B16 swap overheating when cool air in car

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Makahana187

New Member
i have a b16 swapped into my 93 dx. it runs nicely and never overheats when i have it set on defrost and the hottest setting. however, if i move it off of the warm setting and it starts to get cooler in the car, the temp gauge starts to go up and i have no idea why. the weird thing is that when i see it start to overheat, i put it back on defrost and the warmest it can go and the needle drops back down to normal running temperature within about 5 seconds or less. i was wondering if anyone had any advice to help me out with this because it does get a little annoying. i appreciate any help
oh and the car doesn't have the a/c pump installed. i dunno if that that has anything to do with it
 
another thought, did you bleed the air out of the system when you put new coolant in? It stands t0 reason (atleast to me) that the reason you don't overheat while the defrost is on is because you're bleeding off excess heat from the system allowing it to stay cool.
 
The thermo shouldn't be a problem (not saying it can't) if thermos go bad, they stay wide open. So your temp would fall like crazy in cold weather at high speeds. I say you open the cap, get car to running temp and look to see if the water circulates through the radiator when the thermo opens. Also see if the fan turns on. If you didn't burp it (AKA bleed) then you may have air in the line. Makes sense what Doc G said about not overheating with defrost on.
 
your fan should turn on when the temp gets hot and bring the coolant back down to temp, check the thermo switch and fan to make sure it works correctly,if it is just replace your thermostat with a lower temp 160degress or so. also that half size rad you probably have won't handle the heat, may want to consider a Koyo dual core rad.
 
CAFROG said:
The thermo shouldn't be a problem (not saying it can't) if thermos go bad, they stay wide open. So your temp would fall like crazy in cold weather at high speeds. I say you open the cap, get car to running temp and look to see if the water circulates through the radiator when the thermo opens. Also see if the fan turns on. If you didn't burp it (AKA bleed) then you may have air in the line. Makes sense what Doc G said about not overheating with defrost on.
Click to expand...

I have had sevral stick closed before.
 
it definitely isn't water pump cuz i installed a new one when i dropped my engine in. it is possible that i've got air in the lines because i never did bleed the coolant lines. i had figured also that it could be the thermostat but CAFROG said it stays at normal operating temp when i cruise at high speed on the highway
 
re-overheat

First and foremost,bleed the air out of the system by way of a bleeder valve located around the thermo housing.Radiator cap off,engine running,you'll need a 12mm socket and extension to make reaching it easier,should only take 10 to 30 sec tops,when the air stops,close the bleed screw.Check the temp at that point.You will see a black plastic looking diverter valve in line with a heater hose close to the firewall about halfway down.When you turn the heat setting to full hot,you allow full coolant flow through the heater core and alow the fan to aid in cooling.By turning the temp to cool you close off the flow from the core and rely more on the thermostat,so now that you know how the system works it will be easier to diagnose.From what you have posted,I would say change the thermo,and be sure to get the correct temp rated one,be cautious of the install and post the results.Good luck.
 
Thermos are engineered to stay open when they go bad. Not all engineering is perfect but I have never had experience with them closing. Mine went out and the temp fell way way way low on the highway.
Makahana187 Keep us posted
 
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