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Hisun 500 engine thermostat


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I don't see how a thermostat missing would cause overheating. The thermostat is used to get the motor to heat up to operating temp, so you can run a heater, etc. Lack of a thermostat would cause it to run too cool. 

  I'd look for other problems, like the water pump impeller running backwards. It has to push water in a certain direction, or it doesn't work right. I had a jeep that had this problem. The parts house gave me one to fit a serpentine belt. Which went underneath the bottom side of the pulley. Turning it the opposite direction.

Or an air bubble in the system. Today's cooling systems have to be "burped" sometimes. Especially foreign cars.

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I understand operation of thermostat. The question I was asking was why do you call it thermostat housing if one is not there from factory.  Impeller is going the way the engine is turning, no belts. Have bleed air, it just won’t move water to radiator to cool by fan which is controlled by temp which water not moving to radiator will not activate fan. Ordering a new water pump which I see nothing wrong with this one. It is one of very few parts that can be ordered. 

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The engine block casting process is pretty standardised, and would need to have some sort of piece to attach the coolant hose. So they used a typical thermostat housing. That way they don't have to engineer a hose nipple. Then pay to have it manufactured, which would only increase costs. The thermostat housing can be easily sourced. And it's common in any manufacturing industry to source common, non- propietary parts from elsewhere, and not manufacturing in- house. So it's natural to call it what it is, even though it doesn't actually contain a thermostat. That would be my guess.

     I'm sure that you could put one in there if it has the relief cut around the rim. So that the thermostat would properly seat, & seal. Although that wouldn't help your overheating problem. My guess would still be a water pump problem, or air in the system. Of course, not examining it personally, I can't totally rule out a blockage in the system, a clogged radiator or internally collapsed hose or something. But that seems extremely unlikely, and I trust that you've eliminated those possibilities.

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I understand operation of thermostat. The question I was asking was why do you call it thermostat housing if one is not there from factory.  Impeller is going the way the engine is turning, no belts. Have bleed air, it just won’t move water to radiator to cool by fan which is controlled by temp which water not moving to radiator will not activate fan. Ordering a new water pump which I see nothing wrong with this one. It is one of very few parts that  is available. This pump was put on by someone else and leaked oil and water. I pulled and found no gaskets orings. New orings installed, back flushed radiator also visually seen propeller turn with water pushing through. How’re ever I did notice impeller would move in and out like it was spring loaded.  It must be springing out and gear no connecting pump shaft is only thing i can determine.  How many degrees is hot? Curious cause can open bleeder on thermostat housing and it streams out. 

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  • 8 months later...

They notoriously run hot - search this forum for adapting bigger dual electric fans - my 800 does have thermostats (supposedly, I never took them off to see if they are installed -  living in a tropical climate makes  them needless) mine ran hot because some genius installed the license plate over the front grill for the radiator.  I drilled my own holes and made a bracket to mount it hanging down below the bumper - it regularly gets folded off roading but I flatten it back straight enough to keep the tránsito from pulling me over - if you are certain that the pump is working - I would keep burping it for air bubbles - had that problem with a little 3 cylinder Korean car for several months before I finally got it to purge completely - you may have to start it cold, with a hose in the radiator and just keep running the motor and burping the return hose until it gets too hot to hold on to and you can almost feel the circulating water pressure as you squeeze the hose. 

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  • 3 weeks later...

Having same issue with my 750.  I have flushed entire system and bled it over and over.  It gets hot and no water in thermostat housing.  I find no leaks, no water in oil, and no smell of antifreeze in exhaust.  Thinking waterpump but its not leaking and thinking there is not anything in the pump to mess up.

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Water pumps can go bad without leaking. Usually its a bad bearing. You can try taking the belt off, and rotate the pulley by hand.  If the bearing is bad. You'll feel it.

There was another member here that had everything in the cooling  system working. But it still overheated. He said that he found a weak breaker. I'd guess it was for the fan. Typically the fan is the weak link in most of these situations. Although the sending unit is a close second. 

So tell us more about what you've checked so far?

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Well when it first happened the radiator and hoses were cool so there was no flow.  I fojnd when i pulled the bleeder screw on the thermostat type housing there was no water and it was super hot.  I pulled the plug off the sensor on the housing and the light went out.  Connected it back and light xame back on.  I filled radiator and bled it and got flow again.  I ran it and hoses  and radiator got hot and fan started.  I thought I had fixed it but after running it around for 10 minutes it got hot again.  Checked and again no water at thermostat housing bleeder.  Added water and rebled with flont end elevated.  Again hoses got hot and fan came on and 10 minutes of running and same thing.  Radiator and hoses cool again.  I checked for leaks and all tight.  Checked exhaust for smell of antifreeze and nothing.  Checked oil for antifreeze and nothing.  I am stumped.  Engine starts and runs fine.  No leaks found and seems to circulate water initially but then stops.  I have a hard time believing its a water pump but I am runnkng out of ideas.  Oh I also flushed radiator and lines and no obstructions found.

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No the fan does not run because the rad and front hoses are cool.   The rad cap seals tight but not sure how to check it.  I am also not familiar with a leak down test.  What is so strange is it I bleed it and it circulates.  When I run it then it seems to not at high rpms and gets hot.

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My guess is that its a head gasket, just from the weird symptoms. And the low hours, and it being relatively new. But I'm definitely just guessing here. Try the leak down test. Its a conclusive test for that condition. And will definitely answer that particular question. 

Here's another question. Was it doing this when you bought it?

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