Hi guys! Need some help diagnosing my car as I've gone down the list and checked off just about everything and the car continues to overheat. So I recently had a d16y8 redone at a machine shop. I installed it myself and did the Head gasket with ARP head Studs. Bled the coolant system as I had gotten a new aluminum radiator for it along with silicone pipes. When I ran it I ran into a couple small issues (wrong tb gasket causing a high idle) that got fixed. Then it would die when coming to a stop so I eventually came to the conclusion that either the ect sensor went out or the sender went out so I replaced both and the dying went away. I was able to drive it a bit and it was running perfectly until i saw the temp gauge continue to climb higher than the middle. Babied it home as I wasn't far and left it to cool. I decided to burp the system and double check if there was any problems and none arised. Used a small snake camera to check for blockages or see if the water pump was broken even though a new timing kit had just been used and all seem fined. No mixed coolant/oil or evidence of such. Even went as far as flushing the hoses individually and they all seemed to flow well. Replaced the thermostat as it was a failsafe one but i had tested that one and it seemed to open completely. Replaced the fan switch as I had noticed that the fan was not switching on. Fan still wouldn't switch on and continued to overheat. Decided to bite the bullet and redo the headgasket thinking maybe it was a small leak causing problems or a bad water pump so might as well knock both out. Took the cylinder head back to the machine shop and they verified it was still ok. So reused that got a new three layer metal gasket (just like the first time) this time even went as far as using copper spray. Put everything back and still overheating. I did notice that the lower hose takes a long time to warm up and the fan never kicks on (maybe a circulation issue?). Heater works every time so I don't think so. Ordered a new oem thermostat because ive heard the failsafes have issues as well. Still overheating. My next attempt will be to replace the fan switch again since i have warranty on that and attempt with no thermostat maybe theres an extremely reluctant air bubble in there?

To paraphrase here are the items that have been changed and it continues to overheat
New timing belt x2
water pump x2
new hg x2
new thermostat x3
new fan switch
new hoses
new radiator (retried bleeding with old one still same result)

 

Forgot to add the cooling fan and relay are fine. I disconnect it from the sensor and jump it and it turns on immediately.

 

Only a couple things I can think of are - did you ever happen to rewire the plug for the rad fan? Is the fan blowing towards the engine or away? My old tuner did this to me once a long time ago when I first built my engine. Wires reversed and fan blowing the wrong way!
Other thing is maybe check your spark plugs condition? Might be able to tell if it's running very lean/rich?
Maybe post a couple pics of your setup just so we can see your coolant hose routing or get possibly a better idea?

 

No rad fan wiring is untouched. When i jumped it it ran fine blowing air into the bay which caused me to assume the old switch was bad but both were tested ok yet continue to not turn the fan on. All spark plugs seemed fine. Power was fine with the car when it was running. Haven't ran it as much because it does this when idling in my driveway after a while. Not near my car at the moment but it is routed just like this car.

 

When you replaced your radiator, did it come with a new cap? A faulty cap can cause overheating, say when you have it idling, watch the temp gauge and if it gets to the 2/3 mark, check your over flow tank. Hard to say, (I'm just thinking random things) if the cap the cap is not holding its pressure, the coolants boiling point is not being raised in the system and I would guess it would leak into the tank prematurely than what it should be then lead to the engine overheating.
Also if the thermostat is not the proper rating, e.g. Using a 170 deg thermostat compare to a 190 deg, it's circulating coolant before the fan switch can activate causing the fan not to turn on soon enough causes the issue.
Lastly, could just be that a pocket of air is hiding trapped in the thermostat housing not letting the switch to come in contact with the coolant enough to raise the activating temp it needs to be to trigger the fan on.
All in all, if your thermostat is new and installed correctly with the jiggle pin at the 12 o'clock position, fan switch works checked by jumping plug pin connector, rad cap is new and correct rating, system is bled completely of air, water pump is operating, your using a 50/50 water coolant mix, radiator is unobstructed and hoses, ECT sensor is working properly, engine is running correctly for fueling then is the head gasket leaking?
Maybe watch for constant bubbles in the rad filler neck coolant, starting it up with the engine cold, rad cap off until it starts to over flow out the neck.
Idk, I'm probably wrong with some of the stuff, just trying to be somewhat helpful with random ideas..

