engine cooling and coolant problem

[LOCOBLAZER]

So today i ws out in the omni (89) and the temp went up to the hot mark for a second and then dropped down. Assuming the radiator was just low on fluid i continued to the bank. came out and saw a puddle under the car but couldnt find a leak. looked into overflow and noticed it was pretty full and apparently came from there. came home and checked the fluid in the radiator, a little low, added fluid but didnt empty the overflow yet. left to run another arrand and noticed it got hot then came down again. didnt notice a puddle this time and overflow tank didnt overflow. What could be causing this? Sticking thermostat? head gasket? i checked my oil, not milky looking and no noticeable white smoke. please help!

[NAJ]

Is the cooling fan working? If so I would start with the thermostat.Be sure you remove the plug in the head behind the t-stat housing when refilling or you will have air in the system.

[Mudman]

I have an 89 TII and I noticed some wierd things too (don't mean to hijack) my temp gauge will run normal for a while, but then it'll raise a little past half way for a while and sit there. Then after a while it'll drop fairly rapidly to below normal temp. (about the first line on the gauge) and cycle this slowly. I didn't know there was a plug I needed to remove when adding coolant, do you think that this is being caused by air in the system?

Thanks, Zach.

[LOCOBLAZER]

fan is working. i have never removed the plug before. just ran the motor with the rad. cap off until the bubbles go away

[NAJ]

To answer both questions.There is no bleed in a 2.2/2.5L thermostat so it is easy to get air trapped in the system. The proper drain and refill procedure is;
Loosen the rad cap to relieve pressure and then reinstall cap and open the rad petcock, this will drain the overflow tank. when the overflow is almost empty remove the rad cap and the plug in the head behind the t-stat housing,this will drain the rad and block.
To refill,close the petcock,and fill until coolant stays level with the top of the opening in the head,wait a couple of minutes for any air to exit and refill again,repeat this until coolant level remains at top of opening.Install plug in head,top off rad and overflow tank.
Also here is a Chrysler TSB on temp gauge fluctuation for 2.2/2.5L.
SUBJECT: 2.2L And 2.5L Temperature Gauge Fluctuation
DATE: Apr. 8, 1993
DISCUSSION:
Some temperature gauge reading fluctuation on vehicles equipped with 2.2L or 2.5L engines during cold weather is NORMAL. This fluctuation does not indicate a cooling system problem, engine problem, or a malfunction of the temperature gauge.

The temperature gauge will rise until the thermostat opening temperature is met. When the thermostat opens, the gauge will drop to the lower portion of the normal operating range. This occurs because the thermostat has allowed the cold coolant from the radiator to enter the engine. The cold coolant is sensed by the temperature sending unit resulting in a lower temperature gauge reading.

This cycling or fluctuation of the temperature gauge indication will be observed until the entire cooling system temperature becomes normalized (obtains the same relative temperature). The colder the ambient temperature, the longer this condition will be exhibited. In extremely cold ambient temperatures the fluctuation may continue indefinitely

Any customer inquiries of temperature gauge indications above the normal range should be investigated as a potential over heating problem. (See Illustration)

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