the engine is cold,like in the morning.Take the rad.cap off,add water until full.Turn over the engine and let run,while looking at the opening(where the cap goes).Is the water coming out like really fast,maybe as much as a fountain?If so,then it is a head,or head gasket.If you would like to bleed system of air I can tell you how.If there is air in the cooling system,it will run hot.With it cold,or cool,not hot or real warm,fill the reservoir with water up to 3/4 full,over the fill mark.Fill the radiator full,and replace radiator cap,and reservoir cap.Make sure the hose from the reservoir to the radiator is in good shape,no holes or crimped anywhere.start the engine with the ac off.At this point the cooling fans should not be on.There not supposed to be on unless you straight wired them.Before the fans come on by themselves,or the vehicle runs hot,and right before not to soon,cut the car off.Go in the house and get on computer for about 30 to 40 minutes,and go back out side and check the water level in the reservoir.Is it down?if so add more water and repeat process until engine runs at normal temp.The fans should come on,and go off on there own,with the ac off.Let me know the out come.

fill the reservoir with the coolant. it is a GOOD thing you dont see steam or a leak I hope.YOU DO WANT TO CATCH THE PROBLEM BEFORE IT REALLY OVERHEATS OR YOU MAY HAVE MORE COSTLY PROBLEMS. fill the reservoir. BUT, it may only fill the "radiator" once you do this as it cools off. As the radiator water cools it sucks the reservoir water into the radiator. as it heats up and the water swells (increases in volume) it pushes the excess into the reservoir. when the engine is good and hot and you dont have any coolant in the reservoir, that is a sign that the radiator is low or empty also.
when the engine is cold, find the radiator cap and remove it, add as much coolant you can there. fill the reservoir also. If it has been several years since the radiator cap has been replaced, I would do that now ( it is a cheap investment). if the gasket on the cap is not sealing well anymore or the exspansion valve mechanism on the cap is not working properly anymore, then it will let coolant pump out into the reservoir and not hold radiator pressure. if the reservoir is empty the radiator itself is probably too low or empty.

Ford 2000 Taurus

To solve the problem you have the things to do in this order;

) When the engine is cold top off the radiator with fluid. (When the pump was replaced the fluid should have been also)
) Make sure the radiator fluid has anti-freeze in it. This is also anti boil also !
) Add fluid to the overflow reservoir.
) Make sure the drive belt was replaced on the water pump.
) With the engine running, you can add fluid to the radiator for the first minute or so. You want to get air pockets out.
) Replace radiator cap.
) Let car warm up. When it's hot you should get the radiator fan coming on.
) When it get hotter the air-conditioning fan may come on.
) If the fan does not come on, the heat sensor is probably bad.
) If all fans come on, and it overheats, you may have a bad thermostat. Trace the upper radiator hose to where it connects to the engine. That's where it located.

Do not operate the engine when it overheats, You will damage the head gaskets and cause radiator fluid to leak into the cylinders.
If you smell radiator fluid in the exhaust fumes, it may already be leaking.