Denny
Taurus Homeland
Uh oh, what would cause the coolant to boil out of the overflow tank on the SHO MTX?? frown
Coolant overflow from overflow tamk?
- Thread starter Denny
- Start date
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shojuan
New Member
A really hot day, running the car hard, and/or air in your cooling system. If your cooling system is in need of a flush then the first two items will tend to make the coolant get hotter and expand out into the overflow tank more readily then with a nice clean cooling system.
Rick
Rick
shojuan
New Member
Also, if your thermostat is sticking closed (rather than sticking all the way open) then your coolant will get really hot in the block and heads and will boil out. That steam pressure will push the colder liquid coolant that's between it and the radiator cap, out the radiator cap into the overflow bottle. Or worse, your cap blows off. Your would hopefully notice that your gauge was running towards the red zone and shut the car off. My mom didn't when the thermostat stuck closed on her (funny thing was it had been stuck full open for about 30-40K miles). Luckily nothing happened other than me lecturing her about how she should have shut the car off and gotten a tow.
Rick
Rick
Denny
Taurus Homeland
Hmm, maybe that's it.
Would a bad headgasket do the same, and if so, what else should I look for to determine that?
Would a bad headgasket do the same, and if so, what else should I look for to determine that?
shojuan
New Member
Replace the thermostat first. Allow some time for the air to bleed out of the system. The quickest way to check for the bad head gasket is to take the car to a shop for a leak down test. That's assuming you've checked the oil for coolant (brown milky oil) and coolant for oil first. There's a diagnostic method for checking head gaskets by pulling plugs one by one and using a compression gauge, but the rear plugs are tough to get to. Better to let a shop do the leak down test. Then you'll know.
The SHOs are *not* prone to head gasket failure, btw.
Rick
The SHOs are *not* prone to head gasket failure, btw.
Rick
twr
whoohoo
A bad radiator cap will allow coolant to boil back into the overflow bottle. Atleast mine did, new one cured it.
shojuan
New Member
Absolutely. Definately cheaper and easier than the thermostat. A new Stant cap costs about $4. Sorry I didn't think of that in my list above. That's why this forum is great! thumbs_u
Rick
Rick
Denny
Taurus Homeland
Hmm, hopefully these are the only problems then. And the car would start to overheat if those happened right?
What exactly would this "milky oil" look like if I pull the dipstick, it'll be brown? But isn't oil naturally brown/black after being used for some miles
What exactly would this "milky oil" look like if I pull the dipstick, it'll be brown? But isn't oil naturally brown/black after being used for some miles
Rob94
New Member
It'll have the consistency of a milkshake. You'd see bubbles, or at least a foamy appearance.
Denny
Taurus Homeland
Eek, I guess I will check for that on Sunday then. .. frown
rangerj
Active Member
Denny,
Before you give yourself an ulcer worrying about how much it's going to cost to rebuild your engine, step back and do some diagnostics.
Does your temperature guage indicate that you are running hotter than normal? How long has it been since you have changed the radiator cap? If it has been more than a year or two, and you are running at normal temperatures, then change the radiator cap. Buy a top quality cap. DO NOT OPEN THE CAP WHEN THE ENGINE IS HOT!
You can remove the cap, start the car, and watch the coolant flow when the thermostat opens. After the coolant cycles several times, it is a good indication that the thermostat is working properly. If the thermostat is not opening you would be overheating! Is the fan working?
If there is a lot of air (bubbles) in the coolant, or foam, it could indicate a head gasket problem. This can be checked by pressure testing the radiator, and by doing a compression test on the cylinders.
However, keep in mind that at any one of the many hose connections, the engine could suck in air via the vacuum created when the engine cools down. The spring clamps used in production lose some of their tension with age, and/or corrosion.
Any hose that feels spongy, or is very hard, should be replaced.
The hoses themselves also deteriorate with age.
A radiator cap that has lost some of its spring tension can also allow the system to suck in air.
Why isn't the fluid being sucked back into the system from the overflow bottle?
Check for any signs of leaks at all hoses, gaskets, and any place the coolant flows, such as the water pump and the radiator, especially around the tank seals and petcock.
Take your time and do the diagnostics, or you could spend a lot of time and money unnecessarily. Hope this helps, rangerj
Before you give yourself an ulcer worrying about how much it's going to cost to rebuild your engine, step back and do some diagnostics.
Does your temperature guage indicate that you are running hotter than normal? How long has it been since you have changed the radiator cap? If it has been more than a year or two, and you are running at normal temperatures, then change the radiator cap. Buy a top quality cap. DO NOT OPEN THE CAP WHEN THE ENGINE IS HOT!
You can remove the cap, start the car, and watch the coolant flow when the thermostat opens. After the coolant cycles several times, it is a good indication that the thermostat is working properly. If the thermostat is not opening you would be overheating! Is the fan working?
If there is a lot of air (bubbles) in the coolant, or foam, it could indicate a head gasket problem. This can be checked by pressure testing the radiator, and by doing a compression test on the cylinders.
However, keep in mind that at any one of the many hose connections, the engine could suck in air via the vacuum created when the engine cools down. The spring clamps used in production lose some of their tension with age, and/or corrosion.
Any hose that feels spongy, or is very hard, should be replaced.
The hoses themselves also deteriorate with age.
A radiator cap that has lost some of its spring tension can also allow the system to suck in air.
Why isn't the fluid being sucked back into the system from the overflow bottle?
Check for any signs of leaks at all hoses, gaskets, and any place the coolant flows, such as the water pump and the radiator, especially around the tank seals and petcock.
Take your time and do the diagnostics, or you could spend a lot of time and money unnecessarily. Hope this helps, rangerj
NiNeTy Fo SHO
No-mo-SHO Man
FWIW: I had it boiling out of my 94 mtx...my problem was my radiator fan stopped running...got a realy from the junk yard for like 10 bucks and we were back in business. Also make sure there is a rubber seal around the radiator cap...if there isnt, then it would also cause fluid to boil out of the overflow. Thats what happened to me.
Denny
Taurus Homeland
Hehehehe, compression testing is fun! 
If I do that, would a head gasket problem be there if compression is off, or very weak in any given cylinder then?
Rangerj, those were some very helpful pointers, I'll have to check into those. Thanks thumbs_u
If I do that, would a head gasket problem be there if compression is off, or very weak in any given cylinder then?
Rangerj, those were some very helpful pointers, I'll have to check into those. Thanks thumbs_u
Denny
Taurus Homeland
Whoah, I just found this thread I started years ago while searching for a different topic. Odd, because I still have this problem...on a different engine. However, it's the same radiator and CAP. I'm going with everyone hear and going to put money on that. Hopefully this will be fixed once and for all
