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Unread 07-19-2006, 10:52 PM   #1
Fargo
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Why does water boil in my overflow tank

I've had water boiling in my overflow tank 2 times now. Its time for me to figure out whats happening.

Here's a little history. I purchased my 99 Sahara about 3 years ago. I've been able to smell antifreeze on occation ever since I purchased it. Last winter I saw steam coming from the seams where the plastic top of the radiator meets the radiator. So at first I thought my radiator was shot. But then others have told me they will do this because the plastic and the metal expand at different rates. And it will be fine once its at operating temperature.

So whats the reason for water boiling in the overflow? I have never had water leak or lost any fluid. (Other than maybe minor amounts I thought was just evaporation.) I've also never noticed my temp gauge get anywhere near the red line. Only slightly over 210. Maybe 215. I checked the antifreeze with a gravity ball testor and it showed good to 260.

I did a search and tried to check some other things. I tried to check the fan clutch but I couldn't find how the clutch moved seperate from the fan. They seemed to be bolted together. But the fan itself turned with some resistance. I also tried to feel the top hose for water flow. I couldn't feel the water flow through it but after running the Jeep for some time the hose did get warm and I think the temp droped a couple of degrees after that. So I'm inclined to think that my thermostat is good. So did I check something wrong? Or is there another reason my water is boiling in my overflow tank? Thanks for the help.

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Unread 07-19-2006, 11:08 PM   #2
Doatman
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Is your anti-freeze a 50%-50% mix? If not, see if you can make it so, and then replace your radiator cap; it is often overlooked as a culprit. It sounds like you have already looked at the obvious, like clutch, serpentine belt, thermostat, clogged radiator core, etc. Good luck.
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Unread 07-19-2006, 11:30 PM   #3
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There is air getting into your system. You should check the level of antifreeze in your sysyem.Check to see if the over flow is dry then start to drive when your engine is still cold and drive it for a hour or so then stop your jeep & see what happens. The antifreeze will come into the overflow & bubble up/boil. Then when it cools the antifreeze will go back. Perhaps the overflow its not filled to the correct level. The overflow should have levels marked as "Full & Fill" if its dry fill it up to "Fill" or just a tad bit higher with antifreeze. Try it again with the engine cold, drive it for an hour or so & see what happens. Hopefully it will not bubble/ boil in the overflow. If it does check other parts whats mentioned in the last post.

If you can... I suggest to drain all the antifreeze and buy a radiator cleaner & follow directions then fill it with clean antifreeze. Fill it to the correct level & hopefully all will work out.

Good Luck!
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Unread 07-20-2006, 07:18 AM   #4
cincytj
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Quote:
Originally Posted by Fargo
I've had water boiling in my overflow tank 2 times now. Its time for me to figure out whats happening.

Here's a little history. I purchased my 99 Sahara about 3 years ago. I've been able to smell antifreeze on occation ever since I purchased it. Last winter I saw steam coming from the seams where the plastic top of the radiator meets the radiator. So at first I thought my radiator was shot. But then others have told me they will do this because the plastic and the metal expand at different rates. And it will be fine once its at operating temperature.

So whats the reason for water boiling in the overflow? I have never had water leak or lost any fluid. (Other than maybe minor amounts I thought was just evaporation.) I've also never noticed my temp gauge get anywhere near the red line. Only slightly over 210. Maybe 215. I checked the antifreeze with a gravity ball testor and it showed good to 260.

I did a search and tried to check some other things. I tried to check the fan clutch but I couldn't find how the clutch moved seperate from the fan. They seemed to be bolted together. But the fan itself turned with some resistance. I also tried to feel the top hose for water flow. I couldn't feel the water flow through it but after running the Jeep for some time the hose did get warm and I think the temp droped a couple of degrees after that. So I'm inclined to think that my thermostat is good. So did I check something wrong? Or is there another reason my water is boiling in my overflow tank? Thanks for the help.

get someone to pressure test your system and the CAP. dont forget the CAP becuase it is usually overlooked and usually the problem. Your system has to hold pressure because the pressure raises the boiling point of your coolant.
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Unread 07-20-2006, 07:54 AM   #5
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Another simple explanation - water in your radiator is hotter than 212 degrees, the normal boiling point of water, but with the antifreeze and the higher pressure, the effective boiling point is much higher.

