missing coolant, then overheat, now a small leak on pres test? ’05 Civic EX

[Julia Honneffer]

I’m the sole owner of this (US market) 2005 Honda Civic EX (2-door, automatic transmission), currently at 142,000 miles, and I have some kind of coolant system problem. I tend to be longwinded anyway so I apologize in advance for what will be a long, detailed post, trying to provide every potentially relevant bit.

Engine coolant was changed at about 50,000 miles and at 122,000 miles (December 2014).
Only repair related to coolant system: May 2015 replacement of radiator hoses (recommended by a mechanic who was replacing the cam sensor); about 127k miles at that time.
I live in a part of Texas that rarely requires heat in your car, and for short drives (most of my driving) I never expected the car to get that warm anyway…but that winter (early 2016) I did notice my car didn’t seem to have much heat output. Unfortunately, I thought that’s just something that happens as cars get older; figured I wasn’t keen on the price tag of a problem with the heater core, so I ignored it.
There was another oil change at 132k, other routine maintenance, nothing notable or related to coolant system, and I never mentioned to mechanics that the heat wasn’t working very well. I also never actually looked at my radiator or the overflow reservoir.

Late April (a couple months ago) I took my car to the dealership for an oil change. They reported some “maintenance soon” items, but fluids specifically were not marked as urgent – only brake fluid was mentioned as indicating I need a brake job soon. I bring this up because shortly thereafter, I saw the temperature gauge on my dashboard climbing quickly, then suddenly dropped back to normal. I did some reading online and saw this could be caused by air in the coolant system. I learned about burping the system, and I went to check it out. I found there was zero coolant in the reservoir, and radiator was totally dry on top. At this point, it had been less than a month since the oil change, and I’d been out of town with my car parked in the garage for about 2 weeks of that month. There had been no sudden catastrophic coolant losses that I’d noticed (never a drop on my garage floor), so I can’t help but assume that the technician at the dealership that performed the oil change didn’t actually check my coolant level, but regardless, shame on me for not checking it myself in the years I’d owned the car anyway.

So I bought Honda genuine type 2 coolant. Filled it up. Burped it. Although it was summer (we’re at about May 26 at this point in my story), I tested the heater and noted that I got very warm air again. Felt very proud of myself for handling this on my own and wondered how long my car maybe had been super low on coolant…if that was why the heat didn’t seem to work well back in 2016 and it was causing the temperature fluctuations. After some days with short drives, while the engine was still hot, I took a peek at the reservoir and saw fluid was up over the max line. I’ll tell you that I’m kicking myself over and over again for not opening up the radiator cap once it cooled – I assumed I had just filled the reservoir a little too full when it was still cool, so the apparent overfill was because it was warm. Some line about “knowing just enough to be dangerous” might be going through your mind now. Anyway, no noticed problems with the car until Friday (3 days ago), when I was idling in a parking lot with A/C running as I finished up a phone conversation and saw my temperature gauge was approaching the red. I immediately shut the car off. Hours later, I drove home (~15 minute drive, mostly highway) with the A/C shut off and watching the gauge like a hawk. I had to pull over and turn the car off once because the temp gauge was again climbing. I can’t really remember if there was a relationship with it heating up more when I was at a stoplight or moving.

Trying to cut to the chase here. I did not take stock of the overall situation at that time, so I probably don’t have answers to some useful questions (e.g., I didn’t feel the radiator hoses while the engine was warm to compare top to bottom). The thermostat seemed like the most likely inexpensive culprit so I set about draining the coolant so I could change the thermostat. I noticed when I opened the (cool) radiator cap, there was a sucking noise like it had been under vacuum. There was still lots of coolant in the reservoir, but the radiator was not filled to the top. I thought maybe the radiator cap was bad also/instead. So Sunday morning I drained the coolant, replaced thermostat (OEM), replaced radiator cap (temporarily with an after market – plan to remedy that tomorrow), refilled coolant and burped. I do not recall the radiator fans ever kicking on during the burping process, but I was impatient (yes, shame on me again) and it had been probably 30 minutes of the engine running. Once I saw no more air bubbles coming up I shut off the car, removed the leakless funnel, and topped off the radiator. Drove about 20 minutes. Got home, let things cool down, and again see additional coolant in the reservoir. Open the radiator cap, again seemed like there was a slight vacuum, and again it is not filled to the top.

More reading online to try to find out what might cause coolant to expand into the overflow reservoir, but not come back when it cools. I read that the overflow tubing could collapse, or there can be a small leak so that air flows back in rather than the vacuum sucking coolant back. I had verified during the draining process that coolant does flow back through the tube. I also read that an internal coolant leak (e.g. head gasket) can cause similar signs, because the leak still allows air back in. So this afternoon I bought a radiator pressure tester from Harbor Freight – perhaps not the highest quality. I would say that there might be a small leak – over about 5 minutes, the pressure drops about 1-2 psi. Could be user error as this is new to me. I could not find (visual or aural) evidence of an external leak.

