My Suzuki Grand Vitara cylinder head gasket was replaced after it blew up caused by a faulty radiator cap. The vehicle developed a terrible hard start which my local mechanic could not property fix. I've grounded the car for fear that he may mess it up. Please help.

Also check plug and wire, if not coil on plug , as a weak wire or worn plug can cause premature failure of coils .

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."

Yes you can use Car Quest Anti-Freeze in your Suzuki. I would first flush the radiator and heater core and replace the Thermostat as well. It is also a good time to replace the Radiator cap as they wear out as well. I would also recommend getting your cooling system Pressure Tested before doing anything so you know you do not have a blown head gasket.

could be head gasket leaking if there are no obvious leaks from hoses,gaskets,radiator etc

In my parts book it calls for a 16lb cap.
You may have damaged the head gasket before the radiator was replaced. Once an engine overheats, the gasket can be stretched and the head warped. The engine could be burning the coolant.

I dont think you have an head gasket problem.Check that your therostat is working.Try running the engine without it.Or replace it.I would like to now a little moore about this problem,You dont give enough detail on it.

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.

valve seals will not cause this kind of oil consumption, a scocred cylinder wall or broken piston ring will, not sure on the head gasket, does it have a combustion gases present in the radiator surge tank or bubbles while running? if not the head gasket is probaly ok.

Check the passanger side floor board for moisture this could indicate a bad heater core. Then I would check the engine oil and make sure its not milky looking (head gasket). make sure when you fill it let it run with the cap open with you looking into the cap to be sure is circulating and not vapor locked (air pocket)
hope this helps