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Oh, Boy, Now Overheating....

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#1 ·
2003 Concorde LXi. My wife is now experiencing some kind of anomalous overheating issue. This is about the third time it's happened, once to me and twice to her.

There's no particular water loss, no perceptible leaks with the engine off or on, no white smoke out the tailpipe. Last time -- almost two months ago -- we did a pressure test, and found no leaks.

Yesterday, she got home with the temp gauge all the way up, the red light on, and a little water having come out the overflow. We let it cool down, added a tiny bit of water, maybe a half cup, and I drove it. Temp gauge wavered around the middle -- it normally runs just below that. But no overheating. This morning, it overheated again.

I had told her that if it happened again, she should come home and leave the car running, so I could tell if the fans were running. They seemed to be working normally.

Both the radiator and the thermostat have been replaced in the last 5-6 years. It seems to me that leaves hoses as the most likely culprits, unless a water pump can somehow fail silently and intermittently.

Does anybody have some better ideas?

--Al Evans
 
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#2 ·
I would pop the front timing cover off just to be sure its not the water pump. It may be seeping and leaking in a small enough amount that you may not see it. A small leak there would be enough to make it run hot now and then, especially if a little bit of air is getting in.

Other than that I would suggest block testing it to rule out the head gasket.
 
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#3 ·
I would pop the front timing cover off just to be sure its not the water pump. It may be seeping and leaking in a small enough amount that you may not see it. A small leak there would be enough to make it run hot now and then, especially if a little bit of air is getting in.
Thanks. I'm leaning toward this diagnosis. The car has only 81k on it, so I was hoping not to have to replace water pump/timing belt early, but maybe I need to bite the bullet.

Other than that I would suggest block testing it to rule out the head gasket.
This seems unlikely to me. No sign of water in the oil, no white smoke from the tailpipe, seems to happen only once every few months, correlated with the coolant being low and evident air bubbles in the system.

Thanks again for the response!

--Al Evans
 
#4 · (Edited)
There are also two round o-ring/gaskets on the back side of the rear timing cover (where it joins the block - hidden) where the block metal can heavily corrode and pit and start leaking. Some people have had to clean and fill in the pits with J-B Weld and replace the o-rings. Not saying that's the problem, but it has happened to a few with the age of these engines. Might be more prone if coolant maintenance has been neglected. Might rule everything else out before concluding that.

If you remove the timing cover, if that is leaking, you would likely see signs of coolant residue on the block below Mr. Water Pump.

Dan and others (Steph/Paintballdude) may be able to elaborate. I've not had any first-hand experience with that problem, though I suspected it as a possibility on my 3.2 before my timing belt broke prematurely sending it to the junk yard, so I never got around to investigating.
 
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#5 ·
I'd check the fans by running the AC. Also with the thermostat "5 - 6 years" old you may have a sticking thermostat. These are a BIG pain to replace. Before doing anything with the thermostat, check the fan connectors.
 
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#6 ·
Thanks. I did that, both fans seem to be working fine.

It's not overheating as long as the coolant level is normal, so the thermostat is presumably working correctly.

I'm thinking more and more that it's probably time to replace the water pump and timing belt.

--Al Evans
 
#7 ·
I just edited my previous post to correct what I said about the two O-rings/gaskets between the rear timing cover and the engine block (I had mistakenly said that they were between the water pump and the block). Again, if you see coolant residue just below the water pump, that is likely the problem. To get to it and repair the pitting and replace the O-rings, you first have to remove the water pump, and then the rear timing cover. Hopefully that is not the problem, but if it is, better to catch it now than have to tear it down a second time after replacing the water pump.
 
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#9 ·
I think I'm going to declare this "fixed", unless something new happens. I just checked it and added a little bit of coolant to bring it up to the "top" mark. That was the first time I've added coolant since I "repaired" it.

The "repair"? Uh, I put a new radiator cap on. Guess what we didn't check when we did the cooling system pressure test? It finally made a spot on the street under the overflow tube.

<slaps forehead>

--Al Evans
 
#10 ·
Five to six years can be the lifespan of some thermostats. I would pull it out and test it on a stove with a meat thermometer. Make sure to only run distilled water to keep corrosion down. Also check to be sure the hoses aren't collapsing, you can run without Stat if really needed.
 
#11 ·
Thanks. As a matter of fact, the thermostat was replaced a few years ago. It was sticking open, so the car wouldn't warm up properly. Everything still seems to be working fine with the cooling system after replacing the radiator cap, for now.

--Al Evans--
 
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