Topic: Coolant Boiling

[Saggy]

Thanks for the help locating the freeze plug behind the bell housing.  I dropped the transmission and replaced the freeze plug.  Everything went back together properly and the leak has stopped.  I obviously had to dump all of the coolant and refill it to get the new plug in.

I ran it around the block and everything seemed fine.  It got up to temp, the thermostat opened, and I saw the gauge on the dash drop.  I was happy until I got back to the garage and smelled coolant that had boiled out of the radiator.  I also noticed that the electric Taurus fan never kicked on...even while the liquid in the radiator was boiling out.

The first thing I could think of was to test the thermostat that goes through the radiator fins to control the electric fan circuit.  I put a lighter under it and it eventually kicked on...but I don't know at what temperature and I can't think of a way to measure the temp this thermostat kicks on.  Any ideas there?  Also, are there any other possibilities I am overlooking?  If the cooling system was air locked the thermo in the water pump wouldn't be able to pull liquid out of the radiator to make the gauge in the dashboard drop, right?

Anyhow, thanks for the help with the freeze plugs.  And thanks in advance for your help here!

[sharpxmen]

I had it airlocked when i replaced my thermostat, refilled it and was fine afterwards (it boiled).

you can check the thermocouple or sender for your e-fan by sticking it in a pan with water, should kick in close to boiling point (make sure it does not touch the pan bottom, should be suspended in water) - if the water boils and it does not kick in then you have an issue.

also, make sure your radiator cap is holding pressure, if it does not it will boil sooner - they're cheap so you might want to just replace it anyway.

and the least likely cause can be if the thermostat is installed backwards (although i have no idea if the housing is deep enough to allow that).

[Saggy]

It ended up being the thermo switch.  Am I a fool to get another cheap Hayden probe from O'Reilly?  Looks like they have 3 models from pre-set switch temps to adjustable.  I've read a bunch of posts from people who say they're junk.  On the other hand, a lot of people still seem to be using Hayden switches.

Any ideas?

[chardrc]

I used one of the Hayden kits from oriely. is worked good has a variable resistor or something you turn to adjust fan kickin temp. only problem i have had with it is the radiator fins disintegrating around it not allowing it to get a good reading because my radiator is shot. 

[sharpxmen]

just going to ask this anyway although it is a very long shot but i've seen it done before: are you using a relay with that thermocouple or it is directly in-line with the e-fan?

[Saggy]

Running it through a relay.  The relay does trigger the fan when the two leads running through the thermo switch are shorted.

[sharpxmen]

Running it through a relay.  The relay does trigger the fan when the two leads running through the thermo switch are shorted.

i'm using an adjustable hayden with a tread-in probe for the low speed (so not the one that goes thru fins) and a second one non-adjustable also thread-in probe for high speed (both thread in to the bottom of the radiator right where the outlet is) - this way i have some redundancy if the low speed one gets bust since the high speed thermocouple is not used at all and some insurance on hot days if the low speed is not keeping up. The low speed kicks in between 190 to 195, the high speed around 200. The adjustable one uses a thermostat so the life of it is longer than a regular contact type one, but there's always a matter of the electronics going bad so it's good to have some alternative. I think they came up with a 2 speed one for about $40 or so after i bought mine, but imo 2 different circuits/systems is better for insurance.

[Jeffy]

Thanks for the help locating the freeze plug behind the bell housing.  I dropped the transmission and replaced the freeze plug.  Everything went back together properly and the leak has stopped.  I obviously had to dump all of the coolant and refill it to get the new plug in.

I ran it around the block and everything seemed fine.  It got up to temp, the thermostat opened, and I saw the gauge on the dash drop.  I was happy until I got back to the garage and smelled coolant that had boiled out of the radiator.  I also noticed that the electric Taurus fan never kicked on...even while the liquid in the radiator was boiling out.

The first thing I could think of was to test the thermostat that goes through the radiator fins to control the electric fan circuit.  I put a lighter under it and it eventually kicked on...but I don't know at what temperature and I can't think of a way to measure the temp this thermostat kicks on.  Any ideas there?  Also, are there any other possibilities I am overlooking?  If the cooling system was air locked the thermo in the water pump wouldn't be able to pull liquid out of the radiator to make the gauge in the dashboard drop, right?

Anyhow, thanks for the help with the freeze plugs.  And thanks in advance for your help here!

First make sure the fan didn't blow any fuses.  You can wire the fan directly, leaving out the thermostatic switch so the fan turns on when the engine is on.  Also are you using hi-speed or low speed?  You shouldn't need hi-speed.

