Steam at the overflow hose below the radiator cap?

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Randy Gilbert

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I'm picking the brains of the people who know this better than I. I have the 1971 Dart with the 225 Slant 6. Recently (in the middle of the 100 degree Texas heat), it started spewing steam out the overflow hose coming from the radiator. makes me think the radiator most likely was an aftermarket/replacement. Didn't think the 225s had an overflow and I am afraid it's losing coolant/water over the course of driving it during the week. I loaded it up with almost a gallon of water the other day, but won't go to coolant/antifreeze till I know for sure it's not leaking somewhere I can't see. No water in the oil and the engine is still running fine, just the steam especially when stopped after running. Any ideas? Thanks in advance!
 
That's normal. After your shut down the motor , circulation stops and the pressure in the system rises. Keep the level about an inch below the neck and you'll be gtg. If you don't like it puking coolant then get a recovery bottle and correct type of cap.
 
Ok....just wanted to make sure. I didn't remember on the old Dodge Monaco that my grand mother had whether it had it or not. But I saw other pic on here finally that had the basically same set up as mine but with the original style cap, not this flip valve type cap I have. May spend 5 bucks and replace it with the original 16 PSI cap. Also, didn't notice it during the winter so I guessed it was mainly due to the hotter temps right now.
 
All radiators have an overflow. All. Some newer ones go through the recovery tank but there is still an overflow

You may have an air pocket turn the heater on and make sure the hoses are getting hot. You may just be overfilling. You may have the wrong cap or damaged cap or damaged neck. There was a case recently where someone bought a replacement rad (don't remember who/ when/ make/ model) and the neck was built differently that it should have been and required a different type cap

If it is not overheating I would carry extra water, run it a couple days and see if it "equalizes" To do that ignore the overflow unless it's overheating WHEN RUNNING and check it WHEN COLD in the evening. Let it run 2-3 days ad see if it seeks a level that stops puking.

You may have a bad water pump
 
Thanks for the info. I was leaning that way, thinking it was just build up of pressure. It has not over heated at all so I wasn't super worried about it. I can see that the water pump is newer and most likely the thermostat too. I just don't want to dig into it until I have to on that end. Will keep you guys posted on Friday to see where it stands. Thanks again guys!
 
If you're running straight water like you said and not running cooling on 100° day you're definitely going to boil the water after you shut the car off . That's why you're steaming.
 
That is NOT normal. It sounds like there is a leak in the cooling system. Examples: external leak, such as a freeze plug, or internal such as a leaking head gasket.
As the volume of water depletes because of the leakage, there is not enough water left to cool the engine & temp rises until the coolant boils [ steam ]. That is the steam you are seeing.
 
Bewy said:
That is NOT normal. It sounds like there is a leak in the cooling system. Examples: external leak, such as a freeze plug, or internal such as a leaking head gasket.
As the volume of water depletes because of the leakage, there is not enough water left to cool the engine & temp rises until the coolant boils [ steam ]. That is the steam you are seeing.
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I have to agree. If the radiator was filed to the top, it would spill some coolant at shut down but not a gallon. A failed or low pressure cap along with clear water could cause it to loose more over time. If it is a head gasket, the copper colored liquid head gasket fix from Barsleak really works. It cured my 96 4cyl. Camry with same symptoms over 2 years ago. Only time I could see steam at the tailpipe was at cold start and that wasn't much. Its close to 293000 miles now.
 
RedFish said:
I have to agree. If the radiator was filed to the top, it would spill some coolant at shut down but not a gallon. A failed or low pressure cap along with clear water could cause it to loose more over time. If it is a head gasket, the copper colored liquid head gasket fix from Barsleak really works. It cured my 96 4cyl. Camry with same symptoms over 2 years ago. Only time I could see steam at the tailpipe was at cold start and that wasn't much. Its close to 293000 miles now.
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I have no water in the oil. It is clean. Until I can fully flush the system, then I'm of the mind its the temps combined with the fact that I just don't know what the PO did with the thermostat and it looks to me that it's straight water in there and that's what I topped off with to test. After the flush, I will go with the normal coolant/antifreeze and see what happens then. To be clear, there hasn't been a "loss of coolant" as when I added the water to the radiator, I hadn't added anything to that point in the time I owned the car. I was too busy fixing the fuel issues (which now I have to fix again as my grandson broke the bracket on the carb for the choke pull off arm. Yeah, not happy about that.) Once I replace the cap and flush and get the right coolant in it, I have a feeling it will be fine. I had a similar problem with my 63 Chevy PU at one time. One day it just stopped doing it when the heat of the Texas sun died down in the fall of that year and it never happened again.
 
I don't think you said what year car you have.

Earlier cars had a hose running from that nipple under the cap, then along the top of the radiator, down the side and then it ends near the bottom and spills onto the ground. There should be a metal clip on the radiator to hold the hose on the side.

Then in the early 70's, cars started using a closed system with an overflow bottle. You could convert to that pretty easily by getting a new raduator cap, say for a 73 Dart, and a plastic overflow bottle. Expansion forces the excess into the bottle which then gets drawn back into the radiator as it cools.

Go to a large chain auto parts store and "rent" a cooling system checker for free. You can pump up the cooling system at the radiator cap fitting and see if there are any leaks. It should hold 16 psi steadily without dropping. It can also be used to check caps.

It sounds like you are aware that coolant will raise the boiling temperature. Of course do not remove a cap from a hot system. That lever style cap is supposed to relieve pressure but is not Mopar correct.
 
KosmicKuda said:
I don't think you said what year car you have.

Earlier cars had a hose running from that nipple under the cap, then along the top of the radiator, down the side and then it ends near the bottom and spills onto the ground. There should be a metal clip on the radiator to hold the hose on the side.

Then in the early 70's, cars started using a closed system with an overflow bottle. You could convert to that pretty easily by getting a new raduator cap, say for a 73 Dart, and a plastic overflow bottle. Expansion forces the excess into the bottle which then gets drawn back into the radiator as it cools.

Go to a large chain auto parts store and "rent" a cooling system checker for free. You can pump up the cooling system at the radiator cap fitting and see if there are any leaks. It should hold 16 psi steadily without dropping. It can also be used to check caps.

It sounds like you are aware that coolant will raise the boiling temperature. Of course do not remove a cap from a hot system. That lever style cap is supposed to relieve pressure but is not Mopar correct.
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Thanks. I knew they went to an overflow bottle but didn't know when. This one is a 71 Dart with the 225 Slant 6. Love the car but I'm having issues making sure it's "right". Got a messed up wire from the column so I had to install a push start switch in the old lighter hole on the ashtray, and the PO tried to put some cheater gauges under the dash with an aftermarket radio (which this car never came with a radio to start with) so I have to resort out all the wiring under the dash and column to make sure it's all good to go and the instrument cluster is working properly. Yeah, I've got a long road to getting this done especially when it's a fall back car for a 20 year old who can't keep his 350z running for more than a week at a time. LOL.
 
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