Nickolas Owen

Greetings all, I like many before me have a major overheating problem. I have tried many thing and will try to list it out below. You are my last hope for this thing.

The current status is as follows.

New crate 4.2 stroker I6
New 2 core aluminum rad
New heater core
All new hoses
New thermostat

It overheats on the highway with no ac and the heater on, and it overheats sitting parked within 20 minutes. I thought replacing everything to do with cooling with brand new parts would solve my problem but I was wrong.

There is a crack in the exhaust header and I'm getting ready to replace it soon.

What am I doing wrong? I'm sure you will need more details and I'm happy to get them to you. I love this jeep and I really want it to be reliable and right now it's rotting in my garage.

- Nick

Bugout4x4

A curious starting question would be, do you have any specs to what those cylinders were bored to?

Nickolas Owen

It's a 4.7,brain farted. It overheated the same with the stock 4.0.

https://www.high-performance-engines...eps-p/hp24.htm
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Bugout4x4

Cool, checked the specs they say they bore these to. It looks like they say for that 4.7 they bore it to 3.935". What had me concerned is that some engines can be bored too large and it makes the cylinder walls so thin it will run hot all the time. But I am not sure how big is too big on these particular blocks. I'm now wondering how big is too big.

Next question would be does it have the same catalytic converter on it that it had before?

Nickolas Owen

It does have the original catalytic converter, should I look to replace that as well?

Rogue4x4

So you had cooling issues before the new motor?

New head? Reused old parts?

Checked for exhaust gases in coolant, or coolant in oil?

What about water pump, clutch fan, e fan....rad cap...your list is short as far as everything goes...

Suprmn

first, I would get an IR thermometer or find some way to check the temp and make sure its actually overheating. The guage and sensors on these are not fool proof. Second, did you go with a high flow water pump? Those have created issues moving the water too fast. Next, lower radiator hose. Known for getting sucked shut if they do not have the internal spring or are not made strong enough.

Nickolas Owen

Performed the test for exhaust in coolant, it's negative. The only part reused on the engine itself is the oil pan and the valve cover. Water pump and clutch fan have been replaced a couple of times. Same for the rad cap. There is also no coolant in the oil. The electric fan is also new. I even tried the ZJ clutch fan and it didn't make a difference really. What else... So long this fight lol

Nickolas Owen

I've pressure tested the system, and it boils over. I've also replaced the sensor and used my ir thermometer, it is indeed getting too hot. Could be the ambient temp, seems to be doing better right now but it's also only 50* and not 110* outside. I do not have the high flow waterpump or thermostat anymore, tried it no difference. I even tried slowing it down going into the rad. The rad gets crazy hot so I know it's flowing through.

Bugout4x4

A plugged catalytic converter will make anything run hot.

Nickolas Owen

As for the lower hose, I not have a spring but on the same note it's not collapsing. I put a gopro under to watch it while on the highway and it didn't do it in my garage either.

freegdr

What does it get up too temp wise. Does it boil over ?

extrashaky

What brand of radiator is it?

Some people have had issues with overheating with 2 row radiators. What makes a radiator upgrade effective is additional thickness, not the number of rows. In fact, if you have a two row radiator that isn't thick enough, the passages are smaller, don't move as much coolant and are easier to clog. People have had issues buying 2 core radiators that simply didn't move as much as the stock radiator. The Mopar heavy duty radiator for the XJ is actually a big, thick single row.

The other thing that comes to mind is your transmission. How is it doing? Since the transmission either uses the radiator or a transmission cooler directly in front of the radiator, an overheating tranny can dump heat right into the engine cooling system. That really shouldn't be happening at idle, but when you start running out of ideas you look in all the corners.

The lower spring is unnecessary. It was in the original lower hose because the factory pulled a vacuum on the cooling system to help fill it without introducing air that would have to be burped out. After it left the factory, that spring only served to rust, disintegrate and distribute pieces of itself through the cooling system.

The system is under pressure from heat. The water pump is an impeller type that provides flow rather than pressure or vacuum. It's extremely unlikely you would get enough suction from that pump to work against the heat pressure to seal that hose. The pressure in the system would immediately push the hose back open. And even if it did suck closed, that would indicate that you had a major obstruction somewhere that needed to be cleared. All putting a spring in it would do in that situation is hold the hose open and allow a cavitation bubble to form, which would be no more effective than a sealed hose.

Bugout4x4

Now this is the smartest question in here... even mine. I was thinking this earlier. How hot is considered overheating to this gentleman?

andrewmp6

What do you call overheating what temp is the gauge showing ?Have you double checked the temp with a infrared thermometer ?A stock jeep 4.0 likes 210 degrees its happy their and people that don't know jeeps think its overheating when its not.With a stocker its probably gonna run a little hotter then stock so unless its boiling over or over 250 degrees it might just be normal for it.