M45s Excessive Cabin Heat

[milto0n]

I've been having this issue for a long time now. As soon as I close the windows, the cabin just becomes so warm and stuffy. Yesterday, I drove along the cost where it was about 55 degrees and completely overcast and observed the heat that seemed to just radiate inwards. It happens with or without the recirc on. I have 5% tint in the rear, 70% up front with ceramic heat resistant film. MY best guess is that it is just ambient heat coming front the engine bay.

Anyone else have this issue? I'm thinking about buying some heat shield and wrapping the firewall and transmission bellhousing area.

[Ilya]

I can't say I had that issue on my 07 M35x or my current M56x...does your center console or floor feel hot? Especially the tunnel where the exhaust is, etc.? Maybe you're exhaust heat shields are no bueno?

[EdBwoy]

Do you have the OEM headliner?

And silly question - with or without the recirc on, is the HVAC system on or off (whether AUTO or manual)?

[EniGmA1987]

My car has always gotten stuffy unless the AC is circulating air while the car is on. Isnt that normal for heat to build up in a small, enclosed space? I just always drive with the AC on and it is never an issue. Both my cars are this way.

[milto0n]

I honestly can't put my finger on it. This was something that I noticed when I had coworkers (multiple) in my car tell me that it would get so warm the second you closed the windows. It feels like it comes from under the dash, like heat just gets trapped there and even with the windows rolled down, the heat just lingers.

I too have been driving with the A/C on at all times now. Edbwoy, I have experimented with both HVAC on and off, fans high and low.

I know for a fact it is not placebo effect as I drive at least 3 different cars a month for work and none of them pull this (Enterpise rental vehicles). Even the old 2005 GMC Sierra fleet vehicles I drive throughout the bay area are within what I would consider normal. The only reason this is an issue now is that I will be moving to Arizona in the coming months....

[mactaite]

I do remember some of the G35s had this problem. I believe people found air coming in from the battery box but haven't heard anything similar on the M's. Also, a friend of mine has heat coming from the driver side floor behind the center console of his q50. I don't know if he went to the dealer yet. It might be helpful if you had someone drive while you are in the passenger seat to see if you can locate the area of where the heat is coming in from. '

Also, have you done any mods to your car like adding a sound system? Might be too simple but installers sometimes run the wires crazy through the engine's firewall.

[FlawleZ]

This common for any car. It's actually a sign that its insulated well. Your a living breathing human that's warm blooded and probably constitute 20% of the cabin space when inside. Naturally if you have the windows closed with no ventilation your body heat will warm the cabin.

[EdBwoy]

Do you experience the same effect when you drive at night?
And how about the question on the headliner?

[milto0n]

Sorry for the delay, been traveling for work. My headliner is OEM. I have battery cable running through the rubber grommet in the fire wall but I used RTV to create a tight seal.

It's an instantaneous increase in heat. I felt around near my feet and noticed that the surface beneath the carpet is hot. The next step is to definitely have someone drive while I feel around. In the meantime, I'm crankin the A/C.