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Water temp climbing at higher speeds

LBarr2002

LIFETIME
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#1
I posted this on an LS swapper Wrangler FB group and got all kinds of answers. Most revolve around air flow, and got one suggestion I hadn't thought of.

5.3 4l60, 4.88s and 35s in stock appearing LJ. Superior radiator, fan, shroud combo with trans cooler. I have 1,250 miles on swap so far. Prior to last weekend, longest drive was 35 miles with 10 miles interstate. Around town and country roads temp runs 180-195. On the interstate after running 70 for 10 minutes or so, it'll creep up to 210, but as soon as back on country road at 55 it drops back to 195. Last Saturday we did 335 miles pretty much non stop. 60 mph 2 lane, mountain roads, some light trails, and 60 mph home. Temp was 195 for 100 miles to the mountains.. As soon as we hit the mountain climbs it went to 210 and creeped to 230 on one steep climb going slow in traffic. Rest of the day it stayed around 210, and all the way home at 210 except when we slowed down through small towns it would drop back to 195-200.

I know 210 is fine and what it would run in its stock vehicle, but its never stayed at 210 before and I definitely didn't like seeing 230. I have 2 theories.

1)Airflow at speed. I have an arb bumper, winch, stock fog lights. Would too much air be deflected at speed, or is it possible that the air under the hood doesn't have anywhere to go so not letting enough through radiator. I have some louvers I bought for vaporlocking on the 4.0 but never installed. Hood is damaged now so don't feel too bad about cutting it up.

2) Trans heating up and reducing efficiency of radiator. I could put a remote cooler with fan on it, but I don't necessarily like the electric fan under tub with water/mud. If I went this route, would you run it through both coolers or just the remote?

I don't feel like it's an issue with the radiator itself or the fan. At speed is the issue where fan capacity should be irrelevant.

Anybody experienced anything similar? What would you do?
 

LBarr2002

LIFETIME
SUPPORTER
#2
The suggestion I hadn't thought about was flaps in the fan shroud. Spal shrouds have cutouts with rubber flaps over them. At low speed, when the fan is doing the work, there is a low pressure area between the radiator and shroud keeping the vents closed and forcing all air to come through the radiator. At higher speeds, the flaps will open and allow air to pass through the shroud. I might start with taking off the lights, then drilling some holes in the shroud as second option.
 
#3
I feel like a remote cooler would fix your issue. Can you not mount it in the grille? If you did feel the need to utilize the cooler in the radiator I would plumb it to the remote cooler first. This would give you extra fluid as well and that alone would help keep it cool.
 

LBarr2002

LIFETIME
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#4
I feel like a remote cooler would fix your issue. Can you not mount it in the grille? If you did feel the need to utilize the cooler in the radiator I would plumb it to the remote cooler first. This would give you extra fluid as well and that alone would help keep it cool.
But wouldn't a secondary cooler in the grill still just heat up incoming air more? This is all still without AC too so thats going to make it worse.
 
#9
Upon other reading these engines come with a 210 degree stat in them and 220 isnt an issue at all for them. Does this thing have a new water pump in it?
 

LBarr2002

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SUPPORTER
#10
Upon other reading these engines come with a 210 degree stat in them and 220 isnt an issue at all for them. Does this thing have a new water pump in it?
New water pump and new oe replacement 186 degree thermostat.

Yeah, 210 doesn't bother me. Burgundy's yukon sits at 210 all the time, no matter what it's doing. I'd be fine with that.
 
#15
In another life, I ran into a guy who had stuffed a Vortec 8.1 into his TJ. He had cooling issues because the TJ engine bay did NOT move air out worth a darn. He ended up figuring out the airflow through the engine bay and added small 12v fans in the engine compartment to remove the excess hot air. He showed me, it was impressive.

Clarification questions: Is your cooling fan mechanical (fan clutch or direct drive) or electrical? Are the fans engaging properly? Also I'm going to make the assumption that there is plenty of coolant, no coolant air bubbles. Also you've allowed the cooling system to pressurize? Coolant pump in good shape/new? Not trying to be condescending, but ensuring there isn't something isn't mechanically wrong that needs to be addressed.

1. I would recommend with the engine on, at idle, see where the air is going in the engine bay. He used a piece of marking tape (or streamer, whatever) on a stick and mapped it that way. Then make engine bay airflow exits (passive or forced) from there. A few cheapo Northern Tool 12v fans zip tied temporarily would be a concept test. If it worked then you'd know what you needed to do. Or somehow propping up the hood hinges to allow hot air to exit at the rear of the hood (closest to firewall). Wouldn't look good but would provide a cheap and easy concept test.

2. I doubt your fog lights or ARB are "blocking" the air. Its not like its creating a massive vacuum. If anything its creating turbulent flow around the radiator but even then I doubt that as there is a fan creating a suction behind it. If you are keen, bust out the ye olde Fluid Dynamics book and have a go at some calcs. There is some suction behind the fog lights but not like its creating a massive void. Most turbulent flow would return to laminar fairly quickly. Same for the bumper.

