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Coolant level up when engine overheats

23K views 53 replies 13 participants last post by  bedoum 
#1 ·
I flushed the radiator fluid on my TC 2000 3.8 (140k miles) using the recommended Prestone coolant.

The purpose was to resolve the engine overheating problem that occured each time the outside temperature was above 90F or when sitting in traffic for a while.

Since then I have identified 2 new issues:
- I can hear noise from the vents that the A/C normally makes when switching from outside air to recycle air... but this noise is repetitive, it seems each instance the A/C condenser kicks in.
- More annoyingly, I had filled the coolant liquid to the max line after having flushed the radiator fluid: the engine still overheats in heavy traffic after which I noted the coolant line sitting well above the max line, half way between the max line and the top of the coolant container.

I don't understand why my coolant level goes up after the engine overheats:
I had put the front vehicle on ramps after my last fluid flush and let the engine run until it reached its normal operating temperature, after which I switched the heating on to get rid of any air in the cooling system.

Any idea is welcome in helping solve this one. I am thinking of replacing the thermostat next, but I don't really want to add more changes before solving the cooling issues I have right now... Thank you.
 
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#2 · (Edited)
Welcome!

Since then I have identified 2 new issues:
- I can hear noise from the vents that the A/C normally makes when switching from outside air to recycle air... but this noise is repetitive, it seems each instance the A/C condenser kicks in.
Is this the same noise that you would hear if you manually switched from outside to recycle air yourself, like a clicking/door sliding noise?

- More annoyingly, I had filled the coolant liquid to the max line after having flushed the radiator fluid: the engine still overheats in heavy traffic after which I noted the coolant line sitting well above the max line, half way between the max line and the top of the coolant container.

I don't understand why my coolant level goes up after the engine overheats
It's physics at work. The coolant expands in volume when the temperature rises. The system can only hold a fixed volume of coolant, so the overflow goes into the bottle.

Question: Do you notice that the coolant level in the bottle is lower (back to normal) when the engine has cooled off for a while (like overnight...)?
 
#3 ·
Welcome!



Is this the same noise that you would hear if you manually switched from outside to recycle air yourself, like a clicking/door sliding noise?

It's physics at work. The coolant expands in volume when the temperature rises. The system can only hold a fixed volume of coolant, so the overflow goes into the bottle.

Question: Do you notice that the coolant level in the bottle is lower (back to normal) when the engine has cooled off for a while (like overnight...)?
Yes, this is the same noise as if I had manually switched from outside to recycle air myself. :ask_wsign

Yes, the coolant in the bottle resumes to normal level on my following use of the vehicle if my trip does not make the engine overheat. :cool:
 
#4 ·
Yes, the coolant in the bottle resumes to normal level on my following use of the vehicle if my trip does not make the engine overheat.
The one good thing about that is that it usually means that you do not have an internal leak or head gasket problems. If you had a headgasket problem, it usually draws the coolant into the cylinder, thus you lose fluid and have to constantly fill the tank, or the internal leak does not allow the system to be sealed and will not draw the fluid back into the system when the system cools down.
Hope you find your problem.
 
#6 ·
Agreed, I don't loose any coolant, but I will be driving to Florida next month and I would like to pre-empt any issue with the overheating engine a thousand mile from home! :Wow1:

A little more on recent fixes I have made to the car, in addition to the radiator coolant flush:
- replaced the original transmission oil cooler with a bigger one and replaced transmission cooler hoses
- replaced the radiator fan assembly with a new one as one fan was not working on the original assembly

So technically, it should all be working... yet the engine still overheats and the A/C does this ongoing outgoing/recycle noise... :confused:
 
#7 ·
Change your THERMOSTAT... that controls the temperature rise and fall in the engine. It is an inexpensive part, and should cure your problem. I am surprized that no one has mentioned this yet! :eek:
Yes, this was my next planned move, so I may grab a fail safe one from an autopart place today and install it... I'll keep you posted on how it goes from there. Thank you. :cool:
 
#9 · (Edited)
If the thermostat and rad cap and backflush don't cure it and you have verified the fans are running as designed, I would either pull the radiator and have a shop flush it or replace it. A coolant flow restiction will show up quickly when less air is flowing through the radiator as when idling or moving slowly. At speed the added air flow will mask the restriction.

Have you checked for pump flow? Run the engine with the cap removed and watch for continuos flow past the cap opening. Helps to drain some coolant to get the level below the cap opening.
 
#10 ·
I will look on the radiator side if the thermostat replacement does not fix the engine overheating problem.

I have checked the pump flow by running the engine with the rad cap off:
It did drain some of the extra coolant, but I stopped the process as the overflowing coolant was running along side the radiator... I still have that nice coolant smell now each time the car engine reaches its normal running temperature :angry:. I have since then 'invested' in a pump and have planned to extract the extra fluid that way.

I will keep you posted both on the thermostat replacement and pump flow check... won't happen this weekend though, the wife re-assigned me to a kids bday party... :birthday:
 
#16 ·
Yep, the fans are kicking nicely once the engine is hot enough for them to.

