May have figured out why my honda keeps overheating

This is by no means 100% solution because I still think it could be the head gasket. But here are my deductions. The car in question is a 2003 Honda civic with 140k on it. The car has been overheating for awhile, I’ve had mechanics check it out and had a new radiator cap and thermostat put on. Fan and electrical issues were investigated and the car was checked for air pockets. Then it was thought to be a blown head gasket, a pressure test was done to check for leaks first then a chemical test was done to see if the gasket was blown. It came back negative. I looked for the signs of a blown head such as white pummels of smoke and a milky dipstick, it had neither. After investigation online and taking notes on my car I’ve come to the conclusion that it’s the water pump, which was the last thing the mechanic suggested it could be after he said it could be a pinhole leak in the gasket.

The reason I don’t think it’s the head gasket is because everyday I put in 2-3gal of antifreeze and I drive 60mi a day so much antifreeze going in such a short amount of time into the engine without pummels of smoke and a milky dipstick doesn’t add up. I know the a/c hot air acts as another radiator so I usually have it on full blast the entire trip. As I near the end of 60mi I have to idle or drive slowly and I will begin to notice a temperature difference from hot to cold and not soon after the temperature gauge begins to climb and I have to pull over and add more antifreeze. I looked around the engine after it overheated and noticed that around the reservoir there was coolant sprayed everywhere particularly downwards and on the air intake. The reason I think it’s the water pump is because I’ve read that if the water pump malfunctions than the coolant cannot circulate correctly and will cause the car to overheat and this will send it straight to the reservoir.

Does this sound correct to you all? I think I am on the right track since everything else has been checked off

Was there a pressure test done on the system? Perhaps to save an unneeded water pump due to a clogged radiator a thermal check on the radiator should be done.

I forgot to mention a new radiator was installed, and was inspected by a mechanic.

The pressure test that has to be done pressurizes each cylinder in turn thru the spark plug hole.

Bubbles at the radiator cap (cap off) mean a gasket failure.

My '04 at about your mileage showed no white smoke, and clear oil. Coolant migrated from the radiator to to the reservoir repeatedly, with no heat at idle.

Even tho’ the water pump is at the lowest point in the system, it is still sensitive to a (very) low coolant level. An important point to be made is that the thermostat must be installed with the weep hole up so the system can bleed on it’s own with no need to separately bleed.

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When they change the water pump they can check your camshaft timing unless your engine has a timing chain. Hopefully something will help you. Hope you keep us up on the success or failure.

It is correct that if the water pump does not circulate the coolant the engine will overheat and blow coolant into the reservoir and out the overflow.

It sounds to me like you’ve done all the tests and checks to eliminate a headgasket problem. The water pump is a real possibility. The impellers can erode over time, reducing the ability of the pump to move fluid. It’s also possible that the radiator is clogged and unable to eliminate the heat from the engine. The pump can be tested for flow, as can the radiator, and the radiator can be “mapped” to look for clogged tubes. Considering the age of the vehicle, I’d want to do both.

One other possibility is a lining inside one of the hoses collapsing when hot and blocking the flow.

If it were me I’d change out the hoses and the water pump and test the radiator. If the hoses and pump don’t fix it, I’d change the radiator.

Yeah, I think you’re definitely on the right track.

It seems to point in the direction of the water pump. Another deduction is that I go through tons and tons of antifreeze and no white pummels of smoke or milky dipstick, I mean something would have to show after the amount of antifreeze I’ve put in it. That stacked along the fact that I drive 60mi for an hour. Also, it makes this squealing noise especially when I turn the a/c on or when I slow down and make a turn. Heard this could be a symptom of a bad water pump/timing belt. I’d guess the bearing or impelling are shot and the antifreeze can’t circulate and just sits until the car overheats. However, it only overheats after like an hour or so? so is it possible that some of the antifreeze is getting through the piping? Because if none of it were getting through then wouldn’t it just start overheating immediately?

Yes, it is possible.
Regarding the water pump shaft bearing, it’s also possible that the coolant is blowing past that seal. It could be happening only when the pump is spinning fast and the coolant hot, so you wouldn’t even see a puddle on the garage floor. That would essentially prevent the cooling system from pressurizing, lowering the boiling point too low and allowing the coolant to blow out and the engine to overheat.

I think you’re on the right track here.

If you replace the water pump, consider replacing the timing belt.

That’s another thing. When I had a mechanic check it out, after he installed the thermostat and was checking the electricals he let the car sit while turned on for hours. His words were “I can’t get this thing to overheat!” I was thinking oh cool it’s finally fixed, but low and behold it happened again but only when I drove it long distances like the aforementioned. What do you think about the squealing noises especially in cold/wet conditions? do you think that could be an indication of a bad water pump?

I have an '03 Civic EX meaning the VTEC motor. I’m certain you have a blown head gasket. Exhaust gases are over pressurizing your coolant and forcing it out of the overflow tank. When the motor cools the coolant in the overflow tank is not pulled back into the block because the cooling system is no longer a sealed system. You are going to spend a bunch of money and still end up back a square one. I had all your symptoms but less severe coolant loss. I got a new head gasket at 155k miles and all my problems were solved. You don’t have coolant getting into the cylinders and polluting your oil or going out the tailpipe. But you do have a blown head gasket - 100% certain of this.

Ok, but if that’s the case how is the coolant not getting into the engine and blowing out the tailpipe. I had a chemical test done as well and it came back negative. I know Honda’s and this model are notorious for blown head gaskets but still odd how nothing appears anywhere.

Pull the spark plugs. If you have a blown head gasket, the tips of one or more spark plugs will look like it was just sandblasted.

@Keith I don’t quite understand what you mean by sandblasted? I replaced one recently, it was brownish like, kinda rustic. I’ve seen others spark plus like this though and they didn’t have blown heads just old spark plugs.

Just some food for thought, but does this car have an air deflector and if so, is it by chance missing due to a collision, road debris, critter strike, vibration, etc?
The one below is not year appropriate as I just snagged it as an example.

You state that you drive 60 miles a day which I assume means mostly open road. When an air deflector is missing an engine can seriously overheat at highway speeds only.
With low speed, in-town driving engine temps can remain perfectly normal and an engine can idle all day long without a problem even if the deflector is in a roadside ditch somewhere.

@ok4450 Interesting thought, I’ll take a look at it tomorrow as I am about to retire to bed right now. This car was a collision car it’s entirely possible that it’s missing that part. Although, I’d imagine a trained mechanic would have caught that, I’ve taken it to two so far that seemed very knowledgeable.
You said a missing deflector can overheat on highways speeds only and be fine at idle, my problem is the exact reverse.

My observation was based on your comments on page one of this discussion about the symptom.
You stated that the mechanic allowed the car to idle for hours on end with no overheating.
You also stated that it did overheat when driven long distances.

That sounds like what I’m saying.

Yeah, It’s odd it won’t overheat when it is completely not moving. It only overheats after I’ve driven a long distance and begin to slow down. But not when I am driving at high speeds, like the air being taken into the engine is cooling the car off of but as I stop or drive slowly it catches up with itself and starts to heat up.

X2 Uncle Turbo. When the WP/TB were changed at 110K or so, both the WP impeller and the TB were perfect with no corrosion on the WP impeller and no cracks on the inside teeth or outside surface of the belt. I changed them both anyway.

A sandblasted finish is silver colored but a rough or flat sheen. There won’t be any brown or grey or black deposits, the tip will be absolutely clean, almost like brand new, but not shiny. You have to check all the plugs, not just one. If you see it, you will know.