Chrysler Repair: Chrysler LHS overheating, coolant temp, chrysler lhs

Question
Hi Roland, I replaced the high and low relays that went to the radiator fan because we were unsure if the fans were coming on (they are intermidant) I haven't had to add water to the car until yesterday and my friend told me that more than likely there was air in the motor where the water was supposed to be, from when we changed the thermostat, and that it should have been fine now that we had bled all the air out. I haven't seen any smoke or leaks of any kind, the water pump is working fine also, I have a 3.5 liter engine.

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Followup To
Question -
My car (1996 Chrysler LHS) overheated last week and I replaced the relays as well as the thermostat and it seemed to be working fine, my car overheated on monday and we put water in it and made sure the relays weren't knocked out of place and it seemed to fix the problem but this morning when I was driving to work the car said that it was very hot (right below the red line) and I turned the heat up to 90 full blast to cool down the engine and there was not warm air coming out of the heater and then shortly afterwards the gauge went back down to medium and it keeps going up and down, i'm not sure if it is the gauge or if there is a water leak. etc, please help :) thank you.
Answer -
Hi Chloe,
I am not sure which relays were replaced, because I don't believe there are any except for the operation of the cooling fans (which may be the ones you spoke of). If the fans weren't coming on when the gauge read hot, then it could be rather that the coolant temp sensor is not reading the temp of the engine correctly so the fans aren't being alerted to operate.  In any case, you need to determine whether or not you are loosing coolant due to a leak or not (absent loss due to boiling over, for if that happens it may not be a leak). Have you had to keep adding water to the overflow bottle during this symptom or not. Do you notice any white smoke coming from the tailpipe when you start the engine from cold? Do you see any coolant under the car where it has been parked, under the engine?(ignore water under the firewall area if you had the air conditioner 'on' because that would be condensate (clear water), but any colored coolant water would represent a leak).
The fact that the heater didn't put out heat means either that you have air trapped in heater core which could happen when you changed the thermostat, or low coolant level, or an inefficient water pump, or a slipping water pump drive belt. But sorting that out will take a little bit of observation.
So tell me about the first questions and we will go from there. Also, do you have the 3.3 of the 3.5L engine?
Roland

Answer
Well that answers most of my questions. The fans are supposed to only come on when the engine is hotter than it should be, or when the air conditioner is on regardless of the temp of the engine.  Your problem this morning could just be a matter of the air in the system migrating around until it leaves via the overflow bottle. I would verify that when the temp gauge reads higher than 3/4 scale that the fans are 'on' and that the radiator surface seems hot, just to verify that the sensor for the temperature gauge is not overestimating the engine's temperature, or that the coolant temp sensor that controls the engine and fan function isn't underestimating it. So if you aren't loosing coolant, and it hasn't boiled over, and the coolant flow is not in question, and the pump belt isn't slipping then the last reason I can think of for the engine running warmer than you are used to is that the radiator itself needs to be flushed to improve its ability to dissipate heat. If you haven't done that lately that may be a good thing to do.
But let me know if I have missed out on some observation; otherwise see what happens in the next day or so, and be ready to pull over and observe what is going on under the hood when the gauge reads high.
Roland