New engine still overheats

Ok guys I have a 97 XJ that I dropped a rebuilt 92 4.0 in my Jeep. I used nothing from the 92 other than the oil pan. Everything else was swapped over and I made sure to plug the rear temp sensor hole. I put on a new water pump, fan clutch, radiator was two months old before the old engine went bad and it's a CSF 3 row radiator which I have used before and it was consistently 200 until the last one went bad, and the thermostat was also replaced when the radiator was. The Jeep sat for 7 months before the new engine was put in. I had the radiator inspected by a local radiator shop before I reused it. I burped the system several times and there is no more air in the system.

When I am in heavy stop and go traffic, it begins to overheat slightly above 210 to about 215 or so. I cannot for the life of me figure out why it is STILL wanting to overheat! Any suggestions?

Have you cleaned out your A/C condenser? That can hold a lot of dirt and block the radiator. Have you verified the operation of your electric fan? Will it overheat if the A/C is on?

Have you verified your temp gauge is accurate?

DieselSJ said:

Have you cleaned out your A/C condenser? That can hold a lot of dirt and block the radiator. Have you verified the operation of your electric fan? Will it overheat if the A/C is on?

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The condenser is clean, no issues there. The electric fan does work and if I turn on a/c or defrost is does seem to help bring it back down. I only see it overheat in stop and go traffic. When I am driving around in light commuter traffic it stays under 210.

mtbxj87 said:

Have you verified your temp gauge is accurate?

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I don't have a infrared temp gauge to test it.

Your T-Stat was tested right? After sitting that long i would have bought a new on. Remove stat and check to see if it open's and closes.
How many miles are on the motor now? 210 is normal. I don't like it cause i am old school, but everybody tells me 210 is right. Heck with a 190 something stat they should run around 205 to 210. Both of my jeeps run 205-210, now my 89 ran at 190 on a 110 day. 185 Stat in it.

Define "overheat" ?

205-*215* indicated on the dashboard gauge is normal operating temperature, 215-230* is getting hot, and over 230* is overheating. Confirm the gauge accuracy with an IR heat gun on the thermostat housing.

Ben824 said:

Ok guys I have a 97 XJ that I dropped a rebuilt 92 4.0 in my Jeep. I used nothing from the 92 other than the oil pan. Everything else was swapped over and I made sure to plug the rear temp sensor hole. I put on a new water pump, fan clutch, radiator was two months old before the old engine went bad and it's a CSF 3 row radiator which I have used before and it was consistently 200 until the last one went bad, and the thermostat was also replaced when the radiator was. The Jeep sat for 7 months before the new engine was put in. I had the radiator inspected by a local radiator shop before I reused it. I burped the system several times and there is no more air in the system.

When I am in heavy stop and go traffic, it begins to overheat slightly above 210 to about 215 or so. I cannot for the life of me figure out why it is STILL wanting to overheat! Any suggestions?

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As mentioned previously, you may want to re-define "Overheat". When sitting in NYC traffic, on a hot day, I'm usually up around 220, and the only reason I stay at that is because my aux. fan cycles, to keep the temp. down. Even on the highway I'm either right at 210, or just below, when there is a slowdown on the highway (20-30mph) it can reach 215-220. I've seen no ill affects, and based on everything I've read, this is well within the normal range. As even Jeep does not program their Aux fan to come on, until 223 (IIRC) or somewhere in that range. If your staying below 215 in heavy traffic, I'd say your system is working pretty well.

Ben824 said:

I don't have a infrared temp gauge to test it.

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I find most water temp senders to be inaccurate, even new ones.
Here is an useful and cheap thermometer.
http://t.harborfreight.com/infrared-thermometer-93984.html?utm_referrer=https://www.google.com/
Aim at the sender, in the thermostat housing.
You can test the thermometer's calibration by reading the temp of boiling water.

Ok guys sorry for the delay in getting back to this, been busy at work. But the thermostat was never tested or replaced it just seemed to be working ok from the get go and wasn't old hardly at all before the old engine died. I installed the thermostat housing with a seal and no RTV and its leaking a little so I plan to replace the seal and use RTV this time of course and ill swap the thermostat with a 190 just to be safe.

