Overflow Tank doesn't Return Coolant

[Sylvanite]

My overflow tank doesn't seem to be able to return coolant to the radiator. It gets filled to the top, even as the radiator is low on coolant (well maybe a pint from being full). After it got filled to the top (and then some I think) I took it off and cleaned it (turns out there was about an ounce of sludge at the bottom), then tested the the hose and water was able to flow both directions through it. I don't think the sludge was viscous enough to block the flow back into the radiator.

Some maybe relevant background info:
It overheated about about 70 mi ago (on PO), I haven't figured out why
I added more coolant, and drove 70 mi with no overheating
The head gasket is almost new
I wouldn't rule out that there's a coolant leak somewhere

[fixkick]

does the smoke go way on hot motor? tail smoke?????

yes, the tube can fall off or crack , inside the bottle overflow tank.
the radiator coolant as it cools creates a vacuum and sucks the previously hot water in the side tank, back in to the Radiator each night or each cool down cycle.
this keeps the RAD full all the time. the normal evaporation rates are miniscule. a teaspoon a month, or less>?

the only way to be sure there is no leaks in the engine are the 3 classic tests.
1: compression test engine. (i can use my cyl. leak down tester on cylinders and tell you where it leaking by the sounds it makes)
2: the read leak down test.
3: the green/blue dye test (finds exhaust gasses in Rad coolant)

[Sylvanite]

I don't think there's really any smoke, other than some steam when warming up, but not more than normal I don't think. For the record, I meant external coolant leaks, not internal leaks, but I drove a little more and I don't think that any coolant is leaking.

My problem is that coolant overflows into the overflow tank excessively (it went from half full to overflowing on a 10 mile trip), and related to that, the radiator doesn't suck any back in as it cools. I estimate the rad expels a quart of coolant every 25 miles (this is more accurate than my estimate in the original post) to the overflow tank. Of course, the tank isn't big enough to handle this, and it overflows onto the ground. The engine temp seems to be doing fine (according to the dash gauge), and there are no other signs that I've seen of problems in the system. This is really puzzling to me.

[barnbiketom]

the only times I've seen coolant blowing into the reservoir was a sign of overheating(blocked radiator/ bad thermostat/, etc) OR leakage from combustion, as in head gasket etc.. BUT I suppose your RAD cap might be bad too..weak?

When this happens, do you HEAR boiling noises from anywhere??

[fixkick]

the rad side expansion tank is 1/2 full, and rad full
you drive an the rad coOlant expands. and side tank goes to full.
then you park it and as it cools the contraction water in the the rad (its NEAR full. see) and sucks the water from the side overflow tube. both tubes must be good or it cant suck back.
the rad to overflow tank TUBE and the TUBE inside the overflow tank, JUST BE GOOD, NO CRACKS.

if you fill the read 100% and the overflow 100% all cars overflow, this is normal but that side tank was not prefilled correctly
if the rad is full and side tank low, and then overflows. that engine is sick, no matter what gauges tell.

after ALL that gauge can NOT measure AIR, only water nor can it measure exhaust fumes.
try a new rad cap, if the gasket there is split all this fails. all. it's a 12-14PSI system. the cap does that.

MY GUESS IS THE SUCK TUBES ARE BAD.
OR RAD CAP BAD.
WHEN ENGINE IS HOT THE TOP RAD HOSE MUST BE HARD, 12PSI HARD, imagine a baked 12lb ham pushing back (1/2 joking)
but no matter what if there is a problem it will get worse. so early signs all matter
1: misfire
2: pinging
3: water in oil, or oil in water. or carbon floating in the rad filler neck.
4: steam at tail pipe hot engine.
5: water at passengers toes, water anywhere but inside engine, never on ground.

17 to 24 signs and causes here.
http://www.fixkick.com/overheating.html
keep in mind the RAD has excess capacity, and love to hide early symptoms, that is its job1 . excess cooling.
A/c ON SUMMER DAY, UP HILL , 13,000 FEET. HIGH (THIN AIR )

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if the suck tube fails
the rad, level will drops , every day,

its a fact. it fact of pure physics...
when the rad fluid contracts and it sucks air, the RAD level MUST DROP.
like clock work.
so that is why make sure the suck tube works first and not panic on engine eating and burning coolant last.


i have a test for this too. (not you, no scare)

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water in oil
and my compression leak down tool, at piston 1/2 way down (tricky) i can hear hissing in the dip tube and my oil fill cap , oil pan empty.
or hissing at drain hole of pan,
another way is rad and block empty of water
i use rad pressure tool and listen with my small hose to eary in 6 places or more.
not exhaust. ahh..
not intake,
no hissing at head gasket
oops it hisses in the oil filler,ooops......
we do that to decide, fix the bum engine (above) or buy a rebuilt fast.

[Sylvanite]

Thanks fixkick, I think you hit the nail on the head on this. I realized that there was little missing coolant, it had all just migrated to the overflow tank. I'm now pretty sure it's just a bad rad cap (the hose held vacuum good enough to siphon, so I'm guessing it's not the problem).

That being said, could this have caused the engine to overheat in the past? I'm still trying to figure out why this happened.

[fixkick]

sure if the coolant is low. the thermostat will go nuts, at it gets air pockets.
it be cool if its just a cap,, very cool. no pun./