Honda Overheating

'04 Honda Civic-1.7L
First the car started overheating only it was sitting in idle. As soon as you would go or if you revved the engine the needle would immediately drop after a few seconds. Replaced the thermostat. It seemed fixed, but started doing it again, put in a new thermostat incase other one was faulty. Still having same problem.
The system was pressure testing and everything was fine. Then had the system flushed and new thermostat put in. It worked for about 150 miles and started doing the same thing.
Brought it in for the water pump, the old one was corroded and warped so it seemed like the problem. After about 100 or so miles still overheating when idle.
We had the radiator replaced, the old one was complete junk, thermostat replaced too. I drove it like normal in town for a day, the next day it started overheating, this time it was doing it while driving, got to about 3/4 up. Turned the car off for a bit, and it didn’t do it anymore on the way home.
Today I was driving and it was fine for 4 miles, I sat idling for 1 minute, after driving 1 more mile it started overheating, temp gauge got to halfway. I parked it for a bit and started driving, there was no heat coming from the heater, I had it full blast, nothing but cold air. The car started overheating again, once again halfway. Parked for about 3 minutes and then turned it on, temp was fine and it was blowing full heat out, the car temp was fine the whole way home, no more overheating.

The next step we will take is to replace the head gasket and/or heater core. Is there anything else that this could be? Literally the same week the overheating started, the rear lights were having issues and one time there was no power to the windows. Then the door locks would stop and then work again intermittently. The door locks no longer work at all. Not sure if it is just a coincidence, maybe everything is breaking at once. But there has been no loss of coolant and the oil and coolant consistency have been normal too. Any input would be appreciated!

Have you been doing all of your own diagnosis and repair, hoping to guess the right part?

A temp gauge at “halfway” is NOT running hot.

Do the electric cooling fans that suck air through the radiator come on at any point? If not, the relay that asks them to run may be bad, the fan(s?) motor(s?) may be bad, the wiring to the fan(s) may be bead, or the fuse to the system may be bad. Guess the fuse first. It’s cheapest.

Unless it is mysteriously losing coolant, it is not a head gasket issue.

Everything besides the first 2 thermostats has been by a mechanic. It has been run just past 3/4 way, I have become nervous and stop it after halfway as it is climbing because it usually never makes it past 2/5.
When the issue first started there was 2 times that the fans did not kick on when they were supposed to. But they seem to be kicking on as they are supposed to now.
Because the heat went from cold to hot, etc., does that mean the thermostat is sticking?
At this point I am wondering if I should bring it someplace to have the boards, wires etc checked out before I do anything else.

“A temp gauge at “halfway” is NOT running hot.”

Very true. Have you been getting all the air out of the cooling system after all these repairs? Air in the cooling system can explain all or most of the problems that you are having especially the “cold air” and temp gauge readings. Engine temperature sensors won’t work in an air bubble. The power issues are not related to engine temperatures. They are just a coincidence.

The mechanic has gotten all the air out each time. I myself and several others have used this mechanic with no competency issues, I think he did it right.
We have been going down the list of possible causes and I really don’t think this ends with a bad head gasket.

I myself and several others have used this mechanic with no competency issues, I think he did it right.

Just something to consider, but by my count you’ve had it in to this mechanic at least 3 times for an overheating problem and he can’t find it. Any mechanic should be able to find it the first – certainly by the second time, because he should have diagnostic equipment that, assuming he knows how to use it, will tell him exactly where the problem is. I’m not personally convinced that there are no competency issues here.

Until you are sure what the problem is I would strongly recommend against changing the head gasket. First, it’s expensive. Second, shops that botch the job cause all sorts of problems down the road which they then blame on various BS reasons that it can’t be their fault.

Proper diagnostics will tell you if your head gasket is bad. A mechanic saying replacing the head gasket is “the next step” without explaining what diagnostic tests he ran to arrive at that conclusion is not someone you want fooling with your car.

