joe85sti

My 02 civic LX started overheating in traffic one day. I didn't have a chance to really pin down the characteristics of its overheating before I got home, so I started by replacing the thermostat. That didn't work. When I test drove it, thats when I noticed it was overheating at idle regardless of car speed, as well as not blowing heat. At that point, I moved to water pump. Old pump looked great, but got that done with timing belt, etc. That didn't work, so thats when I searched the inter webs and found out about the head gasket issues. I tore it all apart, brought the head to a machine shop, it was flat and didnt need to be milled, put on the new head gasket, drove it for about 20 minutes on the highway....no overheating, coolant level seemed consistent. Took it to work the next day (about an hour drive, all highway), did fine until the drive home, and apparently enough driving had been done to push the coolant into the overflow tank, thus overheating at idle again. I bought an exhaust gas tester, no exhaust gasses in the coolant. I did notice that when I started it up in the driveway, after the thermostat finally opened, it did try to overflow a little out of the radiator, then it settled back down. My only thought now is maybe a clogged radiator? Any advice is greatly appreciated.

-Joe

RobertD

You went through all that and never inspected the electric fan / relays? I

joe85sti

My apologies, electric fans are working. Also, I can be on the highway, put the car into neutral, and it will start overheating. Conversely, I can be stopped and when it starts to overheat, rev it up past 3k rpm and it'll come back down. These are all symptoms of low coolant, and goes away if I top it back off. Unfortunately, it will then slowly push the coolant into the overflow tank again. Since there are no exhaust gasses present, my only thought is a restriction in the radiator, and when the flow rate is high (driving on the highway) it forces coolant into the overflow.

BrotatoChip

Did you burp the coolant system after replacing everything? Could be air trapped inside expanding once the engine warms up.

Wankenstein

Did you check the block for flatness?

Exhaust gases in coolant is only one of several types leak and a block test will not find all types of head gasket breaching.
Do a leak down test (ezone style) on each cylinder at TDC.

joe85sti

I did run it for about 45 minutes with heat on full. Kept the radiator topped off.


I have a compression tester, so I guess I'll do that next. I guess I'll have to bring it somewhere for a leak down since I don't have air in my garage.

joe85sti

I'm confused. My symptom of overheating is from coolant being pushed out of the system into the overflow, thus eventually leaving me low on coolant. With regards to head gasket, the only way a head gasket could cause coolant to be pushed out is by exhaust gasses, right? So if I didn't get a bad result with my exhaust gasses test, it can't be the head gasket causing this. Is my assumption correct?

ezone

Incorrect. Many failed head gaskets will pass that test.

Slumpertcivic

Either bad head gasket, bad installation, or warped / uneven block.

I think by the time the flame front actually gets to the head gasket, the moving piston has already reduced the compression enough that actual exhaust gas doesn’t enter the water jacket, just the preburn mixture and that’s why it doesn’t trigger the coolant test very well.

Wankenstein

Read: http://www.agcoauto.com/content/news/p2_articleid/200

ezone

And not being pulled back into the radiator as the system cools.

Have radiator and cap issues been checked and addressed? (DNRTFA)