2.7L coolant not circulating

My 2004 Tacoma hit 100K. So on Friday I changed the belts, spark plugs, coolant, thermostat, upper and lower radiator hoses. After I made the changes I ran the truck with the radiator cap off and waited to see some circulation but nothing happened- bottom radiator hose remained cold and no heat in the cab. So I disconnected the upper heater hose from the firewall and poured coolant into it and reconnected. I ran the truck again and had heat in the cab. But the bottom radiator hose remained cold. On Saturday I decided that the aftermarket thermostat that I installed must be stuck shut. So I put the old one (which was working) back in. Again I ran the truck but the bottom radiator hose is still cold. I drove the truck but the bottom hose is still cold. What is wrong here???
So my questions are: Is there something wrong that the thermostat is not opening? Is there an air blockage? Or does it take warmer weather (cold here in the northeast) for the thermostat to open? Am I being paranoid? Anybody have a similar issue? Can somebody please run their truck and check the bottom radiator hose for me?
The truck seems to be running and idling normal otherwise. In every car I've ever changed coolant in, it only takes some idling to have the thermostat open. I did check the thermostats in hot water and they both open.
Any help would be greatly appreciated. Thanks.

 

Do you have the thermostat in the right direction? How much coolant went back in after the drain?



green arrow part of stat go into the block.

 

Yes the thermostat is oriented correctly, springs to the engine side. Since I didn't drain the block, I got out about 1.5 gallons of coolant. And that's about what I've put back in, give or take a little, I didn't really measure what came out.
I think there is air trapped in the engine not allowing it to circulate. Thanks.

 

If you are positive you have the thermostat in correctly, the next thing I would try is remove it and run the motor. You should see flow. In the NE it may never get warm however....

If you have no flow, bad water pump. If you have flow, replace the thermostat and keep an eye on your temp gauge. Insure it does not go to high. If it climbs and never stops, then you could have something clogged...

PS did you check your tire pressure?

 

Running it without the thermostat was the next thing I was going to try. I don't think it's the water pump, it's not leaking and I've had no temperature issues with the truck. Usually when the pump goes bad there is leaking or noise, I've got neither. I hear what you are saying though, logically it makes sense. I guess nobody has ever had a coolant air lock in their 2.7L engine block? I'll try the "no thermostat" and repost, though if it's trapped air, I think I'll get the same result. Thanks.

 

Also, I do have heat, so the water pump is circulating water thru the heater core. This also makes me think that the pump is working.

 

I removed the thermostat from the system and ran the truck. The coolant is circulating, the bottom hose is getting very warm as well as the heater hoses. The overall temperature of the truck is not getting warm enough to move the temp gauge needle. Until I get the new Toyota thermostat I will put the old one back in. It must not be getting hot enough to open the thermostat in this colder weather.
Could somebody in a cold climate run their truck at idle for 15 minutes or so and check the bottom radiator hose for me? And tell me if it is heating up or remaining cool? Thanks.

 

my 86 one ton pickup had a problem like you have,,,
and it was said to be a clogged weep hole on the New thermostat
hope this helps you
bob

 

Thanks Bob. The weep hole or jiggle valve on my thermostat is ok. And I have it oriented as specified by the FSM.
I drove to work this morning (32 miles) and the engine temerature was normal, a hair below half. I checked the bottom radiator hose when I got to work and it's still cool. ???

 

I will try to remember to check mine when I get home from work. takes me about 15 minutes to get there. I live in CT but I have a 2nd gen which may make a difference.

That said, you know you have flow as you can see it. It may be that the damn radiator is so good that the fluid leaving it is cool to the touch. Once the truck is warm, and with it running squeeze the hose and feel for pressure.

 

Got some good news, forgot to check yesterday, but today I found my lower coolant hose was cool to the touch. IMO, You are good man, your radiator is working properly,

 

It's been well below freezing here for days. I just installed a new ultragauge and my truck coolant temperature warms 2 degrees (from outside air temp) every 10 or so seconds at idle.

Did you test your thermostat by putting it in boiling water first? I always do that. Is the thermostat a genuine Toyota part or not?

 

Boiling water a good idea, save time of doing the job twice.

 

Water pump impeller might be broken. I've had this happen in other vehicles but never a Tacoma. But if its broke you will get overheating. I doubt this is your case though.

I would buy an OEM thermostat. They are cheap so why not get a good quality OEM apart?

 

Thanks to all that have replied with suggestions and help. Special thanks to Vinnyvavoom who popped the hood and checked the lower radiator hose. And yes I've checked the thermostats (aftermarket and my old oem) in hot water and they both work. However I only checked them after I thought I had a problem. Will do before installation next time. I believe all is working as it should. I think these modern engines are just that efficient. I'll be picking up my new Toyota thermostat tonight after work and will put it in this weekend. Should be good for another 100K!
As a side note: This is a 2004 Tacoma that I've had since new. To date, I haven't had 1 single mechanical or electrical failure at all.
Thanks again.

 

OP - I am more than happy to help (took like 20 seconds), the hard part was just remembering to do it (after a long day at work, I just want to go home and snuggle with the doggies). Although appreciated, no special thanks needed, as this forum is all about helping a brother (or sister) out and I may need the same in the future.
As a side note to your side note: that is awesome, I can only hope that my Taco treats me the same (that is why I spent extra on a 'Yota).

 

I did all the same things to my 2.7 AFTER the water pump/altenator belt broke and it overheated blowing out my radiator. Now my lower hose stays cold and NO HEAT thru vents!! WTF?
I will try to run it without the thermostat for a short to see if the heater works and lower hose gets hot. It is around 70 degrees here today.

 

No heat at vents sounds like air trapped in heater core not allowing coolant to circulate through it. Temp gauge not showing overheating right?

 

They can be hard to get all the air out of, I have a tapered funnel that will fit tight in the radiator, I put all the coolant in that it will hold, then start engine and keep funnel about half full,keeping coolant level in funnel is higher than radiator and run engine till thermostat opens and coolant is circulating.