Overheat 05 LJR S/C - Page 3 - Rubicon Owners Forum
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post #21 of 52 (permalink) Old 09-26-2018, 01:43 PM Thread Starter
Rubi Noobie
 
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UPDATE 9/26/18

Got the Jeep back and ran a wheeling weekend.

On the way out, I had a 1:20 ride. Temp 72 degF. All was well and temp was steady at about 215F over rural routes at about 35-50mph and sustained boost at 2-4psi. Once I hit the highway, things changed.

Twice going 65+ at 7psi up hill (3200 rpm at times) the needle went to the 230+ area. In each case, as I crested the hill and lowered the throttle, it came back in a minute to 220ish. In one zone, the sustained throttle was too much and the needle crept to the red. I took the exit ramp and after going 40mph at low throttle for 30 seconds, it came back to normal...I jumped right back on the highway for more testing.

Conclusion 1:
The Jeep is better than before
It is not bulletproof under any and all conditions
High speed and high throttle is the recipe for overheat now.

I wheeled for 2 days, some times the hill climbs and my gears required 2500rpm and sustained boost. ZERO issues!
I burned through 20 gallons (thanks to my safari tank, I can do that now...) and did not even worry about heat.

Conclusion 2:
The Jeep can handle boosted load all day even at 75F, but all the success is low speed.

Last, I ran back on the highway home. This time ext. temp was 66 deg F
I saw some increase to 215, but it never ran away initially
After 30 minutes, it began to act sort of like before. At this time, I ran the heat on full. Once I did that I could whip on the Jeep at will and never went above 220F
The outside temp was a bit cooler, but the heater being on seemed to reject the extra BTU's I needed in the test.

I ran parts with and without heat to check if it was for real... 8-10 degrees difference was noted on the heater being on.

I got the most heat accumulation going 60+mph at 3.5+ psi.

Conclusion3:
While it's not conclusive, I believe the bullbar, winch and led light might be creating a laminar boundary layer (air) in front of my radiator.
I don't really want to remove that stuff and I like my PS bumper a lot, so I am inclined to think about ways to alter the air flow at highway speed.
I will probably invest in genright louvers for the hood to both expel some underhood heat and, more importantly, to promote a lower underhood air pressure to affect the radiator flow.
I may also try an underbonnet or air dam below the radiator to keep air pressure behind the radiator from increasing due to turbulence of the under carriage.
I am convinced the air speed is setting up a bad flow potential in my setup and the fact I am boosted with an e-fan is taking this weakness to the point where it can cause overheat.
It is my belief that if I did all this at 55 degF or lower, the small active radiator area that I get at high speed might actually be enough to handle the heat and that could cause me to think my issue is solved. 65 deg. F was right on the border where 60+mph was getting me to overheat.

Think Jeeps have no Aero...? Think again. In truth, a conventional setup would not care about the aero effect, but that's not where I'm at.

Case closed for now on the cooling system, but more work is needed on my rig if I want to run 70 mph on a 90 deg. F day with A/C on! ...never turned it on in this test.

FUTURE:

Remove winch and bull bar on a 70 degF day and see if I have similar overheat results (have to wait till warm weather )
Consider louvers on low pressure-high heat areas of the hood to promote flow
underbonnet/airdam (maybe one that I can put on just for driving and pull off for wheeling)
fabricate a giant ram air cone for each side of the winch to direct flow under the boundary layer (ugly, but the Mech E in me, would love to test that...)

Wish I had a great photo on the rocks, but I was leading and always forget to snap a picture of my own...
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post #22 of 52 (permalink) Old 09-26-2018, 07:59 PM
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Stingerís finding of poor fuel pump causing overheating comes to mind. You might want to investigate that as a contributor.
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Bill
05 LJR Sahara #486, 2.5" OME, 285/75/16 BFG ATs, Warn VR8000, HighRock front Bumper, RockHard rear bumper, MORE MML, JKS BL, UCF Aluminum Engine and Transfercase Skids, MCAI, Savvy CAs, Currie Steering.
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post #23 of 52 (permalink) Old 09-28-2018, 10:09 AM
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Quote:
Originally Posted by jjbsilvia View Post
...Wish I had a great photo on the rocks, but I was leading and always forget to snap a picture of my own...
That's one of the problems being a trail leader - no time to snap pictures or take video unless your co-pilot does it.

I do have GenRite louvers on the hood and I made several holes on my GenRite inner fenders - it does help to exhaust heat.

When I had the CrownVic electric fan with a shroud, I had the very same overheating issue at highway speeds, when I put the cooling system back to OEM, problem solved. My winch (MileMarker hydraulic) has a very low profile so that undoubtedly helps with laminar air flow at highway speed.
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post #24 of 52 (permalink) Old 10-08-2018, 01:17 PM
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Can you fit the stock fan shroud and do your best to replicate the stock flaps and pieces that help generate a negative pressure zone behind the radiator? From reading it sounds like you don't have a shroud?

I think Griffon suggested a shroud etc?

Chris
2006 LJ turbo

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post #25 of 52 (permalink) Old 10-08-2018, 01:41 PM
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Like Bill said. I chased major cooling issues for several YEARS and it turned out to be a fuel pump that could not keep up. in tank strainer was really clogged

Put a fuel pressure gauge on the fuel rail. You should be reading about 58-60 psi with the key in the run position. This is not Thee test however. I had to take my hood off to do this but with that fuel gauge hooked up and the hood off so I could see the gauge I ran Stinger up and down some steep hills. Every time the engine came under load the pressure dropped to 40 or so. The computer tried to keep up with things and ended up leaning the fuel/air ratio enough the engine overheated.
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post #26 of 52 (permalink) Old 10-09-2018, 12:53 PM Thread Starter
Rubi Noobie
 
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This is a great insight. I am hesitant to get too excited, as I replaced the fuel tank and serviced the pump (cleaned and inspected anyway...) in the middle of the overheat.

