Radiator cap / heater core

[Coadster32]

Bypassed my heater core today. Easy work, and no issues.

I did get to thinking though...I smelt anti-freeze when I first turned the heat on after the engine got to temperature. This lasts for about 5-10 seconds or so, and then the smell goes away, (after windows are opened of course). No leaks at all in the cab area, and not much if any anti-freeze goes missing. The leak that I have can't be that big, and was thinking perhaps if I switch the radiator cap to a lower pressure, maybe my leaking heater core wouldn't be much of an issue. (yes, I know it's going south). How might this effect the jeep overall though? I know that a lower pressure cap will lower the boiling point, so I could leave the 18lb cap and bypass in for the summer.

Looking for thoughts on running this 4.0L with a lower cap for the winter.

 

[Steel City 06]

You could try Bar's Leaks tablets. Crush them up and drop them in the radiator cap. Basically, it works like the pepper trick, and eventually the debris clogs up any leaks. It's a hack solution but it may work.

 

[Coadster32]

Update to this:

Swapped to a 10lb cap, reconnected the heater core, put in some GM tablets, and have been running all summer in high temps. Jeep doesn't overheat. The A/C works perfectly, but when I switch it to heat, I can still smell the antifreeze.

 

[macleanflood]

Probably have a pinhole leak in your heater core. Might want to pull your dash now before it gets cold.

-Mac

 

[bohuggabee]

Bypassed my heater core today. Easy work, and no issues.

I did get to thinking though...I smelt anti-freeze when I first turned the heat on after the engine got to temperature. This lasts for about 5-10 seconds or so, and then the smell goes away, (after windows are opened of course). No leaks at all in the cab area, and not much if any anti-freeze goes missing. The leak that I have can't be that big, and was thinking perhaps if I switch the radiator cap to a lower pressure, maybe my leaking heater core wouldn't be much of an issue. (yes, I know it's going south). How might this effect the jeep overall though? I know that a lower pressure cap will lower the boiling point, so I could leave the 18lb cap and bypass in for the summer.

Looking for thoughts on running this 4.0L with a lower cap for the winter.

Im confused. Bypassing the heater core and using the heater? Its now just a fan... but if you had a leaking core. There will be residuals in the ducts. Until those burn off or dry. The engine itself will still add some heat to the ducts. And also. Because you removed what is basically a secondary radiator. Less coolant. The engine is going to run a little hotter...

 

[mrblaine]

Less coolant. The engine is going to run a little hotter...

I'm not following how a smidge less coolant is going to affect radiator function. That sound alarmingly like folks who insist that a larger oil filter with increased capacity or a larger trans pan's extra capacity will keep either cooler. It doesn't, it just takes a bit longer to reach the same operating temps.

 

[bohuggabee]

I'm not following how a smidge less coolant is going to affect radiator function. That sound alarmingly like folks who insist that a larger oil filter with increased capacity or a larger trans pan's extra capacity will keep either cooler. It doesn't, it just takes a bit longer to reach the same operating temps.

I made a post trying to find that exact answer. But the heat equates to flow rate, Bernoulli's principle of volume and flow, and your volume of the overflow reservoir. I couldnt find any specs on the engine to exactly calculate. However, yes it wont be a big issue for now. But i suspect the secondary radiator for the heating of the ducts. Is multifunctional. Its designed to fail first and this means the rest of the engine reduces overall acidity from the coolant circulation or mineral deposits inherent in wear

I learned that adding water instead of coolant before a drive cleans the system better. But dont add too much obviously... just adding a hair more to a mixture. It should prevent the erosion of the reduced heater core functionality. By making the solution more base

 

[mrblaine]

I made a post trying to find that exact answer. But the heat equates to flow rate, beenoullis principle of volume, and your volume of the overflow reservoir. I couldnt find any specs on the engine to exactly calculate. However, yes it wont be a big issue for now. But i suspect the secondary radiator for the heating of the ducts. Is multifunctional. Its designed to fail first and this means the rest of the engine reduces overall acidity from the coolant circulation or mineral deposits inherent in wear

You use a lot of words to make it sound like you know what the problem is. Heat is flow rate but not due to Bernoulli, but instead to how open the thermostat is.

