wasr10

Has a D16B JDM motor swap. I've been working on this for the past month now and still no luck. It only overheats on the highway going above 60mph after driving for 20+ minutes. The temp slowly rises, but it never gets to full hot - maybe 65-75% hot, if that. The faster I go the hotter it gets - if I slow down it cools.
It can sit at idle all day at normal operating temp when first starting it up - after getting off the highway, after it overheats, it will idle at a bar above operating temp & no more. Doesn't matter if AC or heat is on. The AC and coolant fan work. No oil in coolant, no coolant in oil and no sweet smell from exhaust. I'm not losing coolant.

Things I've replaced: thermostat, lower hose, bypass hose, radiator and cap, temperature sensor, water pump (and TB), coolant...multiple times. I've pulled a vacuum on the coolant system with a vacuum tool on the radiator (coolant system empty) to evacuate all air and the system held pressure - didn't leak off. Have bled system of air 3x of what Honda recommends (front of car elevated with funnel in rad and coolant level a couple inches above rad - heater on, fan kicks on 3x). Air bubbles seem to take forever to stop when squeezing the upper rad hose. I have no idea where to go from here. Any help would be appreciated.

brags

If i had to take a guess? i would say Your Heater Core is restricted somewhat to the point that its not allowing enough coolant
to flow through it. there by overheating Your engine.

wasr10

I thought about that because it's pretty much the only thing I haven't replaced, but, with the cabin temp being set to the cool side, wouldn't the valve to the heater core be closed not allowing coolant to come through anyway?
It also blows hot air when cabin temp is switched to heat. The car overheats whether the cabin is set to heat or cool. From what I've read that timing belt & water pump I just replaced looks like less of a job than the heater core.
This car is driving me crazy lol

brags

Ok heres Your to-do check. "Your saying it Only overheats after driving on the highway". well then next time Your on the highway and you see your temp gauge up too high pull over in a safe spot blinkers on be safe. pop the hood and (this is what i want You to do) have a close look at Your coolant resevoir from the outside 1st can You see any kind of bubbling like your coollant bubbling in it if its not visible from the outside then open the cap carefully and peak inside can You see any coolant bubling in it. do that check and keep us posted.

wasr10

Ok, I'll do that when I get home from work today and post back here. Thank you

wasr10

Just got back from the little "joy ride". This time it took an hour to overheat. Was giving up and on my way back home when it happened. Pulled over and checked overflow bottle. It was not boiling/bubbling. Only thing I noticed was the low pressure A.C. line was so cold it had light frost in the hot engine bay. High pressure line was very hot. Might be normal...I'm not an A.C. guy so not sure.
Once the car hits the overheat point, it' like a switch that's turned on. Even on the side roads with it driving at a bar above normal...it's still ready to overheat as soon as I get back on the highway. The "switch" this time for it to turn on (from a cold motor) & overheat took an hour. Yesterday it took 20 or 30 mins. Any ideas?

ezone

Make sure that the ground straps are not all frayed out and shot, they have clean tight connections, make sure one is connected from body to steering pump bracket, the other from body to transmission bracket



It's either overheating, or it's not really overheating and the gauge is just lying to you.

Connect a scanner that displays live operating data, then drive it. When the gauge on the dash shows high, see what the engine computer says ECT is.
Then figure out if there really is a problem, and which system has the problem.

wasr10

I checked the wires and they have unraveled(?) a bit and have a slight green tint of corrosion, but none of the strands are broken. The eyelets are bolted down tight and no signs of corrosion where they're bolted down. I'll look into buying a scanner to show the temp at the ECT. Thanks

Troy Morris

could also use a infared temp laser pointer gun and read the hoses.