Have I cooked my 4.0? Epic mistake on long trip

KennethS

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In the past I have used straight water due to its greater ability to remove heat, but as noted that will result in rust and corrosion.

These days I run 25-30% glycol for the anti-corrosion benefits. That percentage gives me freeze protection down to 5-10ºF, which is adequate for here in the desert where it rarely gets below freezing, and I get the benefit of better heat capacity for the 115+ summer temps.
 

Gilaguy23

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Does antifreeze have a higher boiling point than water at a given pressure? I've always assumed that it did, but just realized that I don't actually know.

C&P'ed from a article. Long but interesting.
The specific heat capacity of ethylene glycolbased water solutions is less than that of pure water; in a 50 percent solution, ethylene glycol's specific heat capacity compared with pure water is decreased at least 20 percent at 36 degrees and about 17 percent at 200 degrees. Propylene glycol, another common coolant, has an even lower specific heat. Assuming a 100-gpm (gallons/minute) coolant flow rate and an energy loss through the coolant system of 189.5 hp, the water temperature increase would be 10 degrees, the ethylene glycol water mix would gain 20 degrees, and propylene glycol would gain 33.3 degrees.
Compensating for the reduced heat capacity of coolant/water mixes would require circulating more fluid through the system. Assuming a fixed amount of circulating fluid and radiator capacity, running 100 percent water would be the most efficient coolant in terms of its ability to conduct heat with minimal temperature rise. In other words, of all common liquids, water requires the most heat energy to change its temperature.

However, there are also differences in the vapor point of the three different coolants. Ethylene glycol and propylene glycol have higher vapor points and therefore can absorb heat at higher temperatures without boiling. Yet even with its lower vapor point, water still carries more heat per unit.Don't forget that the coolant is just one part of the total cooling-system "team." You can raise water's effective vapor point by using a higher-pressure radiator cap. For every pound of increased system pressure, water's boiling point goes up by 3 degrees. Higher boiling points also reduce evaporation losses, water-pump cavitation, and heat-soakinduced after-boil. You can get away with a higher system pressure by using a quality aluminum radiator that's rated for higher pressure than is a brass/copper radiator. Aluminum radiators can take more pressure because their tensile strength is greater than brass—this lets an aluminum unit use tubes with larger cross sections an thinner walls. A larger tube also has more wall-surface area, resulting in improved heat transfer.
 

Jerry Bransford

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In the past I have used straight water due to its greater ability to remove heat, but as noted that will result in rust and corrosion.

These days I run 25-30% glycol for the anti-corrosion benefits. That percentage gives me freeze protection down to 5-10ºF, which is adequate for here in the desert where it rarely gets below freezing, and I get the benefit of better heat capacity for the 115+ summer temps.
You can run the recommended 50-50 mix of water/coolant in the hottest desert conditions if you have the OEM Mopar radiator or a damned good non-cheap high-end radiator. Cheap online or store brand radiators have no excess cooling capacity so desert conditions can cause overheating problems where the factory cooling system won't have any at all. I spent 25 years wheeling in the SoCal deserts and even Arizona several times with the OEM cooling system never a cooling problem.
 

Paul Land

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Should I be considering lifting the head and replacing the head gasket or should I just keep driving it and keep an eye on it?

Not Toast but, definitely warm bread. This happened to me 3 times once by my driving. It becomes a ticking clock counting DOWN to CATO.
 

SkylinesSuck

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You said, " but after an extended run if I come to a complete halt the oil pressure drops to nearly zero and the check gauges light comes on".

I missed where he said that.

OP--oil pressure at cold start up will likely be 60psi+ at idle. Hot idle should be around 20psi. It changes with the temp/viscosity of the oil. If you have much less than 20psi at hot idle, either the sensor is bad (good chance) or you have bigger issues. The newer TJ gauges function more like idiot lights and don't present real pressure (I have heard). I don't remember what year you said you have.
You can run the recommended 50-50 mix of water/coolant in the hottest desert conditions if you have the OEM Mopar radiator or a damned good non-cheap high-end radiator. Cheap online or store brand radiators have no excess cooling capacity so desert conditions can cause overheating problems where the factory cooling system won't have any at all. I spent 25 years wheeling in the SoCal deserts and even Arizona several times with the OEM cooling system never a cooling problem.

