Another cooling thread

[JefCooks]

Hey guys. Ive been pouring over this website (and others) for a couple months now looking for tips on bringing down engine temps. On the highway, the trucks stays around 195 just like it’s supposed to. When I kick the A/C on it will jump up to 210, no big deal. Once I hit traffic it will climb pretty quickly, faster with the A/C on of course. It’s never spewed, but it will hover between the final tic-mark and the red area (I’m assuming ~250ish). It has a new 2 core aluminum radiator, new ZJ fan clutch, new 195 t-stat, e-fan works great, new  GMB water pump, new Zerex coolant with 60% water because I live in TX, and new coolant sensors front and back. I flushed the coolant recently even though it was super clean, thinking it could have had a blockage somewhere. I backflushed the heater core and pulled the t-stat so that everything got properly cleaned. I’m at a loss of what to do now. Would hood vents do the trick by evacuating the hot air? Do I need to go 3 core + triple e-fans? I just got back from a test run after installing the ZJ fan clutch and the same thing happened. It’s only 83 right now and overcast. If it’s heating up now, I don’t stand a chance once it’s in triple digits and sunny. Is there a way to tell if any passages in the block are sealed without tearing the engine down? I’m all ears. Thanks everyone. 

[JMO413]

Do you have a fan shroud on the mechanical fan?

[JefCooks]

Yes

[Pete M]

are you rocking the old style e-fan or a newer style with the curved blades?

[JefCooks]

Original

[Pete M]

the later style is a great upgrade.  

 

 

[JefCooks]

Do you think that is enough of an upgrade? This doesn’t happen sometimes, it happens every time I drive it. Once it gets up to operating temp, even just stopping at a red light it will climb 10-15 degrees. Is there a way to check the engine for blockages? Could the PO have installed the water pump wrong? 

[Pete M]

it is ABSOLUTELY a worthwhile upgrade.   Will it fix your problems?  can't say for sure.

 

If your pump was backwards it would overheat all the time. 

 

if it's ok on the freeway, but runs hot when stationary, that sounds like an airflow issue to me. 

 

[AZJeff]

32 minutes ago, JefCooks said:

Do you think that is enough of an upgrade? This doesn’t happen sometimes, it happens every time I drive it. Once it gets up to operating temp, even just stopping at a red light it will climb 10-15 degrees. Is there a way to check the engine for blockages? Could the PO have installed the water pump wrong? 

The reverse flow water pump would actually make the problem worse the faster the engine ran.  

 

Engine blockages would have to be caused by some REALLY cruddy coolant, and/or the use of some of that stupid stop-leak crap prior to you flushing it, but you say the coolant looked OK.  In other words, anything that blocked the smaller passages in the block would have completely obstructed the heater core, and you did not report you saw any issues when you flushed it.

Here in Phoenix, my cooling challenges should be as bad, or worse, than yours in Texas.   I run a 3-row all metal radiator in the MJ/XJ 4.0 engines because of that, and other than my guage being somewhat off, my cooling system works as designed.

 

As far as engine temps, what are you using to measure them?   The gauges on the instrument panel are not terrribly accurate (mine is off by about 15 degrees).  I always confirm temps by using an infrared thermometer and measure the thermostat housing. 

 

At this point, I am suggesting you confirm temps before tearing your hair out.

 

[WahooSteeler]

I'm nowhere near the guy to ask for troubleshooting this stuff, but I fight the same reoccurring overheating problems. That said, have you checked your stat? What brand are you running. For awhile my temps seemed to be TOO cool and I guessed the stat was stuck open because it would stay at 165ish around town but once under load either on the highway or up long grades, the temp just kept rising and never recovered. As a side note, the stat in there was a Stant 195 and only had 3-4k miles on it. Additionally, the PO had hardwired the electric fan to the ignition so it runs 100% of the time. Even though it's not my daily, I didn't want to be restricted from hwy use if needed. I had read so many people post how even a decent brand stat ended up failing them right out of the box or with not much use and then they got an OEM Mopar and voila.......problem solved. So I put in a Mopar recently. Started the truck and let it run til it reached operating temp and BAM, the temp dropped 20-30 degrees.......... stat opened! Then of course it leveled out on temps and I could still see just by movement of the temp gauge when the stat was opening and closing. As many people have said on here several times, OEM Mopar is the way to go whenever you can. Based on my recent experience, that's what I plan to do going forward. This might not be your problem, just adding my 2 cents. 