 

[bohuggabee]

You use a lot of words to make it sound like you know what the problem is. Heat is flow rate but not due to Bernoulli, but instead to how open the thermostat is.

I use lots of words because thats how simple i can explain it. I dumbed it down actually. I study physics man... i love my jeep. Im trying to help people because all i see are trolls now instead of machine heads. I WENT TO GET OIL the girl though i was hitting on her at o reilly’s. Talking about the new mobile 1 vs castrol. Thats how dumb everyone is now. You cant even discuss oils and molecular bonding for boundary layers and viscous resistance to either improve or ruin and engine.

 

[mrblaine]

I use lots of words because thats how simple i can explain it. I dumbed it down actually. I study physics man... i love my jeep. Im trying to help people because all i see are trolls now instead of machine heads. I WENT TO GET OIL the girl though i was hitting on her at o reilly’s. Talking about the new mobile 1 vs castrol. Thats how dumb everyone is now. You cant even discuss oils and molecular bonding for boundary layers and viscous resistance to either improve or ruin and engine.

Maybe try dumbing down to how it works?

 

[bohuggabee]

You use a lot of words to make it sound like you know what the problem is. Heat is flow rate but not due to Bernoulli, but instead to how open the thermostat is.

https://en.m.wikipedia.org/wiki/Bernoulli's_principle

Learn something. Maybe we can actually have a conversation. Im always figuring things out on my own. Im sick of it. I cant talk to anyone... because im called a troll for being smart. Then i get banned for educating and helping people...

 

[mrblaine]

https://en.m.wikipedia.org/wiki/Bernoulli's_principle

Learn something. Maybe we can actually have a conversation. Im always figuring things out on my own. Im sick of it.

I'm aware of the principle and as I stated, it isn't being exploited as you stated. The flow through the system is controlled by the thermostat.

 

[bohuggabee]

I'm aware of the principle and as I stated, it isn't being exploited as you stated. The flow through the system is controlled by the thermostat.

Then i need to see the thermostat to understand why. I changed one on a dodge dakota once stranded in missouri. But i have no idea where it is on my jeep. In that experience. The engine ran cold because the thermostat was useless. It was stuck wide open. Really no reason for them other than modulating thermostatic radiation to the fuel mixture. It got hot. The dodge. So the resistance of the flow of collant prevented the entire system from over heating?

 

[mrblaine]

Really no reason for them other than modulating thermostatic radiation to the fuel mixture.

That's like saying there is no reason for the radiator except to keep the coolant from getting hot. The engine needs to operate within a certain temp range. It is typically more important for it not to exceed an upper limit that causes a breakdown in sealing and lubrication by heat degradation inherent to most lubricants we use. Running too hot is bad for many things. The lower limit is important to a point but mainly what we need is a coolant that doesn't freeze solid and break things.

So the resistance of the flow of collant prevented the entire system from over heating?

Restricting coolant flow via the thermostat is just stopping it from being circulated through the radiator via the water pump.

 

[Steel City 06]

One of the important things with the heater core bypass is that it actually be a bypass and not just deadheading the flow through the hoses connecting the heater core.

As best I can tell there is no integral bypass to the water pump in the 4.0 I6, so simply blocking off flow to and from your heater core can indeed cause some overheating issues since the coolant isn't recirculating through the block.

With deadheaded flow, up until the point the thermostat opens, the lack of coolant flow will result in major hotspots and cold spots within the engine block, in turn causing large thermal expansion stresses, which can either cause a failure outright or result in fatigue cracking in the block through many warm up and cool-down cycles. It can also cause coolant inside the pump to cavitate (or even boil in extreme cases) which will quickly destroy the water pump.

