Hello,

I have seen several threads on this, but none of them match my unique problem. I have a 2001 Honda Civic, that is giving me a headache. At idle I can run the car for as long as I want to. But when I drive it for about 20 minutes, at varying speeds the car starts overheating. When I pop the hood there is steam coming out of the reservior cap like steam engine. When everything cools down I have no fluid in the reservior or the radiator. I have changed the thermostat and radiator. Checked the fan it runs fine, also checked the heator core its not plugged. The reason I changed the radiator is because about a month ago the radiator blew the seal along the bottom by the plastic case, the radiator was less than a year old when it blew. I have flushed the system and ran it for about an hour with the right side jacked up to bleed it. I thought maybe a head gasket. Did a compression test on all cylinders. The range is 180psi -210psi well above minimum. So I am now at a loss. The last thing I can think it could be is the water pump, I changed that last June when I changed the timing belt. The water pump was a certified honda part. So I don't think that is the problem. Also when the car is running at tempature I can squeeze the the inlet and outlet hoses pretty easy on the radiator. Which I would think means no pressure, which would mean water pump. Before I go that direction I was wondering if anyone has any other ideas. Thank you.

Migrane in Ohio

 

Just seeing this now. Did you end up getting anywhere with it? What was the problem?

I'm having an almost identical problem.

 

Slow leaks in the head gasket won't affect the compression readings. Start the engine cold with the radiator cap off, see if anything bubbles out when you rev it.

 

From my unfortunate experience with subarus, this sounds like a classic head gasket leak where the exhaust is blowing into your coolant. Search "ej2.5 l head gasket leak" You wont see it on compression tests. Do this, with engine cool start the car with radiator cap off. Look for little bubbles. If you see them, it's almost certainly your HG.

 

I think he has a bad radiator cap which is not holding pressure in the cooling system.

 

I was in your position for 2 months and its most likely your head gasket. Dont try an use any block/gasket sealents.

 

usually after the overflow boils it builds enough pressure to make a good sealing overflow/rad cap look like its leaking, but only at those high pressures.

 

Sorry guys,

Just checked this thread. The problem was the head gasket. It had a leak between the #1 and #2 cylinders. Changed head gasket and problem went away. I had to take the car to a garage to make sure it was a head gasket though. They put compressed air in the cylinders and then cranked the engine. The mechanic said first two cylinders he checked was sending exhaust into the coolant system. Only cost me a little over 17 dollars, so not bad. Put about 2,000 miles on it since gasket change. So far everything working fine.

 

That is an interesting way of checking cylinder compression. I have never heard of before. But doing so will increase the test pressure that marginal gasket will show up as faulty, I think.

 

Essentially its a leakdown test, and they likely found air coming out of the radiator.