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Old 02-27-2011, 04:46 PM   #126
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The pressure and temperature is not even in the entire system. It's kind of like high and low pressure areas in the Earth's atmosphere.
It's all vented in the same place though isn't it? There is only about 5 lbs pressure in the coolant system on a Volvo. American cars in the1960-80s ran more coolant system pressure , some up to 15 psi, and nowadays more than that. They never "blew" freeze plugs. It'll take more than 5-20 psi to unseat a freeze plug.

Some need to realize that above 15-20 boost, is more than these engines were intended to do without some other mods. Screw in freeze plug would be one of these IMO.

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Old 02-27-2011, 06:45 PM   #127
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Some more food for thought... I've seen/heard of freeze plugs coming out in b21FTs that are nearly stock, with maybe raised boost but not necessarily much else. I can't remember if those were previously replaced freeze plugs or not though. Still, something, aside from super power levels can also have an effect on plugs popping out.
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Old 02-27-2011, 06:49 PM   #128
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Yeah, if the water in blocck freezes or the wrong size plug is installed. I've owned a LOT of b21s & B230, have one with over 500,000 on it. Freeze plugs still in it.
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Old 03-05-2011, 07:14 PM   #129
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It's all vented in the same place though isn't it? There is only about 5 lbs pressure in the coolant system on a Volvo. American cars in the1960-80s ran more coolant system pressure , some up to 15 psi, and nowadays more than that. They never "blew" freeze plugs. It'll take more than 5-20 psi to unseat a freeze plug.

Some need to realize that above 15-20 boost, is more than these engines were intended to do without some other mods. Screw in freeze plug would be one of these IMO.
If you notice from a previous post i made here, i dont think these freeze plugs blowing out should be happening, of course.

But my point is, there's going to be locally occuring high pressure spots in the water passages in the block. They probably dont last very long, but they happen. Just like the water isnt 200 degrees in the whole block. It's all vented in one place, and thats exactly why high pressure spots can occur. The pressure has to work its way back to the overflow bottle...which probably occurs pretty quickly.
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Old 03-05-2011, 07:21 PM   #130
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The water is under pressure right? Do yo really think that little bit of localized hotter water is standing still? No it's being piushed around by the pump.

It has a water pump, remember?
Tell ya what. take a block, seal up all water outlets/inlets. Pressurize it with 120PSI air pressure. See if plugs pop out. Or read this thread where someone already did this.
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Old 03-05-2011, 07:26 PM   #131
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The water is under pressure right? Do yo really think that little bit of localized hotter water is standing still? No it's being piushed around by the pump.

It has a water pump, remember?
Tell ya what. take a block, seal up all water outlets/inlets. Pressurize it with 120PSI air pressure. See if plugs pop out. Or read this thread where someone already did this.
I'm not the one that has ever had a freeze plug pop out, remember? No interest.

And no, the water is not standing still. And thats why the persure will never be 5 psi in the whole system. That hotter water moves into the radiator...and what replaces it? More water, which quickly becomes hotter....
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Old 03-05-2011, 07:32 PM   #132
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Oh, and yeah...my conclusions from this thread are pretty much that this is caused by block squirm...
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Old 03-05-2011, 07:41 PM   #133
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Oh, and yeah...my conclusions from this thread are pretty much that this is caused by block squirm...
Maybe that and poor installation or low quality plugs being used. I've had friends with cars putting out not even 200whp who've had their's pop out.
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Old 03-05-2011, 08:25 PM   #134
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And no, the water is not standing still. And thats why the persure will never be 5 psi in the whole system. That hotter water moves into the radiator...and what replaces it? More water, which quickly becomes hotter
LOL, you need to read upon how cooling systems work.

Block squirm is most likely the culprit on popping freeze plugs. That & wrong size plugs installed by machine shop, which has been covered in Maint section.
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Old 03-05-2011, 08:32 PM   #135
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LOL, you need to read upon how cooling systems work.

Block squirm is most likely the culprit on popping freeze plugs. That & wrong size plugs installed by machine shop, which has been covered in Maint section.

Sounds like you need to read upon how cooling systems work. To think that one vent in one place is going to keep the system the perfect pressure in the entire system is insanity.
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Old 03-05-2011, 08:42 PM   #136
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That is what the pressure release cap does. BTW, at first you said it was water pressure that forced the plugs out. then you say it's the block squirm. now you think there is more pressure in the cooling system than the cap allows for.


Don't you find it strange that American V8s with 2-3 times the cooling system pressure of a B20-b230 do not blow freeze plugs out?

Also, freeze plugs are design to come out if the water in block freezes & expands. If it takes that amount of pressure to unseat one, it seems to me 4-5 psi sure isn't going to do it.

Sure there are 'hot spots" in the block's water passages., most of them are in the cylinder head, and around the block at/near combustion chambers. The freeze plugs are not really all that close to these areas.
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Old 03-05-2011, 08:52 PM   #137
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That is what the pressure release cap does. BTW, at first you said it was water pressure that forced the plugs out. then you say it's the block squirm. now you think there is more pressure in the cooling system than the cap allows for.


