XtremeRevolution and others on this forum:
I've had the same issue with my 2011 Cruze Eco (antifreeze smell periodically in the cabin when it is cold outside, with the heater at above 50%, at freeway speeds for about 10 mins and with minimal coolant loss). I've very much appreciated the way you have handled this forum, and am glad for your proactive and helpful approach. I won't go into alot of detail on my issue except to indicate that I've had it in the dealership twice for this issue, and the second visit resulted in application of the PI (which didn't take because the adhesive on the black tape failed). By profession, I'm an engineer (no, I'm not an automotive engineer, but instead I do system design, and I also do most of my own auto maintenance and repairs). I'm a first-time poster on these forums, so please bear with me if I mess up. Here's what I have to add to help. I've written the narrative below using a tool I use for troubleshooting things and getting to root cause called the "5 Whys." Apologies that it is so long. Please give it a read and let me know what you think. I tried to read the entire 1st forum you created on this issue before generating this document. If you think it may be useful to the engineers at GM who are working hard on this issue, please forward it to them.
Best regards ... cruzex
5 Whys for Cruze Antifreeze Smell (with minimal coolant loss)
- Why is there an antifreeze smell evident in the engine compartment and/or cabin of some 2011 through 2013 Chevrolet Cruzes?
Ans: Since the coolant is a closed system (pressurized at up to the 20 psig rated pressure of the overflow tank), the smell must come from either antifreeze liquid or vapor escaping from the closed system. If it is a large / steady leak, occurring under all circumstances, the leak would be typically be detectable by traditional dealer troubleshooting techniques (dye, pressure testing, etc.), and more coolant / fluid would have to be added to the system regularly.
- Why do some vehicles experience the antifreeze smell without experiencing significant / observable fluid loss?
Ans: The leak must either be a steady by imperceptible / low exchange rate leak (difficult to detect using traditional troubleshooting techniques) or the leak happens infrequently such that only enough liquid / vapor escapes during the leak / vapor “events” to be detectible by the vehicle occupant’s nose(s) (also difficult to detect as it is also hard to catch the vehicle “outgassing event” in the act).
- Why is it challenging to duplicate the events in which the antifreeze smell is detected in the vehicle cabin?
Ans: Many owner’s reports (in the forum) describing the antifreeze smell in the cabin find that it occurs at specific “events.” Namely, that the vehicle has often needed to be warmed up for a period of time with a greater than 50 percent heater setting, and during cold weather and driven at higher rates of speed. Because of the number of factors which have to be present to duplicate the Cruze coolant smell “events” in the cabin, it is challenging to duplicate.
- Why do the difficult to explain / diagnose Cruze coolant smell “events” in the cabin seem to happen more frequently with cold weather, high heater settings, and higher rates of vehicle speed (which would typically not be a worst-case coolant heat build-up / pressure build-up scenario for most vehicles with a traditional thermostat)?
Ans: Typically, most vehicles have high heat build-up / pressure build-up in the cooling system after being driven in hot environments, under high loads, and after stopping / turning the vehicle off (because there is no convective cooling air either from the vehicle moving, or from the fan, to remove the heat from the coolant). In addition, a frequently used remedy to reverse overheating for most vehicles (if they are beginning to overheat during use) is to run the heater as the heat exchange between coolant and the heater core helps act like an additional radiator to cool the coolant. Regarding the Cruze, however, many owner’s reports (in the forum) have described the coolant temperature of the Cruze rising to between 200 and 226 degrees when cold outside temperatures are occurring, and with the heater on with a greater than 50 percent setting and at higher vehicle speeds.
Compared to most vehicles with a traditional thermostat, the observation of the Cruze antifreeze smell along with rising coolant temperature under these conditions would seem counterintuitive. For vehicles with a traditional thermostat during cold outside temperatures, the thermostat remains closed and the coolant is allowed to re-circulate within the engine to allow the coolant to be warm enough to make the heater effective. When the coolant temperature reaches a specific set-temperature, the thermostat opens automatically (due to a bi-metallic material in the thermostat which opens the valve against a spring which has to be overcome for the valve to open) and the coolant is allowed to circulate through the radiator to cool the fluid and prevent the system from overheating / outgassing / etc.
For the Cruze which has an engine computer unit (ECU) controlled thermostat, it appears that either the “electro-thermostat” is waiting too long to open because of the cold outside temperature and extra demand for heating due to the vehicle temperature setting being above 50 percent and / or due to inaccurate ECU sensors or lags in the “electro-thermostat” to respond to the ECU command to open. If the “electro-thermostat” doesn’t open “on time” under these conditions, the coolant temp and pressure within the closed system will rise, and coolant / antifreeze vapor will outgas and / or fluid will escape from the system. The Cruze coolant, under these conditions, will outgas / escape will occur at either the location it is designed to escape from (i.e., the cap on top of the overflow bottle), or from the weakest connection within the system (example in the forum of one instance in which the hose to the coolant tank was oversized, and could allow vapor / fluid escape if pressure / temp was high). Because the vehicle is moving at a faster speed, the vapors will make their way through the hood / cowl seals, and into the “fresh” air-intake and into the cabin (depending on how well these seals are working). The faster the vehicle is moving, the more that static pressure builds up on the hood and cowl seals (i.e., pressure which is trying to force air through the engine compartment and through these seals over to the area (behind the hood / outside the engine compartment) where the “fresh” air is designed to enter the cabin.
