I have a 95 accord v6 with the 2.7L auto transmission, here's my story...
I was working, it was late, very dark and my oil came on, stopped by autozone, topped off my car.
Found out a week later I put too much, caused cavitation and made my car 'spin a bearing'.
So I had the engine swapped out, been downhill since. A friends father found a engine in a junk yard and swapped it out for me for $900, it ran well for about a month and started over heating.
So I start with the basics and move up, fluids are good, topped them off (correctly this time),
New thermostat & radiator cap, should be good now, NOPE! **** was rusty inside and radiator started leaking between the plastic and metals connections from this new pressure!! I did my 1st flush.
So, I changed the radiator and hoses too, do I hear angels singing? No just more gremlins playing their games...
Did another flush, even with a hose in the top and the drain plug pulled out forcing out debri which had lots of rust and chunks of metal coming out.
What's left? Water pump! I pulled everything apart,flushed again with the pump off to remove more debri, installed a new pump, even though the other seemed to function fine, change it to be safe since I'm already there, timing belt looked like it was brand new.
Got the engine all synced up, put back together and started up just fine! It was running even better than before! New fluids all the way around, was riding pretty well, the temperature was staying at its normal spot at 1/4 of the gauge.... And then, the check engine light started flashing(which was new to me that it would flash and not just stay lit) the temperature spiked all the way up to the red in 2 seconds, and fluctuated up and down between 1/4 to above red and fluctuate to which gear I was in????
Went down into 3rd and the temperature dropped, then started rising again and would go between 110- 80% of the max temp on the gauge, obviously began running rough, I turned my heater on full blast but it wasn't hot at all, if I stopped it wanted to die but If I accelerate it runs better until after awhile it can't take it anymore and will severely over heat.
This all happened pretty suddenly last Saturday, and the way it acts hasn't changed at all even with everything I did to try to fix it, ANY IDEAS?????
My career requires me to drive to people's homes and without a car I'm screwed. I'm tired of dumping money into this thing but if a little more will save me from spending a lot more on another car, I'll do it!
PLEASE HELP ME OUT or refer me where to go.
Thank You

 

Did you bleed the radiator and cooling system completely before this began?
I blew the top flange off of my radiator several months ago, didn't bleed the system properly when I replaced the radiator, and had some overheating issues for a few hours before I remembered my mistake.
Where do you live? Because if it doesn't get under freezing during the summer, water has a much higher heat-transfer rate, and since you're probably going to bleed your system don't be scared to temporarily dilute your coolant with more water for now.
TLDR- bubbles like to hide in lots of places, especially the heater core; those reduce cooling efficacy

 

I live in Arizona and as soon as it hit 100, my car took a dump on me. I flushed it several times to get out as much rust and corrosion out as I could. When I removed the water pump I pressed the hose in the top radiator capped and forced water through all 3 holes that go into the pump to clear out more, I likely flushed 3 times and rinsed about 5 times.
The fact that my temperature changes so quickly and dramatically is odd, once it reaches optimum temperature, I'm sure the thermostat opens and then the temperature spikes to red and will fluctuate up and down for a little bit until it eventually just stays in the red

 

Do you see the coolant fan turn on?

If not you may need to replace your coolant temp sensor.

 

The fans turns on, takes a little while, seems a bit delayed but it turns on. I think the temp spikes so quickly that it doesn't even realize it needs to in time. It will literally go from holding perfect temp for 20 seconds, then goes past red in 6 seconds. By the time the fan turns on, it's kinda late

 

Rapid change of temperature suggests either air trapped in cooling system. Did you bleed from the top-of-engine bleed point? If not try this while adding coolant to a cold engine to top off.

If coolant level is fine, then sudden spiking of temperature may be head gasket leak allowing hot exhaust gases into cooling system. New head gasket req'd to fix this problem.

good luck

 

I drained it from the bottom of the radiator, I also used the hose gun (with a handle) placed on top of radiator and forced water through to clear out debris. I also forced water through with the water pump off as well just to be really effective!
I'm not familiar with any upper bleed points other than just pulling off the upper hose on the radiator.
Honestly I'm not mechanically inclined but I'm good at researching and figuring it out. I was to do the timing and pump perfectly so I'm not hopeless, a head gasket is out of my limits though, I don't have any time to pull off such a large intensive project

 

It's a blown head gasket... I heard Liquid Glass works pretty well for a temp repair, any experience???

 

I tried an aluminum powder stop leak. It didn't work.

good luck

 

There can be several issues causing this. One could be a blown head gasket, two could be that the head is warped, 3 could be the temperature sensor on the block which tells the thermostat how to operate. But your best bet is to get a used engine from a reputable JDM importer, and do a swap out, or you could just test all i just listed and find a good head and replace it. PM me if you have any more questions