Hello, I have a 2003 Dodge Neon. My engine overheated on me going 70 plus down the interstate on a VERY hot day. I pulled over and the overflow was "boiling" but nothing was coming out the over flow. I got a ride to work, and now i am trying to fix it. Here is everything i have done. Drained the coolant and flushed the radiator twice (filled with orange coolant), replaced the thermostat, replaced radiator cap, put in Water Wetter which is supose to make it run cooler. The problem was not fixed by any of that. It will stay in between hot and cold while driving down the interstate for anywhere from 15-30 minutes then it gradually starts rasing untill it gets up to the red line, it dings the warning and usually drops back down below the hot line. When i turn it off the coolant seems like it is boiling, but nothing comes out the overflow. Usually the water pump just fails completely right? I dont know why the things i have changed havent worked, and now i am at a los on what to do moving forward. Thanks in advance.

 

Have you pressure tested the system? Are you sure there's not a clog somewhere in the system?

 

No, that was my next step. I plan on taking it somewhere to have the cooling system and engine pressure/compression checked. The more i read online, the more i think i may have a leaking head gasket. I have seen some people say that thiers went in a place where no oil mixed with the coolant, and almost all of the places i have read a "bubbling" overflow bottle led to a head gasket being replaced. Bummer....

 

accually, the water pump doesnt have to fail completley, when i got my car, i was told it had a new water pump, and it didnt, Mine seemd to do the exact same thing, but what was funny when i would drop gear and run the **** out of it, it would cool off. I bet if you took your water pump off, youd find that the impellar blades have rusted off.

 

i hope you're right. yesterday we drove it and it did not get hot the whole time it was a bit cooler and i think the weather might of had something to do with it. what does that mean if it only overheats when its really really hot outside?

 

it means that there's something wrong with the thermodynamic heat transfer and the hotter the air the less efficient the transfer.

sounds like a possible head gasket. I'm doing one right now that's had a new radiator, new water pump, new thermostat and still overheating. I'm the only person that tested the head gasket and found it leaking. all those other parts were a waste of the customers money.

also check to make sure there is nothing blocking airflow through the radiator. I fixed an overheating car that a shop replaced thermostat, waterpump and head gasket only to find a piece of cardboard between the a/c condenser and the rad.

 

You can have the coolant tested for hydrocarbons too. Is the engine oil milky looking on the dipstick?

 

Normally, over heating during low speed driving is due to inadequate air flow thru the radiator (air side) due to blockage from papers, leaves, etc. or a faulty fan(s) not working or tunring fast enough.

High speed (70 MPH) (assuming your grill and the airway isn't block or you don't have holes in your hood near the windshield) means a lack of heat transfer from the coolant to the air (such as an inadequate coolant level, dirty radiator).

If the head gasket is leaking, you should see a coolant loss with no obvious signs (puddles under the car, streams down the block, etc.)

 

The engine oil looks fine.

A mechanic that my dad knows told us to take off the hose to the overflow bottle, and put it in a bucket of water and start the car. He said if it bubbles constantly then the head gasket it leaking. When we first started it is was bubling non stop, but as the car heated up, it quit bubbling. At one point we didnt have a bubble for maybe 15 mins. What does that mean? Also, if we squeezed on the top radiator hose it would make big bubbles, that makes me question this test.

 

If your cooling system is full, there should be no bubbling. It bubbles becuase you have air in the system - which will make you over heat.

The radiator cap must seal in two fashions -

1. The cap must hold pressure up to it's rating point (14-16 PSI)

2. The cap must pull a vaccum to draw the coolant back into the system during cool down.

I would suggest looking carefull at both the radiator neck (upper and lower sealing surfaces, plus the two rubber sealing surfaces of the radiator cap.

I defect in the overflow hose would let the coolant leak on the ground and prevent the siphoning back in during cooling.

If the cooling system is properly intact, would a simple compression test reveal a leaking head gasket (when cool to cold)?