Jeep Son's overheating Jeep and what it did to my Jeep

DaveB

Long Jeep Fan
Location
Holladay, Utah
My son's Jeep that we just put a new stroker motor into ran into overheating issues on the way up to the opening of the archery hunt so I got a frantic call to swap Jeeps so they could make it to where they hunt. So I took up my Commando and traded Jeeps. When I took a look at his Jeep I found that the overflow bottle was too full. I took it home and started to diagnose it. What I found was that the radiator cap wasn't holding the required 16 lb of pressure. This allowed the engine to pump the antifreeze into the overflow bottle. I swapped the cap with a new one and the pressure problem was taken care of. No more fluid transfer so I took it for a test run with my IR thermometer to test it out. I romped on it good going up hill and the temp gauge did go up to around 235 which is a bit on the warm side. With the thermometer I found that the thermostat housing and the head was reading 215 block was 195 and the radiator was around 135. The spot on the head where the meter sending unit was was reading the higher 235 value. I think the biggest problem is where Jeep put the sending unit which is right next to an exhaust port. I am planning on putting a wide band AFR on it to make sure the mixture is good.
On another note I did get a call that they got a 5x5 bull elk opening morning so I ran up to help them out. Since they had my Jeep I had to hike in. They met me about half way out. I had to chuckle at what I saw, four legs sticking out of the roll cage and a set of big antlers sticking out the back. They had managed to stuff a bull elk in the back seat. Luckily they had quartered it out or that would have been an impossible squeeze.
 

Jinx

when in doubt, upgrade!
Location
So Jordan, Utah
That’s awesome. Congrats on the elk and the fix. Glad you figured it out.

I had a similar problem where the gauge wasn’t properly grounded and was reading hot.
 

mbryson

.......a few dollars more
Supporting Member
....
On another note I did get a call that they got a 5x5 bull elk opening morning so I ran up to help them out. Since they had my Jeep I had to hike in. They met me about half way out. I had to chuckle at what I saw, four legs sticking out of the roll cage and a set of big antlers sticking out the back. They had managed to stuff a bull elk in the back seat. Luckily they had quartered it out or that would have been an impossible squeeze.


Pics or it didn't happen !!! (Congrats!!!)
 

DaveB

Long Jeep Fan
Location
Holladay, Utah
Dave, I lwish you had a pic! That's awesome!
Are you running higher flow injectors?
Seems like everyone who builds a 4.0 stroker has overheating issues until they give them enough fuel. (Lean is hot).
Yes I'm running Ford 24 lb injectors, a MAP adjuster and have an adjustable fuel pressure regulator. I just need to install the wide band AFR and make sure it isn't running lean.
 

DaveB

Long Jeep Fan
Location
Holladay, Utah
Hi Dave, just because I am not familiar with the term, What will a wide band AFR do to help?
The wide band Air to Fuel Ratio meter will let you see whether you are running rich or lean over a much wider range of mixtures. It allows you to adjust fuel pressure, MAP sensors and other things for an OBD1 system or verify the ECM changes that you program into your OBD2 computer.
 

smfulle

Active Member
Location
Plain City, UT
Great story and happy ending.
On my rig it's just s half turn on the idle mixture screw.
All that other acronym stuff makes my brain hurt. MAP,OBD2, AFR. OU812 :)
 

DaveB

Long Jeep Fan
Location
Holladay, Utah
Well I hooked up the AFR meter and found that the computer is keeping the mixture at 14.7 even at full throttle. I have read that after 75% throttle its supposed to switch to open loop. I see it drop out of closed loop on deceleration so I'm wondering whats going on. Maybe its time for a new throttle position sensor ?
 

DaveB

Long Jeep Fan
Location
Holladay, Utah
When I had the motor in my Jeep it never overheated but I had a custom adapter that let me put in the bigger throttle body from the 4.7 V8. After some measuring I found that the blade that runs the TPS on the 4.7 clocks the TPS 3 degrees more which puts out a higher voltage at full throttle. I read online that the ECU looks for a voltage greater than 3.9 volts to go into open loop. My sons TB and TPS never goes above 3.8V. I have measure 5 different TPS units from my parts pile and they all match. Maybe I'll have to file one of them so I can clock it a few degrees. I could also add a resistor in line with the ground on the TPS to change the voltage.
 
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