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1998 Dodge Neon: What is wrong with heating/cooling system?
About a year ago, our 1998 Dodge Neon (150,000 miles) began overheating. Fluid levels were checked and they were okay. The water pump was already replaced two years prior, and you can see water swirling around above the thermostat when you remove the pressure cap.
We replaced the thermostat just to be safe, but it didn't stop the overheating problem. Finally, we noticed the radiator had developed leaks. It was obviously corroded, full of holes, and had a lot of the cooling fins falling off, so I replaced it. This did stop the car from overheating, provided we didn't run the air-conditioner on a hot summer day. We got by without the air conditioner to avoid the problem.
Now in the cold of winter, the heater hardly works. If you're driving the on the highway, it will barely start to blow warm air. But if you're sitting at idle, it quickly goes stone cold. What little heat it does give off is intermittent. We manually flushed the heater core itself, but water flowed normally in both directions, so we're pretty sure it's not clogged up.
It's obvious something is preventing the water from circulating through the heater core in winter time, and that in summer there isn't enough circulation to run the air conditioner without overheating. But if there's plenty of fluid, the pressure cap is good, the water pump, thermostat, radiator, and heater core are all okay, what else is left in the cooling system, but the water jacket itself? Could the water jacket be corroded and blocked up to prevent water from circulating? Could flushing out the cooling system cure this kind of problem, or is there something else we're missing?
*** Ramon C. Thanks for trying to help out.. As indicated, the thermostat was the first thing that was checked and replaced. We know how thermostats work. They open and close the flow of water between the engine and the radiator. By staying closed until the water reaches a certain temperature, the thermostat allows the car to heat up quicker in cold weather, instead of immediately cooling off the water. As for the heat exchanger, that is the radiator. We already replaced that as well, because it was full of holes and corroded. It helped a little, but it's something else. There's something preventing the water from circulating through the heater core, even after the car is fully heated, and the thermostat (tried two different new ones to be sure) was replaced.
****Michael S. Thanks for your answer. We removed the hoses to the heater core, and successfully ran water through both of them. I also filled it up with CLR, and let it sit for half an hour, then flushed it out. Water easily flowed in both directions through the heater core, so I'm pretty sure it's not that.
Meanwhile, both the radiator fans and the fan that blows over the heater core work properly. Had the radiator fans not been functioning, that would explain the car overheating in summer, but not why hot water isn't flowing through the heater core. Had the heater core fan not been working, it would explain the lack of heat inside the car in winter, but not the car overheating in summer. There must be something else preventing the circulation of water.
**** Paul H. Thanks for your answer. This sounds like a potential solution. One other thing I forgot to mention is that after running the car for a while, when you shut it off, you always hear what sounds like air bubbles slurping in through what sounds like the coolant in the overflow tank. It's as if a vacuum is being created while the engine is running, then when it shuts off, the pressure is suddenly released. and now air/water is either suddenly rushing back into or being expelled from the engine through the overflow tank coolant. My e-mail address is faithbits@ymail.com, if anyone needs to follow-up.
*****One other detail***** I'm afraid the car may have a bad head gasket. After overheating (due to the old radiator being clogged and falling apart), I noticed once that there was water vapor coming out the exhaust. If there were a bad head gasket, would that explain the vacuum bubbles slurping through the overflow tank when you shut the car off? Could a bad head gasket prevent water from properly circulating through the engine?
****Keith P**** It would certainly be nice if a simple flush or air bleeding would solve the problem. I'm beginning to fear it may be the head gasket. The car is scheduled for a diagnostic on Monday. I'll try to remember to post an update when I find out what it is. Thanks for replying.
****Paul H**** Thanks for the update. Yes, that makes sense. I hope you're right, and that a simple air bleed will solve the problem.
4 Answers
- paul hLv 78 years agoFavorite Answer
From your description and based on the repairs already done, it sounds like an air pocket in the heater core which is restricting coolant flow..especially at low speeds. Any time you open up the system for repairs or if coolant levels get low from a leak, air can get into the system and wind up trapped in pockets in the heater core or heads...what ever is the highest point in the cooling system can get air pockets. An air pocket will restrict or not allow smooth coolant flow which can lead to heater malfunction or overheating/temp swings if the pocket is in the cylinder head.
Since you have flushed the core, It doesn't sound like the core is clogged...nor a bad t-stat or radiator. What I would suggest is you bleed the cooling system.This video shows how to do so in generic terms....
http://www.youtube.com/watch?v=zUpXgAJ1gjU
You basically set the heater controls on high heat, top off the radiator or surge tank if so equipped, leave rad cap or surge tank cap off and start the engine, as the engine warms, open the bleeder screw on the t-stat housing or upper radiator hose periodically to allow air to escape....close and open bleeder until just solid coolant comes out...no air bubbles.....run engine at higher speeds to get all the air out while operating bleeder screw...let engine idle and recheck bleeder screw...open and close to make sure no more air bubbles...test heater hoses to make sure both are hot. Top off coolant if needed during the process and replace cap on radiator or surge tank.
Once you have bled the cooling system of air and topped off all coolant levels in the radiator and surge tank or overflow tank, check both heater hoses going to the heater core from the engine....both should be hot when the engine is warmed up.
Happy New Year....and hope it's a warm one.
Edit: The slurping sounds are an indication of air in the cooling system. Normally, with a full radiator/cooling system and overflow tank, a solid flow of coolant will flow back and forth between the cooling system/radiator and overflow tank via the radiator pressure cap opening or closing as coolant expands and contracts due to heating or cooling of it. As cooling system pressure exceeds the cap rating when the engine is heated up, the spring valve in the cap opens and allows expanded coolant volume to flow into the overflow tank...when the system cools and contracts in volume, coolant is sucked back into the cooling system. If there is an air pocket, the system will balance pressure unequally or not as a solid fluid flow...causing the slurping sound....or the pressure in the engine/cooling system will slurp coolant into other parts under unequal heat and pressure due to an air pocket.
- Michael SLv 78 years ago
Feel the TWO heater hoses that go through the firewall. They should both be hot. If not there is no coolant flow through the heater core, if both hoses are hot then there is nothing wrong with the heater core. If they aren't both hot then your heater core is blocked or there is a heater control valve on one of the hoses that isn't working.
Next to check is the blower motor. Turn the heat up to high, and the fan to each speed. You should be able to hear the blower motor fan and feel air blowing. If you don't you have the problem.
Next is check the radiator fan(s) for proper operation. Some cars have a safety measure that puts the fan on all the time when a relay goes bad. Make sure they are working correctly.
Always check your coolant level when the engine is cold, and you check it at the radiator cap. Should be full to the top.
- ?Lv 45 years ago
Spend a little bit more upfront and have the auto checked over by means of a store. Then you'll be able to comprehend if it is ok or wants repairs. I as soon as proposal that $seventy five. Was a particularly great cost for a 1978 Monte Carlo until I learned that i could not get it to run. But I did sell off some ingredients and towed it to a salvage yard and almost always broke even.
- keith pLv 68 years ago
Your cooling system is all gunged up you need to flush out you cooling system ,you can buy a tin of radiator flush that will clean out the system ,all the instruction are on the tin ,you put the cantents of the tin in the cooling system and you run the car with the flush in for a lenght of time and then you drain off the cooling system and refil with antifreeze as normal .
