QuestionHi this is James Laughlin Again, and i took it to a radiator specialist today and he said the head gasket is fine, but there may be a block traveling around somewhere, and the water pump may be on it's way out, but that could be why it sounds like it's bubbling up because of there being a possible block, all the coolant may be backing up in the system! I'm not sure if any of this is accurate i don't wanna put all this money into it, i mean the car only has 79,000 miles on it, maybe i should have the system flushed and the water pump and the coolant replaced!
Thanks Again,
James Laughlin
AnswerI would like to keep the history of our dialog together so I have copied you first question and my response:
"Hi my name is James and i'm having a serious problem with my 98 dodge neon 2.0 SOHC Engine, well it has no signs of there being a head gasket problem or having a blown or leaky head gasket! which is good, but it keeps getting very hot. I replaced the radiator and tried that first it seemed to limit the problem but it still gets really hot and i need to pull the car over but when i shut the car off even when at normal temperature, it sounds like something bubbling up in the system right behind the coolant overflow bottle! I thought that this may be a block in the system but it has a very nice coolant flow half of the time, so now i am thinking it could be the Water Pump starting to go. because of that bubbling i hear when i shut the car off it sounds like it's all backing up. Well thank you very much for your time, i really appreciate this,
James Laughlin
Answer: Hi James,
What are your "signs of there being a head gasket leak". I don't want to be an alarmist but there are several ways that a head gasket can blow, each of which will have different symptoms. But you may be correct.
There are two main possibilities (and maybe some less likely reasons) for what you are experiencing. One is that the thermostat is stuck shut and preventing the flow of coolant from the engine to the radiator and impairing the flow to the heater core. The other is that there is an internal leak in the engine proper, usually at the cylinder head gasket, which pressurizes the system with exhaust gases and impedes the cooling of the engine and the flow of coolant. If the latter were the case you could also notice excessive white smoke from the exhaust pipe which had the odor of coolant and/or a milky-foamy condition of the oil on the dipstick and/or early after starting the engine the bubbling of gases from the overflow bottle and/or rumbling in the radiator or the engine. The former (thermostat) possibility is easy to check and repair, the latter (head gasket) is of course a more significant engine repair job.
So see which if any of the symptoms might be present when you again start the engine, let it idle, and await the rise of the temperature gauge. Also notice whether the cooling fans come on as the temp gauge moves to the high end of its scale.
You can locate the thermostat in the 2.4L at the front of the engine on the radiator side directly underneath the filler pressure cap and water hose that comes from the top of the radiator. You could remove the thermostat and put it in a pot of hot water on the stove and with a thermometer observe whether it begins to open at about 190F or not. If it doesn't begin to open until the water boils then you need to replace the thermostat. Otherwise, you need to ascertain that it isn't the head gasket.
You can perhaps check the water pump function by observing the flow of water with the pressure cap removed while the engine is in the warming up phase, at idle. If it is really stagnant that could be the answer, but you might do well to go to a radiator shop and ask them for an opinion on that before doing a pump change without good cause.
I'd be curious to know what you find is the answer."
In response to what you have learned and reported to me:
Let us look at some details about the history and present function of the system:
When you say it has 'very nice coolant flow half of the time' can you tell me what you mean by that? Will the system operate normally on one trip and then act up on the next? or what is the behavior when it isn't heating up. Is there any rhyme of reason for the different behaviors that you can conjecture about?
When you say it heats up fast, how fast (time or distance travelled) when you observe it to overheat? Do you have a gauge or just a temp warning light?
Do you ever have to add coolant to the system? If so can you ascertain where the fluid is being lost from? The overflow bottle, the radiator cap, on the ground under the engine or the radiator?
When you go to start the car when it is cold, have you looked at the water level by opening the pressure cap to see if the level is full to just below the cap, or have you observed it to be well below that level and even not visible at all?
What about the overflow bottle: does it fill as the engine warms, does it level drop down as the engine cools all the way down to its original level? Does coolant ever blow out the filler cap of the bottle?
Does the heater work well?
Does the engine run well?
Does the cooling fan come on, and what is the gauge reading when it does come on?
What is the gauge reading (if you have a gauge) when you first hear the bubling sound? Can you tell if it is the radiator or the engine where the bubbling is coming from?
All of these questions may be relevant so please consider each one and respond.
I doubt that there is blockage in the engine, and with a new radiator I don't think there is blockage there either.
For that reason I believe you should check the thermostat:
Have you checked the thermostat's function in a pan of heated water? I notice that I gave you the location for the 2.4 rather than the 2.0L but it is very similar: the 2.0L pressure cap sits on top of a curved pipe that is bolted to the side of the engine. If you remove the bolts you can access the thermostat, but drain off about a half a gallon of coolant from the radiator or catch the fluid from the opening with a pan placed under the engine when you remove the two bolts. Notice the position of the thermostat and that it has a vent hole that should be facing up when you replace it (it mates with a relief in the top of the opening on the cylinder head side of the connection), and put the bolts back in. Notice that the o-ring has a locating dimple as well. Look at the o-ring to be sure of its condition and replace if necessary.
You ought to consider the possibility that your problem is just a thermostat that is not opening at a low enough temperture or not at all... before doing anything like flushing and changing the coolant.
So consider the above and let me know.
Roland
P.S. Please use the follow up option if you reply so the history is preserved.
