2001 Dodge Caravan temperature/coolant problem

Maintenance/Repairs
1

I’ve been trying to chase down an overheating problem on my minivan (with 182,000 miles on it) for months now, working with my local Chrysler/Dodge dealership garage and on my own. Recently, the garage “gave up,” so I guess I am on my own.

The problem started during a camping trip to Vermont in the late summer. The van was carrying a lot of camping gear, etc., and we had it on a long (slow) drive over some back-country gravel roads one day. On the way back to Philly, the temperature gauge shot all the way up, the temp light came on, and a warning “ding” sounded. We let it cool down and noticed that the coolant level was low. We added some coolant and made the several hour trip back to Philly with no problems. About two weeks later, the same thing happened. We added more coolant and things were fine for another few weeks.

We suspected a leak, but did not find anything obvious. Over the years, several parts of the cooling system had been replaced: new OEM radiator and cap (more than a year ago), new upper and lower radiator hoses (replaced when the radiator was replaced), and the water pump (several years ago).

After additional occurrences of the problem, I did find a very small leak (split) in the heater hose coming out of the heater core. I had the garage replace the hose and the tube it was connected to because it was quite corroded. They also pressure-tested the system, and everything looked good. This repair stopped the leak, but not the problem (in other words, it seemed to be a symptom, not the cause). As an extra precaution, I replaced the 1 year old OEM radiator cap with a new OEM cap and the thermostat as well. There are no bleeder valves for the cooling system for this model, so I performed the recommended procedure for removing air from the system several times. Once, and only once, during this time, while investigating the problem with a hot running engine, I observed coolant pouring out of the overflow on the coolant reservoir. This may have been a fluke(?), but I also recently noticed splash marks on top of the engine.

We did notice some other symptoms after the heater hose was replaced. The temperature gauge would go up to about 3/4 (it normally stayed a little lower than a 1/2 when hot), stay there for a few seconds to several seconds, then go back to the normal operating range. The garage said that this was due to the thermostat opening. We never noticed this before (driving the van for many years), and it does not always happen, but, okay, maybe we just hadn’t noticed. Another thing was that the coolant level in the reservoir would be at max when cool, but the level in the radiator would be an inch to several inches below the neck of the radiator–even though both had been filled to full/max days before. Also, we would often hear a “swooshing” sound of liquid under the dash–presumably coolant rushing/flowing into the heater core. We tried again to remove any trapped air, but it did not seem to stop the sound.

The garage pressure-tested the system again–hot and cold. They checked everything over, but after they added coolant to the radiator everything worked fine. They mentioned the possibility of an internal leak, but they were out of ideas.

One thing has remained constant: the coolant level in the radiator drops over time, from a few days to a few weeks. We’re watching the level much more closely now to avoid overheating, and this week I noticed something a little different. The reservoir was at the min mark (when cool), and the radiator level was also several inches below the neck. I filled the radiator with coolant, but not the reservoir (ran out of coolant). A day or so later, the reservoir was above max (when cool), but the radiator was several inches low again! What gives!?

I’ve read about bad/blown header gaskets being a possible cause of an internal leak, but I guess I would expect to engine to ALWAYS run hot and to run rough in a case like this. It’s not (though it does not run smooth anyway). Could it be crack somewhere allowing coolant into the combustion chamber or oil? I guess, but I have not noticed any discoloration to the oil. I drove it yesterday and noticed some significant hesitation while the engine was warming up. Never had this happen before. I’ve always kept the vehicle well-maintained, but could this be the end of the line for what has been a reliable vehicle for us for the past 9 years? Any insights or experience with this kind of problem would be appreciated!

2

Does the heater blow warm or hot air with the engine warm? The wooshing that you hear is a slug of coolant passing thru the water pump and the heater core because the coolant is so low that there are big bubbles of coolant in the system. This is a different type of bubble-one that can’ be burped out.

The transfer of coolant from the radiator to the reservoir is a strong indication of a failed head gasket.

3

Oh, yes, I forgot to mention the heater. When the engine is at normal operating temperature, the heater generally blows out warm-hot air. But one of the symptoms we noticed is that the heat sometimes oscillates between cool (not warm) and hot. Sometimes the temperature would instantly warm up when pressing the accelerator. We had been attributing this behavior to the coolant level getting low. It has always taken the heater in this car time to get warm.

If the head gasket had failed, wouldn’t there be other symptoms? Or other ways of diagnosing? Compression test?

4

To check for a blown head gasket, with the engine cold remove the radiator cap.

Start the engine and while the engine is idling watch the coolant in the radiator. If bubbles start forming in the coolant that’s an indication of a blown head gasket.

Tester

5

Thanks, Oliver70 and Tester. I have seen bubbles in the coolant previously. However, I attributed that to the air that I was trying to “burp” out. I will recheck, however.

P.S. One important detail. Ignore my comment about coolant spilling out of the reservoir overflow. That was self-induced. I remembered that I had removed a fan to look for leaks in the bottom of the radiator.

6

I basically just repeated the same procedure recommended to remove air from the coolant system. In short, I raised the front of the van, turned the heater temperature all the way up, removed the radiator cap, and started the vehicle. I topped off the coolant, but as the engine warms up, some coolant overflows. During the warm-up period, the coolant level drops twice, once when the thermostat opens, and another time for a reason unknown to me (though this is what I was told to expect and what I have observed every time that I have done this). I topped off the coolant both times. There were some bubbles observed during this process, but only briefly. Things get to the point that there are no bubbles observed, even after raising the idle and accelerating in short bursts.

