I can try but I don't know the system configuration on that particular
vehicle.
If the radiator itself has a cap, this would be the one to check, not the
seprate plastic overflow tank.

Yes, that's where the heater radiator is

your hearing the bubbling going thru the core!  There should be no air in
the system,
if there is it could cause high temp problems, and maybe failure of the
intake gasket,

big bucks!

Your Heater Core is located there, it's hooked up to your Engines Coolant
system.  Engine heats the coolant, it runs though your Radiator to cool
down, but some if it runs into your car though a heater core, which is
basically just a mini version of a radiator.  It's Under the dash on the
passenger side inside all the ducting.   When you turn your heater ON, it
opens a valve to allow coolant to flow though it, which heats it up, when
you turn on the fan, it's blowing air though it and then out of whatever
outlets.   If you have Air in your system, you can get all kinds of weird
gurgling noises.   It's just one of those things that it happened after you
had a brake job.  It happens all  the time.  You get you car worked on and
something totally unrelated happens shortly after and then they blame the
person who just worked on your car.   A coolant problem has NOTHING at all
to do with brakes.

I would look in the Overflow tank where you can add more fluid and see if
it's empty, if it is, that's a pretty good general sign that you may have a
problem.  They don't normally just go empty.  You can also Pull off the
Radiator Cap, but ONLY do it when the engine is cool!!!  If you do it when
it's HOT and pull the cap, Coolant will go flying up in your face!!!
Coolant systems are under Pressure!  They are designed that way.  When you
increase the Pressure, you increase the Boiling Point.  When the engine is
cool, it's not under pressure.   After the Cap is Removed, see if it's low.
If it is, and your overflow tank is also empty you may have other problems.
Cracked block, Blown head gasket, etc. Your Coolant is going somewhere.
Sometimes it get's burned  and out the tailpipe giving you white smoke when
you really shouldn't have it, to maybe leaking into the OIL.  Check your
oil.  Is is way past the full mark, and/or a milk shake color?

Maybe it's something simple as your Radiator cap going bad!  That's a cheap
fix.  If someone just flushed your Coolant system recently, I would then
think it wasn't done correctly and that's why your have noises.  Some cars
have bleed screws to get all the air out because the Radiator is lower then
the Top of the engine and so filling up the Radiator would still leave
trapped air in the system.  Normally on a truck or SUV, the top of the
Radiator is higher then the Engine.  Air is going to go to the High part
since it's lighter then water.