My 4runner has the 3.4L out of a 96 Tacoma, so i thought i would post this here.

I changed the radiator (the old one was smashed up pretty bad and leaking so probably wasnt cooling as well as it should have.) Since i changed the radiator, i dont think my coolant is circulating through the radiator. The heater blows HOT and all heater lines get hot, so i know water is flowing through them. The UPPER radiator hose (where my temp gauge is located) gets warm, and the upper portion of the radiator gets warm. BUT the LOWER radiator hose stays cool.

Its like the thermostat isnt opening maybe? Will the heater core still get water pumped to it without the thermostat opening? The thermostat was working fine with the other radiator, and i just got the water pump replaced less that 100 miles ago...

and ive been burping the system all day and cant seem to get any more air out of it

any ideas what the problem may be?

 

Sounds like a stuck thermostat. Does the temp gauge show it getting to operating temperature?

 

THe thing is the dash temperature guage doesnt work (ever since the 3.4 swap i cant get it to work) so i have an in-line temperature sensor in the upper radiator hose to an aftermarket gauge. It will get to around 190* at idle and stays there, but the lower radiator hose stays cold....

 

replaced the thermostat and same thing. Got an OBD II reader, and it says my coolant temp gets to 192*-194* and hovers around there....but the bottom radiator hose is cool...


Am i overthinking this? How "hot" should the bottom radiator hose get compared to the top one?

 

you may want to get a new thermostat- you have probably gotten a bad one...get an OEM. also, you may want to replce your temp sending unit..back of engine near the truck body.

 

pepsibluefloat: i know this is an old thread but I'm having exactly the same problem! the bottom hose feels like its outta the fridge. I get the same impression, there's not enough/any flow, whats more: in my case, I've had 2 water pumps fail since the repair.(less than 1000 miles) any suggestions???

 

make sure the bleeder hole on the T stat is at 6 o'clock position..

 

Yeah I started with that. I even put a fail safe thermostat after the rebuild. New water pump, radiator, fan clutch nd I flushed the block. And I'm getting ordinary temp readings on the dash. Thanks for the reply.

 

I've got close to the same problem. Any fixes on this yet?

 

Afraid not, unfortunately my third water pump just started leaking. As far as flow is concerned, I'm getting full flow however I'm blowing water pump seals like its going out of style. Very frustrated!!! -_-

 

Cheap import pumps or Aisin? What are you using for coolant? Any HG "repair" stuff been dumped into the engine?

 

EXE pump, Toyota red at 30$ per gallon for coolant, no "HG repair". I did however rebuild the cylinder heads in August and hasn't been right ever since...