QuestionThanks for the quick reply Roland-
Turns out there might be a bit more to the story. I just took it off the jacks and test drove it to see exactly how long it took to warm up for myself. It came off the peg in about 5 mins and heated up to normal temp (I assume, since there are no temperature numbers on the gauge-just indices at 1/4, 1/2, 3/4, etc) The heat from the heater was very warm at that point. The outside air temp was around 40F. The earlier complaint was from my wife (who drives the van mostly). She said that she drove for nearly 45 mins and the temp gauge never even got to 1/4 - barely off the peg she said. We had a very very cold front pass through during that time where the temps were around 0-10F the whole day she was at work, and that's when she says it wouldn't heat up. The first time she noticed it (again this was during a VERY cold day)she said it started to heat up as normal, then it suddenly started blowing lukewarm and then remained that way. She said the temp gauge dropped down to below 1/4 at that time. My thinking at the time was that the drop she observed on the temp gauge was when the thermostat opened, and the extreme cold was causing the coolant to cool significantly more quickly than normal, thereby reducing the temp of the coolant that was flowing thru the heater core - resulting in the lukewarm temperature. I thought it was just the normal operation of the thermostat, but inefficient heating because of the extreme cold. The more I thought about it though, the less plausible it sounded. What would all the poor folks in Minnesota and Canada do if cars operated like that 'per normal'? Can reallly cold temps cause the heater to act as I surmised? In the meantime, since it seems to work when its not as cold, I'll wait to get the answer before I tear into it :)
Thanks again
Mike
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Followup To
Question -
The problem with the T&C is little/no heat from the heater. The engine temp gauge also reads very low and the engine takes a long time to warm up. It is a 3.8L . I suspect that the culprit is a stuck open thermostat. If I attempt to run the engine with the radiator cap off to see if the coolant is moving immediately (with a cold engine), I can only do so for about 30 seconds before the coolant wells up to the brim of the filler neck. Shouldn't the radiator be isolated (and therefore no movement of coolant whatsoever) until the thermostat opens? But in attempting to replace the thermostat I have discovered an even more perplexing problem. Embarassing as it sounds I can not even get the radiator drained. The drain plug seems to only turn 1/4 turn CCW and then runs into a hard stop. It feels like if I try to turn it any further it will break (plastic). I called the Chrysler folks and one said just keep turning while a second said I must turn it a 1/4 turn and then 'pull out' on it in order to continue turning it further. I'm 200 lbs and pulling what I consider to be way too hard for it to be designed to work like that, and still not a drop. The manual makes mention of a vent plug, but isn't just opening the radiator cap venting it? Any help on opening that darn drain plug, and whether my guess on the heat problem is correct or not is appreciated. Thanks!
Answer -
Hi Mike,
The fact that the water builds up in the neck may indeed corroborate that the thermostat is stuck open. So go with that as an assumption. On the drain, my suggestion would be to call around to radiator repair shops with the same question and ask for advice. I checked my manuals and none give anything specific. The vent plug (shown on the engine in my Haynes manual) would not be necessary to remove IF the thermostat is stuck open. So it it drains well with the cap ON and the vent plug still in place then that would also be an indication that the thermostat is stuck open.
If worse comes to worse you could remove the thermostat housing and let the top part of the coolant volume leak out to that level, but I suspect a radiator shop mechanic will be able to tell you about that drain plug. I would go with the stuck open theory until you can look at it for sure before working on any other possibilities.
Roland
AnswerHi Mike,
The heater coolant supply comes from the engine and not from the return coolant from the radiator, so it will always track with the reading of the temperature gauge. I believe that your thermostat is opening at too low a temperature and that when it is warm out you don't notice that because the radiator is probably not cooling the outflow from the engine as efficiently as it does when the ambient temp is colder. As the result, the engine will run colder under those conditions than when it is warm outside and the temp is determined by the overall cooling capacity of the system without regard to the opening temp of the thermostat. So I would go ahead with you original plan to open the thermostat housing, ideally after draining it down a few quarts to get the level below the top of the engine. Then test the thermostat in a pan of water heated on the stove along with a thermometer. It should begin to open at 195F.
Roland
