It seems that the tractor is OK.Since I have a few Farmalls in the shed and restored I was cured from buying the gauges over here from big parts supplier called Granit.Had same problems with my tractors.
They are rubbish and the pointer isnt on the place where it should be. Boiling water 212 at right absolute air pressure outside and non pressurized pointer at the middle....
All these gauges are from china india and real bad quality and see these also everywhere on ebay
Happyly we have a guy over here who sells quality 52mm gauges for US and Britsh Farmalls even to USA. Small one man company and he told me these facts.Showed me also internal mechanical differences between his and everwhere sold gauges.
His convincing advice to me.Don t look for the problem to your Farmall but look for a working gauge.How?Just put it in boiling water and pointer must be between N and H of the Cold Run Hot scale.
Also on 176 F it muts be exactly horizontal.
Scale of these gauges are 104F-248F or 40-120 degrees.
Number of his gauge is 67135-D.Also sells oil and ampere gauges for Farmall.
Boiling water has everyone available.....
Just my ten cents.....