Replaced heads, rebuilt engine - blown freeze plug
BubbaFL
08-24-2013, 02:46 PM
My 2002 Windstar 3.8L had a head gasket failure and bent the #6 rod.
I pulled the engine, replaced the heads with new ones from Moore's / AAP, new main and rod bearings, new rings, and replaced the rod and piston on #6 with a new one from Ford. I replaced every gasket on the engine, all Fel Pro, and used new head bolts. Got it all back together, fired her up, sounded good.
I had to fight with the cooling system to get it bled - at first it kept puking coolant out of the overflow bottle. After a few heat / cool cycles and squeezing the top radiator hose while it was running, it seemed okay. Temperature was normal and stable, and cabin heaters were blowing hot.
Drove about five miles, and a freeze plug on the front of the left head blew out.
I'm in over my head here.
Is it likely that the freeze plug was defective?
Or did I seriously screw something up when I put the engine together?
I don't know if I should just replace the plug, or replace the head gaskets again while I have the engine apart.
Would the reservoir cap or hoses blow before one of those plugs, if the system was over-pressure?
Anybody have experience with this or suggestions?
http://farm4.staticflickr.com/3673/9583072569_ef1381b9bc.jpg (http://www.flickr.com/photos/8243457@N08/9583072569/)
CAM00017 (http://www.flickr.com/photos/8243457@N08/9583072569/)
http://farm4.staticflickr.com/3671/9583073081_6cd196aae0.jpg (http://www.flickr.com/photos/8243457@N08/9583073081/)
CAM00016 (http://www.flickr.com/photos/8243457@N08/9583073081/)
I pulled the engine, replaced the heads with new ones from Moore's / AAP, new main and rod bearings, new rings, and replaced the rod and piston on #6 with a new one from Ford. I replaced every gasket on the engine, all Fel Pro, and used new head bolts. Got it all back together, fired her up, sounded good.
I had to fight with the cooling system to get it bled - at first it kept puking coolant out of the overflow bottle. After a few heat / cool cycles and squeezing the top radiator hose while it was running, it seemed okay. Temperature was normal and stable, and cabin heaters were blowing hot.
Drove about five miles, and a freeze plug on the front of the left head blew out.
I'm in over my head here.
Is it likely that the freeze plug was defective?
Or did I seriously screw something up when I put the engine together?
I don't know if I should just replace the plug, or replace the head gaskets again while I have the engine apart.
Would the reservoir cap or hoses blow before one of those plugs, if the system was over-pressure?
Anybody have experience with this or suggestions?
http://farm4.staticflickr.com/3673/9583072569_ef1381b9bc.jpg (http://www.flickr.com/photos/8243457@N08/9583072569/)
CAM00017 (http://www.flickr.com/photos/8243457@N08/9583072569/)
http://farm4.staticflickr.com/3671/9583073081_6cd196aae0.jpg (http://www.flickr.com/photos/8243457@N08/9583073081/)
CAM00016 (http://www.flickr.com/photos/8243457@N08/9583073081/)
northern piper
09-01-2013, 09:49 PM
ok, take this for what it's worth, as I've never encountered the problem that you have...
if it were me, I'd replace the plug, and bring the coolant back to the level it needs to be. I'd then beg, borrow or steal a coolant pressure tester. I have one and have used it before to see what the pressures are for certain leaks etc that I've been trying to find. The one I've got has a "safe" region which I think would be a good indication of what pressure level you're system is running at. If everything seems good from the original build I'd hope that there isn't a blockage leading to pressure and popping of the plug...
fwiw, my 2 cents
if it were me, I'd replace the plug, and bring the coolant back to the level it needs to be. I'd then beg, borrow or steal a coolant pressure tester. I have one and have used it before to see what the pressures are for certain leaks etc that I've been trying to find. The one I've got has a "safe" region which I think would be a good indication of what pressure level you're system is running at. If everything seems good from the original build I'd hope that there isn't a blockage leading to pressure and popping of the plug...
fwiw, my 2 cents
DeltaP
09-02-2013, 07:59 AM
I've never had a new freeze plug blow out of the block. It would take an awful lot of pressure to unseat a proper size and seated plug. I've also never installed them with what looks like RTV as a sealant. They appear to be new freeze plugs. Maybe it just wasn't installed/seated correctly. It looks fairly easy to get at so I'd try a new proper sized plug in a properly prepped hole with maybe a slight coating of permatex or shellac and make sure the coolant system is bled out properly. If it continues to push out coolant I'd be suspecting the head gasket or a cracked/warped head. Fel Pro gaskets can only do so much. Steam can also create tremendous pressure in a short amount of time.
