Weird new theory: Replaced everything - still overheats

[Mike1991Explorer]

Last week I got a check engine light several times after about 15 min of operation. The dash temp gauge doesn't work but after checking all fluids were OK, engine runs well, and the light coming on consistently at about 15 minutes after start, I concluded it was overheating.

With a malfunctioning dash gauge, is there another way to test or confirm it is overheating (besides waiting for the head to blow)???

I spent that past few days replacing thermostat, water pump, hoses, and radiator. Still has original overheating problem (first paragraph). Ideas?

 

[Roadrunner777]

Your only indication of overheating is the check engine light? Am I missing something? My first step would be to replace the sensor and see if you can get the gauge working.

 

[lighttech]

Overheating?

One common failure that slips by most people is the fan clutch. The fan may appear to be spinning, but is it moving at engine RPM ?

Try to turn it by hand. It should have noticeable resistance. If you try to "spin" it, it should IMMEDIATELY stop. If it spins free, or turns really easy, the fan clutch is bad.

Other method:

Does it only overheat when driving in stop and go traffic, but fine on the open road ? Thats another clue.

As someone else suggested, you should really replace the sensor or guage for temperature. It may be a good idea to have the ECU scanned with a code reader to confirm what the CEL (check engine light) is telling you.

 

[Mike1991Explorer]

I tested both temp sensors/senders - with the great tips I found on this forum ! - found they both work, and the dash gauge works too. I think the issue must be thermostat and/or bubble in the system.
Trying that out tonight.
Thanks.

 

[Mike1991Explorer]

After replacing almost every component of the cooling system, here's my new weird theory (bubble with a twist). I'll test it tomorrow.
For 11 months, which is when I inherited the car, the temp gage on the dashboard has always shown cold (left of "C"). I thought it was broken. I now think that was an accurate reading but there was little coolant circulation. However, there was some circulation, but that ended when the water pump died last week. That's what caused the overheating. (Although It doesn't explain why, with a new pump, it still overheated).

Based on research here and my testing, I think there must be air next to the thermostat this whole 11 months.
This is my new theory because after these steps is still overheats:
1. put in a new thermostat, then pulled and bench tested it - works fine
2. put in new water pump
3. replaced both temperature sensors/switches and tested the wiring - reading fine at the dash
3. put in new radiator, hoses, and cap
4. oil and trans fluid look fine, no whiteness or foam, no steam out the rear (no head gasket symptoms)
5. fan turns fine, clutch seems fine

When it overheats the gauge at the dash moves slightly up past the "C" (about 1/10th up). This matches my sensor tests, meaning the sensors work but only pick up the indirect heat as it overheats, not direct heat from the coolant because it's not circulating. With a new thermostat (tested OK), pump, hoses, radiator, there should be no obstruction to coolant flow. After eliminating all else, it HAS to be a bubble that forms by the thermostat, preventing the thermostat from opening, while sensors read low heat because they are located right next to the thermostat. OK, well, it's just theory. Other weird theories?

The only thing I can do at this point is burp the system, which I plan to do tomorrow. Any suggestions for a foolproof burping?

 

[R&T Babich]

If you really think there is an air bubble behind the thermostat causing the problem try this. Some thermostats come with a small hole drilled in the plate around the valve to allow trapped air to escape. The hole must be positioned at the top the of the thermostat when installed to be most effective. Once the air is gone the small amount of coolant flowing thru the hole would not have much effect.

 

[Anime]

How do you know it's overheating if the temp gauge doesn't read correctly?

The needle on the temp gauge is supposed to be near vertical, in the "NORMAL" range, literally in the middle of the word on the gauge, usually between the R and the M. Down to the N is cold, up to L is getting hot and close to overheating.

If the gauge never went past the very left left left C, then the thermostat may have been stuck open. There is no scenario where the engine runs fine with poor coolant circulation. The gauge might be bad, the sensor might be bad, or something might just be hooked up wrong.

 

[Jason94sport]

How do you know it's overheating if the temp gauge doesn't read correctly?

What he said. What symptoms lead you to believe it's overheating? A CEL does not come on if it's overheating. You need to read that code & see what it says. It could be something unrelated like the 02 sensors or the TPS or MAS. Those will throw a CEL after a few minutes of driving & then go off & then come back on.

My temp gauge never goes much above C. Nothing I have done has made much difference. However It will move up half if I have the AC on & sitting in traffic in 90 degree humid south FLA weather though.

 

[surf]

Perhaps the heater core is clogged. Is the upper radiator hose hot and pressurized when the engine is warm?

 

[Mike1991Explorer]

Hi guys,

1. The thermo has a hole in the top (with a little brad or pin in it).
2. The top radtr hose was cold after running it about 10-15 min., BUT at the same time both the heater hoses got very hot and heater kicked it out.
3. I don't know about the gauge really, but I tested the sensors and per instructions I found here, all seems well. The dash gauge did respond to tests so it doesn't seem broke.
4. I tried to gurp the system today. Still have same problems with cold hoses etc.
5. I am concerned it's overheating 'cause right about when the thermo should open (~15min) I get the check engine light AND the bottom radtr hose is cold.

I saw posts on how to test codes, not sure what I am looking for? Do I run it until I get the Check Engine - then do the code test?
UGH

 

[Turdle]

Sorry to suggest something stupid, but is there a chance the belt is routed incorrectly causing the water pump to spin the wrong direction?

 

[Mike1991Explorer]

Hey Success! I tried burping it again but this time I disconnected the heater outlet hose where is exits the heater and left it open. The other end enters the engine next to the temp switch and thermostat. I then flushed the system with the garden hose in the radtr and the water coming out the heater hose.

After that I did the engine code thingy with the paper clip. I was happy to get all 111s - system OK. As I ran the codes I noticed the temp gauge rising higher than I had see it go in 11 months. Excitement - the sensors were finally getting coolant flow. Ran it up and down the freeway and hills without a check engine light coming on, which was what started all this. I pronounce it cured.
Thanks guys!

 

[R&T Babich]

... I then flushed the system with the garden hose in the radtr and the water coming out the heater hose. ...

Hopefully you didn't leave tap water in it.
The minerals can cause scaling and clog things.