As much as it pains me to say it, I have had 3 high end (3" thick and $400) aluminum radiators shit the bed. They started leaking each with less than a year of run time, 1 with zero time off road. I'm skeptical of any solid aluminum radiator in a TJ at this point. I have run them for years in high hp street cars with zero issues but my TJ no likey.
 

SkylinesSuck

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Not Toast but, definitely warm bread. This happened to me 3 times once by my driving. It becomes a ticking clock counting DOWN to CATO.

I wouldn't be so sure. A few things can happen with over heats. First off, you cook the oil so change that regardless. Second, you can blow a head gasket, usually from warping the head, both of which can be addressed. You can also distort the block so bad it puts the cylinders out of round (while the pistons stay round) which causes obvious bad things. Follow on issues can arise if you don't change burnt oil or fix a blown head gasket, but until you warp a head or distort the block to the point your cause damage to the cylinder walls, if you don't have a leaking head gasket, change the oil and send it.
 

Paul Land

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I wouldn't be so sure. A few things can happen with over heats. First off, you cook the oil so change that regardless. Second, you can blow a head gasket, usually from warping the head, both of which can be addressed. You can also distort the block so bad it puts the cylinders out of round (while the pistons stay round) which causes obvious bad things. Follow on issues can arise if you don't change burnt oil or fix a blown head gasket, but until you warp a head or distort the block to the point your cause damage to the cylinder walls, if you don't have a leaking head gasket, change the oil and send it.

Humm, My head's grinding.
head shot.jpg
 

TimV

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My .02 for what it's worth. Haha, see what I did there etc etc.....

OP, you said: "All happened within about 20 seconds from the first noise to the stall."

If that is accurate, very high probability your engine is just fine. It didn't run anywhere near long enough for damage that matters. Change the cooling bits you mentioned along with a thorough flush. Change the oil and filter. Deal with the oil pressure sender if it's actually a problem. Enjoy your TJ.

Everything else is excessive worry to no worthwhile benefit.

TimV.
 

Moglocker

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My .02 for what it's worth. Haha, see what I did there etc etc.....

OP, you said: "All happened within about 20 seconds from the first noise to the stall."

If that is accurate, very high probability your engine is just fine. It didn't run anywhere near long enough for damage that matters. Change the cooling bits you mentioned along with a thorough flush. Change the oil and filter. Deal with the oil pressure sender if it's actually a problem. Enjoy your TJ.

Everything else is excessive worry to no worthwhile benefit.

TimV.

Yes but the problem occurs (or could)losing all the water and having cool air take it’s place,might warp something?
 
OP
Bammo68

Bammo68

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Thanks all for the advice and input. I've ordered a new cooling system which was probably overdue anyway given the state of the OE radiator and will do a routine service / oil change and check. I've also ordered a new high quality head gasket set and will put that in the cupboard just in case...
 
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KennethS

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Phoenix, AZ
Jerry,
I’ve had the Jeep for 21 years and had the factory radiator (that split), an inexpensive aftermarket all aluminum (that failed in a weird way), and finally an auto parts store Murray brand aluminum/plastic. I have wheeled, daily driven in rush hour traffic, and road tripped in 110+ summer temps with the AC on with all of those radiators and have never run hot. Just my experience, but the two aftermarket non MOPAR radiators worked just as well as the factory original.
 

Gollywomper

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Jerry,
I’ve had the Jeep for 21 years and had the factory radiator (that split), an inexpensive aftermarket all aluminum (that failed in a weird way), and finally an auto parts store Murray brand aluminum/plastic. I have wheeled, daily driven in rush hour traffic, and road tripped in 110+ summer temps with the AC on with all of those radiators and have never run hot. Just my experience, but the two aftermarket non MOPAR radiators worked just as well as the factory original.

Cooling wise, aftermarket seem to do fine. It is longevity that they struggle. Lots of stuff will keep your engine cool, nothing seems to last longer than the factory Mopar radiator.
 
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Gollywomper

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I wonder if an aftermarket radiator made back in 1998 would last longer than an aftermarket radiator made in 2023.

Who knows. Manufacturing specifications dictate a lot of that. Aftermarket has no obligation to creat a product that lasts 20 years. If they did would they would be selling for half the price?
 
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