Small coolant leak at the neck of the upper and lower hoses.

[Bad_dude]

Hey guys,
I notice two tiny leaks at the aluminum part where the thermostat housing and the neck where the upper and lower radiator hoses are attached to. The leaks are small and no big coolant loss is noticed. I wonder if these leaks are due to rubber seals failure or do I need to replace both the parts there. I am using the permatex gasket goop to cover the area up but would like to fix it soon. So is it a drain, replace the gaskets and this should stop the leaks?
I have photos attached below.





Thanks.

[Jarrett]

They aren't gaskets but rubber seals. It seems both are damaged but for that to happen in two different locations at the same time is pretty coincidental. Was the thermostat and/or the water neck removed recently and reinstalled with the used seals?

[Bad_dude]

Happy holidays.
No they weren't. The one at the thermostat housing leaked first and now the front outlet housing is. Both were not removed nor reinstalled. The thermostat was replaced by a mechanic right before I bought the car in 2008.
Is it something else that could have cause the leaks? Or is it just wear and tear?
Thanks.

They aren't gaskets but rubber seals. It seems both are damaged but for that to happen in two different locations at the same time is pretty coincidental. Was the thermostat and/or the water neck removed recently and reinstalled with the used seals?

[Fleetw00d]

I don't think I've ever had either of those joints leak on any of my Accords. I suggest paying a little extra for OEM seals; go ahead and replace the thermostat (OEM thermostat comes with a new seal) while you've got it apart, and have your radiator cap checked - if it is causing high coolant pressure, that could contribute to failure of the seals. Torque for the bolts at both locations is 12 N-m (9 ft-lb).

[Bad_dude]

Radiator cap check? How would the cap cause high pressure? I thought it just keep the coolant from leaking out? My cap says 16lbs on the top and it has no leak that I could see. Do I need to buy an OEM cap or could I buy one from Autozone and that will work?
I noticed that when I removed the cap to check, it looks good but even with the engine and not run yet overnight, the coolant tend to squirt out a little. Is that normal?
Thanks.

I don't think I've ever had either of those joints leak on any of my Accords. I suggest paying a little extra for OEM seals; go ahead and replace the thermostat (OEM thermostat comes with a new seal) while you've got it apart, and have your radiator cap checked - if it is causing high coolant pressure, that could contribute to failure of the seals. Torque for the bolts at both locations is 12 N-m (9 ft-lb).

[Fleetw00d]

The cap says "16 lbs" because it doesn't open to let air/coolant into the overflow tank until the cooling system pressure exceeds 16 psi. The higher pressure in the system helps to raise the boiling point. If the cap is working well and doing its part in purging the system of air and keeping if full of coolant, it might maintain pressure even after cooling off. The concern is that for some reason it maintains a pressure even higher than 16 psi. I've always tried to use OEM caps, but that's just me.

[Bad_dude]

So do you guys think it's just worn out seals or is there something underlining in the coolant system? I don't see any obvious other issues. I might have to get a mechanic to do this. I am not allow to work on my car any more. Thanks.

[johnl]

The concern is that for some reason it maintains a pressure even higher than 16 psi.

The system is filled cold and will start off at zero psi (over atmospheric). Fit the cap and as the coolant heats up it expands and the pressure rises until some coolant is expelled into the overflow tank. As the system cools down the fluid is 'sucked' back into the cooling system as the pressure drops to where it started (i.e. zero psi).

So, I think you're right to think that residual pressure in the cooling system after fully cooling down is a cause for concern. The cold pressure should drop back to zero because it's a zero sum game, what pressure builds up must then fall back to zero since nothing has been added to the cooling system, what's blown out is what is sucked back in (and the cap offers no resistance to pressure entering the cooling system, only exiting it).

For there to be residual cold pressure there must be something being added to the cooling system when it's hot, and all I can think of is gas (not fuel, but gas, as in gas) from the combustion chamber. That is, it's possible there is a head gasket leak...

Any time I see multiple leaks occurring more or less simultaneously, I'm always suspicious of the head gasket causing the cooling system to become over pressurised. Usually a leaking HG doesn't cause a cold residual system pressure because pressure usually leaks back into the cylinder from the cooling system after engine shut down, but it might if the leak is still minor and takes more than X pressure to leak through it (?).

Sorry to be alarmist...

[Bad_dude]

No milky oil or any sign of HG leak. Maybe I am just over alarmed and it's time to just replace the seals.
I noticed the overflow bottle does rise when hot and goes back down to low level when it's cold in the morning.

[Losiracer2]

Just replace the seals. I recently rebuilt a car with a blown headgasket and the minute I filled it with water and prestone coolant flush, to get all the milky residue out, it started seeping out the front water outlet going to the radiator.

I bought a fel-pro seal at Autozone, gasket is made by Federal Mogul, so its not crap. Purchased for $2.99 and took care of the problem instantly. I assume the rear T-stat seal is similar in cost.

You don't necessarily have to drain the coolant to do this, just have a simple pick handy, and swap out the seals quickly and reinstall the water outlet neck. A few ounces of coolant will come out. Simply top off, and purge system for air.

[Bad_dude]

That sounds simple. So what about the Thermostat seals? Do I have to drain coolant for this one too? I need something simple. So when the car is cold, does the coolant stays in the radiator or the engine block? I am trying to avoid draining the coolant and what's the best approach to replacing the seals particularly the Thermostat one? I plan on replacing the thermostat too, since it was last replaced in 2008.
Thanks.

Just replace the seals. I recently rebuilt a car with a blown headgasket and the minute I filled it with water and prestone coolant flush, to get all the milky residue out, it started seeping out the front water outlet going to the radiator.

I bought a fel-pro seal at Autozone, gasket is made by Federal Mogul, so its not crap. Purchased for $2.99 and took care of the problem instantly. I assume the rear T-stat seal is similar in cost.

You don't necessarily have to drain the coolant to do this, just have a simple pick handy, and swap out the seals quickly and reinstall the water outlet neck. A few ounces of coolant will come out. Simply top off, and purge system for air.

[johnl]

No milky oil or any sign of HG leak.

I'm not saying you definitely have a HG leak, but wouldn't be surprised if you do.

Oil and coolant very often do mix when the HG fails, but if the failure occurs between a cylinder and the water jacket only, and does not involve the seal containing the oil in the crankcase cavity or oil pressure feed to the head, then crankcase pressures can over pressurise the cooling system with no mixing of oil and coolant (either in the cooling system or in the crankcase).

This isn't uncommon, and may not cause serious or obvious problems until the leak gets worse (which it will). Once the leak gets worse it becomes more likely that it will also come to involve leakage between the crankcase and water jacket, which is when you'll start to see 'the Devils cream' in the crankcase cavity / oil and / or coolant.

I noticed the overflow bottle does rise when hot and goes back down to low level when it's cold in the morning.

Which is normal. However, a small HG leak may cause gas to escape into the cooling system and then into the overflow tank without causing substantial expulsion of coolant, yet.

Note that HG gasket leaks can be temperature dependant, not leaking until the engine reaches X temperature. They can also be load dependant, not leaking until cylinder pressure reaches X pressure. They can also be time dependant, not leaking enough to be a problem until the cylinder pressures have been high enough for long enough. I've experienced problems with leaky head gaskets that would drive all day long around town with no significant issues, but 20 minutes on the highway and the engine would expel coolant and then overheat. This wasn't random, the symptoms were quite repeatable.

FWIW, I'd be keeping an eye on the degree to which the radiator hoses become pressurised in use. Check this by squeezing the hoses with your fingers. Some pressurisation is normal, but if a hose ever feels excessively hard then it's a good bet you have a problem.