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I have 97 civic dx with the non vtec 1.6 engine, and for some reason it is leaking coolant from the top of the overflow tank. The theremostat and cooling fan both work as they should.
I have also pressure tested the system and found no other leaks.
What could it be?
I havent tested for a head gasket leak, but my oil looks fine, as do my exhaust fumes
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Update! Just performed the combustion leak test, passed! No headgasket leaks. No combustion gas in the cooling system.
I will bleed the system tomorrow or tuesday with the no spill funnel
Check the radiator flow: unhook the two main hoses then put some water through the top opening and watch how it flows through. If the water coming out is less than the water coming in then will know.
I’d say that the odds are about 9 out of 10 that the head gasket is the cause. But just so you don’t pull the head for nothing I’d suggest doing a block leak test first.
[quote=”sfgmen415″ post=92087]See my previous post…[/quote]
Sorry, I somehow missed that.
Still, the way this problem can occur is most of the time the head gasket doesn’t leak. But, get on the highway and use wide open throttle to pass someone and the head gasket leaks just enough to push some coolant into the jug. I know of other cases where this has occurred and the block test was negative.
Anyway, after all the air is purged, be aware of your driving habits and notice if the symptoms match the pattern I mentioned above.
GL
[quote=”barneyb” post=92109][quote=”sfgmen415″ post=92087]See my previous post…[/quote]
Sorry, I somehow missed that.
Still, the way this problem can occur is most of the time the head gasket doesn’t leak. But, get on the highway and use wide open throttle to pass someone and the head gasket leaks just enough to push some coolant into the jug. I know of other cases where this has occurred and the block test was negative.
Anyway, after all the air is purged, be aware of your driving habits and notice if the symptoms match the pattern I mentioned above.
GL[/quote]
Not necessarily. The #1 cause of overheats like this is air in the system. The first thing to check with any overheat situation is for air in the cooling system, especially if the system has been recently serviced. I’ve seen many a head gasket needlessly replaced because someone assumed there was a head gasket issue. It’s flawed logic. Yes there are times when a head gasket leak will not show up on a block test but avoid assuming head gasket right off. It doesn’t take more than 20min to bleed a cooling system. I would think that amount of time would be worth it considering the gain. I write about this extensively in my overheat article.
http://www.ericthecarguy.com/faq/what-to-do-when-your-engine-overheats
To the original poster. Keep us posted on your progress.
I would ignore that for now. It’s not likely that the oil is mixing with the coolant. It’s more likely the contamination was picked up elsewhere. I would bleed the system and then see what you have to work with. If there’s a real problem I’m sure it will manifest.
I just finished bleeding the system, I will give an update when i drive the car more, as the overheat problems seem to only arise after driving the car for at least 2 hours on and off. Maybe i will flush and fill the system, as i have no idea when the last time the cooling system received a flushed
In my opinion the only time you need to flush a cooling system is if there’s a problem with sediment or contamination. I’m not really seeing that here, even with that small amount of oil. Normally all I do is a drain and refill of the cooling system every couple of years or 30K or so. That seems to work just fine. However if there’s a lot of sediment in the system that’s a different story. In that case I would advocate a system flush. Otherwise a drain and refill periodically is all that’s really necessary.
So the car is still doing the same thing, not pulling the coolant back into the radiator from the overflow tank, causing it to leak out the top :angry:
For the first two days the car ran fine, fan turned on as needed, and the temp never rose above the halfway point. After driving the car about 35 miles today (mostly highway) i got back home and noticed the temp start to rise, popped the hood and what do ya know the same shit is happening. Overflow tank is overflowing, but why? Ive tested everything, the mechanical parts are good; thermostat, rad, overflowtank, and rad cap. The fans turn on when they should, ive bleed the system, pressure tested the system, and tested the block. What can I be missing
Have you examined the hose that goes from the radiator neck to the jug. That has to seal. Sometimes as it ages the hose gets hard and will be loose. Also, examine the tube that goes into the jug. It too has to seal. If all this isn’t tight the jug will never return coolant to the radiator and the radiator cap will just suck in air.
Back in 1992 I bought a new Plymouth Laser. That car had a aluminum head on a cast iron block. The car was actually a Mitsubishi. Well, you had to be very careful with cooling system maintenance. If that engine was allowed to overheat once the head immediately warped. Everytime you drove it after that a leaking head gasket would blow coolant out of the reservoir and on to the ground.
Eric says not to be hasty but I have a feeling here. So, check out what I said above and if that is all okay maybe have a local shop look it over.
If you’ve bled the system and the problem went away and came back, air is likely getting back in the system. At this point I would begin to suspect a head gasket issue or a combustion leak into the cooling system. They don’t always show up on a block test unfortunately. If it were me, I’d be pulling the cylinder head for inspection.
One other possibility is the radiator cap. It’s the radiator caps job to allow coolant to go back into the system during cool down. Before you go removing the cylinder head, why not pick up an OE cap preferably, and install it. Before you do however, bleed the system again as you likely have air in there again based on your description.
Keep us posted on your progress.
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