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Problems/Service/RepairsIf you have a problem with your HHR, want a tip on repairing or performing a particular service to you HHR here is the place to post!
I started this to open discussion about a problem with my 2006 HHR, 2.4l with 205K miles on it. Some background,
Last June I was on a 200+ mile trip and the coolant temp gauge dropped to zero, the temp display (digital went to 3 lines . It was in the 90's outside and the A/C quit working, and the CEL came on. I tried as hutdown and restart, with no success, then I reset the CEL, and everything came back, A/C, temp gauge and readout. no problems until about a week ago. Same symptoms, only I wasn't using the A/C as it was about 25 degrees out. Not a long drive, but the heat was working fine. Again resetting the CEL and everything came back. I tried resetting the plug on the temp sensor and it worked for a few days. Today went to take it in for an oil change and when I started the truck, the temp gauge didn't move after a block or two, digital readout again was ___ After 2-3 miles, CEL came on. Heat was working good. About 25 degrees outside.
Once I got to oil change place, gauge started working, as did Digital readout, CEL stayed on. On the drive home after oil change (about 5 miles) everthing worked fine except for CEL. I reset that and noticed when I started the truck, the digital readout flashed ___ , then started working.
Numerous eople on here have said it is a stuck open thermostat, I found a few posts with the same problem and they mentioned a bad temp sensor, or damaged wires.
Tomorrow it is supposed to get above 35 degrees out and I will try checking the temp sensor to see if it has any resistance, then try plugging in a new temp sensor to the wiring harness and see if it makes the readout work. My theory is it is a sensor problem or a wiring problem.
If this doesn't work, I will have to take it in and have the thermostat changed with the AC Delco thermostat. I am not really equipped to change it in the cold, and out on the street. whatever I find, I will post here.
.p.s. I do not know what thermostat is in the vehicle but I have driven over 100K miles with no problems overheating. once I had the system flushed and new coolant installed over a year ago.
The t-stat keeps the termp ABOVE 180F, The fan and radiator keep it BELOW 220F.
P0128 means that the temp does NOT reach 180F as fast as the computer expects (that is why it is intermittent). That can because the t-stat is OPEN or because the temp sender is not accurate.
After you fix it you will notice the heat is much warmer and quicker.
"Normal" operating temp is about 190F at highway speeds, Anything below 180F is bad, not good. T-stats DON'T cause overheating!!!! Modern engines must operate at higher temps than last century.
It is 98% most likely the t-stat is stuck. The sensor has no moving parts to wear out, wires can short.
By a "few" I think you mean 100s of posts on the subject.
At highway speeds, I was reading 197 or more most of the time.
We removed the old sensor and replaced with new one. before removing it, temp was reading about 34 degrees. afterwards it was reading about 25 degrees (F)Started the engine and it started to go up right away, which is a good sign.
Playing with the old sensor and some hot water, water temp was approx 120 and the ohm reading was 980, water cooled down to 115 and ohms were 970.. sounds like it was giving the computer a higher temp reading than it actually was. This would explain why I was getting a normal operating temp at around 197-200 driving down the highway. Will do some driving tests later. Got to warm up a but first (me, not the car). only 25 degrees out there now.
When it comes to operating temps THE T_STAT KEEPS IT ABOVE 180F, it controls the minimum temp, it has NOTHING to do with the high temp. (unless the wax in the t-stat leaks out)
P0128 means THE COOLANT IS NOT GETTING UP TO 180F fast enough. On a warm start it might warm up fast enough, on a warm day it might warm up fast enough, on a COLD start it will probably fail.
The object of the t-stat is to be CLOSED t6o encourage warming up and to open above 180f to transfer responsibility to the radiator. My personal experience was at 75 MPH on a very cold day the coolant temp was running at 170F; (this is BAD). The heat was working. On a different car the heat did not work, I had flashback to an old VW.
Some of us old fogeys hang onto the last century thinking that "cooler is better", that is NOT true this century.
OK I get that but... shouldn't the temp sensor read the temperature which in turn informs the computer that it is up to the correct temperature, or taking the correct time to get there? Thus the thermostat could be working just fine while the sensor is messing up how the computer is getting the information.. Kind of like the chicken and the egg.. which was first?? When I started the engine, the digital temp read ___F which tells me the sensor is reading open. The CEL was not on yet. That sounds like a bad sensor as the coolant has not had a chance to warm up yet. After changing the sensor, cold starting the engine, the temp read 25F right away, then started to climb. ONce the CEL is lit, it shuts off the temp readout and the gauge (so it seems) resetting the CEL, the gauge and readout starts working again.
It takes 10 min to change the sensor, and costs $15.. Thermostat takes much longer with draining the coolant, installing and refilling the system (including burping) and thermostat is $58. I made the decision to change the sensor first as the problem is intermittent and consistent with an electrical problem. A thermostat mechanically stuck open (or closed) would be more constant (in theory) In my past job, I have replaced a LOT of bad sensors.
not to say strange things can happen, been there too. I may end up replacing the thermostat too as it is a mechanical device and they do fail. just seems that if it was to fail, it would constantly fail. Stay tuned....
T-stat takes 2 bolts and a skinned knucle, no draining involved, you might drip an OZ on the ground.
As I said by nature the t-stat P0128 is intermittent, it is based on a time dependent AlGorerythm; if it starts out at 60F it gets to 180F faster than starting at 30F.. If the t-stat is stuck open it may never get to 180F.
You said the sensor was reading high, that would not cause the code. Reading low or, more likely not at all might.
The computer calculates a time to 180F based on a lot of criteria usually it is about 2-3 minutes, but computers use micro-seconds.
Usually, the rubber gasket has got itself loose and lodged in the valve, the ACDelco 131-158 does not have that gasket.
Mine was showing ___ after about 0-30 seconds. The CEL took longer. We will be lucky to see anything close to 60 in the next 3 months. Maybe closer to -20 -+20 outside temps.
So the AC Delco Thermostat will not have the rubber gasket?? Rockauto shows a picture with the gasket (??) I looked in my box-o-parts and I do have a Gates 180 degree thermostat that says it is for HHR 2.4L, but I do have one on order that is a AC Delco brand, just hasn't arrived yet. And it started snowing tonight.
On other cars, removing the thermostat caused a gush of coolant. You saying that won't happen on a HHR? I've never tried it , just curious.
The temp sensor didn't leak more than a few drops so maybe(??)
I do appreciate the help and guidance on this forum!
Make sure the rad cap is in tight. Have the AC Delco 131-158 thermostat ready, spring down, to put into place and finger tight those two bolts, several turns .
the cheaper AC Delco professional series wouldn’t cut the mustard either, I have tested that one also.
01-04-2024, 09:21 PM
