I kinda did a quick search and didn't come up with anything concrete but is there any benefit to putting in a S5 radiator into my S4. I am aware the coolant filler necks and all that jazz are different but is that all? Mine seems to be heating up a little past operating temperature and it's not boosting properly.

And just another problem that I HAVE not searched for yet cause it just came to mind (if I do find a solution I'll post it here) but when my car is cold and I put it into neutral while pulling up to a light the car dies unless I downshift through every gear. So a sudden drop in rpms while it's cold causes it to stall? Any suggestions? Trying to get the thing running prime before I list it and that's a pretty big flaw to have! Thanks guys.

 

The S5 radiator is basically the same as the S4 (size & cooling capacity), so if you overheat now, that won't save you.
Assuming your S4 rad is in good shape, of course.

If you haven't yet done so, it would be worthwhile to remove your rad and check for blockage, especially if you have AC...lots of **** can build up between the condensor and the radiator over the years.

 

undertray?

 

My S4 behaved like this, turns out the stock thermostat wasn't opening all the way and there was almost no coolant going through the rad. I first thought I had a plugged rad so I yanked it and flushed it and wasted hours on that all

 

It's a new thermostat but it is NOT mazda OEM. While I know you should always run OEM stats in rotaries or even in most cases I needed one in asap. I don't think that would be my problem.. Or maybe it is. The stalling out is bother me huge too haha.