Puzzling Overheating issue.
 

***ISSUE FIXED***

Trying to diagnose this car I have been servicing.

93 Accord EX 5-speed.

Brief History: Swapped a new engine into the accord with 100k miles about 2 months ago. While engine was out I did a timing belt job (with water pump and balancing belt) with gates kit with all seals replaced, NGK spark plugs, OEM thermostat, valve cover replaced, etc while the engine was out. I haven't refilled the A/C just yet.

Fast forward till last week: Radiator cracked along the top. Original OEM radiator so I figured it was just time. Replaced radiator and cap (new cap is OEM), bleed car tries to overheat. Funny thing is when I tried to bleed with the bleeder valve, nothing but steam comes out. So I was thinking maybe a bad thermostat. Ran to the dealership and replaced. tried to bleed again, same, no antifreeze releasing form bleeder bolt. Removed bleeder bolt and it has the hole and not clogged. Still trying to overheat. Lower hose always stays cool. Thinking maybe water pump is bad or maybe a blockage somewhere. Removed thermostat (no thermostat), car runs normal and gauge never goes past 1/4 on the dial. Rules out a bad water pump. Throughout the entire process, fans do come on like normal.

Where should I go from here?

Thermostat was likely installed either backwards or with the bleeder pin down. You can also test the thermostat by putting it in a pot of water and start bringing it to a boil and watch to see at what temp it opens.

Thermostat was installed correctly per the repair manual. Bleeder pin pointed at 12 o'clock

https://www.hondaaccordforum.com/for...ine=1433782129

Then test the thermostat as described.

Both OEM thermostats opened about 180 degrees

https://www.hondaaccordforum.com/for...ine=1433791255

https://www.hondaaccordforum.com/for...ine=1433791255

Well, issue is fixed. Reinstalled the thermostat and its working like normal. Thanks for the advice. Maybe thinking the thermostat(s) were shut and wouldn't open till after I boiled them. Who knows.

Next time you refill the radiator, crack the bleeder first, turn the heater diall the way to full red, and make sure to jack the front of the car all the way up as far as you can go. Then fill and wait for the coolant to come out of the bleeder bolt and then close it and continue filling radiator to top. When it tops off, close the cap and you're done.

It's likely that a bubble was stuck behind the thermo housing and wasn't releasing. When this happens, the coolant doesn't touch the thermostat and cause it to get hot and open. This results in the fan switch not getting coolant and turning on the fans.

It's likely the front of the car was either straight or possibly sloped downward.