Overheating 4.6L

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broncocliff
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Overheating 4.6L

Post by broncocliff »

Hey all, I need some serious input on what to do next with my stroker. I have searched and read all the forum threads with in this website, which was about 20 pages worth. This thing has been a nightmare since I started this project, cam bearing failure 5 times and now overheating.
This build only has 300 miles on it and now that it is hot it is overheating.
Here are the symptoms over 75*f ambient in Denver, Colorado, a moderate pull up a hill at about 50-60 mph for over 2 minutes. It will go up to 235-240* then the check gauges comes on. Let off the gas a bit and pull off and comes back down to 220* and will be good till another moderate hill climb. It has never boiled over or even puked fluid into the coolant reservoir which is really odd. I installed a mechanical coolant gauge in the port at the back of the head to confirm temperature on dash and it actually shows it getting up to 250*. During last winter it was pretty good when it was cool out.
Engine has a edelbrock head on it, decked block, comp cam, new high flow water pump, new thermostat (3 of them), 3 core all brass csf radiator, new radiator cap, new lower hose with spring in it. Electrical fan is working and mechanical fan clutch is new. I have tried a stock water pump with no change, tried chrysler anti-freeze with no change, wetter water no change.
I have a bosch wide band O2 and it is at 12-13 on the hill climbs so it is not a lean condition. I removed the cat to make sure it was not bad and causing heat, no change there. There are no codes but I tried a new pcm also.
Next thing I was going to try was an all aluminum cold case 2 core radiator, they claim it will cool better then the 3 core. I'm out of ideas from here. I even pulled the head back off to make sure it wasn't the head gasket leaking. This has been a long road with this motor, over 5 years and still not confident in driving it to the mountains.
I have 35" tires and 4.56 gears with a manual transmission.
Please any help would be appreciated.
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Re: Overheating 4.6L

Post by KarmaKannon1 »

Sounds like you have gone through a lot so far. My old Cherokee would run warm and then the radiator went and I installed the nicer of the choices at autozone. Never had an issue after that. I've seen so many mixed reviews on jeep radiators that I'm not sure if high dollar is the way to go or not. A few things I would check if it were my Jeep overheating...
Fan shrouds are intact? I'm assuming yes, but you never know.
Ac condenser isn't clogged and restricting airflow?
Thermostat is working correctly?
I'd also check the temperature drop from one side of the rad to the other. I saw a guy on NAXJA a few years back and he installed a flow restrictor because he thought the coolant was flowing through the radiator too fast to efficiently cool it. If I recall he made it from a cutting board and it did work. Once again, if I recall. Might be worth a shot.
Good luck!
broncocliff
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Re: Overheating 4.6L

Post by broncocliff »

Thanks for the reply. Fan shrouds are intact and good. I installed a new condenser also, Thought it was restricting airflow. Yeah thermostat is opening up and flowing. I have tried 3 different ones. The temperature at the radiator was 190* inlet and 175* outlet when the thermostat housing is 215-218.
I will look into the flowing through the radiator.
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Re: Overheating 4.6L

Post by Cheromaniac »

Unless the 3-core radiator is 50% thicker than the 2-core, each core will be smaller in diameter and flow less coolant. I once tried an aftermarket 3-core radiator in my Jeep and it ran 10-15*F hotter than the stock radiator.
I suggest you go for a slightly thicker than stock 2-core aluminum radiator. Aluminum dissipates heat faster than brass/copper and also saves some weight.
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Bertismyname
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Re: Overheating 4.6L

Post by Bertismyname »

What is your compression ratio? And what cam are you running? If you are at the higher end of the dynamic compression ratio range for pump gas you might be having a detonation issue. Also the altitude is not helping.

Have you tried hood louvers and sealing the frontal are of the jeep, forcing air through the radiator only?