Perhaps the tank replacement did nothing to really remove it from the list, but it was messed with. The point is there was no change to overheat during that time.

It is something I will investigate once the summer comes again. A couple counterpoints here.... My AEM gauge is showing 12.5-14:1 under high boost. only when I lift on a down hill coast or engine brake does it go to 16+:1 and pop like a NASCAR.

Also, I can load the $#!& out of it at low speed without trouble. When I burn that much fuel at high speed it seems to go hot. This is why I suspect the high speed "flow" of the cooling system is the deciding factor. Who knows, if my fuel pump not keeping up is the root cause after all, maybe I actually have a very very efficient cooling system masking it except for limited situations and ambient temps. The AEM showing normal A/F ratios gives me some indication it may not be true though.


Wood, you point out a great observation on the shroud.

1) No I cannot fit the old fan system with this S/C setup
2) The shroud won't fit, but a custom short flashing to try and reduce turbulence at the radiator might be an idea to try
3) I am certain that "flaps" will not help since they are supposed to open at highway speed and I am already overheating at highway speed and load.

Temps in the mid 60's here now. I'm driving it today and it acts like a normal Jeep in terms of temps. I think I need to figure a way to check my fuel pressure just to be sure.
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post #27 of 52 (permalink) Old 10-10-2018, 01:28 AM
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I feel your issue is airflow. Not that I think I'm always right ha ha ha. I added some genright vents in my hood. You should have a negative pressure behind your rad. No issue when going slow with your fan running, but an issue at speed. Seems obvious to me.

Chris
2006 LJ turbo

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post #28 of 52 (permalink) Old 10-10-2018, 09:28 AM
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Quote:
Originally Posted by jjbsilvia View Post
[...]3) I am certain that "flaps" will not help since they are supposed to open at highway speed and I am already overheating at highway speed and load.[....]
My exact experience

John - WB5THT
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post #29 of 52 (permalink) Old 10-10-2018, 05:26 PM Thread Starter
Rubi Noobie
 
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Quote:
Originally Posted by Wood View Post
I feel your issue is airflow. Not that I think I'm always right ha ha ha. I added some genright vents in my hood. You should have a negative pressure behind your rad. No issue when going slow with your fan running, but an issue at speed. Seems obvious to me.
From my last update post:

"Conclusion3:
While it's not conclusive, I believe the bullbar, winch and led light might be creating a laminar boundary layer (air) in front of my radiator.
I don't really want to remove that stuff and I like my PS bumper a lot, so I am inclined to think about ways to alter the air flow at highway speed.
I will probably invest in genright louvers for the hood to both expel some underhood heat and, more importantly, to promote a lower underhood air pressure to affect the radiator flow.
I may also try an underbonnet or air dam below the radiator to keep air pressure behind the radiator from increasing due to turbulence of the under carriage.
I am convinced the air speed is setting up a bad flow potential in my setup and the fact I am boosted with an e-fan is taking this weakness to the point where it can cause overheat.
It is my belief that if I did all this at 55 degF or lower, the small active radiator area that I get at high speed might actually be enough to handle the heat and that could cause me to think my issue is solved. 65 deg. F was right on the border where 60+mph was getting me to overheat.

Think Jeeps have no Aero...? Think again. In truth, a conventional setup would not care about the aero effect, but that's not where I'm at.

Case closed for now on the cooling system, but more work is needed on my rig if I want to run 70 mph on a 90 deg. F day with A/C on! ...never turned it on in this test.

FUTURE:

Remove winch and bull bar on a 70 degF day and see if I have similar overheat results (have to wait till warm weather )
Consider louvers on low pressure-high heat areas of the hood to promote flow
underbonnet/airdam (maybe one that I can put on just for driving and pull off for wheeling)
fabricate a giant ram air cone for each side of the winch to direct flow under the boundary layer (ugly, but the Mech E in me, would love to test that...)"


Wood, I think that comment is right in line with my experience so far.

I will probably do louvers first and then maybe experiment with underbonnet or shroud stuff.
I am reluctant to swiss cheese the fender liners right now because if the louvers really reduce my radiator pressure differential to promote flow, I don't want to disrupt the air flow between the radiator and louver exits until I get some data...

I'll add one more.... I cleaned my air filter to find I was pulling most air from my unblocked engine side (think higher IAT). I also think my exhaust manifold gasket is leaking a bit (higher underhood, heating up the stuff near the bank?) and the fuel pump doing lean at max load was such a great point it is worth looking at.
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post #30 of 52 (permalink) Old 10-10-2018, 09:41 PM
Rubicus Maximus
 
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There is really no escaping the physics of the thing. The stock cooling system is designed to cool the stock engine with stock power output, in hot ambient temperatures, plus perhaps a 10% to 20% margin. Place a significant additional load (i.e. towing) or increase the power output, and you also increase the amount of heat that the system must reject as hot air.

To increase cooling capacity, one must do THREE THINGS:

1) Increase the surface area of the radiator core, to increase the water-to-air cooling. This means a core with high efficiency (aluminum) and/or larger dimensions.

2) Increase the airflow through the radiator core by not blocking the space in front of the grille, adding hood louvers, a larger diameter fan, etc. Do whatever you have to do to keep the fan centered in the shroud opening, and flush the core from the backside using a hose to get out bugs and mud and debris.

3) Increase the water circulation with a larger capacity water pump.

As for WHAT you need to do in an individual case, I'd suggest all three of the above if at all possible, especially if you have made significant power increases.
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