Since the SSR and HHR have very similar hood lines and engine compartments, I have to say that the cooling system on our SS's works just fine as compared to the SSR's. Alot of people on the SSR Forum ending up purchasing an aux fan to complement the fan on that vehicle, including myself. We also had problems where there were many fan failures of the factory fan. Once we had access to an additional fan, it helped our cooling system tremendously.
Now with the HHR SS, it's a whole different story. In the 90's today and very humid, I continued to do my "unscientific" testing of this vehicle. Today's testing was a number of starts and stops in local driving, minor traffic, ran some errands, etc., and I must say this system came through .
Of course I had the A/C on, did you have to ask? But temps driving around ranged anywhere from 198 degrees to 203 degrees, up to 207 degrees while at a light, as soon as you start moving the temp dropped almost instantly. Heat soak does not seem bad at all with this engine, now I am talking about everyday normal type driving, not running at the track, so keep that in mind. The most I seen the temp go up to was 214 degrees after a restart from being in the store for about 10 minutes. Quickly dropped to 207and then to 199 as I was driving down the road. No problem restarting, not slugglish or anything that would be related to heat soak. Nothing at all like I had in my 25th Anniv T/A until I lower the temps for when the fans came on through a tuning program. And the SSR with the aux fan, never had a problem, and that was also an adjustable fan temp control.
MR. ANAL's conclusion, our system IMO works just fine, and I don't see the need for any addional cooling under regular everyday driving...Just thought I pass this info on....

 

yeah there is not much heat soak at all but I have seen it get up to 215 at the track when waiting.

 

I hear you there....but that seems to be the highest it goes that we can see...you 215....me 214...really not bad at all. What was a great feature on the aux fan for the SSR, was that it had a seperate controller for the fan temp, which you could set manually, I had mine set for 199 degrees, and it also came on automatically when the A/C was on, so that you had 2 fans going. It really worked well, and I was really to contact the guy who put the kit together on the SSR Forum to make one up for the HHR if it was necessary. But again, at this point in time, I don't think it is.
We are going down the shore on Monday for a few days, that also will be a good test with the heat we are having.
On a side note, have you ever noticed that when you restart a vehicle after it sits, with heat soak, that the A/C takes a short time to get cool again. Well I have been noticing that the HHR A/C doesn't seem to miss a beat, whether you use the remote start or not. As I stated before, I am very happy with this system.

 

I dont use the AC too much or the remote start but I have notice its cold as heck when I do use the remote start after only about 5 min of sitting running.