As for just bypassing the heater core, that should not cause any significant issues. As long as the recirculation path is maintained (at least until the thermostat opens) there will be no significant changes in the ability of the system to reject heat through the radiator.

 

[mrblaine]

One of the important things with the heater core bypass is that it actually be a bypass and not just deadheading the flow through the hoses connecting the heater core.

As best I can tell there is no integral bypass to the water pump in the 4.0 I6, so simply blocking off flow to and from your heater core can indeed cause some overheating issues since the coolant isn't recirculating through the block.

With deadheaded flow, up until the point the thermostat opens, the lack of coolant flow will result in major hotspots and cold spots within the engine block, in turn causing large thermal expansion stresses, which can either cause a failure outright or result in fatigue cracking in the block through many warm up and cool-down cycles. It can also cause coolant inside the pump to cavitate (or even boil in extreme cases) which will quickly destroy the water pump.

As for just bypassing the heater core, that should not cause any significant issues. As long as the recirculation path is maintained (at least until the thermostat opens) there will be no significant changes in the ability of the system to reject heat through the radiator.

I don't know how it works but it seems to me that if the heater core isn't the integral bypass, then the pump is deadheaded against the thermostat until it opens some. If the HC is, then that likely means the coolant in the block has to be circulating through the HC. Or, the pump can dead head against the thermostat with no ill effect. What am I missing?

I am not in any disagreement whatsover about connecting the heater hoses to each other to form the bypass. Just trying to understand the rest of it.

 

[DuckNut]

I don't know how it works but it seems to me that if the heater core isn't the integral bypass, then the pump is deadheaded against the thermostat until it opens some. If the HC is, then that likely means the coolant in the block has to be circulating through the HC. Or, the pump can dead head against the thermostat with no ill effect. What am I missing?

I am not in any disagreement whatsover about connecting the heater hoses to each other to form the bypass. Just trying to understand the rest of it.

You are correct in your thinking. Coolant is not being circulated until the thermostat opens.

Here is a small caveat. There are some thermostats that have a hole in the flange. This hole allows a small amount of coolant to always be moving. This is beneficial for a couple reasons. If you happen to have a small amount of ice in the lines or core this water may break it, melt it, or move it along to a larger cavity so when the thermostat opens there is not a lot jam with pressure being added possibly rupturing the system. Second, the hole cuts down on cavitation. Cavitation wears out pieces.

 

[Link]

You are correct in your thinking. Coolant is not being circulated until the thermostat opens.

Here is a small caveat. There are some thermostats that have a hole in the flange. This hole allows a small amount of coolant to always be moving. This is beneficial for a couple reasons. If you happen to have a small amount of ice in the lines or core this water may break it, melt it, or move it along to a larger cavity so when the thermostat opens there is not a lot jam with pressure being added possibly rupturing the system. Second, the hole cuts down on cavitation. Cavitation wears out pieces.

Why would you have ice in a proper coolant mix? If you don’t have enough antifreeze in the engine, you won’t have to worry about a blockage in your cooling system….your cracked block will be a much greater issue for you.

 

[DuckNut]

Why would you have ice in a proper coolant mix? If you don’t have enough antifreeze in the engine, you won’t have to worry about a blockage in your cooling system….your cracked block will be a much greater issue for you.

It has nothing to do with proper mixture. It has everything to do with cavitation and improper mixture (which happens all the time).

 

[Link]

It has nothing to do with proper mixture. It has everything to do with cavitation and improper mixture (which happens all the time).

Ummm…reread what you just posted. You just contradicted yourself.

And the hole in the thermostat, if you have one is to allow air bubbles to rise and ultimately rise into the upper radiator hose and ultimately bleed the engine of small amounts of air. The amount of coolant that flows through that tiny hole is insignificant.

No cooling system, if filled with the right mixture, will EVER have ice in it. Never.