1995 Honda Civic Engine Running Hot

Tiny
ANDYNAUTA
  • MEMBER
  • 1995 HONDA CIVIC
  • 4 CYL
  • FWD
  • MANUAL
  • 246,000 MILES
I have a 95 civic with 246000 miles on it. It's the EX wit the 1.6 liter SOHC VTEC motor. Around Thanksgiving I changed the head gasket on it because it was leaking. After putting it back together I've been having problems with it running hot. Initially it wanted to overheat all the time and I thought there might be an air bubble in it so I bled it many times and drove it through a few warm up and cool down cycles. The weird part was that when I revved it up the temp would drop but then immediately clime when the engine speed dropped. It still kept wanting to overheat so I tried jamming a bolt in the thermostat to keep it wedged open. It ran cool like this but of course didn't have good heat. Around Christmas time I tried installing a brand new thermostat. This seemed to work a little better but it still didn't run at a consistent temperature. It ran hotter than normal but not too hot. Still the temp would vary with the engine speed as in it would cool down when the engine was revved above about 3000 rpms. A few weeks after the new thermostat I got a check engine light and it would run poorly after leaving cold run mode and before it was completely warmed up. It ran fine when initially started and after being run for at least 15 minutes but in between these stages it would run rough and often stall. The check engine light was for the water temp sensor. There are two sensors in the head near the upper radiator hose one with two wires and one with one wire. I had broken off the one wire sensor when replacing the head gasket and replaced with one from auto-zone that didn't look quite the same so I thought this was the problem. I tired replacing it with one form carquest but it seems to have made no difference. I am now fairly certain that the code is referring to the two wire sensor but don't know if this is related to the engine running hot. Now once it warms up it runs with the temp gauge right at the bottom of the red unless revved at above 3500 rpms. The weird thing is that it never climbs into the red it just stays right there. After a decent drive the radiator feels cold all over even though the temp gauge says the engine was warm. I live in Houghton MI so the outside air temp is cold and I don't know how much the radiator would heat up. The heat works fine but does not feel excessively warm. The upper radiator hose gets hot but not super hot. It seems like either the engine is not getting as hot as the gauge says it is or that there is not enough coolant flowing through. I haven't lost a drop of coolant since the head-gasket change in November. I'm confused as to how the thermostat works being on the bottom side of the engine of this car because it doesn't seem it would get hot there. I would really like to figure this out and am thoroughly confused.
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Friday, March 20th, 2009 AT 11:04 AM

7 Replies

Tiny
KHLOW2008
  • EXPERT
Hi andynauta,

Thank you for the donation.

The ECT is the 2 wire switch which sends signals to the ECM and if it is faulty or has a loose connection, the engine would run rough and even stall after engine is warmed up. Restarting would be difficult as well.

The 1 wire switch is the temperature sending unit and is only for the gauge.

As to the engine running hot, does the radiator cooling fan run continuosly or does it stop and run intermittently when temp is showing hot?

Revving up engine to get the temperature down could be due to a bad or weak water pump as the coolant flow is insufficient.

Lack of coolant is another possble cause and since you do not have coolant losses, it should not be the cause.
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Friday, March 20th, 2009 AT 11:25 AM
Tiny
ANDYNAUTA
  • MEMBER
The radiator fan never runs that I have seen. I believe the switch for this is in a sensor in the radiator right? So if the radiator isn't getting warm the fan won't run.

How does a water pump go bad if it's not leaking? I thought there were a centripetal pump so there is no pump seal to go bad. My understanding was that they could either start leaking or freeze up but not pump less well. If they can start pumping less well that would explain the problem but I would like to understand how that would happen.

The coolant is right to the top of the radiator, at the appropriate level in the reservoir and has been bled countless times so that should be good.

Thanks
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Friday, March 20th, 2009 AT 11:34 AM
Tiny
KHLOW2008
  • EXPERT
The Fan switch is located on the thermostat housing, not below the radiator.

I have seen many water pumps vanes detached from the shaft. Many others have their vanes worn off, some due to rust and some due to acidity of the coolant used. They would cause insufficient coolant flow.

If the fan is not working, something si wrong. Fan shouls work between 20 to 30 mins upon starting vehicle and work intermittently.

If it is the gauge that is not accurate, it could be due to a bad ground connection at the inner left front fender behind the headlights.
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Friday, March 20th, 2009 AT 2:20 PM
Tiny
ANDYNAUTA
  • MEMBER
Is there a way to test the water pump without taking it out?

Also the fan won't turn on if the coolant by the fan switch never gets warm right?
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Friday, March 20th, 2009 AT 2:32 PM
Tiny
KHLOW2008
  • EXPERT
Yes, if the coolant does not heat up sufficiently, the fan would not work.

If the water pump is bad, the fan would work non stop as the engine is overheating and the fan switch would be providing a non-stop signal to the relay. By bridging the fan switch connector and with ignition switch ON, the fan should work.

The fan does not work even when the temperature gauge is showing shows a high reading?
Is the reserve tank level constant?

There are no recommended water p[ump testing methods and I normally remove the thermostat and run engine without the radiator cap and watch the coolant flow at the cap neck.
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Friday, March 20th, 2009 AT 3:14 PM
Tiny
ANDYNAUTA
  • MEMBER
I checked the resistance on the coolant temperature sensor and I'm getting 4200 ohms when the engine is cold (40-50) and around 300 ohms when it's hot. These values seem normal from what I've read so I don't know what the problem is there.

After shutting the car off I tried cracking the bleeder after the engine had gotten hot on the drive home today and nothing came out. The system does not seem to be building pressure. Is there any reason it would not build pressure other than the radiator cap? I checked the cap and the spring feels good and the seal looks good but I don't know what else would cause it to not build pressure. The level in the reservoir does go up and down as the engine heats up and cools down.
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Wednesday, March 25th, 2009 AT 5:24 PM
Tiny
KHLOW2008
  • EXPERT
If the level in the reserve tank moves up and down by a substantial level, the radiator cap is bad. The pressure valve is faulty.
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Thursday, March 26th, 2009 AT 6:44 AM

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