Depending on how complex the computer algorithms are for the ECU’s control the Cruze’s “electro-thermostat”, various scale-factor errors on such sensors the Inlet Air Temp (IAT) sensor, the Coolant Temperature Sensor (CTS) and etc. could be giving inaccurate readings to the ECU while it is making the decisions regarding when to open the “electro-thermostat”. I’ve experienced a situation in which a CTS on a GM Saturn that I owned became “cracked” and let coolant seep in and affect the accuracy of the CTS, and these inaccurate readings to the ECU caused overheating, and additional issues / errors with the vehicle emissions calculations that he ECU performs at the start of a “drive cycle.” Possibly one or more sensors on the Cruze become inaccurate over time (e.g., a non-linear output, or where the sensor’s output reaches a limit when the ECU expects it to be giving an output which varies with the outside environment). There were a few reports in the forum in which specific temperature readings were recorded from the DIU as to when the coolant smell event occurred. However, if the sensor which provides the data to the ECU that the DIU is displaying is inaccurate at specific temperature ranges and gives erroneous readings to the ECU, it could cause the ECU to wait too long to open the “electro-thermostat” under the specific conditions of the Cruze coolant / antifreeze smell “event(s)” The “electro-thermostat” itself could also cause an issue if it becomes degraded over time, and requires more drive current from the ECU (only a guess / speculation here) when the vehicle’s coolant becomes hotter, and this could occur if they allow the coolant to become hotter in the Cruze when it is cold outside, and when more demand is required from the heater, and when they know that lots of forced air cooling will be occurring due to highway vehicle speeds.
Having sensor errors creep in over-time, and / or having some of the sensors which are received by GM having calibration errors could explain why the onset of the issue is delayed for some Cruze owners, and why not all Cruze owners have the problem / issue. Also, unique to the Cruze 1.4 l engine (as some in the forum have also discussed) is the turbo charger which may be adding (speculation here) to the cooling system heat load while the vehicle is driving at freeway speeds, and this heat load may build up (speculation here again) more rapidly than expected (under the cold-outside / high interior heater demand condition) and help push the coolant temperature over the set-point for opening the “electro-thermostat” (especially if the CTS has lost its accurate calibration or was not calibrated properly to begin with). In addition, the forum records that some of the Cruze antifreeze events are occurring with the Cruze Eco (which I also have) and this vehicle has a set of vents at the front of the car which are supposed to close at highway speeds to reduce drag / increase gas mileage. The Eco also has smaller cutouts in the grill for fuel economy as well. It could be that the highway speeds (plus cold temp, plus higher heater setting) and Cruze Eco antifreeze events could have a link … as the Eco’s have less air moving through the engine compartment / radiator to cool the engine, and perhaps combined with an inaccurate sensor (or two) the ECU program is not adapted for the Eco and lets the cooling system “overheat” and vent coolant.
- Why doesn’t the PI that GM implemented with the dealerships consistently work to solve the “Cruze antifreeze smell in the cabin” issue?
Ans: 1) It’s not really a solution at all to the real problem (as many have stated / alluded to in the forum, and which XremeRevolution has recently relayed), but instead appears to be a temporary attempt to remove the smell symptoms after the venting / outgassing event occurs. If the system was working “as-designed” then the system wouldn’t need to “vent” as it is designed as a closed-loop system (others have made this observation also). It’s not supposed to lose coolant liquid or vapor unless something goes awry and it needs to vent to protect the system. Well designed pressure systems (and the Cruze cooling system is a type of pressure system) have a “relief valve” so if the pressure rises above the design point, it can vent to prevent the pressure from rising to the point that something “blows up” and hurts someone. It is likely that the Cruze cooling system may have been designed to keep the coolant temperature / system pressure at the correct values under most operational conditions, but if there is an inaccurate sensor or two providing bad data to the ECU, then off-nominal operational / environmental conditions could cause it to vent.
2) Many have had to have the PI “fix” reapplied multiple times because the 3M tape that is used to hold the rubber vent hose in place can’t stand the heat and the tape detaches, and the vent hose is no longer held in position. This happened to mine after the PI, and now I get the smell of “too hot” rubber and sometimes the coolant smell under the conditions in which it is cold outside (30 to 40 deg F), heater set at 50% or more, and vehicle moving at freeway speeds for a period of time which has caused others to have the Cruze antifreeze smell issue.
