Issue of Coolant draining out
 

Hi everyone.
I am new here. I have a 2006/07 Honda accord v6 EX.
for a while now i have been experiencing that when i drive it hard (flog it) downshifts and all the coolant seems to find its way out of the radiator through the radiator cap! i have gone through quite a bit of caps to no avail.
I just had a thought that maybe my thermostat is faulty and is sending erroneous messages to the engine making it push out water. Is this possible? i scanned my car and did not get that code that shows that the thermostat is bad. is it possible that the thermostat can be bad and does not show up on a scan? Also can the problem be a bad/faulty thermostat?
What i would really to know is what i should do in order to solve this once and for all!
thank you.

The thermostat isn't an electrical sensor, so it won't show up directly in error codes.

To solve it once & for all, you have to figure out the REAL problem.
Does it leak out at the cap? Or does the overflow reservoir bottle fill itself up & spill over?

Either way, you have replaced the radiator cap. But take off the cap (when it's cold) & look closely at the radiator neck. There's 2 different places where the rubber gaskets of the cap need to seal against.

- The uppermost rim of the neck seals against the larger rubber ring of the cap. Look for nicks & gouges that would prevent an airtight seal against the rubber gasket. Leaks here would result in the coolant moving to the reservoir bottle as the engine heats up, but then air would be sucked back into the radiator when it cools down. Your radiator would gradually empty itself while coolant would overfill the reservoir bottle & leak out there.

- There's a second lip down several mm inside the radiator neck. That seals against the smaller rubber plunger of the cap. This would allow coolant & then steam to leak out to the reservoir bottle, probably you would see some steam and it would bubble through the reservoir bottle.

While you're looking there, look real closely all around for any fractures in the neck or even anywhere close to where you see the leak.

Unfortunately, damage to either one of these sealing lips of the radiator neck means a new radiator...

And I'm going to move this over to General Tech where more people will see it. The "new member" forum is mostly for welcome & introduction stuff.
WELCOME!

Thank you for your prompt response and directing my posting to the proper page.
i have checked and really didnt see any damage on the neck of the the radiator and also the radiator caps. so what do i do?

Check the overflow tube that runs from the neck where the radiator cap is, and runs to the overflow reservior.

Sometimes that hose leaks at the connection next to the radiator cap. Try putting a small hose clamp on it.

Where exactly do you see evidence of leaking?

If the outer/upper seal at the cap is OK, then the coolant would go through the hose over to the reservoir bottle & leak out there.

How about that hose being old & cracked?

Yes check to hose for "fitment" and cracks.....PS, I would try something like a "zip tie" on that small hose from the rad to the overflow.

Hi,
Thank you all for your responses.
I have checked my over flow hose and it seems ok, went as far as blowing and sucking both air and water through it and it seemed ok, where i seem to have issues is that my coolant seems to overflow from the cap out (sort of forces its way out of the cap).

So then the cap would be my first thing, but you've replaced that. That leaves the uppermost lip of the radiator neck which seals against the outermost rubber ring inside the cap. The only other thing I can think of is hairline cracks in the plastic around that area.

How about the seam between the plastic upper tank & the metal "core" of the radiator? Or if you see the coolant above that point, would there be a plausible way for it to blow around while driving the car?

Are you SURE the overflow hose is not leaking? On my daughter's Accord I was so sure it was the radiator and/or cap and I changed the radiator and new cap. It STILL leaked!

So I put a hose clamp on the overflow hose and the problem went away. try it, it's just a couple of bucks