Overheating Problems

[Gantos]

I'm not sure what model Nissan you have but I have a 1988 GQ 4.2L petrol model with carburettor that had an overheating problem that had everyone baffled. Overheating problems are the worst kind and difficult to solve sometimes, the GQ 4.2L seems to have more than its fair share of overheating complaints.
In my case, apart from the engine getting too hot especially when the air conditioner was used , it was noticeable that the water cooling system was unusually pressurised which everyone diagnosed as a blown head gasket or warped head or the head going soft, common in Nissan GQ's I was told.
None of these turned out to be the cause and the cause was actually the two carburettor water heating hoses that were original and had never been replaced because they are almost inaccessible underneath the carburettor. One hose comes off the back of the water pump housing and the other comes in up higher, one hose was breathing in air when the vehicle was traveling at speed but not leaking water, it was acting as a one way valve. A traveling air pocket(s) was formed in the head and presumably causing hot spots or interfering with the thermostat.
Once both hoses were replaced, and this was a difficult job, the overheating problem was solved.

Hope this response helps someone else with a similar problem, I was at my wits end and looking at removing the head.