Lyonz24

Ok, I have a 2000 Monte Carlo LS with a 3.4 liter in it. Have not had any problems with the car untill now. All of a sudden my car started overheating and the heater was not blowing out hot or even warm air, sometimes it can be driven and wonthave any problems, but most of the time itover heats. every once in a while the Low Coolant Light comes on then goes off(when it overheatingthe heater doesn't blow out warm air, when it is not over heatingthen it blow out hot air).I am running out of money from these SURE things not being a sure thing. So this is what i have had done so far and still have the same problems as just described.

+Replaced heater core

+Had Air bled from the Line

+Replaced thermostat

+Had air bled off the line

+Had starter replaced (just my bad luck)

I keep haveing to take it back in. I checked othergarages and as desribed they would've done the same things as done. So, if anyone may of had same problem or can give me a clue I would greatly appriciate it. Thanks

Ducroix

Have you checked to see if the radiator fans are running properly and if the radiator isnt shot itself?

Ducroix

I just found a buliten that may help

Bulletin No.: 00-06-02-001 File In Section: 06 Engine/Propulsion System Date: January, 2000 Subject:
Engine Running Hot, Overheating and/or Loss of Coolant (Polish Radiator Filler Neck and Replace Radiator Cap) Models:
1999-2000 Passenger Cars and Trucks with Composite Radiator End Tank Condition Some customers may comment on one or more of the following conditions: ^ Engine running hot ^ Engine overheating, and/or ^ Loss of coolant/low coolant message Cause The radiator filler neck may have an imperfection in the sealing surface. Correction Important: DO NOT REPLACE THE RADIATOR. Using a piece of 400 grit wet/dry sandpaper backed with a flat piece of wood, polish the filler neck sealing surface using a circular motion. Replace the radiator pressure cap with a cap of the same part number as shown in the GM Service Parts Catalog. Warranty Information For vehicles repaired under warranty, use:

mitchell03

The last post makes since on the overheating problem but not the heater. The only thing i can think of on that is thermostat might still be sticking even though new. If possible I would try removing the thermostat completley and see what results you have if the problem is fixed you know what it is and if not you have spent no money just time Also have you ever used any stop leak in the radiator that will stay in the system and can cause thermostat to stick and could keep causing problems with new ones so I would flush the system

gto8u

no heat = no water in heater core or restricted flow
over heat = no water in radiator or restricted flow or bad fans or no fan operation
stuck themostat = good heat at heater core but over heat...thats not the problem
bad fans = over heat at idle but may be fine cruising depending on ambient temp but still will have heat inside
keep in mind of course, if coolant is boiling or vaporzed heater core will not transfer heat because water pump is not pushing anything.
if your're in freeze country, make sure coolant/water ratio is correct.
other things to check...lower radiator hose collaps...if the radiator is restricted, the lower hose can sometimes suck closed....that why they usually have an inner spring. This could cause occasional overheating.

So..make sure coolant is full. start engine from cold and turn heater on low..leave rad cap loose..check to see how long before heat (2-3 minutes). Then keep hand on upper rad hose to feel for themostat opening or watch coolant flow and watch for air bubbles in coolant (maybe 5 minutes) tighten cap and Let idle till fans kick in (10-15 minutes) then hold at about 2500-3000 rpm and watch lower hose for movement or collaps. Also check back for heat after fans kick in and feel upper hose for boiling.
flip on AC also to check for fan operation (some models)
If overheats fast while at idle with no bubbles, you may have defective thermostat
If overheats fast with a lot of bubbles even when cold, you have bad head gasket, craked head or block.
If overheats slowly at idle and fans never kick in...do AC check to see if fan works then...if so you have bad fan temp switch (not relay)
If fans never kick in, do a hard wire to battery positive ti test fan itself
If fans kick in and still no over heat, do high rpm test for lower hose collaps.
If lower hose holds in place, start all over but leave cap off and bring up to normal temp, look in rad and rev engine and watch for coolant level drop...a little is ok but if 4-5 rows of core expose, you may have restricted rad

Good Luck
.