Hi honda-tech, i'm battling an issue with my 95' gsr.\

I just had a JDM front end conversion done to my 95' gsr.

I had gotten in a front end collision, and thought this would be a good time to do the conversion.
The radiator was damaged in the collision, so the shop i had do my conversion sourced a brand new aftermarket radiator.

They finish the conversion, i drive the car home and proceed to wire the jdm headlights and mess with fitment.

I finish the final touches and take the car out for a test drive. For the first 10 minutes of driving the car has no issues whatsoever and the coolant temp is exactly where it should be.

I get in line at the costco gas pumps, and i see my temp gauge slowly rising. By the time i get to the pump, the temp is on H.

I park the car and pop the hood. The coolant feed hose (top hose) is slightly warm, the return hose (lower) is ice cold. The radiator fan won't turn on. I am assuming because the radiator was still ice cold, even tho the engine coolant temp is high.

I let it cool off, I get back in, stick the key in the ignition, and the gauge reads about 1/4 the way up, after sitting in the cold for 2 hours.

I need to get home and my phone is dead so i start the motor and drive 10 minutes back home. 1 minute into driving the temp sensor is back on H. I drive the rest of the way home with it on H. made me very unhappy driving while it was overheating.

I also tried using the heater, with the heater fully open, the heater core produced very little heat, just slightly warm air.

I assume the thermostat is stuck closed, and is preventing coolant flow. which is odd because i put in a brand new OEM thermostat only 1 year ago.

I purchase another brand new OEM thermostat and switch them out.

Doesn't fix my problem. When i first test drove the car after the front conversion, the temp didn't go past 1/2 until i got to the gas pumps 10 minutes away. Now, the temp gauge is at 1/2 and climbing 30 seconds after cold starting the car. as if something happened during my test drive.

The coolant in the engine is definitely not exchanging with the coolant in my radiator.

I take apart my cooling system and check for clogs, maybe the shop left a rag in one of my hoses. Not the issue, both of my coolant hoses are in great condition with no obstructions, they are less than 1 year old Mishimoto hoses.

I flow check the radiator, maybe the radiator the shop sourced was a faulty unit or has obstruction in it. Not the issue, water flows through the radiator unobstructed.

Now I am thinking it is a faulty water pump. I really don't think this is the problem, however I am not ruling it out.

I am going to scour my Hanes manual for some more information. I was just posting this to hopfully find someone who has had this issue and hear how they fixed it.

I did try searching this issue, however all the posts that came up were unsolved or some ghetto fix.

Thanks honda-tech!

-Gary


update:

I tested the radiator fan by jumping the connector directly to the battery, the radiator fan works perfectly. It just doesn't turn on. Engine temperature is hot, radiator temperature is cold.

Hanes says that if the lower radiator hose is cold and that the upper is warm, its the thermostat stuck closed. However i just switched that out and there was no change.

Hanes says that if there is a problem with the water pump, there would be a leak if its the gasket, and a howling sound if its the bearing. There is neither a leak or a howl.

I think it could be a faulty sensor...

 

thinking it could be air in my system.

 

Pretty sure its my coolant temp sending unit. the temp read halfway between C and H this morning after sitting in the cold for 12 hours. Definately a cold motor yet the sensor read halfway up. Im headed out to take one off one of my spare motors on the other side of town. Ill post results.

 

After reading your post, I think it points towards the coolant temp sender. Our Odyssey had a problem like that, where it internally shorted and consistently went to "H" every time the car was on, even when cold. Before that, a few years ago it had an intermittent problem like yours, but went away.

Another test you could do is unplug the coolant temp sender while key on and see if the gauge drops back down to cold.
The coolant temp sender on the side of the cylinder head reads for the gauge & ECU only, the radiator fan is controlled by the coolant temp switch located on the thermostat housing, so it actually has no relation to the gauge showing HOT, and turns on at the physical temperature of 196-203 degrees Fahrenheit or 91-95 degrees Centigrade.

 

The temp sensor that ties into the thermostat water neck, you should test it.

Take a paper clip and plug it into the temp sensor harness plug. Does your fan turn on then?

 

Thanks for commenting, you are absolutely right. I tried unplugging the sensor, and the gauge went down to C. I was than certain it was my thermo sensor

• 37750-PH2-014

So I drove to the other side of town, took a known working spare out of one of my spare motors. I switched them out, oddly enough the bad one looked to be in better condition than my spare one. Switched them out, PROBLEM FIXED. My gauge is responding perfectly and I am stoked.

TLDR: bad

THERMO UNIT (DENSO) - ACURA (37750-PH2-014)

 

That's crazy, but glad you got it fixed and then posted the resolution.

im having a brain fart, where is the coolant temp sender? Is that the sensor on the side of the head?