I find this pretty critical! If the engine is hot to the touch, you should have ZERO problem getting heat out of the heater core. But if it's not blowing very hot, then something is up. And you are working on the two items I am thinking. Either a clogged heater core OR a failed thermostat. Usually a thermostat fails in an open position, but I am sure there are times it could fail in a closed position. You can test the thermostat, remove it and toss it into a pot of boiling water, see if it opens. If you want, you can get another thermostat to compare results with. Could also have a partially clogged heater core. If you ever used a "stop leak" product, good chance that is where you are having problems. Also, from a cold start, have someone watch the radiator hoses, see if one collapses when the pump starts. If so, this is a sign that you have a clog somewhere (or I actually ran into a failed radiator cap once on a LeSabre that did that).

I actually had a cracked radiator on the 2000 Black Monte this past spring. Crack with high on the side tank. I found it because it left a small puddle of coolant, but never had a temp issue. If you think the radiator has a crack, you could do a loan-a-tool from the parts store for a radiator pressure tester. Bump up a little pressure, look and listen for signs of a leak.

All depends on the capabilities of your scan tool. I have access to a GM Tech II, a Scangauge II, a bluetooth OBDII device paired to my laptop, the DHP Powrtuner and HPTuner. All can read the temp from the PCM but all have a different interface to get there. A lot of those cheap bluetooth OBDII tools can pair with your phone and use a cheap/free app and tell you what the temp is being reported by the PCM.

The silver thing is just cast aluminum. They could break for a variety of reasons. Could be as simple as over tightening the bolt that connects the dog bone to it. Sadly, it has been pretty common to read people state those break.

 

I have a new thermostat in now, but I'm gonna remove to test flow, I have never put any stop leak in my car, however I had the rad serviced a few years back at a rad shop and have'nt had a problem but ny son in law who is helping me with this says somebody put stop leak in it because of a grey sort of residue he found in the rad inlet neck ! could that cause this??

 

It is possible if someone ever used stop leak it has now presented a problem. Just the concept of stop leak is to "clog" small holes. So if it can do that, sounds like it can find other areas to clog. I know someone who helped a friend of his unclog a heater core that was plugged because of that junk. I will never pour that stuff in my car.

 

Wow, this is getting involved, logic will prevail, only so many things it can be and you have investigated almost all of them, real trooper.

I have an extra engine mount if you want to buy it. It is the extra heavy duty one from the Supercharged 3800 Grand Prixs. I was going to use it, but my original is still holding strong and now its just gathering dust.

 

OK! after all this drama with my car. leaking coolant,found water pump leaking, replaced,elbow o-rings melty, replaced, heater hoses mushy, replaced, thermostat gasket melty, replaced, both rad hoses flimsy, replaced,flushed heater core, flushed rad and engine,coolant temperature sensor, replaced, battery completely died, would not jump ! on charger showed less than 6 amps,charged overnight. Googled weak/dead battery causing engine overheat...never heard of this but it says a bad or super low battery can cause engine overheat and etc, due to so low voltage to the computer etc that is telling engine what to do ! ?? anyway, charged battery overnight, cranked right up, coolant circulating with thermostat out, heater core bypassed. cooled down, replaced thermostat, coolant circulating but still seemed hot to us? upper rad hose hot but circulating? I bought Dorman upper intake plenum kit mainly cause I thought it was the next step, PLUS it was on clearance at rock auto for $38 & change ! I decided to take in to reputable shop I recently found to double check our work, not to damage engine further if it had. shop said : " I think its fine! I think your just freaking out! infrared temp gun shows 198 degrees upper hose/water neck and 160 degrees lower, thermostat opening, ran fine over to shop! He said we had done everything he would have and to drive it, watch my gauge and coolant and bring back if something went wonky !! SOOO I guess it was just the water pump and we over diagnosed everything ? I still need to drain rad and add some coolant since weve been putting water in it and hook my heater hoses back up ! Thanks to everyone who stepped up to help me with this dilemma, Hopefully this is the end of this problem? Also this rant has to be the longest run-on sentence in history !!! Thanks again, Claydoh