Weird overheating issue, troubleshooting stumped

brian.evans

New Member
1993 Civic LX, bone stock

I got my overheating issue fixed after my radiator replacement. Apparently it is more of a pain to get all the bubbles out than I thought. That was about three weeks and 2000 miles ago. The car was running fine since then, including a 1000 mile round trip to Mayo Clinic.

Yesterday on my way home from work the car went hot, not all at once though. It was fine for 20 miles or better, then I noticed it slowly climbed to halfway between normal and red zone. It stayed there for about four miles, then started to climb again. We were having 30+ mph winds and in heavy morning commute traffic on the highway so I was trying to limp it home.

Popped the hood, noticed the fan hadn't kicked on. Jumped the fan switch wires, kicked on just fine so I'm assuming the relay needs replaced. If anyone knows where I can find one that isn't $50 from Honda, let me know please. I left them jumped for now. They were jumped (fan constant on) the entire rest of this story.

I limped it home, taking care to not get even close to red zone. Took two hours to go 15 miles, the fan running constantly all the while.

What I've done so far:

1. Checked thermostat with boiling water and cold water. Opens and closes fine. It was open upon removal, so no stuck shut condition.
2. Checked fan switch just to further diagnose the separate fan issue while I had hot water in a pan. Continuity noted in boiling water, so that's good.
3. No noticeable oil in coolant and vice versa.
After I did the first three things I thought maybe it had gotten air in from a leaky radiator cap, so I bled the engine in accordance with the proper procedures per the manual. I parked on a significant incline and let it run for quite a while. The car had been running for almost an hour, spot on temp right where it always runs. So it was at operating temp by a long shot. I took it for a drive. Five miles, fine, ten miles, fine. Twelve miles, temp went hot. Limped it home. Then........
4. I did a combustion gas check on the coolant through the radiator fill neck. The fluid turned yellow, indicating combustion products in the coolant.
5. Later after the kiddos went to bed, --Compression check on all cylinders as follows:
1-180
2-182
3-210
4-190
It appears the one year old plug well gaskets need replaced again because my plug tops were covered in oil, especially number 3, which I'm assuming when I pulled it out caused some oil to fall into the cylinder and accidentally made that one a wet test. The car was cold too, which I didn't realize was supposed to be hot until afterwards. Maybe I have a small gap and it only opens when hot. (??) I'll recheck when I come off shift on Monday morning.

Where do I go from here? I'm at the end of my troubleshooting ideas.

Just occurred to me, I don't know how long the fan hasn't been turning on like it was supposed to. So, I wonder if I slowly fried the HG?
 
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Kenneth

New Member
5+ Year Member
Try a leak down test. It's supposed to be better at diagnosis of hg leak. Of course you've already found traces of combustion gases in the rad, but this should pinpoint the problem area, for hg inspection, after removal. And help confirm the problem is the hg.
 


lethal6

Your Mom's Moderator
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Thread Makers: Thread titles must summarize the technical question or problem, and the first post must include the year, trim, and any mods for your Civic.
 


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