overheating and the oil pressure drop?

2006 JEEP WRANGLER TJ
600 MILES • 4.0L • 6 CYL • 4WD • AUTOMATIC
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I think the vehicle listed above is the ‘Sport’ version according to the VIN. My mechanic has installed a Jasper remanufactured 4.0 liter inline 6. Which is an exact replacement. It has been exchanged for a warranty with Jasper because of overheating and the oil pressure drop. The new engine is now installed. He has also installed several new thermostats to troubleshoot. It has a new radiator, water pump, fan clutch, etc. Everything functions fine. It reads a little warmer on the cluster temperature gauge than it used to with the old engine. Where it used to be 210 is now 215f. After its warmed up and on a hot Arizona day the Jeep will overheat when I shut it off at a gas station. Sometimes deep into the red line and I have to wait for it to cool off, sometimes not so hot and I can start it and it drops temperature immediately as the fan gets going and it starts moving. I instructed him to use MOPAR coolant at 60/40 mix. I noticed this new engine is very sluggish because of overdrive. I turned that off on the highway so I can travel at highway speeds without having to floor it constantly. The transmission was rebuilt some years ago, it is a 4-speed automatic. I feel that we are at a point where I need to buy an aluminum performance radiator and a hood louver to help this engine drive cooler, but I don't want to do that and have it remain the same. I also want to mention that we have a new remanufactured PCM and the Jeep has some other upgrades. Flowmaster exhaust all the way back with cats, Cold Air intake with KN filter, 33” tires on a 4” suspension lift, I have had it regeared to 4.56. There is a slip yoke eliminator and new drive shafts, front and rear. I just yesterday updated my Superchip and tuned it to 91 performance. This really helped with the highway drive. The sluggishness is gone.
What are we missing with the engine that is causing it to run hot and overheat when shut off? All of the upgrades mentioned were on it before the engine swap. It used to never overheat until the engine swap.
Thanks for reading and helping!
Jul 6, 2022 at 9:19 AM
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JACOBANDNICKOLAS
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Hi,

Does this only happen when you turn it off and then back on shortly after? The engine coolant isn't circulating with it off, so it can sit and increase the temperature of the coolant. If you were to start it under the conditions you would normally wait for it to cool, what would happen? Does the temperature drop somewhat quickly?

Now, if you are using 4.56 gears and the OD is off, how high are the RPM's when driving at highway speed? Those are steep gears.

Let me know.

Joe
Jul 6, 2022 at 9:01 PM
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Hi Joe,

Thanks for looking at my issue.
The warm running temperature according to my gauge is 215f.
It used to be 210f on the original engine. There are two scenarios. First, I stop to get gas, the gauge reads 215f because the engine has been running and is warm, I start the engine, get a "Check gauges" light on the cluster, and see the temperature gauge is buried in the red. Wait until it cools off and start it, the temperature drops back down to 215 and I am on my way. 2nd, same but this time when I start it it does not read "Check gauges" and the temperature needle is just before the redline maybe 250f and I start it and watch the needle quickly drop to 215f and I am on my way. As long as the engine is on, it doesn't overheat. (Pre tuning) The 4.56 gears barely made any improvement or change at all. RPMs are at 3200 max when overdrive is off and going 65 on flat highway. With overdrive on it is around 2,200RPMs and very sluggish, have to floor it to maintain speed at the slightest uphill grade or climb. (Post tuning) no more sluggishness. Operating awesome.
I am going to check that my mechanic did mix my coolant properly tomorrow. I also have an appt scheduled with a different mechanic next Tuesday. Just to get a different pair of eyes on it.
Jul 6, 2022 at 9:25 PM
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JACOBANDNICKOLAS
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Hi,

I suspect if you were to start and drive it when the gauge's light turns on, it would cool down fast just the same, but I understand your concern.

The operating temperature, 215F, really doesn't sound bad considering where you are located. I have a question. Is there any coolant loss? Also, when it reads 250F, have you ever heard of boiling under the hood? Coolant, when mixed properly, will usually have a boiling point upwards of 270F. I'm just curious if you ever noticed anything out of the ordinary as far as the coolant itself.

Let me know.

Joe
Jul 7, 2022 at 12:56 PM
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Hi Joe,

I agree, as soon as that fan turns it starts to cool off. As far as this new engine is concerned, it has about 600 miles on it and never has dropped a leak of coolant. I also have not seen steam or heard a boil. I bought an antifreeze tester today and it reads -29f. I'm not sure how accurate these are but it looks like the mechanic mixed the Mopar antifreeze correctly. It is a nice red color and the radiator is full. As well as the reservoir. I am not upset about the gauge reading 215f, just used to seeing at 210f after 15 years in Arizona. I thought that might be a clue as to what is wrong. It just plain runs hotter with this new engine. I am curious about your response to the gears. I got those done after many years of friends telling me, "you need to regear this thing". I finally had it professionally done at a driveshaft shop. They said those were the best I could do with my diff housings and recommended it. Do you think the transmission needs help cooling down? I see there are lines at the bottom of the radiator going to it. Jeep gets a lot of love, money, and service. It gets fresh fluids and oil as needed and has since 2007 when I bought it. That being said it was quite a surprise when I had to replace the block at 124,000 miles.
Jul 7, 2022 at 2:07 PM
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JACOBANDNICKOLAS
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Hi,

There is a chance the engine being new is simply tighter and running a bit hotter. I would put more miles on it to see if it changes.

Let me know.

Joe

Jul 7, 2022 at 3:13 PM