1989 Astro. No engine heat

!989 Astro with 4.3 motor that will not heat up. Two stats. No change. clamped off upper Rad. hose. Engine will not get over 150 degrees. 143 degrees at thermostat housing. Help please.

1) How cold is it in Minnesota?
2) Are you sure the thermostat is in correct.
3) Is the coolant fan running?
5) Block the grill, so there's less cold Air going through the radiator core.

Temp 10 above. Checked with Cnev dealer on stat. Yes it is in right. Fan is working. Yes the Rad is blocked off. Also as stated in post, I clamped off the top hose. Engine will not warm up.

Is the fan normally on @ 10f ?
Are you using a digital hand held Thermo temp gun to check Temp?

The blower fan works as it should. Yes my temp gun is a digital infared. The motor itself does not build heat.

Does this also happen when the interior heater controls are set to OFF?

Yes it does

The engine coolant fan shoundn't run 10f!
Is this an electric fan?

Fan is not Ele.

It's probably a bad thermomatic, or mechanical fan clutch.
It shouldn't move much when cold.

I had an '88 Astro with a similar setup. The clutch fan would run almost full lock when cold due to the viscosity of the fluid in the clutch hub. That shouldn't matter if the thermostat is functioning properly. If there is no coolant flowing to the radiator all the air in the world flowing through it will not overcool the engine. I've had numerous car with fixed fans as well and never overcooled.

Is there a weep hole in your thermostat? Is the thermostat rated at 195°F? Is there adequate coolant in the system? Does the van have rear heat?

That is why I never understood people who put cardboard in front of their radiators- unless just the air flow across the engine is a big issue, a good thermostat should keep the engine warm.

It doesn't get very cold where I've been, only down to about -42°F (-41°C). I've never needed cardboard because it's so warm in the winter. I suppose if you lived somewhere that got truly cold you might want to do that.

There is a different problem here. A baffle in the grille won't hurt right now but obviously proved that air flow through the radiator is not the problem. Coolant is getting cooled somewhere and unless the thermostat isn't closing completely it isn't the radiator. Check that - The thread starter also pinched off the upper radiator hose and that didn't help, so I'd suspect a rear heater or really good heater core sucking all the heat away or low coolant/poor coolant circulation.

What is the concentrate of coolant? (How much freeze protection?)

New ...$18,00 thermostat. Drilled 1/16 weep hole.Seems to be a lot better. Will find out in the am as I head to the twincites. Will be -20 when we leave.

Cool! I mean... Hot! (I hope.)

Are you thinking the old 'stat was cold or leaking?

Back home and all is well. Had to stop about 60 miles from home and take off my jacket. Rear heater was off and front heater was on low. Wife is happy so Im happy. Thanks to all that sent a post. Take care. P.S. Was - 19 when we got home about 6PM.