coolant overflow line pouring out coolant

OK all,

Coolant and overheating issues continue. So after I overheated I discovered there was basically NO coolant in my system. I discovered that coolant had been pouring out of the overflow line up next to the cap at the top of the radiator. I had noticed a small wet spot on the front differential, where the coolant was dripping from the hose on the overflow, but did not realize it was basically pouring out all the time I was driving, there was just no evidence of that.

So I refilled and did a few tests and discovered that as soon as the engine hit running temp and the thermostat opens, coolant immediately starts to pour out of this overflow.

So I thought HMM weak spring on the rad cap maybe.....so I replaced the cap and next time out, same thing, thermostat opens and coolant immeidately pours out of the overflow valve, even with new cap...like the whole radiator is a solid clogged wall and coolant has nowehre else to go.

There is definitely not too much coolant in the system. So i was thinking maybe the rad itself could be the problem but when I refill via the radiator the coolant gets down through it with relative ease, making me think the rad is not too clogged up....but not sure...

So if we assume the cap is OK, why would coolant pour out So QUICKLY after the thermo opens? I'd like to explore any other avenues before the investment cost of "let's see if it's the radiator".....especially if it does not clear up the issue.

Anyone else been through this?

 

Just a shot in the dark, but fill system again completely full (cold) and with radiator cap off, start and bring up to op temp. Watch for bubbles in the radiator. The last time I experienced something similar to your symptoms, it turned out to be a crack in the cylinder wall. A blown head gasket or cracked head can also lead to blowing the coolant. Normal expansion/contraction of coolant should not drain the system, even though some overflow will normally occur.

 

So maybe my massive overheat broke something more significant......or was caused by something more significant....Hmmm OK thanks!

Other thouhts/views????

 

sticky thermostat ?
slow to open fully ?
pressure will build right before the t/stat opens
you could try drilling a small relief hole in the t/stat body to help bleed possible air.
are you using the by-pass hose between block and head ?

 

If there is a cracked head, cylinder wall or blown gasket wouldn't there be coolant showing up in your oil? When I bought mine the radiator was badly clogged and had some fluid overflow, I assumed the fluid was being pumped in and had no place to go so it overflowed. I had if flushed down at the shop it had held fluid ever since.

 

Not necessarily. A cylinder wall crack will usually only be into the water jacket and the coolant would have to go through the rings to get into the oil (which it can do-as in broken rod/piston when the coolant refuses to compress even at 7:1). A blown head gasket or crack can go either way depending on the failure location. Bubbles are a very positive ID of a compression leak to the coolant system as most owners of Subaru 2.5L's can attest.

 

Check the seat where the radiator cap seals first. Could be cracked, distorted, etc. This will allow coolant to bypass the cap seal and flow out. Simple check.

 

What he said.

 

All good thoughts. Also, after re-filling coolant some systems need to be "burped" to get air out of the heater core, by-pass hoses, or whatever. If not an over-heat and large overflow can result.

Or if you severely overheated the engine, a head can warp, making the gasket leak.

 

How much antifreeze are you loosing out of the overflow tube? If you completely fill the radiator when the engine is cold, the antifreeze will expand as the engine gets warm and then hot. The antifreeze will expand, and as a result the pressure will rise until the radiator cap pressure is exceeded, at which time the pressure is regulated by releasing the excess antifreeze into the overflow tube.

After 1 or 2 heat/cooldown cycles, the overflow should stop. When the engine is cooled, the coolant contracts, and the radiator will not be completely full when you open the cap.

I suggest that you connect a longer rubber hose into the overflow and zip-tie a 2 liter soda bottle to the grill and catch the expelled fluid. Not permanently, but to see how much antifreeze is actually coming out.

If you suspect that the headgasket is bad and causing cylinder pressure to leak into the cooling system, you can find this problem by pressurizing the cylinder with air (using the adapter from a cylinder compression tester, which has a spark plug thread on one end and air hose connection on the other). Open the radiator cap, and when the cylinder is pressurized, the coolant will bubble when the leaky cylinder is found.

Good Luck

 

How much antifreeze are you loosing out of the overflow tube? If you completely fill the radiator when the engine is cold, the antifreeze will expand as the engine gets warm and then hot. The antifreeze will expand, and as a result the pressure will rise until the radiator cap pressure is exceeded, at which time the pressure is regulated by releasing the excess antifreeze into the overflow tube.

After 1 or 2 heat/cooldown cycles, the overflow should stop. When the engine is cooled, the coolant contracts, and the radiator will not be completely full when you open the cap.

I suggest that you connect a longer rubber hose into the overflow and zip-tie a 2 liter soda bottle to the grill and catch the expelled fluid. Not permanently, but to see how much antifreeze is actually coming out.

If you suspect that the headgasket is bad and causing cylinder pressure to leak into the cooling system, you can find this problem by pressurizing the cylinder with air (using the adapter from a cylinder compression tester, which has a spark plug thread on one end and air hose connection on the other). Open the radiator cap, and when the cylinder is pressurized, the coolant will bubble when the leaky cylinder is found.

Good Luck

 

Also note this test with pressurizing the cylinder has to be done with both valves closed.