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Discussion Starter #1
Sorry for the long text but thanks in advance for anyone who reads through and attempts help.


First off I have a 2008 Dodge Charger 2.7 L V6
5 days ago my car was Idling with the A/C on when I heard coolant bubbling over into the reservoir. I immediately shut the engine off due to the heat getting close to the redline. I waited for it to cool down to make the 3 mile drive back to my house but when I tried it would begin over heat within seconds of me putting it into drive. Hours later, I refilled the coolant, (which was very very low) & checked all my hoses which looked fine. When I had my car Idling, my engine would maintain temperature, however when I turned the heater on it was still somewhat cold air even with the engine warm. When I shifted it into drive it would start overheating within a minute.

Next I did a compression test to see if I blew a head gasket. My results were: 155 165 150 175 160 170. My oil looks fine, exhaust looks normal smells normal and my spark plugs all looked the same so I am confident it isn't that.

Finally I drained all the coolant and replaced my thermostat. When I pulled the old thermostat out it wouldn't open with heat so I thought I solved the problem. Unfortantly after I placed the new one in, I have the exact same issue:

Car will maintain temperature while idling. Heater does not give me much heat until I shift into drive. Once I'm in drive I have about a minute before the engine starts to overheat and my coolant boils over into my reservoir.
I checked the bleed valves on top of my engine coming from my radiator and it was mostly steam or a lot of bubbles coming out. Also, the radiator from felt cold to the touch despite my engine overheating. (I'm not sure if this is normal)

My question is, could this be caused by air still in my coolant system I need to flush out?
A blockage to the radiator?
or any other feedback would be extremely helpful

Thanks so much!
 

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Welcome to Allpar. A cold heater core and radiator may mean that there is no coolant circulation. The hoses should get warm.
A back-flush may unplug them if this is the problem. If they are restricted by harder deposits, they may need replacement.
Make sure that the electric cooling fan works.
No circulation could also be a water pump issue. Bleeding all the air out is important. Too much water in the 50/50 HOAT coolant mixture will readily boil.
Being an all-aluminum engine, cooling is very important. Overheating can be fatal for head gaskets and a compression test may not catch a smaller compression leak into the water jacket. An orange HOAT coolant must be used in a 50/50 mixture. How many miles?
 

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Discussion Starter #3
Alright, thanks so much for the ideas. I'm gonna drain all the coolant out because I know I'm at probably 30% coolant 70% water, do a reverse flush in the mean time. When I refill I'm gonna slowly do it to make sure there's no air and I'll let you know the results.

I have 85K miles on my car already and the electric fan is working fine.

Thanks again
 

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Second update, I checked the bottom hose going from the thermostat into the radiator and it was cold like there was no circulation. So once my engine cools I will do a flush through my engine to see if there's a blockage, and check my thermostat to see if I had very bad luck and replaced my old thermostat with another bad thermostat.
 

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I would assume nothing. Such as the impeller in the water pump still being attached to the pulley. Or the spring in the bottom hose being there and preventing suction from causing the hose to flatten out and pinch shut. A total lack of circulation is damned rare IMHO. If you yank top and bottom hoses stick a water hose in the top and water roars out the bottom then this would certainly cloud an opinion that the radiator is horribly clogged. On my car if I ran into such a symptom with the mileage it has (80,000 miles) the water pump gets changed, automatically.. Pich off the TOP radiator hose, disconnect a heater hose from the engine, pump up the pressure tester and see how much water comes out the disconnected hose bib. I haven't seen a compression leak yet that did not blast out of the overflow or fill the crankcase with coolant.

Best of fortune to you and please post your findings. I'm near 70, and feel when I stop learning, I start dying.
 

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Third update, pulled my thermostat again, tested it and it opened right when it should no issues. Next I stuck a garden hose to flush every possible direction there could be a blockage, nothing! Checked my heater hoses which were fine no leakage and held pressure, then put it all back together. So here's where I'm stuck. Due to my engine over heating when in drive and absolutely no heat coming out of my vents, it seems my coolant won't flow into the radiator or back up into the heater hose. Now with a water pump failing, I should hear whining if it's the bearing or see any sort of leaking if it's cracked right? I'm planning on replacing that pump tomorrow just going to take a day to give my mind and body a break. What else could cause these symptoms?

Thanks for your help!
 

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Even though the thermostat is at the lower hose, the flow is still from the upper hose, through the radiator to the lower hose and back into the engine. The thermostat must be oriented correctly to have heated coolant open it, otherwise it stays closed. Coolant will always circulate through the heater hoses regardless if the thermostat is open or closed.
With the engine running, the pump will keep a positive coolant pressure at the top bleeder screw. By opening this screw carefully (beware hot coolant), you should get a spurt of coolant. You can do this while the engine is still basically cool and before steam has a chance to form. If you aren't getting pressure here, then I suspect a detached or damaged pump impeller. It can still be quiet if this happens.
41726d1348177828-car-overheating-no-heat-come-vents-pump.jpg
You have confirmed that there is no blockage.
No circulation = no pump.
The 2.7L water pump is chain driven under the front cover. Is would be difficult for a first timer in a driveway with hand tools, but I am unfamiliar with your tool resources or level of expertise.
 
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