about a month ago i bought an 86 audi 4000s. It runs fine no problems. But it seems to run hot. About 3/4 of the way up. Occasionally it creeps a bit more then this and the temp light blinks on for a second.
The top hose is hot bottom is cool. I figured this meant thermosat. Changed the thermostat and I would say the new t-stat is not opening either. Still running hot.
Any tips?

what car do you have, engine, year, etc.....

86 4000S. Four cyl. 1.8. Sedan
I'm wondering if the tstat is wrong or not working. Maybe I need to go with a different temp tstat.

The fans are also not kicking in properly. Right now I'm assuming the problem is the tstat. When I get that working if they're not running I'll check those sensors. Right now I've got them hard wired to run constant until I get this probelme figured out.

on my VW passat I had a problem, same engine, I bought a new stat but it didn't have a hole in it, so I had a huge air buble inside my engine.
I would recomend taking out thermostat out and cheking it. Sometimes even new is bad.
cheking:
thermostat + boiling water. opens good, doesn't bad. by puting it into water and boil the water at the same time.

also make sure you don't have a blockage in your engine somewhere, cause if your top hose is hot and bottom is cool that would definitely indicate fluid not passing through the motor

pulled the thermostat out and bypassed it. Now it's running right. So I guess I have a defective new tstat. And it's the only one they had in stock.
By the way, it's a pain in the butt to change this tstat.

It’s been a long time since I had my 4000. What temp is the stat? If you have one that is 80C or 88C drop in a pot of boiling water if it opens up it is not the stat but air trapped under the thermostat or the water pump. Check the manual there might be a special air bleeding procedure.