 

It came with a new cap. I tested both the new and old radiator with and without caps. But i have bled systems before with the cap off and the fan should kick on and off beforehand right? this one doesn't kick on. Ive let it run at small intervals hoping it levels itself out but it never does. I'll doublecheck and see if theres anything going on with the overflow. But as far as I recall nothing has been leaking or acting erratic. It is a 170 deg .thermostat both of the failsafes and the new oem honda one which were all tested just in case. Heater fan works well with heat as well. I'm guessing its an air pocket as the lower hose seems to be a bit too soft and got better once the thermostat opened but regardless the fan never kicked on and it seemed to be fully bled. Even tilted it and raised it a couple times. Head gasket has been done twice now and both times ive checked the pistons to see if they've been cleaned by the coolant, checked for contamination in the oil, and the exhaust ports but the headgasket seems fine. No white exhaust smoke either. Appreciate the random ideas truthfully as I've been scratching my head with this one for a while and everything's brand new at this point.

 

I realize I was wrong when mentioning the comparison of different temp thermostats.. if it was opening it should be cooling and letting the overly hot coolant to the fan switch turning on the fan.
Last 2 things that has me curious:
- were the replacement fan switches rated for the correct temp to trigger the fan?
- could a lower temp thermostat help resolve your issue since you say the lower hose stays cool, has me thinking the thermostat is not opening and not activating the fan switch thus causing the problem.

 

They should have been. One was the original which tested correct. The aftermarket one I am replacing today but even when the thermostat opened and both hoses were hot the fan still didn't kick on. I shut it down shortly after because the temperature kept rising. I lightly grazed the radiator top and bottom and it was hot at both points so not clogged (aside from me previously checking with a garden hose). This time I ran it a bit longer and some bubbles did come from the lower hose but still no activation from the fan. Might try burping again given the bubbles. Again everything was working fine before it started to overheat but now i have no fan actuation even though i've replaced all those parts. Again thank you for the ideas to double check.

 

^As is sits

Tried today again and still overheating. Waiting for it to cool but seemingly no change in coolant level. Has anybody had experience with these hoses failing. Were new and the fan used to kick on but thats where I'm leading. Also cracked open the fan switch sensor slightly to bleed any air pockets that might be there with no luck.

 

My condolences there Mr..
Have you inspected the plug for the switch? Is a prong broken off inside?

 

I've replaced the switch and tested both outside and they both worked. Prongs on both sides are intact.

Update: Thought maybe the head was warped and did the head gasket again with copper gasket spray just in case as cylinder 2 and 4 seemed washed out but shop confirmed it was straight. Still was overheating and have since decided to bite the bullet. Pulled the motor and trans and decided to deck the block in case that was warped and had the head checked for straightness. Machine shop took forever with turnaround but I received it a couple days back. Installed new head-gasket , turned it on and its still doing the same thing. That was yesterday. I thought maybe the aftermarket red silicone hoses failed? So I replaced them with new gates rubber hoses and it's still doing the same thing. Decided to drill out the jiggle valve and that seemed to help with the lower hose but still no fan activation and temp continues to rise although a bit slower. Even with the fan jumped it seems to be a bit hot and not staying in the middle. Each time I've redone the cylinder head I've used a new belt and water pump. Old radiator was thrown back in just in case same result. Feel like im overlooking something or slowly losing brain cells here

routing

close up of heater hoses

 

Update: did a block test and no sign of exhaust gases so everything seems to be sealing properly.
I also did a coolant pressure test and found to slight leaks fixed those. Ran the car and seemed to take longer to overheat but still no fan activation and it still seems to overheat. Coolant pressure test seems to drop after a while but can't seem to find another leak as of now going to look at the heater core and surrounding area.

 

Also forgot to add I'm running it with no thermostat and that still isn't helping.

 

Update: Finally some headway! Decided to top off and check again now that I readjusted the hoses and it seemed to be holding pressure. I ran it and even though it started to overheat I jumped the fan again and this time it stayed at operating temp both with and without the heater. Now to diagnose why the fan isn't clicking on. Will try to flush out both heater and engine/radiator side as it seems that the lower hose has no pressure? Maybe theres a blockage causing an air pocket near the fan switch. Also going to replace the fan switch once more as its still in warranty.