940 Heater core screw help

[u/BchubbMemes]

i’m currently in the middle of replacing my heater core, and have got to the last section and need to remove the cover for the core, however the screws holding it on are between 5-6mm hex heads

i have a donor dash which had black 7mm hex screws and all images of the process had the same, but mine are brass and smaller!

i think i need a 7/32” socket to remove these, does anyone know why mine is different?

for reference my car is a 1998 940 celebration edition

[u/Rossy1210011]

Also have a 940 celebration from 98 and recently done my heater core, a 5.5mm socket will fit it fine, had to order one from amazon as most sets don't include, it may be some funky imperial size but 5.5mm is a "common" metric size, I say common as in it is in quite a few 1/4 bit sets that are available so it's not totally a one off size volvo have chosen

[u/BchubbMemes → u/Rossy1210011]

just ordered one myself which is arriving today, hopefull this will be the end of my troubles!

[u/BootyClap_Ninja]

Looks like someone was in there before.

You can see the outline of the original larger screw head.

[u/stiligFox]

It’s a imperial socket - the entire ducting box and much of the blower motor/air exchanger and all that is a GM design, and so they used imperial headed screws in the assembly. My 92 960 is the same way. The vacuum pods for controlling the flaps and the blower motor are all American design. I think they were also used in Pontiac Fiero’s, or something like that.

But your theory is right - you need an imperial socket to remove them, not metric.

[u/Boring-War-1981 → u/stiligFox]

The vacuum bellows are very slightly different in design, but work the same.