I have an 87 honda accord 2.0 carb. The temp gage and heat only work when sitting still. when driving the heat turns cold and the gage drops. I was told it could be a vacuum leak but not sure on that. Any ideas? Also any place i can find a heater hose routing diagram?

 

Check coolant level. 94

 

Is the thermostat really old?

 

i think it is really old and i have a new one ready to go in as soon as it gets warmer round here. Thats my first step. It has a bad freeze plug and leaks a lil coolant which i keep topped off. would the bad freeze plug cause loss of pressure in the system as well as loss of coolant causing my problem?