 

[eaglescout526]

Well since we are talking about MoPar T-stats, Chrysler uses MotoRad brand T-stats now and clearly swears by them for their 5.7L hemi. 

Here is a part number of the kit they sell that includes the gasket:

[75sv1]

Auto Trans? Open or Closed coolant system?  Changed the pressure cap? If Auto trans, think about running a trans cooler. Also, Mr. Gasket has a large opening thermostat. Its a copy of the Robert Shaw. Also, Hessco radius the inside of the thermostat housing. You'll see where the 90 degrees comes to a point. Just round that out. Don't know if that helps much or not. I don't deal with the heat you are. 

 

    OK, read you sig. Auto and 92 so closed system. 

[JefCooks]

It’s not a Mopar, but I did replace it with a brand new Mr Gasket 195* t-stat last week when I did the flush. I’m hearing some bubbles when I turn it off so I think I will try to burp the system and see if that does anything. Thanks for all the input so far. 

[Jeep Driver]

2 hours ago, JefCooks said:

It’s not a Mopar, but I did replace it with a brand new Mr Gasket 195* t-stat last week when I did the flush. I’m hearing some bubbles when I turn it off so I think I will try to burp the system and see if that does anything. Thanks for all the input so far. 

Mopar or Motorad only

[WahooSteeler]

3 hours ago, 75sv1 said:

Auto Trans? Open or Closed coolant system?  Changed the pressure cap? If Auto trans, think about running a trans cooler. Also, Mr. Gasket has a large opening thermostat. Its a copy of the Robert Shaw. Also, Hessco radius the inside of the thermostat housing. You'll see where the 90 degrees comes to a point. Just round that out. Don't know if that helps much or not. I don't deal with the heat you are. 

 

    OK, read you sig. Auto and 92 so closed system. 

91 and 92 would be an open system.....

[Minuit]

What about the radiator cap? If you hear bubbling, my first thought would be that the system doesn't hold pressure and the coolant is boiling at too low of a temperature. The radiator cap is what holds the pressure back and if it leaks the system will not pressurize.

[75sv1]

1 hour ago, WahooSteeler said:

91 and 92 would be an open system.....

Yeah, I got the two mixed up.

52 minutes ago, Minuit said:

What about the radiator cap? If you hear bubbling, my first thought would be that the system doesn't hold pressure and the coolant is boiling at too low of a temperature. The radiator cap is what holds the pressure back and if it leaks the system will not pressurize.

This is where I was going with it. People have a lot of problems with the closed system. If you are loosing coolant, try replacing the radiator cap. Its a good idea to replace them every 3-5 years. I'd check what radiator AZJeff installed. Someone from out there installed a Mishimoto  a few years back, when they first came out. Brought his temps down. He was running a factory HD Radiator before that. 

[AZJeff]

A couple of things to note:

 

1.   the thermostat should have the small vent holes in it to allow the system to "burp" properly on a 4.0   The Mopar brand ones have this, but you can take a quality aftermarket one and drill two 1/16" holes 180 degrees apart just inside the seating surface and create the same effect.  (Be sure to orient the thermostat so the holes are at the "6" and "12" o'clock positions when it is installed.

 

2.  the pressure cap for a 4.0 is an EIGHTEEN POUND cap from the factory.   Everyone tries to sell you a 16 lb. cap, so beware.

