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justinsbg, ASE Certified Technician
Category: Honda
Satisfied Customers: 990
Experience:  ASE certified in Brakes, Electrical, HVAC, and Engine Performance. Currently a lead diagnostic Technician.
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Civic: 2004 Civic 1.7L AutoOverheating after front end

Customer Question

2004 Civic 1.7L Auto
Overheating after front end collision. Radiator was clogged and cracked. Replaced but after 6 months and 60k miles it started overheating again after a long trip through some mountain areas. Also consistent and noticeable loss in mpg.
I can drive car all day long off the freeway no issues, no coolant loss. When I'm on the freeway, the coolant overflows from reservoir. That causes car to over heat when I slow down. If the drive is long enough it'll overheat even at freeway speeds.
No smoke in exhaust.No oil in coolant or coolant in oil. Spark plugs look fine. No misfire. No check engine light. Car runs and drives just fine otherwise.
Submitted: 2 years ago.
Category: Honda
Expert:  justinsbg replied 2 years ago.
Hi,My name is ***** ***** I would be happy to help. Reminder, I have not been paid at this point and won't be until I receive a positive rating from you. At that point I will receive a portion of what you've already paid Just Answer.I have 8 years experience with strictly Honda/Acura vehicles. With the information you've provided I would be inclined to say that there is a head gasket issue, but what I would try first is replacing the thermostat and bleeding the system. If the thermostat is stuck closed it would cause overheating due to the fans not coming on. I can tell you from experience that the 2001-2005 Honda Civic has a real problem with head gasket leakage so don't be surprised if you have this problem after you replace the thermostat. Once you replace the thermostat the system needs to be properly bled. This can be done by parking the vehicle on an incline with the front of the vehicle pointed towards the sky (as much a possible). Take the radiator cap off and fill it up with coolant. Start the vehicle and let it run while filling the radiator as necessary to keep it filled. Let the engine idle until the fans cycle. Once they they cycle one time turn the inside fan on high and the heat on high. This will draw coolant into the heater core to remove any air inside. Let it run with the heat on high for a few minutes and turn it off. This will be messy because the coolant will overflow from the radiator at times, but it has to be done. They make what's called spill free funnels and you can purchase them for about $25 bucks if you want to do this without making the mess. After completed install the radiator cap and re-check for overheating. You can go ahead and rate me positively. Don't worry, there won't be additional charges for asking questions after you rate so if you need more information just ask me. Thanks.
Customer: replied 2 years ago.
I've already done the bleeding with a spill free funnel on my inclined driveway. I replaced the thermostat about a week ago with a honda thermostat. Bubbles just keep coming after the thermostat opens and more so when I rev the engine to 2000 rpm as the manual suggests. I tested the bubbles coming out of the radiator and it tested negative for hydro carbons at least ten separate occasions. If there was a head gasket failure, wouldn't it test positive?I also wanted to rule out the heater core so I bypassed it. I pressurized the cooling system and it held pressure overnight. I also performed the other two tests with the pressure tester. First, start the car cold with the tester in place and watch for a quick rise in pressure which would suggest a bad head gasket. That didn't happen. Second, let the car warm up and pressurize to 20 lbs and if the needle fluctuates a head gasket is bad. It didn't fluctuate. It rose steadily to about 24lbs and fell again to 15 lbs when the fans kicked on.
Customer: replied 2 years ago.
I had listed what I have done so far when initially asking this question. I don't see it anymore on my end. Do you see it on yours?I'm a little hesitant to agree that it is a head gasket. The first time the overheating started, I took it to 2 mechanic and both said bad head gasket. I replaced the radiator and the problem was gone for 6 months or 50,000 miles. I drove a lot then.The second time it started overheating I did notice coolant was leaking from radiator hoses. The worm style hose clamps had become loose. I replaced them with the spring type but the issue of overheating wasn't fixed.1) Flushed cooling system
2) Bypassed heater core
3) Replaced water pump and timing belt
4) Replaced Thermostat and radiator cap with genuine honda parts
5) Replaced Radiator - Denso from Rock Auto.
Customer: replied 2 years ago.
I forgot to add6) replaced spark plugs - they were worn but clean. Not burning oil or coolant.
7)Replaced air filter
Expert:  justinsbg replied 2 years ago.
Yeah, I don't see that previous list you gave. I didn't know you'd done any of that. If the coolant is overflowing into the reservoir after some driving that is a pretty good indication that there is internal pressure building up and it's pushing the coolant over into the overflow. This would indicate a that the head gasket is leaking. How long does it take for the engine to start overheating?
Customer: replied 2 years ago.
20 to 30 miles on the freeway. I can drive all day long off the freeway 45 mph and it won't overflow or overheat.The reason I have been doubting a head gasket is because the block tester has been negative. I tested again last week... If the head gasket were busted, wouldn't exhaust gases go into the radiator? I mean that would cause the pressure build up in the cooling system wouldn't it?
Expert:  justinsbg replied 2 years ago.
We do not use that form of testing to determine a blown head gasket. Sometimes getting too technical can be misleading. We take the spark plugs out, bring each cylinder to TDC, and apply shop air through a air hose that screws into the spark plug hole. If the head gasket is leaking the air pressure will force coolant out of the radiator. That's how we do it. It's a great way to test for leakage. I've never actually heard of testing for head gasket leakage using the method you've explained and I've been servicing vehicles for over 10 years. If the overflow bottle is filling up when driving it would either be due to head gasket leakage or stuck thermostat. You said you've changed and bled the thermostat so that leaves the latter. We replace probably 2-3 head gaskets a month on this model civic. It's HIGHLY common.