2006 Tahoe Cooling system running to cool. 5.3L Flex

[Matt Friend]

I got a 2006 Tahoe 5.3L flex that needed an engine. found a remanufactured (z code engine) had installed with new water pump, radiator and thermostat ( have replaced 3 times wit factory 178 degree stat). Now the engine runs about 165 to 175 on the road. When idling it will get up to about 210 and will stay there all day idling fans turning on and working normally. But when I drive temp drops back down to 165-175. Has anybody sean this and know what the issue might be?

 

[Matt Friend]

I got a 2006 Tahoe 5.3L flex that needed an engine. found a remanufactured (z code engine) had installed with new water pump, radiator and thermostat ( have replaced 3 times wit factory 178 degree stat). Now the engine runs about 165 to 175 on the road. When idling it will get up to about 210 and will stay there all day idling fans turning on and working normally. But when I drive temp drops back down to 165-175. Has anybody sean this and know what the issue might be?

I’m checking temp with obd scanner and gage both are close.

 

[mattbta]

If your radiator was replaced, you might be missing the restrictor in the hose from the rad to the surge tank. Without that restriction, these engines will run too cool. The lower thermostat doesn't help, either.

 

[Matt Friend]

If your radiator was replaced, you might be missing the restrictor in the hose from the rad to the surge tank. Without that restriction, these engines will run too cool. The lower thermostat doesn't help, either.

The thermostat is the factory temperature from Chevy dealership. How can I check the restrictor in the hose? The upper and lower radiator hoses were replaced. Not not the hoses to the surge tank.

 

[mattbta]

I'm not entirely sure. This thread seems to indicate it originally was part of an OEM radiator, but the OP was able to put something in that hose. https://www.tahoeyukonforum.com/thr...rating-temperature.108432/page-7#post-1300016

Good luck.

 

[Matt Friend]

The thermostat is the factory temperature from Chevy dealership. How can I check the restrictor in the hose? The upper and lower radiator hoses were replaced. Not not the hoses to the surge tank.

I'm not entirely sure. This thread seems to indicate it originally was part of an OEM radiator, but the OP was able to put something in that hose. https://www.tahoeyukonforum.com/thr...rating-temperature.108432/page-7#post-1300016

Good luck.

i will give this a try and see what happens may take a day or two. Thanks for all you help this issue has been driving me crazy.

 

[Geotrash]

I got a 2006 Tahoe 5.3L flex that needed an engine. found a remanufactured (z code engine) had installed with new water pump, radiator and thermostat ( have replaced 3 times wit factory 178 degree stat). Now the engine runs about 165 to 175 on the road. When idling it will get up to about 210 and will stay there all day idling fans turning on and working normally. But when I drive temp drops back down to 165-175. Has anybody sean this and know what the issue might be?

Are you basing your estimates off the gauge or from the OBDII data stream? The factory thermostat on mine is a 190ºF. Mine stays between 190 and 197 on the highway and will creep up to 200 (as measured via OBDII scanner with real-time data display).

 

[Matt Friend]

I'm using a OBD scanner live data stream and the gage they are both reading very close to the same temp.

 

[Matt Friend]

Are you basing your estimates off the gauge or from the OBDII data stream? The factory thermostat on mine is a 190ºF. Mine stays between 190 and 197 on the highway and will creep up to 200 (as measured via OBDII scanner with real-time data display).

I'm using a OBD scanner live data stream and the gage they are both reading very close to the same temp.

 

[ks03]

Not to dismiss the possibility of an aftermarket radiator missing the restriction but...
Went through this when I bought mine, ended up being the coolant temp sensor. Took an IR temp gun and pointed it at the head next to the sensor and compared to scan tool reading to diag