Hey guys,

So I figured I'd start my own thread instead of continuing to piggy-back off another members.. this is going to be long, so please bear with me.

A few months back when it started getting really cold here in Calgary, AB - I began noticing that our 2003 Dodge Grand Caravan was having some heating issues. The first thing I noticed was that after starting it on cold mornings and letting it run for awhile, it would still be quite cold when we got in. I started paying more attention and realized that the heater was intermittently blowing hot air and cold air. It would blow hot air when we were moving, but as soon as we'd stop, then it would blow cold air. It was more obvious whenever the temperatures got below -10C.. and VERY noticeable when it get's down to between -20C and colder. 0 degrees and up, it works completely normal, or at least it seems that way.

I checked the coolant level and it was fine, so then I came on here and posted about it, and a few of you advised me to replace the thermostat. A few members also suggested putting some cardboard in front of the radiator when it got that cold, however I have a few friends with Caravan's who aren't having this issue. At the same time I was looking in my Hayne's manual for troubleshooting heating issues and it mentioned that when your vehicle is at operating temperature, and you touch the upper rad hose, if it's still cold, then the thermostat is most likely stuck closed and needs to be replaced. So I went out and checked, and sure enough, it was cold. Went to the parts store and got a replacement thermostat, and after fighting with getting those little tabs on the housing bent back out of the way, I got it replaced. Started up the van in my driveway and it as soon as it warmed up, it was blowing hot air again just like it's supposed to. All was well.. or so I thought.

Over the next few days/weeks I noticed that the van - with the new thermostat installed - didn't seem to be warming up as fast as it should be. Normal operating temperature for my van is about one notch below the halfway mark on the gauge (4th notch up from the bottom), give or take a little bit. I was keeping an eye on the temperature gauge, and it would warm up quite quickly to about the 3rd notch, and then stay there for ~30 minutes or so before it would finally move up to the 4th notch. I thought this was kind of strange, but figured maybe with the new thermostat, this was normal.

Fast forward ~1 month and the van starts doing exactly the same thing again! Cold when stopped, warm when moving. Did I get a dud thermostat? We're having another cold snap here in Alberta (-25C with a -35C wind chill) for the past week or so and I finally got fed up yesterday and went back to the parts store. Got another thermostat to try. Installed it last evening (in my driveway at -25C like a true Canadian!) and everything was working great again. Blowing nice and hot even when stopped. Drove it around for awhile and things seemed good.

However this morning on my drive to work, which is ~15 minutes, the van only warmed up to just below the second notch on the temp gauge! Normally it will make it to normal operating temperature during my commute with no issues. So it was just blowing "warm" air. Also, I noticed that there's coolant leaking from the bottom of the thermostat housing, directly onto the exhaust manifold, which is causing quite a bit of smoke when I'm stopped. I'm going to have to take it apart again and make sure the gasket is seated properly. However, even with the slight leak (think, drip... drip.... drip) I don't think it should affect it warming up properly. I'm so frustrated at this point!

Both times I assumed that the thermostat was sticking closed, however after posting here and reading on the internet, the common consensus is that if the thermostat is sticking closed, the van should overheat.. or at least get quite hot. However, mine has not gone over the halfway mark on the gauge this whole time! I tested the first replacement thermostat last night in a pot of boiling water, and it did not open up, so it does look like it failed. But with the fact that this 2nd new thermostat is installed and the van isn't warming up properly again after sitting overnight.. it just seems to me like something else is wrong. Other options I've seen mentioned are the water pump starting to die and "slipping", or maybe the heater core being plugged up, and/or an air bubble stuck somewhere in the system.

At this point I'm thinking I need to get the leak resolved first, and then maybe take it to Mr. Lube (Canadian "quicky lube" type place) and get the coolant system flushed out. Although, during my last oil change they tested the coolant and said it was fine.

I'm really trying to avoid the dealership, because the labor costs are always ridiculous. Any/all advice would be appreciated!

PS - It seems that if there are any little 'hidden' problems with vehicles, a good ol' fashioned Canadian winter will help you find them!!