3. Do some data logging. Get a cheapo OBD2 reader and data log a hill climb vs. driving your happy self to get some fried chicken vs. highway crusing. The main issue here is your engine load went WAY up in the hills and that is where all the temp is coming from (obviously). But the load can be quantified. See if there is a difference between highway loaded and slow traffic hill climb loaded. Do you have any sensors on the transmission? Can you record that? I doubt transmission heat is your main problem but it isn't helping. Also rule out the temp gauge itself. Is the engine actually overheating or is the gauge faulty? Make sure that is checked before going down the rabbit hole.

4. Your AC work? Go in the hills and hit the AC. The condenser has a fan and will naturally push extra air across the cooling package. See what that does. I have seen vehicle engine temps cool off with the AC on because of the sudden introduction of an extra fan.

I would say this needs to be addressed soon. Its only going to get hotter and driving around with eyes glued to the temp gauge isn't fun.

This is all I can think of right now. Imma go grill.
 

LBarr2002

LIFETIME
SUPPORTER
#16
In another life, I ran into a guy who had stuffed a Vortec 8.1 into his TJ. He had cooling issues because the TJ engine bay did NOT move air out worth a darn. He ended up figuring out the airflow through the engine bay and added small 12v fans in the engine compartment to remove the excess hot air. He showed me, it was impressive.

Clarification questions: Is your cooling fan mechanical (fan clutch or direct drive) or electrical? Are the fans engaging properly? Also I'm going to make the assumption that there is plenty of coolant, no coolant air bubbles. Also you've allowed the cooling system to pressurize? Coolant pump in good shape/new? Not trying to be condescending, but ensuring there isn't something isn't mechanically wrong that needs to be addressed.
It's a complete unit from Superior. Radiator, shroud, and electric fan. The fan is ecu controlled and working properly. Coolant is good, new 16 psi because old one didn't seal on this radiator. Water pump and thermostat are new because of leaks after install.

1. I would recommend with the engine on, at idle, see where the air is going in the engine bay. He used a piece of marking tape (or streamer, whatever) on a stick and mapped it that way. Then make engine bay airflow exits (passive or forced) from there. A few cheapo Northern Tool 12v fans zip tied temporarily would be a concept test. If it worked then you'd know what you needed to do. Or somehow propping up the hood hinges to allow hot air to exit at the rear of the hood (closest to firewall). Wouldn't look good but would provide a cheap and easy concept test.

2. I doubt your fog lights or ARB are "blocking" the air. Its not like its creating a massive vacuum. If anything its creating turbulent flow around the radiator but even then I doubt that as there is a fan creating a suction behind it. If you are keen, bust out the ye olde Fluid Dynamics book and have a go at some calcs. There is some suction behind the fog lights but not like its creating a massive void. Most turbulent flow would return to laminar fairly quickly. Same for the bumper.
I have a lot of obstructions...
20191027_162339.jpg
3. Do some data logging. Get a cheapo OBD2 reader and data log a hill climb vs. driving your happy self to get some fried chicken vs. highway crusing. The main issue here is your engine load went WAY up in the hills and that is where all the temp is coming from (obviously). But the load can be quantified. See if there is a difference between highway loaded and slow traffic hill climb loaded. Do you have any sensors on the transmission? Can you record that? I doubt transmission heat is your main problem but it isn't helping. Also rule out the temp gauge itself. Is the engine actually overheating or is the gauge faulty? Make sure that is checked before going down the rabbit hole.
The ECU supposedly can see trans temp, but my code reader can't. I checked Brooks' Bluedriver this weekend and it couldn't either. I need to get ahold of a more sophisticated reader.

Water temp gauge is new Autometer gauge in passenger side head. Ecu temp is in stock location on driver's side head. I have verified autometer gauge against what the ECU is seeing.

4. Your AC work? Go in the hills and hit the AC. The condenser has a fan and will naturally push extra air across the cooling package. See what that does. I have seen vehicle engine temps cool off with the AC on because of the sudden introduction of an extra fan.

I would say this needs to be addressed soon. Its only going to get hotter and driving around with eyes glued to the temp gauge isn't fun.

This is all I can think of right now. Imma go grill.
I haven't installed the AC compressor yet, but there is no additional fan for the ac condenser. When I do the AC, it'll only get worse.

I'm convinced it's airflow related. The question is whether air can't get in or air can't get out. I haven't had the time to test that yet.
 
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LBarr2002

LIFETIME
SUPPORTER
#17
We're going to get scientific here...

I ordered a cheapo pressure differential meter. We're going to try to compare under hood pressure to atmosphere and in front of grill pressure, to determine if air can't get in or air can't get out.
 
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