Once you get the antifreeze/water mix into the overflow, the pressure is much lower, making the boiling point lower, still higher than 212 most likely, but a lot lower than inside the radiator/cooling system in general.

That's the scientific explanation. Now as to why you have having cooling issues, I would suspect that you have either a gummed up thermostat, radiator core, or hoses, or a combination thereof.

Replacing the t-stat is VERY easy, but be sure to get the proper one for your Jeep. If you replace the radiator, go aftermarket and get an all metal one, none of that plastic/metal binding that DC uses on Jeep radiators.
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Unread 07-20-2006, 09:05 AM   #6
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Coming from my first love - turbo buicks - I have seen this many times.

Check all the easy stuff above - then a compression test is in order. A blown headgasket or cracked head will do the same thing. The hot exhaust gas leaking into a water jacket superheats the water and boils it....

I hope its as easy as a thermostat or cap - but don't drive it too much if you can't figure it out. Its not doing it because it doesnt like you - there IS a reason.
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Unread 07-20-2006, 11:04 AM   #7
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Quote:
Originally Posted by cincytj
get someone to pressure test your system and the CAP. dont forget the CAP becuase it is usually overlooked and usually the problem. Your system has to hold pressure because the pressure raises the boiling point of your coolant.
x2

If you can see the coolant bubbling out/steaming from the radiator, it's not holding pressure.
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Unread 07-20-2006, 11:12 AM   #8
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You ether have a blown head gasket of a cracked head!
You are getting compression gases in the cooling jackets of your engine.
Pull your plugs and do a compression test.
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Unread 07-20-2006, 11:30 AM   #9
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Your radiator is simply not holding pressure, in fact you saw steam escaping from the seam where the leak was. Because there is no pressure in the system, the coolant boils at a lower temperature. The steam escapes into the overflow bottle because it rises to the top of the radiator, then passes through the vent line to the bottom of the overflow bottle - that gives the boiling symptom.

Time for a cooling system refresh:

1) New radiator (many options, use the search feature)
2) New radiator hoses and clamps
3) New heater hoses and clamps (only under the hood)
4) New radiator pressure cap
5) New thermostat and gasket
6) Flush block and refill with 50/50 coolant and distilled water
7) New serpentine belt

While the belt is off, check for bearing play in the water pump. If you find some, it is the perfect time to do the pump and pump gasket.

You can do this yourself if you have a shady place to work. Make sure you have all the pieces needed. Be carefull when you do the heater hoses, the valves are plastic and break easily, so carefully slit the old hose and peal it off, don't pull.
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Unread 07-20-2006, 01:32 PM   #10
Fargo
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Quote:
Originally Posted by BEANS
You ether have a blown head gasket of a cracked head!
You are getting compression gases in the cooling jackets of your engine.
Pull your plugs and do a compression test.
I think I'll ignore this post because I don't like this answer

I really hope your wrong here. That does not sound good at all. But thanks for giving me another place to check.
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Quote:
Originally Posted by mrblaine View Post
...there's very little that is more permanent than a temporary solution
Quote:
Originally Posted by Oman Jeep
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Unread 07-20-2006, 01:38 PM   #11
Fargo
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Quote:
Originally Posted by KaiserJeep
Your radiator is simply not holding pressure, in fact you saw steam escaping from the seam where the leak was. Because there is no pressure in the system, the coolant boils at a lower temperature. The steam escapes into the overflow bottle because it rises to the top of the radiator, then passes through the vent line to the bottom of the overflow bottle - that gives the boiling symptom.

Time for a cooling system refresh:

1) New radiator (many options, use the search feature)
2) New radiator hoses and clamps
3) New heater hoses and clamps (only under the hood)
4) New radiator pressure cap
5) New thermostat and gasket
6) Flush block and refill with 50/50 coolant and distilled water
7) New serpentine belt

While the belt is off, check for bearing play in the water pump. If you find some, it is the perfect time to do the pump and pump gasket.

You can do this yourself if you have a shady place to work. Make sure you have all the pieces needed. Be carefull when you do the heater hoses, the valves are plastic and break easily, so carefully slit the old hose and peal it off, don't pull.
Do you feel pretty confident that this is the case? That I am loosing pressure at that seam. Or should I get a pressure check before I purchase a new radiator?

