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[Wilf]

I replaced the radiator, hoses, and radiator cap. Also inspected thermostat and looks new and works perfectly (hot water test).

[Wilf]

Update …
I’ve done a perfect bleed, just burping it and verified that the gurgle in the heater core is 99% gone. I did this using the spill-free-funnel and the car on a incline, modulating the rpm a bit and idling. That takes a good 25 minutes to do.

Then while mellow driving around it seems to hold the state and no new bubbles are introduced.

To get the problem to recur, I drive up a hill nearby that has approximately a 500 feet vertical rise over 1 km. The bubbles don’t appear to manifest at the top of the hill, but in fact after I get down the hill using engine braking (1st and 2nd gear, often sustained 4000 to 4500 rpm).

So … even after a perfect bleed. air is getting back into the system after either 1) a hard drive or 2) a hard engine brake after a hard drive.

To check if combustion gases, I bought an OEM test kit tested twice, for even longer than required, and both tests came back negative that it is not combustion gases.

So this really has me stumped.

1) No loss of coolant. Either reservoir goes a little higher (from air in system displacing coolant) or it goes back to normal, after air is burped and system re-capped.

2) No leaks. Vacuum test for 4 hours, no leaks. Pressure test 4 hours, no leaks.

So … something is either sucking the air into the system (on cool down when engine braking at high rpm??) or under high load.

The mystery continues.

[Wilf]

Radiator and hoses replaced. New Honda coolant. New rad cap. Inspected thermostat and all working perfectly (did hot water test). The block tubes and thermostat look pretty much new. No leaks anywhere.
Just looking at the engine layout, there is a 1 to 2 foot climb from the block to the heater core. So maybe it is just crazy difficult to remove the air bubbles in the heater core. I don’t even see how jacking the car would make them come out. I guess I’ll just have to live with annoying gurgling sounds when the heat control is over to full-hot and the car is accelerating.

[Wilf]

Thanks. I already have the ball joints. But maybe I can return them. This is definitely cheaper this way!
edit: although I wasn’t aware that the tie rods and inner tie rod end would get wear.

[Wilf]

By Tie Rods, do you mean just the tie rod ends?

[Wilf]

I believe I also detect this problem (2005 Honda Element AWD with 288,000 kms). Coils replaced around 188,000 KMS and spark plugs are only 15K kms old.
It goes away completely as soon as the engine is hot.
It is a very mild misfire, noted by more rumbly idle and harmonic when at higher rpms. Now, I could be wrong since not tested.

[Wilf]

[quote=”nightflyr” post=204312]Not likely..
In this situation the only possible cause would be the water pump impeller.
But as I said, if this was a design issue more cases would have surfaced.
May I ask..
If you know you have a leak in the radiator why not replace it?
And if there is a possibility of combustion gases do a gas test.[/quote]

Totally. I have ordered a replacement radiator and will install that as soon as it arrives.
That will eliminate that possibility and then we will see!

[Wilf]

[quote=”nightflyr” post=204308]The T stat is inside a closed loop.
Unless there is a crack in the housing that should cause an issue.
The only other situation in which air bubbles can occur is due to cavitation.
But if this was an issue due to design, there would be many more reports of it happening.[/quote]

Cavitation – perhaps in the block heater or heater control valve?
Or something else?

[Wilf]

[quote=”nightflyr” post=204305]Still comes down to if the system is purged of air and completely full.
Then after a time you have air introduced.
You either are:
Taking combustion gases into the cooling system.
Or drawing air externally into the cooling system.
Now if a combustion gas test yields a negative result your left with a external leak with in the cooling system.[/quote]

I’ll throw this out — What about the thermostat?
Is it possible for air to enter the system when the thermostat moves its valve?
Anyone heard of that?

[Wilf]

[quote=”nightflyr” post=204303]On the same school of thought …
If it is leaking coolant out through a pin hole.
Then why is it not pushing fluid back into the over flow?
You can’t have half the equation work one way and the other half work in the opposite.[/quote]

Reservoir hose has no leaks and is unobstructed.
Squeezing one of the fat engine coolant hoses causes a slight volume increase in the reservoir level.
Pinhole leak appears at very bottom of radiator, so maybe gravity + shaking + time + heat/cool cycles is why the small leak manifests there – even though the system appears to be overflowing and up-taking normally.

[Wilf]

[quote=”nightflyr” post=204300]Has anyone done a combustion gas test?
Something else..
if there is – A small leak in the lower driver side of the radiator is noted, perhaps 2 ml per hour of hard driving.
This doesn’t show up in a pressure or vacuum test.
If coolant can leak out air can leak in.[/quote]

That is what I thought. Mechanic seems to think it would suck back from the reservoir before coming in through that small leak (pin hole?).

I should add, I did replace rad cap and that also made no difference.

[Author]

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