My top radiator hose gets very hot. The bottom one not so hot. After idling for about 5 mins the reservoir tank gets filled with HOT radiator fluid. Shouldn't it suck fluid from the reservoir tank instead of shooting fluid into it?

I also replaced the inside of the thermostat with a new one. Same problem so I know that's not the problem. I tested my radiator plug to see if it works by using a paper clip and sticking it to one end and the other. I turn the key to the on position and it spins! so its not my radiator.

Could a malfunction fan sensor cause coolant to shoot out through the reservoir tank? Does the fan sensor tell the thermostat to open up?

 

idle brings ur temps wayyy uppppp. mine idles for 5 minutes and my temp goes up half way. it dumps the HOT rad fluid into reservoir cuz the temp of it keeps rising, thus biolding more pressure. if your actually driving, the cool air cools off the antifreeze, liek its supposed to...idk if that helps at all

 

If your upper hose is hotter than the lower all the time then its a thermostat problem. On a working thermostat, when the temp is in operating temperature the thermostat opens, when it opens the lower hose gets hot like the upper, also when it opens the hot coolant activates the fan switch on the thermo housing turning on your fan.

When your coolant gets to hot it boils over to the reservoir.
Hope this helps

 

cool it makes sense now.. no wonder it was shooting out through my reservoir. I bought a new fan sensor and installing it tonight.. I hope that was the problem because I already tried a new thermostat and it did the same thing.

 

Make sure you thoroughly bleed the cooling system.

 

seriously...try a new rad cap and save yourself some issues if that is the problem. i was confuse like you are once even swaped out motor thinking my head gasket was the issue. it turned out to be the cap...try it. 12 bucks

 

Waterpump or thermostat.

 

I havent installed the new fan sensor yet but I am really considering bleeding the cooling system thoroughly as I read that it may contain bubbles or air pockets that may not allow the sensor to fully read the temperature accurately. Btw how do you bleed it properly without any air pockets? is there a link you can give me?

 

I also believe that the cap may be the issue also. BUT I been using the same radiator and the same cap and hoses from my gsr swap. I havent done anything to the radiator besides swapping out the motor for another one. But I will consider trying a new cap for better coolant pressure.Thanks

 

What year/engine?

 

It cant be the thermostat because I actually bought a brand new one and installed it. I had the same problem of overheating as well as the fan not turning on. As for the waterpump I actually changed it to a new one so thats not the problem either. But what does the waterpump actually do? just wondering

 

I bought an automatic 96 jdm h22a motor with an estimate of 30,000 miles. Its actually an h2b swap using a b16 transmission and the qsd kit.

 

water pump cycles coolant through your motor to cool it. Sometimes new thermostats can be bad also just to keep in mind, There faily cheap and if you have a defective one it could be your problem.

 

Bleeding cooling system:

-Park car on an inclined driveway with front end higher than rear.

-Turn dash heater ****/lever to MAX heat.

-Follow instructions below. Skip step with bleeder bolt if you don't have one.

 

I heard there was a way to test the thermostat by putting it in boiling or hot water.. then you can actually see it contract. Is that true? just to test if it works?

 

wow, I swear I read this somewhere a long long time ago but I never really considered doing it. I will definitely try this tonight with the old fan sensor just to see if it works. Thanks alot! I will let you know in a bit after I try it

 

I will be back in a bit.. Just gotta clean out the garage so I can put the car in it and work on it. BRB

 

Hey RonJ@HT,
I actually took off the fan sensor and stuck my pinky through the hole and guess what? My pinky didnt even touch the coolant and its longer than the sensor itself. I guess it means that I havent bleed it properly and filled up the thermostat with coolant correct? maybe thats why the sensor didnt read the temperature and turned on the fan because it wasnt even touching the coolant!

 

In theory that would work. Cause a thermostat opens at a certain degree to let coolant flow. I have never personally done it or heard of it. But it sounds correct.

 

I actually tried it last night. I took a sauce pan and boiled water. Then I dropped the thermostat in it and you can see it start to open up. It was pretty cool so it means that my thermostat was working

 

heres the update. I drained the cooling system last night and refilled it with the correct procedure. I even took off the bleed bolt to make sure its filling all the way up and bolted it back on as soon as I seen water stream out with no air bubbles. Then I followed procedures and started the car to wait for the fan to turn on. It still didnt turn on. I tried using the new fan sensor I bought at autozone but it turns out that its the wrong one so I have to return it later today.

 

how long should the fan take to work within starting up? Im still waiting for the fan to come on but its not after idling for at least 10 mins. Its not overheating either and the temperature idle sits just below the half way mark

 

It depends on the outside temperature. The process may take 30 minutes in some cases. Has the coolant level dropped in the radiator during the procedure?

 

well my car temp gauge stays just below the halfway mark between hot and cold. It doesnt shoot fluid into the reservoir tank anymore but my radiator is steaming because the fan is not turning on. Therefore I have to use a paper clip and stick it in the radiator plug in order for the fan to turn on. Then I drove it around the blow with the fan constantly spinning and it doesnt over heat. You think it may be my fan switch sensor? it has to be.

 

Yes, replace the fan switch.