My new Mini I just finished has a lg aluminum radiator, a 180 degree thermostat, and a elec fan set to come on at 180 degrees.

Day time driving the engine runs at a steady 200 degrees, according to gauge and verified with a heat gun. And the heater works just fine.

At night the engine runs at 180 to 190 degrees and I get no heat out of the heater, just cold air.

Any ideas?

 

maybe you have some air trapped in you system.What type of fan are you using? i would recommend that you get a tropical fan if you don't have one. I also run an electric fan to pull air through my rad. it helps when driving in town.

 

I think you are too cold at night and the therm is not opening

I'd pull the fuse from the electric fan for a time and let the car run w/out it.

If you had not said you had heat during the day I'd suspect a clogged heater hose or a stuck or incorrectly installed valve for the heater . . .

p.s. I run a tweeked 1275 in Florida with a stock radiator and have no overheat issues. I did once when the car was smack new 2 me. It over-heated within 20 minutes of ownership. I stopped, smaked the thermostat housing with a hammer, cooled 'er down and have not had another problem in 7 years . . .

Are you moving the heater valve pull at all during your 'tests'?

 

I am not using the engine fan, just the elec. fan.

 

Yes I have moved the heater valve. It's also new.
So here's what I am thinking.
Durning the hot day, with the 180 degree thermostat open the engine runs 200.
At night when it's cooler, the thermostat doesn't open, so I don't get any heat. If I go to a 190 degree thermostat, I'm thinking durning the day I'll still run 200 but at night 190 with the hotter thermostat, am I thinking right?

 

Yesterday I put a 195 degree thermostat in. Put about 40 miles on it durning the day and the water temp stayed at 200. I haven't drove it at night in colder temps yet.

 

It's working great, staying at 200 day time, and 190 at night with plenty of heat.

 

glad you got it sorted