In the 13 years I have had this Jeep if it runs over 210 thats abnormal and something it up. When I had this EXACT same combo of parts (stock new water pump, 195 thermostat, CSF 3 row all brass radiator, and new stock fan clutch) I never ran over 210 even in stop and go traffic in the middle of the Georgia summer. Now if I sit in stop and go traffic in this fall weather the temp creeps up which has me concerned since everything is new (aside from the thermostat) including the engine!

Here is what it reads when I am cruising and in lite traffic.


And here is what it reads when it begins to run hot.


Now I am concerned because this is unusual for this Jeep especially in this time of the year. Also I battled running hot issues on and off over the past 2 years that I believe eventually lead to the demise of my old 4.0 because I had it since it had 75,000 miles and was very very good about maintenance on it until it went out at 265,000 miles. It should have made it to 300,000 with how well I took care of it aside from battling running hot issues from defective junk all aluminum radiators from ebay and champion.

Now the only thing that is not EXACTLY the same as before is I have a temp sensor in the Jeep from advance auto parts and not Mopar. I am going to get a infrared temp gauge as soon as I can to figure out if I my Jeep is really overheating or if the sensor isn't completely accurate.

There is absolutely NOTHING wrong with those temps.

You are putting too much faith in the factory gauge. They are not meant to be taken so literally with such small units of measure.

If you have access to a scanner?, use it. That will show what the ECU is seeing. Is the e-fan kicking on when its that hot?

DieselSJ said:

There is absolutely NOTHING wrong with those temps.

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In the 13 years I have had this Jeep, the only times it creeps over 210 is when there is a problem so thats why this has me concerned. And in the last year and half when this has been the issue, my motor eventually gave out. Either the wrist pin broke or the stock aluminum piston fatigued and let the wrist pin rip through it. We all know aluminum doesn't stand up to excessive heat well so the chance that the running hot issue lead to the eventual failure.

This is a completely rebuilt engine and it is under 300 miles into break-in. Being such a crucial time period that will determine the ultimate lifespan of this engine, overheating, even a slight bit has me concerned. I did not pay to have the engine replaced so this will not fall back on a warranty if something is indeed wrong. I put this engine in myself and bought the engine second hand from someone who ended up not needing to use it. So if something goes bad I'm screwed.

Digger87xj said:

You are putting too much faith in the factory gauge. They are not meant to be taken so literally with such small units of measure.

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In the past it has always been pretty reliable, so I am just going on 13 years of history with this Jeep.

mtbxj87 said:

If you have access to a scanner?, use it. That will show what the ECU is seeing. Is the e-fan kicking on when its that hot?

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Well I work at a dealer so I can ask if they will let me borrow a DRB3 but those things are expensive despite the rarity that they use it anymore. I would need to have it with me driving around because it only runs a little hot in heavy traffic.

Ben824 said:

In the 13 years I have had this Jeep, the only times it creeps over 210 is when there is a problem so thats why this has me concerned. And in the last year and half when this has been the issue, my motor eventually gave out. Either the wrist pin broke or the stock aluminum piston fatigued and let the wrist pin rip through it. We all know aluminum doesn't stand up to excessive heat well so the chance that the running hot issue lead to the eventual failure.

This is a completely rebuilt engine and it is under 300 miles into break-in. Being such a crucial time period that will determine the ultimate lifespan of this engine, overheating, even a slight bit has me concerned. I did not pay to have the engine replaced so this will not fall back on a warranty if something is indeed wrong. I put this engine in myself and bought the engine second hand from someone who ended up not needing to use it. So if something goes bad I'm screwed.

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You are talking major overheat for a piston to fail. We have had the racer up to 245+ for longer than I care to admit. And overheat typically won't break a piston, it will melt a hole in it. Broken a the wrist pin is just plain fatigue. 265K is a lot of miles.

The temps you are posting are well within normal operating limits. Calm down. Plus a new engine will generate more heat as things get broken in. Relax. Drive it.