I should add – I’ve seen no white smoke in exhaust, oil on dipstick looks great, and the coolant that I drained out also had no obvious (to me) contamination.

So…. what should be my next step? Is it possible that incomplete burping can cause this behavior with the coolant overflow, and would it also explain what looks like (maybe) a slight inability to hold pressure? Is there anything else I can easily look at myself? I’m preparing to move (I guess I’m glad this happened BEFORE I was in the middle of a 2,000 mile drive) so I do need to get this sorted out somewhat expediently and will probably take it to a professional mechanic….but I’d love any suggestions, feedback, heads-up, speculation for fun, etc.

Topic

[Todd]

Read through your whole post.
First off its looking like a head gasket leak issue. From what you have described. Some times the leak can start out small, and then progress and get worse over time. Possible that the coolent is just leaking into your combustion chamber and no we’re else.
What I would do is- buy yourself a decent engine Compression Tester. And perform a Compression test. Eric has a video on how to do it properly. Also many other sites that explain how to do it.
If two adjacent cylinders are reading lower than the rest, than that’s a sign pointing twords a head gasket leak.
Also wouldn’t hurt to pull your spark plugs and see if they look like there all burning a white to tan color which is what they should look like. If any spark plug is wet with coolent than that would be a sure sign of a head leak.
Some time’s you can see coolent sitting on top of the piston, by looking down the spark plug hole with a flash light. But by then you would have noticed white smoke from the exhaust, and your engine would be harder to start at times.

[Julia Honneffer]

[quote=”NikolaTesla” post=189400]Read through your whole post.
[/quote]

This alone is worth thanking you for…I know it was not brief.

Head gasket certainly isn’t the issue I’d be hoping for, but your comments help prepare me for that potential outcome. In particular, we are rapidly approaching a realm where I think I’d be over my head, not to mention exceeding the limits of my marginally-equipped toolbox. I will check back in once I have something more to add…. But thanks very much for taking the time to read and comment.

[Mike]

You mentioned you had the rad hoses replaced a few years ago. If they are held on with worm-drive clamps, I’d check to make sure that they are tight. These clamps have have damnable tendency to loosen up a bit after they’ve been cinched down for the first time. Can’t explain why, it just seems to be the nature of the beast.

Since you’ll be under the hood anyway, it might be a good idea to do a quick visual check for other potential leaks. Thermostat housing, core plugs, heater hoses, radiator body, anything else you can think of. If you’re dealing with a slow seep, you probably won’t find puddles of liquid coolant, but look for signs of dried deposits.

[Julia Honneffer]

Great points and much less painful than a bad HG. I will check it out when I can, but I ended up dropping the car off with a professional this morning (I am scheduled to drive about 2000 miles starting Friday so I woke up this morning and felt like my timeline warrants recruiting some professional help).

I noticed one other thing after my original post last night. Immediately after driving around, when I opened the hood, I thought I could hear a “blip blip blip” like air bubbles through liquid (the sound of an airlock on a carboy for anyone who homebrews). Would that point to anywhere more specific or rule anything in/out? Without any white smoke or misfires, and considering the oil on the dipstick looks great, I’m having a hard time putting head gasket on the top of the list yet…but since I didn’t have a compression tester, I’ve not done the other checks suggested by NikolaTesla so I know there are things I could be looking into still to support or refute that possibility and I don’t want to seem like I’m ignoring advice already given….just trying to balance my sense of urgency and limitations.

Also for what it’s worth, I normally apply my diagnostic skills to cats and dogs, so I’m way out of my element in terms of mechanical knowledge/experience, but I thoroughly enjoy the approach of diagnosis as long as I’m not potentially making something worse.

[Julia Honneffer]

[quote=”QuirkyJules” post=189413]…I thought I could hear a “blip blip blip” like air bubbles through liquid….[/quote]

I know that’s in conflict with my original post that specified no visual or aural sign of leak. I *think* that there was no sound when I applied 15 psi from the pressure tester, but of course I may have missed it. The bubble sound seemed to be during engine cooling immediately after shutting it off. The rate of “blip” was maybe one per second – quite slow. And now this is like a splinter in my brain!

[Julia Honneffer]

Wanted to update. Hopefully this is the only thing they find – they already did a compression test and block test (dye) and both were fine – the upper radiator hose apparently has a small leak that sealed itself up when the hose was warm, but allowed air in as it cooled.

Kudos to Evil-i …. I wish I’d not been pressed for time as this probably would be an easy DIY fix; easier than some of the rest of the stuff I already did myself. Live and learn; and indeed I learned a lot! Hopefully this thread helps others as I don’t recall seeing this source of leaks as being listed on the “overheat troubleshoot” page. Of course I’m sure all the possibilities of leaks are too numerous to list them all.

Unless they find something else, I won’t have further updates. So just wanted to thank everyone who read, and especially the two people who provided suggestions.

-Julia (who has a new appreciation for all things related to engine cooling)

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