One of my ignition coils of my suzuki grand vitara has overheated and burnt out. why

no engine told at all or country.
sold all over earth, with many engines sued.
cracks happen for 2 reasons
overheating the engine
or using only water for engine coolant, in winter , it turns to ICE cracks the engine block and heads in 1/2 total destruction easy as pie done wrong.
recalls, TSB pages
USA car, at the makers TSB pages , 1 hit only on word CRACK
quoted:
TS 35 12103, Special Coverage Extension for Specific Crack(s) in the Cylinder Head

SPECIAL COVERAGE EXTENSION FOR SPECIFIC CRACK(S) IN THE
CYLINDER HEAD.
MODEL(S): GRAND VITARA (JB) WITH 2.4L ENGINE
YEAR: 2009 (START OF PRODUCTION THROUGH JULY, 1 2009)
Engine overheating with possible Internal Engine Noise. The engine coolant
may leak from the cooling jacket into the Camshaft Housing of the Cylinder
Head. There will be no external coolant leak and there will likely be evidence
of coolant contamination in the engine oil.
CAUSE: Suzuki has determined that certain 2009 Grand Vitara vehicles may develop
a crack(s) between cylinder head bolt(s) and casting plug(s).
CORRECTION: A special coverage extension will apply for vehicles beyond the basic
warranty limits. The coverage allows repairs to be made for customers at no
charge for parts and labor up to 7 years or 102,000 miles, whichever comes
first, from the date of first use, at authorized Suzuki service points. Cracks in
locations other than the specified areas of the cylinder head do not qualify for
the coverage extension."

what engine? DOHC 2.0 Liter? 4 cylinder or V6 and what year.
making a wild guess, on engine, you have coil packs.
on mine 2004 i have 4 coil packs. called COPS.
if one is dead, then its mostly bad.
The ECU/PCM drives the coil pack direct.

A LOT depends on WHICH ENGINE your 1999 Suzuki Grand Vitara is equipped with.Ignition timing is not adjustable on any engine except the 2.5L V-6.
To adjust the ignition timing on the 2.5L V-6, a scan tool must be used to turn off the computer timing control to check and adjust base ignition timing. Base ignition timing specification is 4-6 degrees BTDC.

sounds like the head is warped

1999Suzuki Grand Vitara is equipped with Coil On Plug (COP) ignition. You must remove the ignition coils to get to the plugs.

It depends on the engine size for the belt routing.

Click on the "x" for the diagrams on the following engine sizes:
FIRING ORDER AND BELT ROUTING Firing Order and Belt Routing X90, Vitara & Grand Vitara Fig. 1: 1998 1.6L engine Firing order: 1-3-4-2 Distributor rotation: Counterclockwise
Fig. 2: 1999-02 1.6L engine Firing order: 1-3-4-2 Distributorless ignition system (coils over No. 2 and 4 cylinders)
Fig. 3: 2.0L engine Firing order: 1-3-4-2 Distributorless ignition system (one coil over each cylinder)
Fig. 4: Accessory V-belt routing- 1.6L engine with A/C
Fig. 5: Accessory V-belt routing-1.6L engine with A/C and P/S
Fig. 6: Accessory V-belt routing-1.6L engine with P/S
Fig. 7: Accessory serpentine belt routing-1.8L and 2.0L engines
Fig. 8: Accessory V-belt routing-1.8L and 2.0L engines
Fig. 9: Accessory V-belt routing-2.5L engine with P/S
Fig. 10: Accessory V-belt routing-2.5L engine with A/C and P/S

u need a diagnostic tool to check if there is any error codes and take it from there

so your radiator is new...have the cylinder head check for warpage and top head gasket leaks...this one of the common causes of overheating

Its probably not boiling what you are getting is preasure from the engine which can be caused by a faulty head gasket but as you have that changed then it must be a crack or warp in the cylinder head. Get the head preasure checked for cracks and warp. If ita warped get it skimmen if cracked you will need to replace.

Try to feel the ignition coil while the engine is running. Is it too hot? A defective ignition coil will run but will be producing a lot of heat, and when its already too hot, it will stop to function. Let it cool for a while, then it will run again.