Help. Only get heat when moving.

[whitewatermd]

So this just started on Christmas. I started the car to warm it up. Ran for about 10 mins before leaving to go to my parents house for Christmas. Came out to the car and it was nice and toasty. Drove up the road and came to a traffic light. As soon as i stopped moving, the heat turned luke warm. When i started moving, it heated right back up. I noticed today, that the heat does not feel as hot as it normally does. It used to be so hot that i would have to shut it off... I reecently replaced the thermostat, but the heat worked fine after that. Also, the temp gauge indicates that it is running slightly cooler than right in the middle, but it has been that way for a bit now. Any thoughts?

[Ceeker]

yeah, same problem I'm having..did you replace the thermostat with the same one (temp wise)? Secondly did you make sure you bled the system well enough. You still might have air trapped in the system or it is staying stuck open. There is also one other thing people over look. On m20 engine the thermostat has an arrow and it should be pointing up. on oem stats that is. I changed almost EVERYTHING in my cooling system and I still have the luke warm issue. My only thought is the thermostat is the wrong degree. I put a 71 in and now going to replace it with an 80-German made. my car is running consistently just above 1/4 mark on the temp gauge.

[hotballs]

Ceeker pretty much described most of the issues it could have. If you did a flush or some coolant work the system needs to be bled with the bleeder screw on the top of the tstat housing. With air in the system the heater won't fully work.

For me a working thermostat is a working thermostat. I've had bad luck replacing thermostats for "preventive maintenance" with faulty ones or ones that opened later/earlier than the one that worked that was in there in the first place.