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I have a 2001 Civic DX coupe 1.7L vTech auto trans. Ever since I bought this vehicle about six months ago it has been losing coolant. It would lose coolant to the point to where it would overheat or come close to it and I would have to immediately shut it off. My friend and I performed a pressure test and found that it was losing a little bit of pressure but not enough to denote a bad head gasket. Also, there was no Telltale sign of oil in the antifreeze, a vapor trail out of the exhaust, or white spark plug fouling.

So, I ordered a new radiator and we put it in. First, let me back up and let everyone know that even though it was overheating it didn't seem as if the antifreeze was leaking anywhere on the ground. So, anyway we put in the new radiator and we also swapped out the fan relay. I drove the vehicle for a couple of days and it started to it exhibit the exact same behavior.

I have checked the codes and none of the codes that I have are saying anything about a temperature sensor anything to do with the coolant system. In fact, the only code I get is for a bad catalytic converter and I didn't start getting that until I replaced one of the O2 sensors, so I don't really think that it is related since this vehicle has exhibited this problem since day one which was before I changed that O2 sensor.

I am getting to the point of being totally stumped with this vehicle. We have jumped both of the fans and have determined that they both operate as they should. Also, as I have stated before the fans will come on in a pulsing interval if I turn the blower motor on inside of the vehicle. So, what do you guys think? Could it be a bad temperature sensor? Could it be something else? Any leads would be greatly appreciated.

 
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Glad you found this forum, the problem your having is 99.9% likely a blown head gasket.

That comment that it losses pressure on a pressure test is unusual so I am giving .5% chance it’s just leaking from the waterpump or somewhere.

We have 1,000s of posts in here about this exact topic, read up and feel free to ask questions.

 
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I had the exact same problem. Like the guy above said, most likely blown Head gasket.

 
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Normally, I would be inclined to agree with you. However, when a pressure test was done on it from the radiator it was only losing about 1 psi every three quarters of an hour. I attributed that to the radiator having a small leak in it. As stated before, upon inspection of the old radiator there was a pretty big stain on the fins that went all the way down and some of the tabs that married the plastic to the aluminum we're actually pushed out. I just assumed that the small loss of pressure was due to that. That is not to say that the head gasket couldn't be bad. It is just that the spark plugs aren't fouled and have any white deposits on it, it doesn't start hard, there is no oil in the antifreeze and vice-versa, and there is no visible leak from the exterior of the engine where the head meets the block. Lastly, there is no trail of white smoke coming out of the exhaust pipe. Also, there is no scent of antifreeze inside the cabin which would typically denote a leaking heater core. Lastly, I am not convinced that a faulty head gasket would cause my fan issue, would it? If so, I would like some more details about it. Thanks in advance again

 
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https://www.civicforums.com/forums/3...reference.html

 
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These cars don't show the typical head gasket symptoms, read the link in the post above mine

 
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I see. I looked at the post on top of yours and my friend is looking for a chap exhaust gas detector to confirm. It is my DD so I can only have it laid up for a weekend, and with almost 300k I have no idea what kind of condition the head is in. I may be looking for another head to send in to make sure it is true before a head gasket swap. Thoughts?

 
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Edited your post to make it more legible, talk about a wall of text

I agree with the others though, almost certainly a failed head gasket. When mine went bad the only signs were low coolant in the radiator, way too much in the reservoir, and overheating. I had no visible leaks, no white smoke, no coolant in the oil, etc.

You can easily find another head to get cleaned up and swap to over a weekend. Just make sure it comes from a DX or LX, the EX will not work unless you mount a VTEC solenoid and not use it.

 
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Good to know. It looks like I am on the hunt for a head then. Sorry about the wall of text. I was using the voice to text option on my phone at that time.

 
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Head gasket, timing belt and water pump changed. Now, getting misfire on cylinders 2 and 3. Changing coils does not change misfire. Car did not have misfire before head gasket change. At first it would misfire when warm but not cold. Now, misfire regardless if warm or cold. Did not do compression test (lack equipment) but no misfire on any cylinders after coils changed 100 miles before head gasket change. Any ideas? Only codes thrown is cylinder 2 and 3 misfire.

 
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Did you check the plugs? Or just swap coils?
Are you 100% sure that timing is correct?

 
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spark plugs were changed with no difference in misfire. Also, would the timing being slightly off only affect a couple of cylinders and not all four?. I do not believe that the timing was off, but the mechanic is going to check that after doing a compression test tonight. Any other leads?

 
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Also, the more investigation that I have done on this forum, the more that I have heard that a dirty EGR and/or clogged EGR ports can lead this to happen as well. Perhaps, disturbing the intake when the head was taken off knocked some soot loose and clogged ports?

 
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Lastly, tech is going to swap out injectors and see if misfire follows as well as checking valve lash for all cylinders. Will report back later on tonight (feel free to add $0.02 as tech will be working on it in about 6 or so hours from this post).

Thanks for the help so far, everybody!

 
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UPDATE: Tech cleaned EGR and ports and now no misfires and smooth idle. So far, so good. I am going to start putting some miles on it to see if:

1) It stopped losing coolant (puking it into the overflow.
2) If it doesn't throw any other misfire codes due to any residual pieces of soot in the ports

A preemptive thanks to those of you who directly helped by replying to this thread or who helped indirectly by starting another thread that led us to the answer.

I will keep you all posted at 60 and 120 miles.

 
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Glad that seems to have solved it

 
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Misc info for those who are interested.

Compression test (cold) results:

Cyl 1: 120
Cyl 2: 120
Cyl 3: 130
Cyl 4: 130

 
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There's nothing to worry about regarding compression at least

 
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Drove it down to KY (340 into a 400 mile trip).. Ran fine until it blew a rod going 65 down a mountain grade. F*ck Hondas. I abandoned at a gas station parking lot after limping while it was hammering for 4 miles. I went broke getting back home $500+ later

....and I thought mitsus were bad.

 
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ouch!
sorry to hear about that...

 
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A stock engine throwing a rod is likely caused by really low oil or severe overheating.

 
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Sounds like it may not have stopped the coolant leak after all...