Overheating and coolant leak

I have a 1999 Acura TL 3.2L and it’s been overheating and losing coolant from somewhere. The thermostat, radiator cap and radiator hoses have been replaced. I’ve also purchased the temperature control switch which hasn’t been replaced yet. I also purchased the water pump, timing belt and serpentine belt tonight which will be picked up in the morning. I’m concerned that the water pump and timing belt are not the cause. After reading a couple of other posts I’m pretty sceptical. I’ve blown a head gasket before and there’s no obvious signs of that being the case here. No mixture of water/oil, no white smoke from exhaust, no bubbling in radiator/reservoir and no steam from radiator. Now, here are my symptoms: temperature gauge reads H when idling or driving slow, at high speeds or continuous driving the temperature gauge is normal, if the gauge does reach H once I begin driving it will return to normal, when the temperature gauge reads H there are no signs of overheating (steam from radiator or exhaust), the fan only works if I turn the AC on or it continuously runs for 15-20 minutes after I turn the car off and I’m putting 1-2gal of water in it at this point daily until I can find the root of the problem. I’m not rich and can’t afford that much antifreeze daily. If I add water to the radiator with the engine running I do see the flow in the radiator. The hoses are new and flexible when squeezed. There’s no obvious location where the water is leaking from. However, my fiance put it up on ramps this morning and claims he spotted a leak towards the back of the motor, well since it’s in the car sideways, I’d say more towards the firewall side of the motor. I’m pretty sure that’s the general location of the water pump which is the reason I ordered it. Then I looked up the symptoms of a faulty water pump and it does have some of the symptoms but not enough for me to conclude that it’s the problem. I was also told to consider the freeze plugs being the culprit. Which, I feel would be a more likely cause considering the amount of coolant loss. I’m just trying to weigh the symptoms and likely causes. I’ve read several posts and articles with no definitive conclusion. I’m not a mechanic by far but I do have general knowledge and plenty of experience with Honda’s and Acura’s. I’m hoping you all have some good ideas and suggestions for me to try to get to the root of the problem. TIA. Oh, I’m sure this will be asked at some point. It’s got 289k miles on it, I bought it used from a private owner and no I don’t have a history on the repairs and maintenance. I can only say that the maintenance has been done properly since I’ve owned it and I have not replaced anything major. I personally replaced the VVT, Starter, Alternator and Thermostat. Everything else has been normal maintenance oil/filter, transmission fluid, air filter, radiator flush, fuel filter, brakes, tires, battery, spark plugs and regular checking of fluids/filters. If there’s anything else that you need or want to know feel free to ask. I appreciate all responses whether they’re helpful or not. At this point I’m willing to try any suggestions. Thanks again and I look forward to the feedback.

If you were losing 1-2 gallons of coolant a day from leaking frost plugs, it would be blatantly obvious. There would be a massive puddle wherever you park the car. Rusted-out frost plugs will leak all the time, whether the engine is running or not. A defective water pump might leak only while the shaft is rotating (i.e. when the engine is running) and not leak when the engine is turned off.

Still, unless the coolant is leaking out onto the ground, it must be going somewhere: into the oil, into the transmission fluid, or out the exhaust. At 289,000 miles, the engine may be worn out.

There’s no obvious location of the leak. It’s not in the oil, I have checked the transmission dipstick, there’s no steam/smoke from the exhaust and fluid doesn’t leak when it’s off. Also, there’s no sludge in the radiator. This is a problem that began recently. Honestly, I didn’t notice the loss of fluid until my AC was repaired a couple of weeks ago. The AC worked when I bought the car and I noticed once the weather started getting hot that it was blowing warm air. I assumed it just needed to be charged. We went to buy a can of Freon and as soon as he hooked it up the gauge went to red. The woman at the auto parts store said that indicated a blockage in the system. I called my uncle who is a Master HVAC/refrigeration Tech and he said he didn’t think that was likely. So, I took it to him and he charged the system with no problem. He seems to think that the gauge from the auto parts store was faulty. Either way, the AC works fine and I haven’t noticed if it doesn’t lose coolant if the AC is off or not because it’s been between 95-102° constantly here for the past month plus my interior is black leather. No AC and black leather are definitely not a good combination at those temperatures. Also, despite the milage it’s a good running car and I’d like to get some more life out of it before making the decision to get rid of it. I only paid $600 for it so if I need to put a little money into it to keep it going I’m not opposed to that. I’d just like to find out what exactly is causing the problem.

You say the radiator fans only run when the A/c is on. Anytime te temp is higher than normal, the radiator fans should be running. I don’t know what contols the fan on this car but I am sure some of the pros on this site do . Maybe one of them will give insitght. In the meantime I would change the radiator fan relay.

That was something I looked into. Conveniently, none of the auto parts stores around have it in stock. I need to order it. However, that’s how I stumbled across the Temperature Control Sensor. Which, I have already purchased but the location is making it really difficult to replace. That’s on the to-do list for the morning. I’ve also read several articles and posts that say the one fan only comes on when the AC is on and the other fan is for controlling the radiator temperature. Which, it seems to only engage when I turn the car off. Both fans do function, I’m just not positive that they’re functioning properly.

A 1999 you bought for 600.00 . This thing is probably past it’s useable period and could just keep costing money and causing frustration . Just start ;looking for a replacement as it seems you have gotten your moneys worth out of it.

1: 289,000
2: you’ve probably put $200 of parts in it already.
If I had a car with that many miles on it (and I do) and was having problems, the first thing I would do is check the integrity of the engine before I put a dime into it. Starting with a compression test. If you have bad cylinders, rings, valves or heads all the other money you put into it should’ve gone towards your next vehicle. Cars don’t wait for you to be able to afford another one before they wear out.

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I would recommend that your cooling system be pressure tested both cold and hot. Also, the fan off while the engine is too hot should be diagnosed. A quick fix would be to connect it directly to a switch you control. I suspect that an emissions test could tell you if antifreeze is in the exhaust. Finally, the water near the firewall might simply be the A/C condensation. Based upon the amount of fluid lost daily (you don’t say how far you drive) I am still guessing a head gasket problem.

This does not seem like a leak to the outside. This is almost certainly a serious head gasket leak, and the engine is probably toast from overheating so many times if it wasn’t already.

I’m guessing that the poorly functioning radiator fans caused it to overheat the first time, causing the head gasket to warp and fail. There’s no saving that engine now.

If you were losing 1-2 gallons of coolant from an external leak, you’d notice wetness somewhere. So clearly the water is going into the engine.

With 289k, it’s time to send her to the junkyard. Stop pouring money into a sinking ship.