# Van running too cool? Bad Thermostat?



## TheOtherMe (Apr 1, 2014)

I have a 2011 Routan that is primarily driven by wife. I was driving it the other day and noticed that the temp gauge stopped at 180 degrees and stayed there. I'm pretty sure it use to go to 200 degrees, which is top dead center of the gauge. Other than the temp, there are no noticeable problems with the van.

Any one else encounter this? If so, is this causing any problems by running cooler?


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## Zambee500 (Jun 23, 2011)

Thermostat is 195* so the operating temp should be around there, close to straight-up "noon" on the gauge or maybe a needle's width below 200 mark when fully warmed up. It will go up a little bit above 200 (e.g., 200-220) if pushing things like towing or going up mountains in the summer time.

I'm having same problem as you and have been for ~25k miles ever since the timing belt job at 100k miles, which included coolant replacement along with the water pump replacement. Before that my van warmed up fairly quickly and needle more or less stayed straight up near 200*. Now it takes much longer to warm up and the needle bounces around somewhere between 170 and 195 pretty much constantly while driving. Even did it during middle of hot Georgia summer when ambient temps were in the 90s. When idling in garage or driveway for long periods it will stay at 195 though, or even creep up slightly over 200, but not by much before dropping back down to 195. But when driving around the needle bounces around 170-195. 

I went around in circles on this with the mechanic who did the timing belt, and he says it's perfectly normal, but then he can't really say why it didn't do that before the timing belt/water pump job at 100k miles.

Top offenders would be bad radiator cap or thermostat is stuck open or bad coolant temp sensor. So at around 110k miles I had all three replaced (by another mechanic), and I was certain it would 'fix' it and things would go back to normal. But it kept doing the same thing with long warm-ups and the needle bouncing around 170-195*.

Then I had a radiator leak last summer at 116k miles and I had the radiator replaced. I suspect air was trapped in the system the whole time causing the temp to misread, and hence the needle bouncing around. Air pockets will also cause extreme heat increases which could also explain the radiator springing a leak. So I was optimistic that the temp problem would go away after the radiator was replaced. But no - same thing with needle bouncing around between 170-195*.

At 119k miles I had another coolant leak at the Y-tube diverter. Very common problem (see other threads). Had it replaced with metal Y-tube and new hoses/clamps. Again, I thought this could have been the source of air in the system. But it's still doing the same damn thing with long warm-ups and needle bouncing around between 170-195*.

I am at a loss at this point, but I suspect there is still air in the system. Or I got a bad t-stat or coolant temp sensor or rad cap when I had those replaced. This is not _*normal*_ behavior though. Although based on number of posts about it on the Chrysler minivan forums, it is not uncommon behavior. But not normal.


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## Zambee500 (Jun 23, 2011)

If you want a lot of reading on this, start here:

http://forum.chryslerminivan.net/showthread.php/53265-Cooling-Too-much!

Post #63 on page 7 has some good info on the radiator cap and filler neck being a source of air in the system, which can cause faulty air temp readings.

Then see posts 73 and 78 on page 8, where the coolant temp sensor and bad radiator cap were the cause.

Again, I'm at a loss but that thread does 'prove' to me that it's not normal for the temp gauge to be bouncing between 170-195*.


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## TheOtherMe (Apr 1, 2014)

Zambee500 said:


> If you want a lot of reading on this, start here:
> 
> http://forum.chryslerminivan.net/showthread.php/53265-Cooling-Too-much!
> 
> ...


Thanks for the link. I will read up on it. I'm hesitant to start randomly replacing parts for the very reason you experienced. I appreciate your input. :thumbup:


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## Zambee500 (Jun 23, 2011)

Have you had to add any coolant? Not sure if it applies to MY2011, but I believe the earlier Routs and Chryslers/Dodges had a TSB on the OE radiator cap. The seals do go bad. 

Replacement rad caps are only $6-7 out the door on Amazon. RockAuto has them for $2-4 if you are also purchasing something else - shipping charges otherwise eat up the lower price. But that is a very low cost part to throw at it and might be worth a shot. 

If you do decide to have the thermostat replaced, the coolant temp sensor is only ~$25 and labor should be redundant as long as you're already in there.


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## SnakeEarl (Dec 11, 2013)

I will likely be replacing the thermostat in a 3.6L dodge caravan (2011) this weekend for the same reason! I'll let you know if it fixes it. It should. The low temperature (especially with highway driving) is likely due to the thermostat being stuck open. It take a long time to warm up. 

Having the engine run cooler (not at optimum temp) may cause a decrease in fuel economy. It may also not allow certain parameters to be met for fault codes (ie. coolant temperature has to be a certain number for a fault code to set)...


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## TheOtherMe (Apr 1, 2014)

Zambee500 said:


> Have you had to add any coolant? Not sure if it applies to MY2011, but I believe the earlier Routs and Chryslers/Dodges had a TSB on the OE radiator cap. The seals do go bad.
> 
> Replacement rad caps are only $6-7 out the door on Amazon. RockAuto has them for $2-4 if you are also purchasing something else - shipping charges otherwise eat up the lower price. But that is a very low cost part to throw at it and might be worth a shot.
> 
> If you do decide to have the thermostat replaced, the coolant temp sensor is only ~$25 and labor should be redundant as long as you're already in there.


