What is your question?
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What is your question?
2004 Honda Civic EX, no prior mechanical 
issues 110,000 miles&now 117,000 miles has shown hot by temperature 
gauge(sometimes above H) but very infrequently Never overheats or runs poorly.Replaced 
timing belt&water pump@105,000.I replaced 
spark plugs after it started happening. I brought it to a mechanic 
immediately 1 year ago when I first noticed this happening who drove it for a 
week and couldn't reproduce it.Fluid wasn't missing and he replaced 
thermostat since he had no other ideas.Ever since it has happened 
sporadically and intermittently.Sometimes months between instances.My 
driving is predominantly long trips of 2+ hours weekly at least&it runs fine 
and rarely shows hot.When does usually at end of trip, a few times early. When hot, driving hard or revving engine doesn't seem to make it any worse.

The 1 time I tried revving engine MIGHT temporarily helped.Heat or AC doesn't seem to help or hurt I don't think.With heat I THINK it sometimesblows cooler than I would expect
What makes this problem better or worse?
Nothing, very sporadic and infrequent
How long has your 2004 Honda Civic had this problem?
1+ year
1 Reply
If you ever show hot above the H, damage in the engine may have occurred that could cause an intermittently noticeable issue. I would check your cooling fan operation to see if it is coming on as needed, check for any restriction of air flow at the radiator. You will find the source of the problem with enough testing and hands on attempts to recreate the concern in a test environment.
Thank you for answering. I appreciate it. Given it is so extremely infrequent with months between instances even with thousands of miles of driving between instances, would this likely exclude a head gasket do you think?
No, it would not exclude a head gasket. I've seen Honda's that have head gasket breaches that continue to drive for thousands of miles, with symptoms occasionally cropping up as you describe. This doesn't mean that's what's wrong with yours, just means you can't exclude it until you can determine your cause of concern. As a quick test that anyone could do: with the engine cold, open your coolant reservoir and smell the inside. If you smell exhaust at all, even a hint -- you have a head gasket breach now (or if it was repaired in the past, could be from the past too still). If it smells like coolant and coolant alone - you likely do not have a breach. Exhaust gases get into the coolant as much as coolant gets into the engine when you have a head gasket leak. This is a "sniff" test that I've done for years with reasonable success. Of course, this does not replace a proper diagnostic test, and is not a valid official test procedure, but it's a good thing for the novice consumer to do.
Thank you so much. Mechanic checked fans and connections, did a pressure test on cooling system but due to adding half a gallon of fluid, is recommending radiator replacement. Wouldn't pressure test mean radiator is likely fine?
Mechanic also didn't smell any exhaust in coolant in reservoir.
Hello, what is the reason given for radiator replacement being needed? If it is leaking, I would understand. Or, if there is some kind of restriction preventing proper coolant flow, or if there is debris blocking air flow, I also understand that. But get a good explanation first and some kind of guarantee on repairs.