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Richard, Dodge Technician
Category: Dodge
Satisfied Customers: 4141
Experience:  Over 24 years of experience as lead tech and shop foreman.
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1999 Dodge Caravan: 3.3L..overheating..coolant, both fans are working

Customer Question

Our 1999 Dodge Caravan w/3.3L engine stated overheating last week. It is full of coolant, both fans are working. I have changed the thermostat, serpentine belt, and radiator cap but to no avail. The temp rises normally to mid range and stays there for about 10 min then the temp rises to maximum and high temp warning light illuminates.
Submitted: 7 years ago.
Category: Dodge
Expert:  Richard replied 7 years ago.

Hello and welcome to Just Answer!

When does the engine overheat, when idling or on the highway?


Has the temp gauge been fluctuating lots lately, example does the temp gauge go over to hot and then come down quickly?


When the gauge goes over to hot are the rad fans running?


Have you checked the cores inside the rad to see if they are stopped up?

Customer: replied 7 years ago.
The engine overheats on the highway. It obtains normal temp range in an the normal amount of time and remains there for about 10 min then within 5 min it will peg out the gauge. Both fans are running when I checked them while it was overheated.
The car will cool to about 3/4 on the gauge if I turn on the heater, but ii does cool to mid range after sitting with the engine off for 10-15 min.
I pulled the front grill today and checked the radiator core and for deformation of the cooling fins and it was clear and the fins okay
The temp gauges have not been fluctuating at all. The engine had been functioning properly until a few days ago.
I checked the engine oil and transmission fluid levels and they are at normal levels and color. I am not losing any coolant either.

Expert:  Richard replied 7 years ago.

I assume you have checked the a/c condenser in front of the rad for a restricted air flow, from bugs, dirt and bent over fins, is that correct?


Have you tried to spray cold water onto the rad with a garden hose when it starts to overheat, to see if the temp drops?

Customer: replied 7 years ago.
I checked the radiator for obstructions/bug etc. It was clear. I drove the car to church this morning and discovered that it only overheats when it is driven. It overheated on the way home, when I slowed to 30 mph or less, it started to cool down. After I parked the car and let it run, it cooled to the normal range. I checked the transmission fluid again and discovered it is turning black. It is shifting okay and I have not noted any other problems, but I may have a clogged transmission filter or torque converter problems.
Expert:  Richard replied 7 years ago.

I have never seen a torque converter or transmission filter cause an engine to overheat.

It will cause the transmission to overheat, but not the engine is the cooling system is functioning properly.


The a/c condenser is in front of the radiator and you can't really see the radiator unless you pull the a/c condenser ahead. Are you sure there is nothing between the two?


When the vehicle is being driven faster, it does need extra cooling because the engine is under more load. Have you checked inside the radiator to make sure the cores aren't getting stopped up? The small cores that the coolant flows through will plug up over time with scale and reduce the flow through the cores. The rad has to be inspected inside to see if they are getting plugged.


Let me know!




Customer: replied 7 years ago.
Thanks. I pulled the entire front bumber cowling off to check it. It is not obstructed. I read on the net that some guy had one that the Torque converter had caused it it overheat. That transmission oil cooler just doesn't look like it is big enough to induct enough heat to cause the engine part of the radiator to not effectively cool.
I did a lot of experimentation today and this damn thing just isn't working logically. I am a very experienced helicopter test pilot and maintenace officer and am very good at troubleshooting. It acts like the themostadt closes intermittently and I know it can't. It is new and is acting the same as the one I pulled out. The upper rad hose get very hot, so I know water is flowing.
The overheating occurred intermittently today. Sometimes turning off the A/C would reduce the temp and others times it wouldn't. Sometimes it would not overheat with the A/C off and others times it would. I dropped it off at my trusted mechanic's garage for him to look at it. I don't have time to fool with it anymore and I need it fixed for a long trip this upcoming weekend.
I'll let you know what they do to fix it.

Expert:  Richard replied 7 years ago.

It still is possible that the thermostat you installed is sticking! I would get them to double check that and for the time it takes, replace it if they can't find anything wrong.

I would get them to check the lower rad hose for collapsing, pressure check the new rad cap to make sure it is holding pressure.


I can't see this problem being caused by a torque converter or water pump. Water pump rarely wear out.


Let me know, what they find!

Customer: replied 7 years ago.
Hey it's finally fixed!
2J's Automaotive in Saginaw, TX had to do extensive troubleshooting.
They did the following:
1. Replaced the themostadt-they thought the same as you-----NoFix
2. Cleaned radiator and A/C cooling fins-------No Fix
3. Replaced water pump----No Fix
4. Replaced radiator -- FIXED
They diassembled the the radiator after they replaced it and it strarted cooling. The interior plastic baffle located about mid-way down on inlet/outlet side of radiator had cracked/broken. This allowing water to bypass the cooling core and go back into the engine without being cooled. The intermittent overheating must have occurred when the plastic baffle was failing and was moving around intermittently opening and closing the opening causing the water to be routed through the cooling core. It would be very difficult to detect this defect without using a borescope to see the interior of the radiator. They gave me the defective part of the radiator and would be glad to send photos. Send me an email address of a place post the photos.

I am an old guy and am not familar with the new plastic radiators. I guess it cuts down on the corrosion, but they create a whole new set of problems.

Thanks for your help and I imagine we would have eventually fixed it through replacement of all those same parts. I just didn't have time to do it and needed the car fixed by Thursday. I guess we all learned something out of this.
Expert:  Richard replied 7 years ago.

That is great, I am glad they were able to find the problem. You can just insert your photos in this window. There is an insert icon beside the you tube icon and looks like a tree. I would like to see the pictures! I don't recall seeing that on these rads, I have seen the cores plug with scale inside.

Thank you,