Brian McGrew

Greetings all... This is going to be a bit wordy, I hope someone can help me out here!

I have an '04 EX Coupe with the 1.7L engine and 4-Speed automatic transmission (1HGEM VIN). About 180,000 miles on the car. I've had it since December. The previous owner wasn't so good about the maintenance but I've been meticulous about it. I got the car because it had been overheating for the past two years and she bought a new one and gave up on this one. Ugh, so, here we go.

As of today, it's still overheating. It doesn't matter if it's idling and not moving, rolling down the street and 30MPH below 2,000RPMS, on the freeway at 65MPH and 2,700RPMS or on the highway at 80MPH at 3,200RPMS. The problem is, this overheating is random. I can't make it overheat and I can't make cool down --- according to the temperature guage.

Radiator replaced 11/2011
Water pump replaced 1/2012
Radiator cap/cool reservoir replaced 1/2012
Timing belt, serpentine, power steering belts replaced 2/2012
Battery replaced 2/2012
Right and rear motor mounts replaced 2/2012
Transmission and cooling system flush 4/2012
(Wait to accumulate more money)
Fan control switch replaced and full oil/lube 06/2012
Coolant Temp Sensor replaced 06/2012
Thermostat replaced and full flush 07/2012

I've worked on it myself, as well as half dozen other mechanics. The system has been pressure tested at least two dozen times. At least four combustion leak tests that I can account for, maybe more. Heater core isn't clogged, the heater will cook your goose to well done!

Of course there are many scenarios where the thing appears to overheat, but the perfect, and most common one is... I drive Southern California freeways frequently in off-peak non-traffic times. Going down the freeway at 70MPH, just above 3,000RPMS with the A/C on. Temp gauge reads just below the middle point, which is normal. Temp gauge will start rising and A/C cuts out. Temp will continue to rise to hot, but the car is not exhibiting any other symptoms of being hot other than the A/C cutting out. The A/C will cut out reliably when the temp gauge goes above half.

I don't lose coolant, I don't burn coolant and I don't smell coolant. I bought the burping funnel and I've ensured multiple times there's no air pockets in the system. Not once have I had coolant boiling over, which I would expect if it really was overheating (please, correct me if I'm wrong).

Where do I go from here??? I don't know what else to do or check? I'm lost and so is the mechanic that does most of my work (and he's good, old, and been doing this a long, long, long time). WTF!!! Could this be an electrical problem, or an ECU problem, or what???

This is my primary vehicle and at 12MPG and the cost of diesel, I can't afford to commute from Lake Havasu, AZ to San Diego (for work) every other week.

So, Honda guru's ... What am I missing here? Where do I go from here??? Help!

Thanks,

-b

Brian McGrew

Oh, and, the fans are coming on normally... As needed when the A/C isn't on, and on constant when the A/C is on.

EM2abe

Seems like you've replaced everything. And if it is still overheating but not losing coolant anywhere then this is surely a one of a kind predicament. I've read and experienced leak tests and all those... Some come back positive for leaks, some negative... The same goes for monoxide tests in the coolant. In the end the gasket is still changed and the head gets resurfaced. Afterwards, there were no problems... If I were you, this would be the last thing to replace, and I am 100% sure your overheating problems will go away. I've been reading plenty of people scenarios and I guess this is what I always suggest, and personally, with this motor, I feel like this is the only true way to go about fixing it... Especially if everything else has been replaced. Kinda stupid, but yea. As for your coolant never running low, that is odd. But your coolant doesn't have to run low to be overheating. I'm curious about that one though. Either way, I still think the head gasket needs changing and the head needs to be resurfaced.

anibis

It's true that D17's have a terrible record with HG failures and they can be very difficult to prove with 100% certainty, I just don't think this case really fits.

The car is not going through any coolant. Mysteriously losing coolant is one of the few symptoms of a HG failure on these motors. There would be no way for the HG to fail and the coolant not be effected, either by air getting in the system or coolant being burned off, it's usually both.

When a HG does go in these cars the motor overheats because of air in the system and/or low coolant. Usually you can add coolant and bleed the system and the car will run fine for a few days, maybe even a few weeks, however the problem always comes back.

The car has been overheating (according to the gauge) for 2 years. If the HG has been leaking for 2 years it would be VERY bad by now, most likely causing misfires and losing a bunch of coolant. Once there is a failure it will get progressively worse over time. I gather you continue to drive it even when it's overheating? If the engine was really overheating you would destroy it rather quickly if you continued to drive it day after day.

I would think there's either a problem with the coolant temp sensor or a short somewhere, possibly the ECU itself. The A/C is cutting off so the ECU thinks the engine is overheating, it's not a gauge issue.

You said you replaced the coolant temp sensor, did you use oem? Was there any change in symptoms after you changed it?