 

3.  The CSF three row (all-metal) radiator is about as good as you can get for the space available.

 

The MJ/XJ cooling systems are sort of marginally designed.  When all parts are 'in spec.' the system will cool under even the toughest climates in N. America.  But, if one part of the system is not up to snuff, then all bets are off.   The system does not tolerate parts that have deteriorated due to poor maintenance.

[WahooSteeler]

5 hours ago, AZJeff said:

A couple of things to note:

 

1.   the thermostat should have the small vent holes in it to allow the system to "burp" properly on a 4.0   The Mopar brand ones have this, but you can take a quality aftermarket one and drill two 1/16" holes 180 degrees apart just inside the seating surface and create the same effect.  (Be sure to orient the thermostat so the holes are at the "6" and "12" o'clock positions when it is installed.

 

2.  the pressure cap for a 4.0 is an EIGHTEEN POUND cap from the factory.   Everyone tries to sell you a 16 lb. cap, so beware.

 

3.  The CSF three row (all-metal) radiator is about as good as you can get for the space available.

 

The MJ/XJ cooling systems are sort of marginally designed.  When all parts are 'in spec.' the system will cool under even the toughest climates in N. America.  But, if one part of the system is not up to snuff, then all bets are off.   The system does not tolerate parts that have deteriorated due to poor maintenance.

 

AZJeff, I know the "burp holes" on the stat is a common recommendation for closed systems, which I have, but to clarify is this a recommended idea even for open systems? And I am asking the same question regarding your last comment that MJ "cooling systems" are marginally designed? So are you stating in your opinion both the closed AND open systems are marginal? I certainly see plenty of people with open systems still complaining of overheating issues in their MJ/XJs so that seems to support your comment and also feeds the never ending open vs closed debate.   

[JefCooks]

The rad cap looks to have been replaced when the PO replaced the radiator. I don’t know the “pop-off” pressure of the cap (to use a carb term).

When I got home today, the truck was registering 195-210. I parked it and let it idle to see how hot it would get with no ac and a pretty cool day (for TX). It got up to the third tic-mark again after several minutes so I opened the hood, wondering if it would help to get the hot air out of the compartment. It did not. Later tonight I’ll put it on an incline and try top burp the system without getting into the t-stay again. 

[Jeep Driver]

1 hour ago, JefCooks said:

Later tonight I’ll put it on an incline and try top burp the system without getting into the t-stay again. 

This is not your problem. 

 

If you are serious about solving your problem-

 

Start with Motorad or Mopar stat. 

Replace your rad cap. 

Divorce your trans or at the very least run a cooler........cooler first then to rad. 

Replace the fan as stated. Use override switch for heavy traffic or really hot days- Efan full time. 

 

What is the replacement radiator? I was under the impression you did this work but apparently it was the PO?

[Jeep Driver]

I'm also curious about something else-

 

How many miles on the engine/trans?

 

What does your engine compartment look like? Clean? or saturated with oil?

[WahooSteeler]

JefCooks, I hope you don't mind but I'd like to ask questions on your thread because a lot of what is being said are related to a thread I was about to start. If you'd prefer to keep this thread strictly to your situation I respect that completely and will still start a new thread. 

 

Comment/question to your above post about burping the system. Since you have an open system, I thought parking the truck on an incline was not necessary, i.e. that was for burping closed systems? 

[Pete M]

1 hour ago, WahooSteeler said:

Comment/question to your above post about burping the system. Since you have an open system, I thought parking the truck on an incline was not necessary, i.e. that was for burping closed systems? 

 

'tis a good question.  I've got nothin'.   

[Jeep Driver]

On 6/23/2019 at 10:36 AM, JefCooks said:

Ive been pouring over this website (and others) for a couple months now looking for tips on bringing down engine temps.

 

1 hour ago, WahooSteeler said:

I thought parking the truck on an incline was not necessary, i.e. that was for burping closed systems? 

 

 

He's been dealing with this for months.

 

If you have air in your system you'll know it immediately.............not months later.