AFAIK that's about normal (at least in summer), as 50-60-70°C exhaust will heat up air and steel (the PSU breath "fresh" air through its fan, which pushes the hot one through the rear PSU grille), whether there it's foam lined or not, particularly considering that you have a very inefficient, outdated and hot PSU (I'm also expecting it's noisy: if it isn't noisy, then it's under cooled, and that adds up to rear air heating).
Your CPU temps look fine too, so seemingly there should not be any induced (I mean, by the case) significant overheating.
I can't say about the winter season, because the referred ambient temp and the expected load should not heat up enough your PSU (and therefore the air coming from), though it should have taken into account you have such a very inefficient (and possibly under cooled) PSU.
Please take note that a proper PSU fan swap in case would reduce the PSU noise (if any), but it could also worsen that rear heating (worsening the under cooling).
Well for winter season I can't really remenber how hot to the touch the metal psu rear is
. But I suppose isn't that hot. To my knowledge this PSU uses the Yate Loon D12SH-12 (2,200 rpm, 88 cfm). I will test with the cooler from my other PSU a Corsair CX430 that uses the same fan. Now that I think better maybe my fan is too old and RPMs are lower, cause the last time that I open my CM PSU I had to lubricate the fan (rattling/clicking noise). I know is low end PSU but is better that any generic and it has like 76% efficiency at full load and 80% at lower loads.
About the noise , both PSUs that I own that have the YLD12SH-12 don't buzz/whine or vibrate (when they are new at least) the only thing that I can hear is the sound of the air like a woosh but isn't loud (at least for me).
I think you might even drop a PM to our co-forumer Abula, about that: he's well experienced about purchasing and dispatching any kind of IT equipment in South America so, in case you needed, perhaps he might also help/advice.
Ty! I will keep that in mind.
Well I gues I will test my CM psu using my other psu fan (corsair CX430) and see what happens. And I'll keep the foam in his place.
Thank you "quest_for_silence" you have been awesome !.
PS: I now is kind of topic but do you have any recommendations about online stores that sale the Yate Loon D12SH-12. My first choice would be Aliexpress. Or if u now a fan model (from other brands like cooler master, nexus etc... ) that I can use to replace my old D12SH-12. I'm mainly interested in the 88cfm spec.