Need some help here. Does the coolant circulate all time thru the recovery tank or just when thermostat is open? Here’s why I ask. Changed out radiator to a cold case all aluminum 6 months ago. The other day I got a P0128 code, temp to low. Took to dealer, they said thermostat. Put in a new 195 and still only 175 from obd port. Tech is telling me radiator is over cooling. Not sure I can buy that. This just started and has never happened in cool weather before. Any ideas guys? 2006 H2 I am thinking faulty new thermostat it is always pushing thru recovery tank. Could somebody look at there 2 and see coolant is flowing all the time thru tank. Update here, new recovery tank cap. Nope. Clamped off recovery tank hose between rad and tank, back to normal temps. What’s up here. Update. Factory Gm radiators have a orifice inside outlet to rad recovery tank to limit flow. I have a feeling that it’s not built into my radiator. Have read that if you have replaced your radiator with aftermarket plastic radiator and having low temp prob. Remove and replace with gm. Example some have used Napa rad and had this prob. Won’t go back to gm but keep aluminum rad and use some type of orifice to fix. Need to find out orifice size.

 

 

is your clutch fan seized?

 

Hummerz, thanks for the response. I can throw cardboards and towels over rad in the garage and get the temp temp to 185 on gauge and obd scan, soon as I take them off, back to the low temps. It’s got bugged why I see flow thru the recovery tank all the time. I just believe at this point a bad new stat. My garage was 60, temp from left side of rad to the right a 15 diff.

 

Nope, spins easy by hand

 

deleted,

 

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

Possible DTC P0128 or the engine will not reach operating temperature after a radiator replacement. Some replacement radiators may be missing a restriction orifice that is built into the right side radiator tank. The restriction orifice is molded into the nipple that feeds the radiator surge tank.

The engine may not reach operating temperature, or set DTC P0128 due to excessive coolant flow to the radiator surge tank.

Recommendation/Instructions:

If SI diagnostics have been completed for DTC P0128 and no problem was found, contact the customer to discuss radiator replacements, and check the vehicle history for previous radiator replacements. If the radiator was replaced for a cooling system concern, or replaced during a front end body shop repair, it may be missing the radiator surge tank restriction orifice. Remove the surge tank hose from the radiator and visually inspect the radiator tank nipple that feeds the surge tank. If the radiator is missing the surge tank restriction orifice there will be an increased amount of coolant flow to the surge tank. Excessive coolant flow may induce DTC P0128.

If the radiator surge tank restriction is missing, the radiator needs to be replaced with the proper replacement radiator as listed in the GMSPO parts catalog.

This sounds like your issue,

Neal

 

Yep, not going back to factory gm, but will figure out what size orifice and go from there. Have contacted case case radiators

 

Sorry, I went back and read your first post, you figured it out

Just got to figure out what size orifice and put one in there

Neal

 

Thanks for the input Neal