Do you have oil coolers in front of your radiator?
Is your fan clutch working?
I worked in a jeep dealership for about 7 years. I rarely saw a jeep overheating for what appeared to be no reason.
Are you 100% sure that you got all of the air out of the cooling system.
I fill jeep cooling systems by pulling the heater hose off of the thermostat and sticking a trans. Funnel in the thermostat housing and filling it with the front of the jeep in the air. These engines are prone to trapping air at the rear of the engine. If you have a coolant temp sensor at the rear of the head you can pull that out while filling. That will help push 90% of the air out.
Good luck.
broncocliff
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Re: Overheating 4.6L

Post by broncocliff »

Bertismyname wrote: July 15th, 2020, 7:15 am What is your compression ratio? And what cam are you running? If you are at the higher end of the dynamic compression ratio range for pump gas you might be having a detonation issue. Also the altitude is not helping.

Have you tried hood louvers and sealing the frontal are of the jeep, forcing air through the radiator only?

Do you have oil coolers in front of your radiator?
Is your fan clutch working?
I worked in a jeep dealership for about 7 years. I rarely saw a jeep overheating for what appeared to be no reason.
Are you 100% sure that you got all of the air out of the cooling system.
I fill jeep cooling systems by pulling the heater hose off of the thermostat and sticking a trans. Funnel in the thermostat housing and filling it with the front of the jeep in the air. These engines are prone to trapping air at the rear of the engine. If you have a coolant temp sensor at the rear of the head you can pull that out while filling. That will help push 90% of the air out.
Good luck.
No oil coolers in front of the a/c condenser. Fan clutch is new and is working, I tried a grand cherokee fan clutch also with no change. That thing was an power grabber, dogging the engine bad with that clutch.
I use a snap on cooling system vacuum filler, it puts a vacuum on the hole cooling system so there is no air left in it. I could try to pull that sensor and make sure there is no air in the system.
broncocliff
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Re: Overheating 4.6L

Post by broncocliff »

Cheromaniac wrote: July 14th, 2020, 10:30 pm Unless the 3-core radiator is 50% thicker than the 2-core, each core will be smaller in diameter and flow less coolant. I once tried an aftermarket 3-core radiator in my Jeep and it ran 10-15*F hotter than the stock radiator.
I suggest you go for a slightly thicker than stock 2-core aluminum radiator. Aluminum dissipates heat faster than brass/copper and also saves some weight.
Ok thanks for the reply, I think the last step is to try the cold case 2 core radiator. If that doesn't work, may be going back to stock and selling this freaking thing!!
broncocliff
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Re: Overheating 4.6L

Post by broncocliff »

I do have hood louvers I ordered but haven't put them in yet. Seems like at highway speed it should be blowing enough air out to not need them. I got them more for wheeling and slow mountain driving. I will try to get those installed and see if that makes a difference.
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Re: Overheating 4.6L

Post by gonridnu »

I run a 3 row copper brass radiator with a 4.7 in Las Vegas and it cools fine in triple digit temperatures. I doubt your problem lies there. Hood Vents are not the answer for an overheating problem like this. If they do indeed help it will only mask what is going on. I am curious about the rest of the jeep. Do you have a winch and lights that might be impeding air flow? Also what is the over bore on your block?

It does sound like you have hit the bases though.

I used to own an engine shop and I have seen where a freeze plug gets knocked into the block and does not get removed causing an overheating problem.

I would check your total under load timing with an adjustable gun to be sure it isn't retarded as that will build heat. I would also consider getting a Hesco water pump with a billet impeller that is a better design than stock. I saw a noticeable difference on my gauge (did not verify with mechanical 'cause I don't have an overheat problem). It may not solve what is going on but it might help.

My compression is 9.3ish -1 static and I forget the dynamic number these days but it was on the high end of acceptable. You can get away with a full point more compression at altitude of about 4500 feet. You can also get away with almost a full point more compression with an aluminum head. I am curious if you took those into consideration? I run a little under geared right now with a 34" tire on a 4:11 gear. My winch sits way down in my bumper and does not obstruct airflow at all. I do run the stock factory tranny cooler and of course A/C if mandatory here. Just throwing some stuff at the wall to see if anything sticks.
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Re: Overheating 4.6L

Post by Flynhigh »

Did you solve your overheating problem? If not hear is a crazy idea. Is the water pump turning the right way. I briefly read about different pumps on jeeps having impellers that needed to be rotated either clock wise or counter clockwise depending on the application.
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Re: Overheating 4.6L

