coolant not venting back into overflow tank

[cerberusaardvark]

hey yesterday i just did the radiator and coolant system flush and after i added back in the coolant, a little over two gallons in total, i let it sit for the night.

in the morning i checked on the ex before i drove it and found a giant puddle of coolant on the ground, but the overflow tank was bone dry.

i know the hose isnt blocked because when i was flushing the radiator the water would bubble to the top and transfer over.

did i add too much? i waited for the stat to open and kept pouring in coolant through the funnel till the level stayed steady in the radiator.

i guess when the engine cooled it spat out all the extra coolant onto the ground from someplace. does this mean one of my hoses is suspect? because i replaced all those too.

 

[Anime]

It's generally a bad idea to add coolant to a radiator while it's hot and the engine is running, both for safety purposes and how such a system works. You're really lucky the hot coolant didn't bubble over onto you and cause burns or other serious problems.

You're better off filling the radiator with the engine cold, putting the cap on halfway (first click), then running it with the heater on until it gets to operating temp, letting it cool, then refilling it again, running back up to operating temp with the heater on again, then cooling and refilling again, topping off the overflow reservoir at the end.

The lack of flow to the overflow reservoir might be due to the radiator cap, if the spring is too strong or the rubber gasket is swollen, it can block the coolant from getting out the hose even when the system pressure is trying to force it out.

If you don't purge the air out of the system correctly, you can also get an air bubble that rises to the top of the radiator, and will keep coolant from escaping because there will be an air bubble trapped there, rather than coolant.

I'd suggest a new Motorcraft cap from the dealer, they are rather inexpensive. Purge the air using the factory procedure and between the two, hopefully that solves the issue.

 

[cerberusaardvark]

yea it felt odd to have the rad cap off while the engine warmed up.

in doonze's flush manual he says thats how you burp the system. funnel in, pour the coolant in till the bubbles stop, then once it sucks down out of the funnel into the radiator take the funnel out.

haynes manual say the it can take a little over two gallons of coolant, which is how much i added. it looks like it spat out at least a gallon... should i be worried about low coolant? or was that just the systems way of equalizing when there is too much?

 

[mintford]

Park with the front of the truck higher than the back (air bubbles will go up and out of the radiator cap) Fill the cooling system and once the radiator seems full, keep squeezing the upper radiator hose to burp the last of the air out. Turn the heater on high. With the engine running, you will know that there are no air pockets and everything is good when the temperature gage shows normal operating temp AND the air blowing out of the vents is hot. If there's an air pocket, you won't have heat from the vents. Once it cools down, check the reservior. You usually have to top it off a little then. Like Anime said, a bad radiator cap would interfere with the overflow tank function. I bought a large funnel that screws on in place of the radiator cap. It holds extra coolant, allowing coolant to replace the air bubbles that come out. (all without making a mess) I haven't seen them in the auto parts store though. I got mine from the Snap On truck. I'm sure you allready know, don't stand over the radiator opening with the cap off while doing this. If there is an air pocket, hot coolant can suddenly spew out.

 

[LXNavajo_94]

I had a similar issue with mine when I flushed the radiator. The hose that goes back to the overflow was clogged up with gunk from the radiator. The pressure from the returning coolant pushed the hose off the nipple at the filler neck.

 

[swshawaii]

i know the hose isnt blocked because when i was flushing the radiator the water would bubble to the top and transfer over.

I had a similar issue with mine when I flushed the radiator. The hose that goes back to the overflow was clogged up with gunk from the radiator. The pressure from the returning coolant pushed the hose off the nipple at the filler neck.

Ditto Anime. If there's no air in the system, start with the radiator cap. No surprise if it's the original in your '94. GL

 

[cerberusaardvark]

lol it was definitely the original rad cap. i replaced it with one that claims to twist to 16 ft lbs, the old one was 15. when i pulled off the old rad cap i extracted a plug of nasty brown and orange sludge that was hanging onto the bottom.

i conducted an experiment today- i filled the overflow tank to the cold fill line after my ex sat all night. i drove to work and checked the overflow tank, it was empty. then when i went back to check on my car i discovered a big puddle of coolant on the ground.

so this tells me that when the system pressurizes and the stat opens it sucks in extra coolant like its supposed to. but, after then engine shuts off and things cool down, the extra coolant comes out somewhere.

i replaced all hoses and clamps with worm style clamps, all the fittings were dry.

could it be that the water pump has the power to pull out the coolant, but not to push it back? idk, just guessing.

maybe its just one of those weird things.

 

[Anime]

The new factory caps have a max psi of 16, but are really still about the same 13-15 as the old ones during regular use, but a slightly higher psi is fine anyway.

If you've got sludge in the system, you should probably do a drain and flush to clean all of that out of there, it might be what is clogging stuff up.

The water pump just circulates the coolant in the system, it doesn't pull or push coolant in or out of the overflow reservoir, that's a function of pressure and suction regulated by the thermostat and radiator cap.

You need to find out where the leak is coming from, there might be a loose clamp, cut hose, radiator crack, or something else that is only opening up under pressure after the engine is off. It might still just be a clogged hose to the overflow tank, but fixing where the leak is coming from might also allow the pressure to cause the cap to open and the coolant to flow back to the reservoir.