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Repair Questions and Answers.

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 #382062  by Steve From MA
 January 25th, 2020, 3:47 pm
First some back story the water pump and radiator were both replaced within the last 40k miles when the Timing belt was replaced. Car has been running fine for months with no issues and no observed leaks. (The wife now drives the car 90% of the time so my time to notice things is limited)

About a week ago I noticed that the interior heat switched from warm to cool while driving (at least a 5 plus degree change) at the same time I saw the temp gauge move up very slightly from 1 bar below half way to halfway. Further down the road after a few miles the heat came back and the temp dropped back to 1 line below middle where it normally runs. The wife proceeded to drive the car for the next week without commenting on any issues.

Today while sitting in a parking lot waiting 5 minutes for a pizza to be ready (having driven the car 20 minutes) the cars heat again went from warm to cold while we were both in it. I rev'd the motor a few times only to see the temp gauge start creeping up above half and no heat in the cabin just cool air. I turned the car off and looked underneath to see a small puddle towards the front of the car. Waited 20 minutes then proceeded to try to nurse the car home - about a 6-8 mile trip. The temp gauge went up and down a few times but never above 3/4 and after the first few minutes of driving settled at the middle of the gauge. Heat inside the cab seemed intermittent. Got the car home and let it sit for 30 minutes, found no leaks under the car but the reserve was low / almost empty. I refilled it and have had it idling outside now for 20 minutes without issue. vent control works as normal changing temp up and down and the car is idling 1 tick below halfway as normal. Could this be indicative of a sticking thermostat or failing / plugged heater core?

(In summary the motor starts to overheat when I loose heat to the cabin but it appears to be intermittent)
Our bmw had a similar issue but it was caused by an aux water pump that the chrysler doesn't have.
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 #382063  by FIREM
 January 25th, 2020, 4:52 pm
Coolant level is critical on these cars. Biggest question is why was it low on coolant. Must find the leak. Rent a cooling system pressure tester, pressurize the with the engine cold and full to 16-18 psi. If nothing shows warm the engine and test again. One sneaky leak is the lower intake manifold heater tube oring. Leaks into the valley between heads and may take a while to show up.
Heat coming and going, temp gauge floating will happen with a little as a quart low on coolant.
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 #382073  by hrmwrm
 January 27th, 2020, 3:41 am
yep, you got a leak somewhere. especially the cabin heat is indicative of it.
coolant level isn't high enough to flow through the heater core.
as said above, likely culprit is the oring sealing the heat supply tube to the intake.
could also be the lower intake gaskets.
but you have to lift the lower to replace the oring, so fixing the oring will fix the other, as you'll need new gaskets anyways.
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 #382078  by In-trepid
 January 27th, 2020, 1:07 pm
I would also check on the heater return pipe that runs from the back of the engine down over the starter and to the thermostat housing. I have found that these rust at the bend and "sweat" coolant when under pressure. Eventually they rust through and cause a major leak. They are a pain to replace, but easier than the heater feed pipe under the lower intake. Good luck!
 #382126  by Countachqv
 January 31st, 2020, 12:09 pm
Noone mentioned this but if the reservoir cap is old get a new one! This happened to me. Coolant in the bottle was vanishing mysteriously. For a while, I suspected my wife pumping it out at night while I slept but after several all nighter stakeout, I turned no evidence of that.
So I did the next best thing: pressure test. Nothing. Then I replaced the cap just because it is something you do as regular maintenance and sure enough, the coolant stop disapearing. I guess when it gets hot it can evaporate from there over time. fix was somewhere like $3.
If coolant gets low and not getting in the oil try to find the rate of loss. You gotta leak somehow
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 #382130  by Steve From MA
 February 1st, 2020, 1:23 am
Thanks for all the input, I ran the car in the yard a few days ago and found that the only leak i could find was coming from the area below the expansion tank (small but present). I also noted some fluid on the side of the tank that appeared to have come from the cap. I proceeded to replace the tank and cap with a new unit from the local stealership ($57 including tax so nothing horrible) So far the fluid appears to be remaining level. The wife drives the car 30 miles each way to work and so far it has made the trip two days without issue. I'm going to keep an eye on it for the next week and cross my fingers that the problem is solved.
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 #382132  by Countachqv
 February 1st, 2020, 7:58 am
Steve From MA wrote: February 1st, 2020, 1:23 am Thanks for all the input, I ran the car in the yard a few days ago and found that the only leak i could find was coming from the area below the expansion tank (small but present). I also noted some fluid on the side of the tank that appeared to have come from the cap. I proceeded to replace the tank and cap with a new unit from the local stealership ($57 including tax so nothing horrible) So far the fluid appears to be remaining level. The wife drives the car 30 miles each way to work and so far it has made the trip two days without issue. I'm going to keep an eye on it for the next week and cross my fingers that the problem is solved.
Told ya! only 2 possibilities for mysterious coolant loss with no trace on the floor or the oil:
1. The wife pumping it in the dead of night :devil
2. The cap.

I think your bottle wasfine and could have save the $ unless the cap chewed the top over time