12Ounce
09-02-2013, 10:00 AM
There is something seriously wrong with the cooling system ... it may be simple, and easy to fix ... but it is serious.
When you rebuilt the engine ... was the block "vatted"? That usually cleans the block down to bare metal, including the coolant passages.
As things are reassembled, the coolant passages have to be kept clean ... of shop rags, gunk, etc, etc. Is the radiator clean? Try running with out a thermostat as a test.
..... Also if the heads were serviced by a shop, they usually glue on a little temp sensitive plug that will "record" any high temperature event. ??
When you rebuilt the engine ... was the block "vatted"? That usually cleans the block down to bare metal, including the coolant passages.
As things are reassembled, the coolant passages have to be kept clean ... of shop rags, gunk, etc, etc. Is the radiator clean? Try running with out a thermostat as a test.
..... Also if the heads were serviced by a shop, they usually glue on a little temp sensitive plug that will "record" any high temperature event. ??
ajb0009
09-02-2013, 10:05 AM
It looks like the plug came out of the head, not the block, correct? Did you contact Moore's where you purchased the heads from? It does look like it was put in with some type of sealant, which I have not heard of being done either. I am a little concerned that you were initially having problems getting the system bled (pushing back into overflow bottle), but in the end it seems like it was good (heat out of both cores in back). My guess would be that the plug was not installed correctly by Moore's. By the way, hats off to you for undertaking such a gigantic project. I have not heard of anyone having the problem that you had on a 3.8.
northern piper
09-02-2013, 07:22 PM
it "would" take a lot of pressure to blow out a plug (never heard of that happening ever... aside from when fluid has frozen in an old flathead V8 I've worked on and that pressure popped the plug out) so I'm thinking replace the plug with a new one, confirm normal pressure, and hope that the plug was poorly installed. I too haven't used or heard of any sealant for installing freeze plugs, tho I know for instance that when some people work on rear dif seals or bearing/seals behind wheels they'll use some gasket sealant, despite it not being called for in any manual.
I'd carefully document what has happened tho as, as 12ounce says, maybe something got left in a passageway during reassembly and that isn't your responsibility.
I'd carefully document what has happened tho as, as 12ounce says, maybe something got left in a passageway during reassembly and that isn't your responsibility.
tomj76
09-03-2013, 11:42 AM
Consider the pressure needed to blow out a properly seated freeze plug, vs. the maximum pressure of the radiator cap, or the radiator, or the hoses...
So, you either have a way for pressure to build up in the head without entering the rest of the cooling system (in fact so isolated that it blew out the freeze plug without relieving that pressure into the cooling system), OR the freeze plug was never properly installed.
If a restriction is the reason for the failure of the freeze plug, then it seems likely that there needs to be TWO restrictions to create a space for extreem steam pressure to build up. Those restrictions might allow some coolant to pass (in fact they need to allow coolant to pass well enough to fill the cavity) so the pressure could be relieved if the rate of boiling was slow. However, when the engine is running to put out power to propelle the car, then you would be adding heat at a much faster rate, and the steam might not be able to escape quickly enough to relieve the pressure, leading to enough pressure to blow out the plug.
You might try draining what is left of your coolant, then fill the radiator with water. I don't think you'd need to remove the thermostat, because the bypass will carry sufficient volume of water for this test. If the water poors out the freeze plug slowly, then this implies a restriction.
One possible way to create a restriction like this is to put the head gasket on with the wrong orientation.
So, you either have a way for pressure to build up in the head without entering the rest of the cooling system (in fact so isolated that it blew out the freeze plug without relieving that pressure into the cooling system), OR the freeze plug was never properly installed.
If a restriction is the reason for the failure of the freeze plug, then it seems likely that there needs to be TWO restrictions to create a space for extreem steam pressure to build up. Those restrictions might allow some coolant to pass (in fact they need to allow coolant to pass well enough to fill the cavity) so the pressure could be relieved if the rate of boiling was slow. However, when the engine is running to put out power to propelle the car, then you would be adding heat at a much faster rate, and the steam might not be able to escape quickly enough to relieve the pressure, leading to enough pressure to blow out the plug.