I'm leaning more and more on a thermostat issue... which I have not had the opportunity to do this week end; so it will probably have to wait until next week end before I can do the thermostat replacement.
I will keep you posted.

Thank you for your feedback, very helpful! :)
 
#24 · (Edited)
Thermostat problem is likely. Is the top radiator hose getting hot when this problem starts or is it cold?

"Fail safe thermostat" can be a problem right from the get go as it may trip with hot air bubbles in the system after a refill. I have had my problems with them and would not use another one. If you do buy one, check how it operates, and if it is a "one time" fail safe type (my experience). I would use a regular Mopar thermostat from the Dealer.

Air conditioning issues may be related to a very hot radiator, the ambient temperature sensor near your radiator (if like the one on my 2002), picking up a very hot ambient temperature and telling your air conditioning to kick in in response. Do you have automatic temperature control?
 
#28 ·
Thermostat problem is likely. Is the top radiator hose getting hot when this problem starts or is it cold?
This is a good question, I never popped the hood up when the problem occured but instead let heat ventilation clear the extra heat in the engine while carrying on driving. I will check this next time it occurs... that said, the hose on the top of the radiator may be hot just due to the radiator being hot as it sits right on top of it. Either way, I will check if the hose on top of the radiator is hot or cold next time the problem occurs.

"Fail safe thermostat" can be a problem right from the get go as it may trip with hot air bubbles in the system after a refill. I have had my problems with them and would not use another one. If you do buy one, check how it operates, and if it is a "one time" fail safe type (my experience). I would use a regular Mopar thermostat from the Dealer.

Air conditioning issues may be related to a very hot radiator, the ambient temperature sensor near your radiator (if like the one on my 2002), picking up a very hot ambient temperature and telling your air conditioning to kick in in response. Do you have automatic temperature control?
I only have the 2 classic blue (cold) to red (hot) little temperature levers to adjust the cabin temperature for each the driver and passenger side.
 
#25 ·
One of your hoses could be collapsing. You may have a bad head gasket too. While the stat is easy to blame I have not seen one fail to your extent in many many years. Was any service work done on the vehicle prior to this happening? Especially cooling system. If so than poorly bleeding the system would be a likely culprit. Many amateurs believe all one has to do is drain and refill a cooling system. Those days are gone. Also if this was done I would not be suprised to see serious engine damage (warped/cracked head, bad HG and so on) due to mishandled coolant flush.
YOu say you believe you do not have a bad head or HG but again you're assuming as it appears you have not done any testing. BTW slapping a compression tester on it does not suffice.
Start with your stat and PROPERLY bleed the system and make sure everything is up to proper level. If it persists I'll lay odds there is engine damage
 
#26 ·
One of your hoses could be collapsing.
I had a disagreement with you or DaveinColumbus about hoses collapsing. MY lower one would get sucked flat when the t-stat would close, but Noooooo, you guys wouldn't believe me. I ended up wrapping a heavy wire tightly around it to keep it from flattening.

You may have a bad head gasket too. While the stat is easy to blame I have not seen one fail to your extent in many many years. Was any service work done on the vehicle prior to this happening? Especially cooling system. If so than poorly bleeding the system would be a likely culprit. Many amateurs believe all one has to do is drain and refill a cooling system. Those days are gone. Also if this was done I would not be suprised to see serious engine damage (warped/cracked head, bad HG and so on) due to mishandled coolant flush.
YOu say you believe you do not have a bad head or HG but again you're assuming as it appears you have not done any testing. BTW slapping a compression tester on it does not suffice.
Start with your stat and PROPERLY bleed the system and make sure everything is up to proper level. If it persists I'll lay odds there is engine damage
ALL VERY GOOD POINTS !!!!
For all we know, he just has a bad radiator cap, though. :ask_wsign
 
#27 ·
I say start with replacing the thermostat. MAKE SURE that you use RTV when sealing it back up or you more than likely will be heading back to the parts store for another gasket. Also a good thing to do is to take the new thermostat and drop in in a pot of boiling water and MAKE SURE it is opening before sticking it in your van. This way you can be certian that the thermostat is not the problem(if it still overheats). You will also have to 'burp' your cooling system to get all the air pockets out of it. I usually(on other cars, never had to do this on the van yet) get it to temp so the thermostat opens(feel the upper hose, it should be hot), then let it cool. Open the cap, top it off, and repeat as necessary to completely fill the system.
 
#30 ·
"I disagree with your statement of having caused possible engine damage by mishandling coolant flush: would I have let the engine in an overheating state, damage would have been caused, quite certainly. I consistently got rid of the excess heat by running the heat ventilation inside the vehicle's cabin to quickly resume back to a normal operating temp. In short, I have seen no change in performance with regards to engine power or pick up... amazingly enough, something on this vehicle was designed right!"

