Civic overheating issue

[Miles ruud]

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

Topic

[college man]

If your overflow is leaking then your losing coolant.
which will make your coolant level low causing the
overheat. Replace the overflow tank.

http://www.ericthecarguy.com/faq/what-to-do-when-your-engine-overheats

[Miles ruud]

The overflow tank is not cracked. It seems as if theres is to much coolant causing it to overflow, very oxymoronic, i know. Would this be caused by a bad rad cap?

[EricTheCarGuy]

It could be your radiator cap. There’s more info in the article College man posted on that. It also shows how to check for a head gasket issue. I believe the information you need is in that article however.

Good luck and keep us posted.

[Miles ruud]

Put on a new radiator cap, but it still overfills the overflow tank. Im getting a new overflow tank later today

[Bill]

Try replacing the radiator cap. It might not be holding pressure on the cooling system.

[Miles ruud]

Ive changed the rad cap, and the overflow tank, and the same thing is still happening

The next thing i plan to do is bleed the system, when i get my no-spill funnel

[Miles ruud]

This is so f%*#ing frustrating, because ive checked everything and its still overfilling the overflow tank, yet the are no leaks in the system. My last guess is that i need a new radiator

[Miguel]

I would definitely look into the head gasket being blown. You can buy and or sometimes rent a block tester at a parts store to test for combustion gases in the cooling system. They are easy to use and usually contain a blue liquid and if it turns yellow it means a combustion/exhaust gas is getting into the cooling system. There are videos on youtube on how to use them.

[Lee Ann]

Did you have a chance to bleed the system (that you had mentioned as one of your next steps)?

Is it possible there is rust/scale build-up/blockage in the radiator that might be remedied by a flush (drain flush and fill) of the system?

How does your coolant look? Is it cloudy or transparent (compare the coolant in your overflow tank to fresh coolant from the coolant jug)?

[Miles ruud]

I havent bleed the system, but would air in the system cause coolant to overflow from the overflow tank? Also i will try to get my hands on a combustion leak test kit

[Lee Ann]

I would say yes, if the air pocket in the radiator is large enough, the coolant may be inhibited from returning to the radiator. But it’s the valve in the radiator cap that controls the flow between the overflow tank and the radiator. I know you said you replaced it but could the new one be faulty (I hear that from time to time new parts can be defective)? Use OE parts as much as possible. Have you replaced any hoses or had any service to the cooling system recently?

Also, do you have other symptoms that warrant a block test? How does your coolant look? Is it cloudy or transparent? And do you have thick white smoke from the tailpipe that persists (I just now read that you said your exhaust fumes seem ok)?

[EricTheCarGuy]

Not sure why you replaced the overflow unless it was damaged. Did you look over the article that was posted? In it was how to bleed the air form the system as well as how to check for a head gasket issue. If you haven’t looked that over yet you might want to as there is likely information in there that will help you.

Keep us posted.

[Miles ruud]

I replaced the overflow tank because there were 2 small holes on the top of it where the cap screws on, also it was hard to see the coolanf level in it as the outside of it was fairly dirty. My coolant looks the way it should. I havent got a chance to bleed it yet, the non-spill funnel will arrive monday, also i havent had time to ger my hands on the headgasket test kit. I have read the article, and watched your videos talking about cooling system issues, thet very detailed as it pretains to each procedure preformed to test the different componants of the cooling system.

Here a little more info on my driving habits.

I drive the car about 40-60 miles per day through the pot hot filled streets of San francisco. I traverse many steep hill, and idle a good bit in traffic.

Though today in the morning I checked the overflow tank and rad levels and both were up to par, and the car gave me no trouble all day, only turned on the heater when the weather called for it

[Chris]

If the Thermostat, Water Pump, Overflow Bottle and Radiator Cap are in good working condition then most likely you might have air in the system that needs to bleed, which you can do by parking the car on an incline with the front of the car higher than the rear. With the engine off and cool open the radiator cap and top off the radiator. After filling the radiator fill the overflow bottle the max line. The only way for the overflow bottle to fill up with coolant is if the car gets hot, the pressure pushes up on the radiator cap and causes coolant to fill the bottle from the radiator. If it still happens then u need to change the radiator.

[Chris]

Anytime you have overflow and the bottle fills up you will have air in your system which will cause overheating and more coolant will continue to fill the bottle and spill over on the ground.

[Author]

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