1990 Accord LX gets hot

I have a 1990 Accord LX. In the spring of 2004 I had a new radiator put in with new hoses and cap. I installed a new (170 degree) thermostat myself.
That summer (or whenever it is warm) the temperature gauge starts to move up when the AC is on or when the car is full of adults (5) and it has to work hard (AC or no). It never gets to the point of boiling over because I turn on the heat and it comes back down right away. During highway driveing or cold weather it is never a problem. It's also not a prolem in the summer time with just 3 of us in the car and no AC. Both fans work. Finally, when I turn the car off the fan kicks on much more frequently that it used to, even if it has not gotten hot while driving. The thermostat has a bypass of some sort(a hole in the flange with a loose pin in it. Could I have installed that incorretly? Could it be the temp sensor? Thanks for any info you can give me.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Things I would be looking at..
1. Is the car actually getting hot? You would need to take a manual temp reading of the fluid for this. 2. Is the mixture of coolant the proper concentration? 3. Are there air bubbles in the system? 4. How is the flow of coolant? Is the water pump bad?
I am not sure if the thermostat could be installed backwards on your car but if it was you might get overheating all the time.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thank you for your input. How do you know if the water pump is bad? I bought the car used and do not know when it was last changed (car now has 200,000 miles on it). There is no leakage of coolant anywhere.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
test reply

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I had same experience. as days gets hotter i get more heating problem. My only way to control it was to go below 80 and keep heat max.
the problem got worst and worse. There were air bubbles in cooling systems. i flushed it many times and same thing kept happening. more airbubbles... Everytime i flushed air bubbles out of the system, everything seems normal for a while until overheating repeats with airbubble.
Finally a mechanic pin pointed the problem to busted head gasket. Ever since I changed the Head gasket, car's been good.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.