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.

Also, I will double check that the coolant system was properly "burped."

YES that's a huge issue I totally forgot about.

I had a Ford Escort years ago that would only overheat on the highway, it was perfect around town. It had a restricted flow radiator, new radiator solved the problem. It is possible that the three row radiator could be flowing too much water and not removing enough heat. In a stock car we set temp by changing to size of the restrictor we used in place of the thermostat. We ended up with a 5/8" hole to keep the temp where we liked it in Bakersfield. The 11/16" hole ran hotter due to the water moving too fast through the system.

Absolutely do the flush and tests before anything drastic. But...

Back in NYC and NJ driving cabs, we used to crack the hood open so that the summer heat and AC would stress the engine less. The latch of course holds the hood down from flying off. Sometimes I do that now (very rarely).

Do you use the internal air recirculation setting on the vent system? If you do, you'll find you can shut the AC off for 10 or 20 seconds and still be blowing quite cold air. That might be enough for some hills. You could cycle the AC on/off during longer climbs.

Also, easier than adding another radiator fan would be simply to wire a switch to bypass the ECU's control of the OEM radiator fan and turn it on whenever you wish.

I added a Spal 11 inch pusher fan on the front of the triple core radiator and it helped dramatically. I am still using the 12 inch Mishimoto puller fan with the aluminum shroud. The two work fine together.

Also, I added the Spal relay kit and tapped into the Civic's existing fan sensor. Both fans come on at the same time. The Spal relay kit is well worth the money - the quality is top shelf.

The 11 inch fan fits perfectly on the front of the radiator. If a 12 inch is used, it will "fit," but will rub against the vertical center reinforcement beam that runs across the radiator intake duct.

The only down side so far is that the Spal fan has straight blades and is much louder than the Mishimoto. The Mishimoto also has straight blades, but does not spin at the same high rate as the Spal and appears to move less air despite the higher CFM rating (~950 cfm vs ~1,100).

In the winter, I might pull the fuse on the Spal and just run the Mishimoto to reduce the noise. In motion it is difficult to hear, but around town, it sounds like a hint of a leaf blower. The curved blade fans are supposed to be quieter, but slightly lower CFM. Spal did not have a pusher in that size with the curved blades.

Here are the Spal part numbers that were used.
11 inch Spal pusher fan: 30101502 11" Medium Profile Fan - Straight Blade - Push
Spal relay kit: FRH

The high performance Spal fan has a taller motor by one inch over the medium profile that I used and will rub against the AC line that crosses the front of the radiator. There are three different motor heights (low, medium, and high performance). If you don't have AC or are okay with significant bending (medium profile requires moderate bending) of the AC line, then go with the high performance version for additional CFM.

I have done a moderate amount of testing in the mountains at altitude in the heat with the AC and it has not broken 50% on the gauge. I have a desert trip coming up and it will be around 110F so that should be an exceptional test.

Let me know if there is any questions regarding sizing, wiring, performance, etc.

Update
 

I did more driving in 110F and in the mountains and the car generally runs below 50% on the gauge. In some extreme situations it will sit at 50%, but if the AC is turned off it quickly drops back down to its normal 40% gauge location.

Overall, the pusher fan has made a significant improvement. Highly recommend.