When I converted to efans I replaced the stock 28 inch radiator with a 2 row core 34 inch radiator and 05+ efans. It was fine until it started cooling off this fall and it got to where it would take 10+ miles to finally reach 195 and stay there. So I replaced the Oreilly motorad thermostat that was in it with a genuine GM one. Looked up by the vin number there was a part number change and I got the new style water outlet and separate thermostat. It fit just fine but ever since I've hard gurgling in the heater core after every cold soak and it actually doesn't heat up as fast as it did before. Now that the temps are dropping into the 20s and 30s sometimes it never gets up to 195 on my 24 mile morning commute. I get decent heat just not up to full temp. Seems like its bypassing somewhere for one but I'm not so sure my radiator isn't a little too big for the 5.3 liter. What do you think?

 

its a stock temp thermostat or colder like a 160?

 

Stock temp genuine GM replacement. It actually heats up faster if I let it idle than if I'm driving.

 

Interesting. On my morning commute it gets to around 100F before I get on the highway, then takes about 4-5 miles to get to 194 and it stays there until I get off the highway. Outside temps are 40-45F.

 

I'll try to do another test tomorrow morning if I remember.

 

This morning, I got on the highway at 80F, 4.4 miles later it reached 195F. Outside temp was 44F. I was going 65mph the entire time. IMO, the outside temp should not have much effect on how fast the engine heats up, only on its starting temp.

 

You have to remember you are rushing 44* temps through the radiator at 65mph. It's gonna keep it cool, and more so keep it from heating up as quickly. May not make a huge difference but try letting it warm up at idle. Without the fan clutch, it should warm up fairly quickly. Mine comes up to normal operating temp with serious heat blowing within 5-10 minutes of idling, in 30* weather.

 

If the thermostat isn't open the air going through the radiator doesn't matter, right?

 

That's my assumption as well.^^^^^

 

Shouldn't.

When driving 65-75 MPH, my truck won't get to 195, stays around 185 with the
stock thermostat, stock 28" radiator. Sounds to me like your thermostat may be stuck open.