Where is your probe mounted?  It needs to be at the top of the radiator near the inlet hose.   If it is adjustable when what's it set at?  I have mine cranked down to 180 which turns on when the gauge temp is 195 almost exactly.

I use a Flex-a-lite adjustable thermostat which is basically teh same as the hayden.  Also, make sure the thermostatic switch is on the switch circuit and not the fan circuit as most switches aren't setup for high amps.

[Saggy]

I hadn't considered running the high speed through a thermo switch too.  I have it running to an on-off-on switch on the dash.  I can't tell you how many times the kids have been playing and flipped that switch.  It made a whole lot of sense when I was single with no kids.  Wish I had thought that one through! 

I like your idea for a redundant circuit with the high speed.  I might have to borrow that from you.

[Jeffy]

I hadn't considered running the high speed through a thermo switch too.  I have it running to an on-off-on switch on the dash.  I can't tell you how many times the kids have been playing and flipped that switch.  It made a whole lot of sense when I was single with no kids.  Wish I had thought that one through! 

I like your idea for a redundant circuit with the high speed.  I might have to borrow that from you.

You shouldn't need the Hi-speed.  But if you do you'll need a high amp relay.

[sharpxmen]

You shouldn't need the Hi-speed.  But if you do you'll need a high amp relay.

that was my thinking, since it will [almost] never be used it is less likely to fail (both relay and thermocouple) and be available if the primary one does not work. I used a 50 amp relay for that.

I hadn't considered running the high speed through a thermo switch too.  I have it running to an on-off-on switch on the dash.  I can't tell you how many times the kids have been playing and flipped that switch.  It made a whole lot of sense when I was single with no kids.  Wish I had thought that one through! 

I like your idea for a redundant circuit with the high speed.  I might have to borrow that from you.

you can find my setup here http://4bangerjp.com/forums/index.php/topic,10360.0.html
not the usual (it's overkill) but just so you can an idea.

[Saggy]

Damn, man.  Nice write-up.  Will definitely study that to see what I can borrow from it.

I swapped out the thermo switch with the constant temp Hayden 3652.  It is supposed to come on at 185 and off at 165.  It didn't fix the problem.  Coolant still comes out from the cap.  By the way, I also tried a new cap just to make sure it wasn't a worn spring or gasket on the cap.

The probe is pushed through the radiator fins just below the upper hose.  It has always kicked the fan on in the past.  Not sure what has changed here.  I have noticed that I have more coolant in the overflow container than usual.  It may even be just above the line.  I don't understand how the coolant overflow works so not sure whether this could be a problem or not.

Could this be as simple as removing some liquid from the overflow container?

[sharpxmen]

from which cap is the coolant coming out of? the overflow has 2 marks, cold and hot, you fill it cold to the bottom mark, let it warm up and should be around the top mark (again this is hot), if you fill to the top mark when it's hot then it will overflow. So if you did that then you don't have a problem. if you get bubbles in the overflow tank (after all the air purged out if you opened your radiator cap recently) then it's boiling, otherwise it isn't. Is the e-fan coming on at all?

[Saggy]

It is coming out of the spring cap on the radiator.  The efan never comes on.  I am going to have to check to see if the overflow is at (or maybe an inch beyond) the top mark when the engine is cold or hot.  I know it is there, just can't remember when.  It seems like it is there when the engine is cold.

I had isolated it to the thermo switch because when I manually switch the high speed fan on with my in-cabin switch the radiator doesn't boil out.  But replacing the switch didn't make the fan come on before coolant came out the rad cap.

[Saggy]

Did some reading on how the overflow tank works thinking maybe I had it overfilled when the engine is cold.  Sounds like as the liquid in the radiator heats and expands, the radiator cap opens the first stage spring which lets coolant flow out of the radiator neck through the hose to the overflow tank.  When the engine is turned off, the cooling liquid creates a vacuum which sucks the liquid from the overflow tank back into the radiator.  So now I understand why you were asking which cap coolant was overflowing from.

I'm totally confused about why the e-fan isn't being kicked on by the thermo switch though.  The placement just below the upper hose used to trip the switch.  I took the radiator cap off and watched coolant circulate as the thermostat in the water pump kicked in so I know that is working.  Shorting the leads that feed into the thermo switch turns the fan on so I know the relay, fan and in-cabin on-off-on switch are all good.

The only thing that has changed is the freeze plug leak has been fixed.

Is it possible that I got another faulty thermo switch from O'Reilly?  Should do some plumbing and install a probe that contacts the coolant rather than the through-the-fins probe?

Totally flumaxed by this one.