Personally, if you’re only overheating at idle, I suspect you still have a fan problem.

It used to overheat only at idle, now it overheats at idle and while running, a few times the car has been turned off and back on with no issues at all on the drive home.

The testing showed no issues, it has been checked twice. The mechanic cannot figure out the problem. So I should bring it to another mechanic?

" So I should bring it to another mechanic ? " The answer to that question is so easy a Caveman could do it.

Not very nice! I am literally looking into it right now to see where else I should bring my car to. I am just wondering if that is the only conclusion. Was curious if anyone had other thoughts as to possible causes for the problems listed.

"The mechanic cannot figure out the problem. So I should bring it to another mechanic?"

Classic symptoms of Honda Civic head gasket failure. My '03 ES had all your symptoms, head gasket replacement was the fix that finally worked. That was about a year ago at 150K miles. It is fine now with 10K miles since the job was done.

After several thermostat changes, the thermostat used in the '01-'04 Civics has a bleed hole that should be installed “up” which allows the cooling system to vent air and eliminate the need for burping.

Also the heater control should be set on Hot when filling and burping. That opens the valve between the engine and the heater core. At least that’s how it is on my 1999 Honda Civic. Watch the valve move when you operate the Hot - Cold lever or dial on the dash. It’s just in front of the firewall.

It could be a head gasket on the fritz, but there are tests a shop can make on the coolant and various pressure tests to usually rule that in or out. Replacing the head gasket wouldn’t be done as a way to test if that’s the problem or not.

These are the questions that need to be addressed

  • Is the radiator cooling fan consistently turning on and off at the correct temperature, and running at the correct speed?

  • Is the cooling system holding pressure, and operating at the correct pressure?

  • Is the water pump output flow as much as it should be?

  • Has the cooling system (including the heater core) been properly bled of air?

  • Does the thermostat open and close at the correct temperature, and open to the correct dimension, as measured in a pan of hot water on the stove?

  • Has the radiator been flow tested?

Going to try bleeding the cooling system and will check the thermostat tomorrow.

That would be a good opportunity to also check for any signs of bubbles coming to the top of the coolant in the radiator.

Is there any chance the temperature gauge could be a little wonky; maybe due to an iffy temperature sender or a sender connector with corrosion or scale on it? A poor sender connection increases the resistance in the circuit and that can artificially drive the temp gauge needle higher.
Maybe checking it out with an infrared thermometer to verify that it’s actually overheating would be a good idea.

With the A/C off only one of the fans should cycle on depending upon the engine temperature.
With the A/C on both fans should run.

You refer to the fan(s) not cycling on several times but seem to be fine now. Does that mean a single fan, the A/C on or off, etc?

I don’t think the temp gauge is reading wrong, it actually did overheat one of the earlier times. And the instrument cluster has been replaced too(speedometer & rpm gauge weren’t working).

When I referred to the fans not cycling on before. The cooling fan wouldn’t turn on unless the A/C was on. It stopped doing that after the water pump was replaced and no issues now. These intermittent issues are what make me wonder if something electrical is going wrong too.

“the instrument cluster has been replaced”

No offense intended, but are you absolutely sure you got the correct cluster for your application?

Meaning . . . are you sure it’s not for a model with a different engine, for example?

Was this replacement cluster used or new?

The cluster change throws a new wrinkle into this and like db4690 I would also be concerned about the fitment.
The temp gauge, like the fuel gauge, should have 2 leads that are hot in the cluster and the ground lead goes through the temp sender which is a variable resistor.

I’m going to correct my earlier post about resistance and gauge readings. My mind must have wandered off the reservation so to speak.
With increased resistance the temp gauge needle will be driven lower; not higher. This also applies to fuel gauges.

The temp sender could be checked with an ohmmeter. At normal operating temperature I think it should show about 40-45 ohms resistance and a couple or 300 hundred when cold.