Post by Jeepdad »

On this forum and others I constantly see threads about 4.0 or stroker overheat issues. For background I have worked for US Korean and Japanese service departments among other automotive related areas since 1999. There is a reason that manufactures will void power train warranties on lifted vehicles with bigger tires it puts more stress on all the components it’s like towing all the time with worse aerodynamics and more rolling resistance. That being said if you are on this forum you either have a Jeep with a stroker or or going to build one and most likely you have a lift and or bigger tires. Most strokers are on engines bored 30 over here is a fact bored over engines will have less cast iron to remove heat and place the combustion chamber closer to the oil and coolant galleys. Every 10 over bore on a 4.0 the engine will run 10 degrees hotter so 30 over is another 30 degrees to operating temperatures. Then add the extra load from heavier tires and more rolling resistance and worse aerodynamics and people ask why they run hot or overheat. My XJ was not designed to work like that with a factory cooling system and to make it worse it was originally set up the 1st few years with a much smaller 2.8 V6 and the surface area for the grill that your air for cooling is coming through never got bigger when they squeezed in a 4.0 I6. You need to upgrade the cooling and oil cooling system to fix the issue. Once you have determined that you don’t have a major issue like a blown head gasket buy better than stock items. You don’t see NASCAR using parts from Rockauto do you? Get a radiator with more capacity I run a Mishimoto it takes an extra gallon over stock and for good measure I also run water wetter with my 50/50 mix. Next a high flow billet water pump I use a flow cooler it you get a “high flow pump” from the parts store and the impeller looks like the factory one return it and get a real performance one. Fans I deleted the factory setup run a Mishimoto triple electric fan with a shroud and a fan speed controller. I also have a Mishimoto 180 degree thermostat and Mishimoto radiator hoses. Next you need to cool you oil I run a flow cooler for up to 500 hp have it in front on my ac condenser and have a plate on the oil filter so now I have a 7.5 quart oil change versus the 6.0 stock 25% more oil will help to cool as much as extra coolant does. Spark plugs also matter if you gave stock compression you are fine but I am 2 points over stock and have to run premium gas if this is you then you usually need a cooler plug I run a 2 step cooler plug. Cold air is the best and a snorkel is the coolest air I have regular k&n intake as I don’t want a snorkel but I do have a hood that is not only vented but has spacers so it’s like a cowl hood plenty fresh air in and let’s hot engine heat out. Exhaust cannot be stock with a stroker you for sure will need a header and full down pipe and exhaust I run 2.5 inch but that is holdover from pre stroker and will be upgrading to 3 inch next year. Lastly for cooling I have 1 extra trick on an XJ behind the bumper in the core support there are 2 good size holes with about 7 inches high and if I remember correctly 21 inches long. I took a hole saw put 4 holes in the center of the bumper bought a 6x7x2.5 inch aluminum heater core and have it hooked to a Spal fan and have it running in a separate loop that would normally run on the factory heater core loop. This is kind of overkill but if it is ever super hot and it’s crawling and I don’t have the benefit of air at highway speed I can flip the switch and I now have a second custom radiator. Plenty of factory forced induction cars such as the Camaro Zl1 have extra radiators that actually has 3 the main one and 1 in the front of each front wheel well. Between the custom radiator and my Mishimoto I have 2 extra gallons of coolant. We had almost 30 days in the 90’s where I live and my Jeep runs at 210 I could have it run cooler if I wanted but I have the Fan speed controller set up to keep it in factory operating range. You want to stay near factory temps it will remove the moisture from your oil make sure that the oil viscosity is correct for your engine internals and get you the best mileage. I know this is a long post but a few things to consider 4.0 and stroker engines in lifted Jeeps will run hot. You need to remove heat and you can’t go with cheap parts on a custom rig and expect premium results and sometimes you need to think outside the box like my custom auxiliary radiator. Things like removing a thermostat or putting a hole in it don’t work also a high speed pump removes coolant fast you do not want it to sit long in the engine were it can boil. I hope this helps people and that is why I posted this.
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Re: Overheating 4.6L

Post by tommy »

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