7

BTW, the heat was coming out nice and hot and constant.

Any other ideas?

8

X2Tester. Those bubbles will be small in relation to the burp that will splash coolant out of the tank. It sure sounds like a HG to me.

9

I had a similar mystery once, it tunred out that the radiator could not keep up with the demand of the water pump and the lower radiator hose was collapsing preventing coolant from flowing, thus engine overheat. No flow, no heat, and high pressure could cause blowing coolant out the radiator cap. The car lived on after replacing the lower hose.

10

Barkydog. Both upper and lower radiator hoses are a little over a year old. The garage and I have checked them over, and they SEEM to be okay. I did notice that the top radiator hose gets warm/hot, but it is easy to collapse by hand. Other posts have given me the impression that the hose should be firm when the engine is warm. For better or worse, it’s not.

Oliver70: Could you briefly explain how a bad head gasket would cause the coolant system to lose coolant? Wouldn’t compression in one or more cylinder’s be affected? I would think a compression test would reveal any problems, right?

11

The cylinder pressure in the typical compression test might not fall off slowly enough. The head gasket leak that we’re talking about here might just barely drip coolant into the cylinder, but it is enough to defeat the vacuum side of the radiator cap that allows coolant to be pulled back into the radiator on cooldown. Those drips of coolant, tho tiny, go into the cylinder and leave by the exhaust, lowering the coolant level over time.

12

I am with the others that mentioned a head gasket leak. From what you stated about the symtoms it seems like there is no question about it. Have the coolant checked to see if there are exhaust gases getting into it. That will tell you the story real quick.

13

Well, I am not sure that there is anything left to suspect except the head gasket, is there? It would be quite an expensive repair though. There does not seem to be any way (unless compression was affected) to narrow down which gasket needed to be replaced, so both heads would need to be done. Also, what if the head were warped? That might just be it for this vehicle. I’ll see if I can get the tests done that have been mentioned.

14

You don’t want to a compression test to detect for a leaking head gasket. But instead a leak-down test.

A leak-down test pressurizes each cylinder at top-dead-center. So if compressed air is introduced into a cylinder and if there’s a head gasket leak at that cylinder, you’ll see bubbles in the coolant in the radiator.

Tester

15

I am going to get in touch with another garage in my area and see if I can get a leak-down test done. It might take me a while to get it scheduled.

16

Having the coolant checked for exhaust gases will tell you a lot about the issue. If other things are okay with the vehicle then it still may be worth keeping it for a few more years at least. I would check into the cost of installing a rebuilt engine since the one you have has fairly high mileage. You might also be able to find a low mileage used engine out of a wrecked vehicle at a reasonble cost. You have weigh the costs against buying another vehicle alright. We sure like our '02 T&C van.

17

I finally got the van to a garage and they checked the coolant for exhaust gases, and it appears that the test was positive. It does seem like the problem is a blown/damaged head gasket. The garage recommended putting a used engine in the vehicle because they cannot (will not) offer a warranty for replacing a head gasket. However, while the van is in fairly good shape otherwise, the cost of getting a used engine installed is just more than the van is worth.

Any thoughts about just getting the head gasket itself replaced? It is not really a job that I could take on personally. Any idea of what a reasonable garage would charge to replace one bad gasket (assuming that only one gasket is blown)? It does not appear that any coolant is getting into the crankcase. Can the situation go on for a while by just replacing coolant frequently (maybe a gallon a month at this point)?

18

Thanks for coming back and offering up the diagnosis. I wonder why they are reluctant to replace the head gasket? A head gasket job is a common thing for a shop to do. … hmmm … Ok, did you ask them to replace the head gasket, and only do that? Usually replacing the head gasket involves some other work too, like having a machine shop flatten one or both of the mating surfaces. Sometimes valve work is recommended also. Maybe what they are saying is they won’t guarantee the job unless the other work is done too. Suggest to ask them again to clarify their reluctance.

It’s also possible this particular shop doesn’t do that kind of work. They’ve found it is too time consuming and has too high a risk of customer dissatisfaction with the result. But another shop in town might have more experience and be willing to give it go.

The other option of course is to do what the shop says, install a replacement engine. You might want to reconsider how you look at it from a financial viewpoint. Whether to do a job like this isn’t so much a function of how much the work costs in relation to the car’s value, but a comparison between doing the work vs. junking the car & purchasing a replacement vehicle. Figuring in to the mix the cost of add’l taxes, depreciation, higher insurance costs, etc. associated with purchasing a replacement.

19

Are your radiator fans coming on when the rad fets to the 3/4 mark. You might need a radiator fan relay. On my 2003 it was no top of the steel front bumper, just to the drivers side of the radiator and UNDER the bumper cover. Also, make sure your fans are turning the righy way (it is too long a story to tell).

20
"Can the situation go on for a while by just replacing coolant frequently (maybe a gallon a month at this point)? "

Yes, you can buy a lot of coolant for the ~$1400 head gasket job (for both heads; I’m not sure they could determine which head needs the gasket if the leak is small.)