My coolant level is at max in the overflow bottle so that does not appear to be an issue, but thanks for the feedback.



SnakeEarl said:


> I will likely be replacing the thermostat in a 3.6L dodge caravan (2011) this weekend for the same reason! I'll let you know if it fixes it. It should. The low temperature (especially with highway driving) is likely due to the thermostat being stuck open. It take a long time to warm up.
> 
> Having the engine run cooler (not at optimum temp) may cause a decrease in fuel economy. It may also not allow certain parameters to be met for fault codes (ie. coolant temperature has to be a certain number for a fault code to set)...


I'm curious if replacing the thermostat requires a full system drain and refill or just a top off from what is lost when the thermostat is removed. I hope this solves your problem. I'm tempted to just do the same, but I've experienced other car issues in the past where I kept guessing and replacing parts. Too many incorrect guesses can get expensive.


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## Zambee500 (Jun 23, 2011)

TheOtherMe said:


> I'm curious if replacing the thermostat requires a full system drain and refill or just a top off from what is lost when the thermostat is removed. I hope this solves your problem. I'm tempted to just do the same, but I've experienced other car issues in the past where I kept guessing and replacing parts. Too many incorrect guesses can get expensive.


I can't speak for the 3.6L, but with the 4.0L engine on the '09-'10 years the thermostat is kinda far back in the engine bay sort of in front of the driver's seat/steering wheel, and it was quite a bit lower than much of the radiator and hoses. So we did drain quite an amount of coolant to get the coolant level below where the thermostat is located. I'd say it was somewhere around a gallon. You might be able to find a good youtube vid of someone doing a coolant change (or thermostat even) on a 2011-2016 T&C or DGC to see what it looks like on the 3.6L.

For the 4.0L the coolant temp sensor was right next to the thermostat, and as I said earlier, for the low cost of the part and DIY it didn't seem like throwing away too much money doing them both. I was a little disheartened to see in that other thread I posted a link to that the updated part for the coolant temp sensor had the probe a little bit longer than the original OE part, so I am hoping that isn't my problem. 

I've also read elsewhere that it's possible or even easy to not have the thermostat properly seated allowing some coolant to bypass the t-stat, which could somehow cause temp fluctuations. At this point I give up, at least temporarily/indefinitely, as I've got other issues going on that affect drivability that I got to get sorted out, as well as a potentially expensive problem with the pax-side sliding door that is locked closed. I might just need to find a good brown-needled pine tree near the street to park next to when thunderstorm season rolls back around.


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## SnakeEarl (Dec 11, 2013)

TheOtherMe said:


> My coolant level is at max in the overflow bottle so that does not appear to be an issue, but thanks for the feedback.
> 
> 
> 
> I'm curious if replacing the thermostat requires a full system drain and refill or just a top off from what is lost when the thermostat is removed. I hope this solves your problem. I'm tempted to just do the same, but I've experienced other car issues in the past where I kept guessing and replacing parts. Too many incorrect guesses can get expensive.


The 3.6L thermostat is easy to replace. I would just replace coolant that is lost unless you are around the 100,000 mile mark and are due for a fluid exchange anyway. The 3.6L thermostat is right up front on the passenger's side and comes as a complete housing you just bolt on. It also has a bleed screw to remove the excess air in the system after replacement.


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## SnakeEarl (Dec 11, 2013)

I put the thermostat in. It ran slightly hotter. I noticed the radiator cap was not getting hot. So I also replaced the radiator cap. I also realized that the radiator was low. I would recommend before replacing anything, top off the radiator, as the overflow system is horrible. It does not have a pressurized coolant reservoir. You should top off the radiator first, and then add to the overflow tank. I will monitor it some more now, but I feel it may have been related to the coolant level. It would keep sucking in from the overflow after it cooled (like it is supposed to). At least the thermostat and cap were only like $20.00! Check temperatures with a temp gun. Check to make sure it is full first, then check temps of hoses with temp gun, then check radiator cap to make sure that is hot to the touch at temperature, then I would change the thermostat if none of those fix it.


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## JordanAMC (Mar 23, 2017)

Zambee500 said:


> I can't speak for the 3.6L, but with the 4.0L engine on the '09-'10 years the thermostat is kinda far back in the engine bay sort of in front of the driver's seat/steering wheel, and it was quite a bit lower than much of the radiator and hoses. .


I was recently dealing with my '09 Routan which would not reach operating temperature (stayed around 120-130 degrees, no heat through the vents). Replaced the thermostat (it was stuck open) which had just been installed less than 5000 miles ago. All is well after replacing the thermostat and housing and burping the air out of the coolant system.

As for the location of the thermostat on the 4.0L V6, it was right at the top of the engine on the driver's side, beneath the intake manifold (I suppose, given that the engine is mounted transversely, that it's technically on the upper middle of the rear of the engine). Couldn't have been in a much easier location, although there was a thick (read: stiff) wiring harness in the way of the upper most thermostat housing bolt. For anyone tackling this or dealing with this problem, it's a quick and cheap replacement of the thermostat. Two bolts. Follow the upper radiator hose to and boom, there ya go. Good luck, and make sure you purge the air out of the system when you're done!


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