95 Civic VX Engine Cooling Issue
 

I have a 95 VX with 270k miles that is 99% stock. The engine was replaced with a JDM 20k miles ago and I have been running the 49 state (I am in CA so I had the lower efficiency ECU) VX ECU with the five wire O2 for the last 150k miles.

The car is used for road trips and can run hot while climbing mountains and driving across the desert in the summer. Think 110F with the AC on at 70 mph in some cases. It also runs hot on mountain switchback roads at 35 mph.

I have upgraded to a Mishimoto triple core radiator, high pressure Koyorad cap, and a Mishimoto 1,100 CFM puller fan with aluminum shroud. The thermostat, water pump, and radiator hoses were recently replaced with new Honda OEM parts. Redline Water Wetter was added to the coolant. I have tried both 87 and 91 octane fuel and the problem does not change.

The engine and AC both function well. The AC condenser is stock. The engine does not have a warped cylinder head and engine ignition timing is correct. The stock VX grill block was also removed. Both the AC and radiator fans come on correctly.

Right now on a hot day, the temp will start to rise when going uphill with the AC on. If I turn off the AC then it will drop back down to about 45% location on the temp gauge and stay there. It used to run even hotter with the stock radiator and fan, but the situation is still not satisfactory.

Anyone have ideas on how to resolve the engine cooling issue? I was thinking of adding a pusher electric fan on the front of the radiator. I am completely open to suggestions. Thanks!

Is the car pushing water out of the radiator or is it just a gage thing? If it is under 230 and holding pressure I would just run it.

If I continue to let the temperature climb, the coolant will overflow into the bottle. Eventually it will boil over entirely.

Letting it run a little hot led to the original engine having a warped cylinder head gasket and needing to be replaced. I don't want this new JDM to go the way the original engine did.

I wish it were only the gauge, because then, as you mentioned I would be ready to roll without any changes.

Have you tried back flushing the system?
Almost sounds like a blockage somewhere.
Or your idea of running hot is off.
What do you have to tell you the temp other than the stock gauge?
The VX has a higher temp thermostat then other civics, 195 degrees fully open.

I can look into getting the coolant system flushed and double check that it passes a pressure test. Neither of these have been done recently. It isn't consuming any coolant as long as it is kept cool (normal operating temperature).

Right now, I only have the temp gauge on the dash. It does seem to match what I find in the overflow bottle and with the final failure of the original engine. I could potentially add a separate temp gauge to confirm.

I also suspect that the lean burning aspect of the VX engine helps with MPG, but generally runs hotter than a standard Civic. This combined with the high air temperature driving, could push the cooling system.

I had a 92 VX , and the runs we did thru California and Nevada were never an problem in the summer heat, the only thing is we didn't have AC, so that may be the issue.
Has the AC system been checked out?
if the compressor keeps running it will just build up a ton of heat.

Interesting data point regarding your VX not having AC and not having any cooling issues. Was your VX from California or was it a 49 state car? The CA ECU might run a little cooler.

The AC system was serviced about 2 years ago. This included a new compressor, orifice tube, dryer, etc. It seems to cycle on and off correctly. On a hot day, it would most likely be on most of the time.

I also wonder if the triple core radiator is hindering more than helping. I have heard that triple core radiators can make it difficult for the electric fan to do its job. Some favor upgrading from the single core to only a double core. This could be unsubstantiated though.

I had the same rad as you but Mishimoto cap that cam with the rad, but stayed with the stock fan.
I did use Redline Wetter Water.

Did it run cool? Could it deal with hot days in the mountains at high altitude and desert crossings at 110 F with the AC on?

My car will drive around Los Angeles all summer with the AC on without issue. It is only in these more extreme environments that the coolant system becomes an issue.

Also, I am going to double check the voltage at the fan when it is running in case there happens to be a surprise voltage drop. It should read around 12 volts at idle.

I wished it had AC lol, those years of civcs were the worst for air flow thru the cabin.
I'm thinking the AC is your problem.