Started overheating one day when idling, but hit the gas and temp went back down. now overheats within 5 minutes and doesnt go back down. coolant seems to disappear slowly, coolant in radiator is bubbly, and heater doesnt work in the car

it's old, 20 years.
needs service big time and overheating that bad is never good.
tow it to shop , pay for diagnosis.
or RTM
https://eautorepair.net/Marketing/Default.asp

1: a full compression test and leak down test is , needed first.
2: then spark tests, or new spark plugs and boots
3: and fueling tests. lots even bad fuel, low fuel pressure ,etc.
the CATs don;t just fail/good;/fail/good. never.

the cause of overheating must be found. and the cure for any overheating damage,
lacking tools and skills , ? check fuses.
in the morning dead cold engine only, OFF the RAD cap, must be full UP of 50% antifreeze (not water) or it will overheat.

Weak cap comes to mind

150 miles at least also check ur air filter change nice clean one

Head blown from belt coming off and overheating, bad thermostat maybe.
Fans checked so their good
Coolant full so that crosses out water pump
Maybe the belt hit something when it broke

For car running hot and overheating issues, I suggest to you go through this help links. Click this link below and go through the troubleshooting procedure to take care of the problems: ----Car runs hot? http://howtobyme.blogspot.com/2011/11/car-runs-hot-in-traffic.html
-----------All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html
Car freeze overnight and started overheating while driving?http://technoanswers.blogspot.com/2012/01/car-freeze-overnight-and-started.html-----------Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

---------------------------
Car overheats and Air blows hot at idle?
http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
--------overheating? http://schematicsdiagram.blogspot.com/2011/12/buick-century-overheating.html
----------Car engine Overheats and transmission starts slipping?http://schematicsdiagram.blogspot.com/2011/12/car-engine-overheats-and-transmission.html
----------This details will help.Thanks.

Let it run for about 10-15 minutes after it cools down. After the 10-15 minutes (but don't let it overheat) squeeze the top hose to see it it's hard. If it is, it's probably the thermostat, and the coolant isn't flowing through the engine to the radiator. It's just staying in the engine and getting hot.

First the reason the heater is not working is because there is air in the system and these engine are known to trap air.There is a bleeder at the top of thermostat housing to remove the air.Take the radiator cap off while the engine is off and cold and add coolant/water mixture till fluid streams from bleeder screw(will need to be removed) then tighten screw and install radiator cap.Let it idle and see if it over heats and pay attention to the cooling fan operation and heater operation.If it does not overheat after 20 minutes the take it for a drive and see if it overheats.I fit does not overheat idling but does overheat driving you have a bad radiator.Dexcool is great for pugging radiators and heater cores.It is possible to flush the radiators and fix sometimes but new ones are not that expensive.I would probaly replace.If it overheats idling and fans are working suspect a bad thermostat.Good Luck!

Removal of the thermostat from the cooling system is not a good idea. This upsets the coolant flow rate in the system, and that can cause the engine to overheat, even when no other problem with the cooling system exists.

Try to identify the cause of the overheating.

Ensure that engine tune, or other engine mechanical fault condition is not the cause of the overheating, then go through the checklist following:-

1) Check engine cooling fan/s are operating as required when engine temp rises above cut-in threshold - check fan control relay is ok,
2) Check for collapsing radiator hose on suction side of water-pump when motor revs raised above idle.
3) Check coolant reservoir pressure cap is serviceable,
4) Check coolant system is properly filled - carry out any bleed off procedure specified to clear any air locks- (ensure heater core coolant flow is turned on).
5) Check for combustion gas bubbles in the coolant reservoir while the motor is running - this indicates a blown head gasket. If in doubt, take it to a radiator shop and ask for a combustion gas check on your radiator.
6) Check condition of radiator core:-
i) for blockage of air flow to (bugs/grass etc),
ii) for core internal blockage to coolant flow,

If all above ok, replace the thermostat again (also ensure it is not installed upside down) - faulty new thermostats are not unheard of.

hi  ernie try changing the thermostate first as this can cause this  D