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This is an issue that I've been having for over a month now. I really hope someone can help

I have a 2000 Civic DX (non v-tech, 4c 1.6L engine, automatic) with (currently) 177k miles on it. My father is a retired mechanic of 35 years, and even HE is perplexed at the issue.

I have an overheating issue, and here are all the things that have been checked/replaced:
- thermostat has been replaced
- liquid gasket seal has been used
- fan switch has been replaced
- engine coolant sensor has been replaced
- fan relay has been replaced
- compression test found no head gasket leaks
- block check on engine shows no cracks or leaks
- heater core appears to be functioning just fine
- a/c has been serviced and refrigerant has been added
- engine block re-grounded, as salt caused corrosion around the grounding contacts. a secondary grounding cable was also added.

Symptoms:
The car is *literally* eating coolant. Even when there is coolant in the reservoir, the radiator is empty. In some circumstances, the coolant reservoir has been empty after it was filled right before a short trip.... it's been a while since that has happened though.

We have checked the head gasket, heater core, engine, fans, and electrical system. There is no reason why the engine should still be overheating after all of this unless there is either a crack in the head, OR a head gasket leak that isnt being detected. Since the compression test turned out 135 lbs, we're even more perplexed than we were before ...

We originally thought about installing a fan toggle in the cab of the car since the fan doesn't seem to stay on as long as it should; this model uses mini connectors, so the standard bypass relay we were going to put in won't work. Even if we put the toggle in for the fan, it won't fix the issue with the engine eating coolant.

I have sunk more than $1000 into my car in the last month and could have had a new engine by now, hoping that someone can shed some light so that my dad and I can get to the bottom of the heating issue.


** There are no visible leaks or ground residue of coolant **

 
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So far, two suggestions have been made by friends after I shared this through facebook...


1) Water Pump / Impeller

2) Transmission


Thoughts?

 
Rep Power: 169

If you water pump were leaking, you would know. There would be obvious signs, not only as a puddle under your car, but there would be burnt coolant around your timing cover.

If your impeller was not turning, your car would overheat during idle.
Your fans have nothing to do with your engine being cooled while you drive.

If your coolant is mysteriously disappearing, yet you have no leaks, its pretty obvious you're combusting the coolant. Just because your car passed the compression test does not mean there is no head gasket breach.

What does your exhast pipe look like? Any white residue is a indication of coolant being combusted in the cylinders.

I would suggest a radiator sniff from a smog tech. That will tell if you if any hydrocarbons are entering the coolant system. If the smog detects ANY hydrocarbons, your head gasket is blown/head is cracked.

 
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While I appreciate this feedback, I have a difficult time thinking that the car would pass a block test twice if there were a problem with a head crack or a blown head gasket. I suppose the best thing to do at this point would be to take it for a smog test and see if it passes, and if not, see if something else is found.

There are no indications of residue near the exhaust.

The car overheats while it *is* idle if it idles long enough.

There is no indication that the engine is seizing at all, and the car, overall idles and runs fine. I had a blown head gasket in a car about 10 years ago, and very distinctly remember how crappy it ran right before I saw the puff of white smoke come from the exhaust.

Oil levels, and other engine fluids are all fine.. only the radiator seems to be losing it's level, and the radiator is only a few hundred miles old.

Thanks again for the feedback.

 
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check the lines going off the rad at the bottom going to tranny, i personally would drain a little oil from engine and tranny and check for coolant in the oil. if it was going into combustion then ud prolly smell it in the exhaust as well along with white smoke

 
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I had an oil change done in the middle of all this and there was no coolant found in the oil according to the guy who did it.

 
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you could also take off all hoses from ur rad and putting one on at a time while blocking off the others then switching until you find out where the lost fluid is going. this will send u in the right direction then it ll be pretty obvious what the prob is

 
Rep Power: 169

Trust me, my car is doing almost the same thing. I have a 99 Civic Ex that was overheating and I replaced almost all the parts that you did, did a compression test, all cylinders were 180ish, took it to a mechanic and did the combustion leak chemical test and it passed. Then I took it in for a smog sniff and sure enough, 343 ppm hydrocarbons found in the coolant system, indicating a blown head gasket or cracked head.
My radiator too would not stay full, even though I had coolant in the overflow, but I was not losing coolant. Yours sounds like its blown or cracked even worse then mine, but it sounds almost like the same situation.
Get a smog sniff first, its much cheaper than a full smog.

 
Rep Power: 169

There doesn't need to be a fluid exchange in order for the head to be cracked or gasket to be blown, thats only one way of many that it can fail.