Rad overflow keeps filling

[MarkM66]

'01 Honda Civic, 220k miles.

A few weeks ago the overflow tank filled, and then over filled.

The temp gauge never reads hot, so I figured it was a bad radiator cap (original cap).

Replaced the cap, and it seemed fine. Today I was changing the oil and saw a few drops of coolant under the car. The overflow tank was full again.

I do keep the fluid in good condition with drain and fills yearly. But the overflow did seem kinda oily/dirty inside.

I drained it, and inspected the thermostat, so I'll go ahead and replace that since it's out.

Any ideas on what's causing the overflow to fill?

 

[Brons2]

Blown head gasket, perhaps. What does the oil look like?

 

[MarkM66]

Oil doesn't show any sign of 'milkyness'. Just gets black.

 

[38sho]

oil doesn't have to be mixed with coolant to have a bad headgasket....

 

[The_Jeff]

You could have a screwed up radiator cap that doesn't allow it to suck coolant back when it cools down. But it still lets hot coolant out.

 

[Chris142]

Make sure that the neck where the Radiator cap seals is smooth. Check the new cap to be sure that it's not defective.

If these are ok then the only other option is a leaking headgasket thats pushing coolant out. Probly wont see milky oil unless it's really bad.

 

[MarkM66]

If it's a head gasket, how should I diagnose?

 

[Chris142]

Chemical test

 

[Vikas]

Before doing anything else, make sure you have Honda cap there.

 

[MarkM66]

I pressure checked the system.

Static; just pressurized the system to see if it held pressure. It passed.

Dynamic; install gauge, start engine to check for pressure spikes, passed. Also started engine pressurized the system with the pump to check for erratic reading on gauge, passed.

I also pressurized the system, and pulled the plugs one by one to see if I could hear or see anything suspect. I didn't.

My next step is to get the chemical test. I saw online that some people rented them from Autozone, but mine doesn't rent it. I'll keep checking.

 

[MarkM66]

Well I got Napa bock check chemical test. And it tested positive for combustion gasses in the coolant.

It must have a really small leak. So apparently the head gasket has failed, or there is a problem with the head.

It still shows no signs of a problem, in terms of how it drives, but I guess I'll tear into soon.

I'm thinking of just swapping the head to a reman'ed head from AAP. Since I can get one for about $350 with discount code.

 

[mechtech2]

It may be nothing, at this point, except the remnants of an overfill.
But a head gasket or similar problem is possible.

 

[MarkM66]

Originally Posted By: mechtech2
It may be nothing, at this point, except the remnants of an overfill.
But a head gasket or similar problem is possible.


Thanks. I think I'll keep driving it, and keep an eye on it to see if it gets any worse.

 

[MarkM66]

I put a re-manufactured head on it from AAP. Took about 12-14 hours, and my back still hurts from all that leaning over.

But it's running fine.

The EGR ports in the injector plate was completely blocked with carbon. I'm not sure if that means there's an issue with that system, or if it's just because of it's milage.

 

[mechtech2]

EGR ports and valves get carboned up.
This is normal.
Not good, but normal.