You might try draining what is left of your coolant, then fill the radiator with water. I don't think you'd need to remove the thermostat, because the bypass will carry sufficient volume of water for this test. If the water poors out the freeze plug slowly, then this implies a restriction.
One possible way to create a restriction like this is to put the head gasket on with the wrong orientation.
12Ounce
09-03-2013, 12:34 PM
Tomj76 applies some commendable logic to the problem :... How indeed could pressure exert a force on the freeze plug without that same pressure being felt on the pressure relief cap, etc. etc..?? Good stuff!
But I would add that pressure might have been only the secondary player. If there was a "hot spot", a coolant void perhaps, in the cylinder head ... thermal expansion in the aluminum head may have caused the head to expand away from the plug ... allowing it to almost fall out on its own.
But whose to say .... it may have indeed been a poor installation of the plug. ??
But I would add that pressure might have been only the secondary player. If there was a "hot spot", a coolant void perhaps, in the cylinder head ... thermal expansion in the aluminum head may have caused the head to expand away from the plug ... allowing it to almost fall out on its own.
But whose to say .... it may have indeed been a poor installation of the plug. ??
tomj76
09-03-2013, 08:07 PM
Good point that if the head overheats, there might be a loosening of the freeze plug.
I checked the CTE of steel vs. alumium (since the plug is probably steel while the head is definitely aluminium). This may not be the right comparison since the freeze plug is bent from sheet metal, and the internal stress of the steel after bending may actually be more important for how tight the plug is held in the hole as the head overheats than the expansion of the metals. However, the steel certainly expands more slowly than the aluminium, which means that the hole gets larger more rapidly than the plug filling it, causing it to get loose.
The difference is ~6 ppm/degF, so a head that reaches 300 degF with a 1" dia freeze plug might have 6 ppm/degF * 300 degF * 1" = 0.0018" more clearance. I think the tendency of the freeze plug is to try to flatten out as it gets hotter, which counteracts the CTE effect, but that's just my guess.
Either way a hot freeze plug says that coolant isn't flowing to that spot very well, and the only question to answer is why. However, if coolant flows to the plug very easily, then other than the possiblity that a different spot could be getting hot instead, the plug could have been poorly installed. In that case it might be worth inspecting the other plug(s) for tightness.
I checked the CTE of steel vs. alumium (since the plug is probably steel while the head is definitely aluminium). This may not be the right comparison since the freeze plug is bent from sheet metal, and the internal stress of the steel after bending may actually be more important for how tight the plug is held in the hole as the head overheats than the expansion of the metals. However, the steel certainly expands more slowly than the aluminium, which means that the hole gets larger more rapidly than the plug filling it, causing it to get loose.
The difference is ~6 ppm/degF, so a head that reaches 300 degF with a 1" dia freeze plug might have 6 ppm/degF * 300 degF * 1" = 0.0018" more clearance. I think the tendency of the freeze plug is to try to flatten out as it gets hotter, which counteracts the CTE effect, but that's just my guess.
Either way a hot freeze plug says that coolant isn't flowing to that spot very well, and the only question to answer is why. However, if coolant flows to the plug very easily, then other than the possiblity that a different spot could be getting hot instead, the plug could have been poorly installed. In that case it might be worth inspecting the other plug(s) for tightness.
BubbaFL
09-08-2013, 12:38 PM
It looks like the plug came out of the head, not the block, correct? Did you contact Moore's where you purchased the heads from? It does look like it was put in with some type of sealant, which I have not heard of being done either.
The core plug came out of the left head. I'm not sure what the blue stuff is - it's hard as a rock, definitely not RTV.
Moore's said they have only heard of this kind of thing once or twice, and suggested that there might have been an air pocket.
I replaced the freeze plug with a rubber one (their suggestion), and it seems to be holding just fine.
Seems like it was either an air pocket, or just an improperly installed / defective freeze plug.
Thanks to all who replied!
The core plug came out of the left head. I'm not sure what the blue stuff is - it's hard as a rock, definitely not RTV.
Moore's said they have only heard of this kind of thing once or twice, and suggested that there might have been an air pocket.
I replaced the freeze plug with a rubber one (their suggestion), and it seems to be holding just fine.
Seems like it was either an air pocket, or just an improperly installed / defective freeze plug.
Thanks to all who replied!
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