 

Thermostat stuck closed - the van will overheat
Thermostst stuck open - the van will warm up much slower
Waterpump problem - the van will overheat

It's not unheard of to find a series of bad tstats. A flush is a good idea but have it done at a trusted shop or even the dreaded dealer. I wouldn't trust these specialized in and out joints to flush my toilet. Could have corrosion circulating through the system. If you haven't yet, try an OEM tstat from your dealership. Better chance of getting the correct temp tstat and the one Chrysler specifies.

 

Thanks Cougar.

To add to this. Just got back in the house from taking apart the housing/gasket/thermostat again and cleaning it up and re-assembling it. That stopped the leak I had.

The van is now warming up, but still isn't warming up as fast/hot as it should IMO. The guy at the parts store mentioned that sometimes the water pump slips at low RPM's, but then speeds up at higher RPM's when driving, and this can sometimes explain the hot when driving/cold when stopped problem, so I decided to test this out as well. When I'm parked at idling, the air coming out of the blower is warm. When I rev up the engine to 2000 rpm or higher, the air is definitely hot. So I have a feeling the water pump is starting to fail too.

At this point I think I'll drive it as is for the rest of the winter, and then in the spring when it warms up, do the water pump and flush the heater core myself (if it's a DIY job).

While doing all this, I also noticed that the rear blower is blowing cool air, even when the front is blowing hot. I remember seeing a thread about this as well, so I'll have to look that up too.

Thanks!

 

It sounds to me that you got a restricted Heater Core.
When you sit at Idle, coolant flow is minimun because the Water pump is spinning at slow rate. a semi-restricted heater core will have have enought coolant flow to carry enuff heat.
When you are moving at Higher RPM, you get more coolant flow thru the heater core.

I agree with Cougar, do NOT go to quick lube place and buy anything more than Oil change, over priced air filter and wiper blade. Spending $50 there only buys you a chance to spend another $300 next week.

I know it is freaking cold outside, but since you have experience doing thermostat, i KNOW you can flush the heater core too.

Find the 2 hose behind the engine that goes INTO the firewall, those are ur 2 heater core hose, Unhook both, and shove your Gardening hose into one of the heater core hose and blast it out with Hot/Warm water. Repeat it on the other hose like 5 times, ur heater core should be free.
yes, it will be a huge mess in ur garage, but it is just water...

Some people recommend using a Bottle of Cooling system cleaner first if you want .
And I hope you never used "Stop leak" in ur vehicle.

 

I have an 2005 caravan it is doing somewhat of the same thing I start it and it takes forever to heat up. Same as you I changed the thermostat and it did nothing. Ever sence I bought the van 3 years ago it has had a slight rattle somewhere inside the motor compartment a fried of mine that is a mechanic is going to do a pressure test to the coolent system he figures the bering is gone in the water pump and is causing it to not circulate properly.

 

Just as an update.. (completely forgot about this for the whole summer until a month ago when it started getting really cold out again.)

steak59 nailed it - thanks man! Managed to flush out the heater core forwards/backwards with the garden hose. Problem solved. The rear heaters started blowing nice and hot after the original flush, but have since started blowing cool/warm again.. not sure what's up with that.. might have to flush it again?

But otherwise, the "cold air when the van is stopped" is completely gone. Blows nice and hot all the time from the front vents.

 

Try a bottle of Cooling system cleaner, follow the instruction on the bottle. Undo the Lower Radiator Hose and shove a gardening hose into the heater core outlet from the engine, and completely flush the engine. Maybe there are junks inside the engine and clogging up your heater core again.

If you can do this yourself, as above mentioned, I don't trust those quick lube place to do anything more than an oil change.

 

*decided to start a new thread*

 

i have a 2003 dodge 1500 4.7. I am working on a no heat issue. The upper heater core hose is cold and the bottom is hot. I am confused if it's the heater core or the water pump.
so far i have flushed the heater core, change the Tstat and changed the rad cap and think i bled the air out. Running out things to do...