SER_GTR is right, Get the water body checked and the thermostat replaced if it is too old... Most probably the water isn't flowing properly through the engine if you got the engine overhauled and stuff...
But might i tell you this that i am sure you preferred a desi sasta mechanic for your Engine overhaul.. No offense brother...
The reason why im saying this is no educated Mechanic would go for double gaskets...
If you live in Lahore, visit Fazal motors. The guy is my uncle... And its not that i promote him here... I say that because he is an educated person and he really knows what the issue is rather than doing garbage work which sastay mechanics do and ruin cars...
I got my alto overhauled once by mistake from a cheap mechanic, i thought it saved me 15000... But the end result was, engine degraded within just 2 MONTHS!!!
and when i visited Fazal Motors, He told me the bores were'nt properly designed and even the pressure applied on the bolts of the head was far more than the standard requirement. He even told me that alot of places where slip should not be present in bolts, the mechanic had spoiled it all...
I then got it re-overhauled for more money, but then the car never gave me issue and i used it for more than a year without any fault..
Anyways sorry for deviating from the post, ..
Check with the water bottle as i instructed you, if that is fine, get the double gasket removed to a single one, then check
1. Water body
2. Thermostat controlling the temp.
3. Also get the Heat sensor checked, sometimes it gets too old and spoiled and doesnt give correct input for the fan to start automatically..
if these don't work, then im sure you're engine didn't get proper overhauling