Chrysler Repair: 1992 New Yorker 3.3L overheating, radiator flush, temp gauge

Question
I have a 92 New Yorker with a 3.3. It gets hot when i'm on the highway going 65-70 mph (apeed limit of 70). If i'm in town, or keep it below 60, it doesn't even get warm, the temp stays at quarter warm mark. The car has 270,000 miles on it, i've changed water pump and thermostat. Both sides of rad about same temp and all hoses get hot.  It also has a problem with no heat in car, but the heater core seems to be working (both hoses get hot). The car runs like a top, the engine has never had a bolt turned on it, which is quite impressive for 270,000 miles (tranny requilt twice so far however). Please help if you can.  Thanks.

Answer
Hi Mike,
Are your fans coming on when the temp gauge reaches 1/2-3/4 scale? By the way, you didn't define "overheating". Do you mean it just rises to 3/4-7/8 scale or does it go to the top with blow off of steam? Any signs of true overheating are relevant of course, but it is normal for the system to run up to 240 or thereabouts without overheating because of the pressurization of the system. If the fans come on and it stays below 7/8 scale reliably and you don't loose coolant then I would be content. Remediation might include a radiator flush if that hasn't been done, and of course a possibility is a waterpump impeller/drive belt slipping. Also, check to see if you have air trapped in the system by using the bleeder valve near the thermostat housing: after attaching a 1/4" hose to direct the flow over the front end of the car where it can be collected for reuse, open valve, then add coolant to the overflow bottle until it comes out the bleeder hose, and squeeze gently on the upper hose to remove all air, then close bleeder.
Roland