Don't you find it strange that American V8s with 2-3 times the cooling system pressure of a B20-b230 do not blow freeze plugs out?

Also, freeze plugs are design to come out if the water in block freezes & expands. If it takes that amount of pressure to unseat one, it seems to me 4-5 psi sure isn't going to do it.

Sure there are 'hot spots" in the block's water passages., most of them are in the cylinder head, and around the block at/near combustion chambers. The freeze plugs are not really all that close to these areas.
You don't even have a clue who you're talking to.
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Old 03-05-2011, 08:58 PM   #138
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I'm sure you both know exactly who you're talking to, this is the internet.
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Old 03-05-2011, 09:11 PM   #139
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I'm sure you both know exactly who you're talking to, this is the internet.
haha....my point is, he's trying to argue with me about something i agree with him on, and have agreed with him on the entire time...I dont know why he thinks i said high pressure was pushing freeze plugs out. I just know that the system is not the same pressure at all points...its obvious. I never said it was enough to push freeze plugs out.

My dad used to have a v8 with 500 horsepower.....never had a freeze plug come out.

Infact....I've seen people have engines with water in them freeze, and not push the freeze plugs out.
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Old 03-05-2011, 09:23 PM   #140
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Old 03-06-2011, 04:08 AM   #141
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Electric pump and pump/fan controller installed and tried two days with hard driving with studded rally tires on a frozen lake. Worked excellent. Engine ran a little cold on highway driving in sub freezing temperatures. The controller will run the pump in pulsed mode until the set temperature is reached, but without the thermostat this was to much cooling. Davies Craig recommended to install the thermostat and drill two 5 mm holes in it to avoid pump cavitation when engine is warming up. This will not be necessary during the winter.

Next is a all aluminium radiator and a air valve connection on the expansion tank to run a 30 PSI pre pressurised cooling system. This will raise the boiling point of pure de-mineralised water to 250 deg F.
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Old 03-06-2011, 08:34 AM   #142
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youre driving with *wateR* in the radiator on a *frozen* lake?....
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Old 03-06-2011, 01:50 PM   #143
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I don't have cooling problems but I still worry about the freeze plugs. I choose to go with a high capacity aluminum radiator that keeps the engine happy under load in the heat. But, because of various issues I haven't done any high RPM tuning of my engine yet or done really any high RPM driving. I would go with an electric pump if there were a quality set-up available that enabled variable pump speed related to engine temp requirements. Seems like this would be a good way to speed engine warm-up as well by keeping pump off until coolant was warm.
Briliant! ide buy one.
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Old 03-06-2011, 02:02 PM   #144
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thermocline resistance is common to all crossflow ratiators. Best cure is biger flow radiaters{scun knuckels}
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Old 03-06-2011, 02:47 PM   #145
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youre driving with *wateR* in the radiator on a *frozen* lake?....
That is next, winter is soon over.
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Old 03-06-2011, 08:10 PM   #146
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That is next, winter is soon over.
Whats the point in not using antifreeze exactly?
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Old 03-07-2011, 06:35 AM   #147
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Water is the ultimate coolant, it has far better heat capacity and conductivity than antifreeze, so pure water will perform better. By running a pressurized system the boiling point of water will rise and local boiling will not be as likely.
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Old 03-07-2011, 06:56 AM   #148
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yeaah....Guess you dont live here.
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Old 03-07-2011, 07:24 AM   #149
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My dad used to have a v8 with 500 horsepower.....never had a freeze plug come out.
Sorry buddy, but 500crank out of a V8 is nothing, we're in Michigan, you should know this. . . not to mention it has no bearings whatsoever when it comes to Volvos.

This'll be a bit long, but give it a read.

I'm surprised nobody has mentioned this before, but the problem might be the saving grace pressure release cap that keeps being brought up over and over.

We've already established the following:
The two most likely causes of freeze plug blowouts are block vibrations, and localized pressure pockets.
When water is under pressure, the boiling point rises, as with any liquid.

Now, take your motor, operating at 10psi coolant pressure. Now floor it, build a bunch of boost, and a TON of heat. Now, find that one itty bitty spot where coolant creates a circulating current in the head/block instead of flowing to that radiatior. That water/coolant/mix of whatever you like in just a second or two can easily shoot up an extra hundred degrees or so. . . Sweet, no biggie, we have antifreeze, wetter, and system pressure to keep it from boiling. . .

Now, that pressure valve releases. This isn't some fancy valve, a little plastic doohicky with a spring. It might let the system hit 11psi, open and close right back up at 9psi. But what if it's just a little plastic doohicky that sticks open for ten seconds? Now you've lost nearly all cooling system pressure, and suddenly the boiling point of that extra-hot spot of water is suddenly twenty degrees too low?

BOOM! Flash boil, and now you've got a few ounces of water/antifreeze flashed into steam. If someone wants to do the math we could figure out what sort of localized pressure that'd create. . . the water sure isn't moving out of the way fast enough. . .

Given a large enough pocket of heat, you could easily see several hundred pounds of pressure when there was no more then ten half a second before.
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Old 03-07-2011, 07:55 AM   #150
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yeaah....Guess you dont live here.
Excellent and informative posts.
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