I did see the steam coming from the seam 1 time. And I can smell it from time to time. But I don't know where the smell is comming from. Is there any validity to those that say this steam is normal because the metal and plastic expand and contract at different rates until you are at operating temperature.
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Quote:
Originally Posted by mrblaine View Post
...there's very little that is more permanent than a temporary solution
Quote:
Originally Posted by Oman Jeep
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Unread 07-20-2006, 01:52 PM   #12
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If you have a blown head gasket or cracked head you will displace a lot of coolant into the overflow bottle. The exhaust gases will replace the coolant.
The level will rise and maybe blow coolant out over the engine bay. It will not all go back into the radiator when it cools down.
The coolant will start to darken up, and will smell funny.

If the rad cap is leaking, then the pressure will bypass the cap and coolant will overflow into the bottle, but only to the expanded level .. it will all be drawn back in when it cools down.
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Unread 07-20-2006, 02:35 PM   #13
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Get a radiator pressure test if you want - it shoudn't cost anything. Or you could just wrap a cloth around the top radiator hose and squeeze it to feel for system pressure once the engine reaches full temperature - the hose will be stiff with pressure, squishy without pressure.

The leak could be a bad hose, a bad pressure cap, or even at the thermostat gasket. However YOU SAID you saw steam coming from the radiator seam and in spite of what you were told, that is NEVER OK. Check along that seam and you will probably see water marks from evaporating coolant which is the final confirmation.

The stock Jeep radiator is aluminum center core with plastic end caps. The caps have a plastic foam gasket and the core flange is simply crimped around the plastic flange. Yours lasted 7 years which is longer than most. Replace it with a quality aftermarket unit. Do your homework first - lots of threads in every Jeep Forum I read about radiators.
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Unread 07-20-2006, 02:37 PM   #14
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Quote:
Originally Posted by Fargo
Is there any validity to those that say this steam is normal because the metal and plastic expand and contract at different rates until you are at operating temperature.
My 98 has steamed slightly once in a while over the last five years, and I have also heard that it is due to the plastic/metal issue. about 4 years ago I replaced the water pump, flush & refill, thermostat and serpentine. just last month i did another flush & refill and new belt and of course inspected everything - no issues. just follow everyone's advice here on checking/testing to be certain that you have ruled those issues out. Kaiser's advice is excellent if your system is due for it
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Unread 07-20-2006, 06:47 PM   #15
Fargo
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Quote:
Originally Posted by KaiserJeep
Get a radiator pressure test if you want - it shoudn't cost anything. Or you could just wrap a cloth around the top radiator hose and squeeze it to feel for system pressure once the engine reaches full temperature - the hose will be stiff with pressure, squishy without pressure.
The shop I called quoted me $20 for a pressure check. Thats why I wondered about getting it when I tend to think that is the problem. I did check the top hose a little bit last night and I couldn't feel any pressure. Once again leading me to think that is my problem.

Quote:
Originally Posted by KaiserJeep
The leak could be a bad hose, a bad pressure cap, or even at the thermostat gasket. However YOU SAID you saw steam coming from the radiator seam and in spite of what you were told, that is NEVER OK. Check along that seam and you will probably see water marks from evaporating coolant which is the final confirmation.
I did see steam this winter and I can see evidence of water marks from coolant along the seam.

Quote:
The stock Jeep radiator is aluminum center core with plastic end caps. The caps have a plastic foam gasket and the core flange is simply crimped around the plastic flange. Yours lasted 7 years which is longer than most. Replace it with a quality aftermarket unit. Do your homework first - lots of threads in every Jeep Forum I read about radiators.
Acutally I think I've had a problem since I purchased the Jeep 3 years ago. Almost from day one I could smell coolant but never knew where it was coming from until I saw the steam last winter. Then this summer it boiled in the tank for the first time. That was when I really began to think I had a problem.

So I will double check the hose presure and maybe get a pressure check. But from what I've read. It sounds like I will be purchasing a radiator. I have already looked a little and found 3 core metal radiators at www.radiatorbarn.com and www.radiator.com. Are these reputable places to buy from? Is there anything in particular I should look for or ask about? I'm just trying to do my homework here. Which is a good brand. I think I saw CSF somewhere, are they any good?

Edit: Also where should I get the hoses from? Will auto stores carry them. Do I need a factory thermostat or can I pick that up at an auto store as well?
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Quote:
Originally Posted by mrblaine View Post
...there's very little that is more permanent than a temporary solution
Quote:
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