You can disagree all you want but it IS a possiblility. Sorry. NOt meaning to offend but I have had to repair damage of this type myself due to mis-guided self service attempts. And NO you do NOT need to overheat these engines (according to the gauge) to do damage. Improperly bled a cooling system will cause spot overheating that will NEVER show on the gauge or manifest in a way you'd actually see until it's too late. I hope this has not happened to you...........really. Go with the new stat and a new cap. This time while bleeding the system down forget about the front end being up (no real need). Now buy yourself a pair of silicone cooking gloves (yes you read that right). Fill the system start and allow to heat up ad as necessary. Now comes the fun part. Make sure the bottle is at max or slightly above btw. Now hold the glove on the rad neck allowing the system to come to temp, the stat to open and you'll feel the "burping". The system will burp out the air and than suck down more coolant from the bottle allow this to continue until burping stops. The system is bled. If the burping does NOT stop than odds are you have a cracked head or bad HG
 
#31 ·
Thermostat definitely a possibility

My experience with this car (and lots of others) in a hot Australian summer climate is that the thermostat is most likely the cause of overheating. Definitely replace it - they are relatively inexpensive - and you will be improving your van's reliability. The other good thing about a new thermostat is that it will open & close at the correct time - not delaying the cooling or heating of the engine, but controlling the temperature as designed, at optimum levels.
One of the first jobs I had to do on my Voyager was to replace the thermostat, after I noticed the heat gauge going up just a bit over the "normal" point shortly after driving down the road. (It was returning to normal agan after a little while, but the process was somewhat delayed - this a sign of a failing thermostat - best to replace ASAP.):ThumbsUp:
Regards, Andrew
 
#35 ·
Engine Cooling Problems: update!



So I purchased a new thermostat last week, in addition to the matching seal, a new radiator cap and upper + lower radiator hoses. I tested the new thermostat as recommended, putting it in boiling water which showed me that it was working as expected. I then installed the new parts I mentioned above.
I was able to put the engine cooling system through its first stress test today, i.e. after a half hour drive with the A/C on at an external temperature of 75 Degrees F, I let the engine run on park with still the A/C on:
-1st observation: the air from the vents got warmer almost as soon as the car was parked. Air felt like normal ventilation temp vs. AC cold air.
-2nd observation: I still have that external/recycle air noise coming out of the vents both from the front and the back of the vehicle.
- 3rd point: although the radiator fans kick in as they should, the temperature gauge slowly worked its way up after about 10+ minutes of sitting on idle in park with the AC still on.
- 4th check: I let the temp gauge go up to three quarters or so and resumed my driving: the air from the vents got colder and the engine temp gauge resumed to its normal (slightly below half way) mark within the first mile back on the road.

I believe the next step is a new radiator as I am not loosing a drop of coolant anywhere.

I will keep you posted as per how that paid out...

:nut:
 
#37 ·
On the engine cooling side, I bled the system by filling the radiator and bottle , then started the engine, allowing it to heat up and adding fluid as necessary. I did this until the bottle was around the max. The system did burp out some air, sucking down more coolant which level I adjusted until the burping stopped. I also noted no loss of coolant.

The front is clean as I 'slapped' on a new larger transmission cooler a couple of months ago and I had the front bumper off for this installation: there wasn't an excessive amount of debris or bugs but I dusted off what I could while I was there.

On the AC front, I ran it with the car on park today with an outside temp of 63 F: the AC is not dispensing much cold air while the engine is sitting on iddle and the vehicle not moving. I am tempted to re-fill the system with freon (or whatever is used now) to see if it makes any difference.
I also noted that with an outside temp of 63 F, the car was not overheating... which remains consistent with the overheating issue only showing when the outside temp is around 75F+ and the vehicle moving slow or stopped.

I'll be inquiring about a new radiator next week, feel free to let me know if you have any recommended brand for a driver side outlet rad.

Thanks.
 
#39 ·
If you're going for a radiator rebuild/replacement, consider having the radator shop (if you're going to one) install a small threaded plug in the "top tank" (if vertical) or side "inlet" tank" (if cross flow). I then connect a threaded hose connector to it and conveniently mount a pressure gauge 0 - 16 or 20psi to the tank. This tells me if the system is operating properly, or over pressure, or even under pressure.
It has saved me "face" many a time.
:lol:
 
#45 ·
I'm baffled why some are having problems with bleeding air out of cooling systems. I've flushed/drained cooling systems at least 50 times over the years and have never had a "bubble" issue. Most of the time it's on a level surface. I fill the system, crank it up and let it run with the cap off topping it off as it runs. Once full I let it continue to run and allow some coolant to overflow as it expands. I rarely see bubbles. I then install the cap, let it build up pressure and look for leaks. Takes 15 minutes tops. Once cool I top off the coolant reservoir.

Forgot to add I turn on the heater as soon as I start the engine.
 
#46 ·
No problems here either except for a 1993 Dodge Shadow with a 2.5L engine which seemed to retain some air.
Just run until warm (about 10 minutes) with the cap loose. Let it cool down. Add coolant. Take a short drive, check it again. Finish the job. I also keep track of the quantity drained out, if I think of it (not in a rush), for comparson purposes.
 
#53 ·
Well at least you found the problem and fixed it. Too many times it's those simple overlooked things that bite you. I've been there. Might want to take the time to see exactly where the harness is damaged and either solder or splice the wire together. Then you won't wish you had.
 
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