4.0 Cooling Issues

[Tigerman]

Hello Folks,

I took a drive today to the "local" off-roading spot and on the way there noticed that my temperature gauge was reading a bit high. If I remember correctly it always was slightly below 210 and now it was slightly above, actually more than slightly.

Take a look at the picture.

I was kind of puzzled in the beginning, thinking that it had to be the long climb or something, but it wasn't the first time I had been on that road and the needle never moved past 210 before.

Anyway.... When I finally stopped to inspect the coolant and the reservoir I saw the water (distilled water at the time) boiling in the reservoir with its level steadily rising. When the Jeep cooled down, the level went down and below normal, so I though AHA!!! I have a leaking cap that is sucking in air, pushing the coolant into the reservoir and the coolant is low, so all I have to do is replace the cap and add coolant.

• Stopped by the local Autozone, picked up a new 18 lbs cap, got some distilled water and happily got on the way, but!!! no cigar. The problem persisted, so I turned back home. (No more boiling though and the cap was definitely bad)

Thinking about the issue on the way, I figured I could replace the thermostat (God only knows when the last owner did that) and do a full flush of the system. Thermostats are cheap as dirt and coolant is not so expensive either.

• Picked up a standard 195 degree thermostat, new gasket, coolant and replaced/flushed it. No cigar either, same thing!

I can feel the coolant going through the hose, when I squeeze it, but there isn't much flow in my opinion. I do not have another Jeep to compare it to, so I can only compare it to my Ram 1500, which definitely has more flow in the hose. I also noticed small leaks around the top of the radiator where the edge of the plastic is.

What do you think my problem is?

Is it possible my water pump is bad? (I have only been running water for a month, always proper coolant before)
Can I get away with just replacing the water pump or should I do the radiator as well?
How can this be properly diagnosed?

Thanks in advance

 

[MountaineerTom]

It very well could be the pump since you tried a new cap and it didn't work. Do you know if it's the original, or a MOPAR pump? I don't know what the '98 pump impellar is like, but on my 2006, the MOPAR pumps are that plastic like material. A few years ago, I had to put a water pump and radiator on. OEM pump started leaking and radiator cracked on top within days of each other. I was taking the Jeep on a trip very soon and went with parts from a local parts store due to time constraints. The pump had the old style metal impellar on it. My Jeep seemed to run just slightly warmer after I put that pump on. Could have been a combo of the pump and radiator, I don't know. This past November I completely rebuilt my entire cooking system and went back to a MOPAR pump and radiator. The cooling has gone back down to where it was originally at when I bought the Jeep.

I've seen where the metal impellar pumps wear/rust down to almost nothing, but I'd think you would have to severaly neglect your cooling system for that to happen.

 

[D M]

I had a similar problem, I noticed mine was always to the right side of 210, When I was doing an oil change I decided to take a peak in the radiator, rusted out completely, coolant looked like literal shit... literally. I took out the thermostat and added blue devil radiator flush in distilled water, no coolant to try and flush everything, radiator, heater core etc. I drove my daily routine for 4 days, flushed and refilled with the cleaner and water. Did that entire cycle about 3 times and finally replaced my radiator (with an OEM), thermostat and a new water pump. Now my temp gauge is to the left and just barely touching 210. Hope this helps

 

[Tigerman]

It very well could be the pump since you tried a new cap and it didn't work. Do you know if it's the original, or a MOPAR pump? I don't know what the '98 pump impellar is like, but on my 2006, the MOPAR pumps are that plastic like material. A few years ago, I had to put a water pump and radiator on. OEM pump started leaking and radiator cracked on top within days of each other. I was taking the Jeep on a trip very soon and went with parts from a local parts store due to time constraints. The pump had the old style metal impellar on it. My Jeep seemed to run just slightly warmer after I put that pump on. Could have been a combo of the pump and radiator, I don't know. This past November I completely rebuilt my entire cooking system and went back to a MOPAR pump and radiator. The cooling has gone back down to where it was originally at when I bought the Jeep.

I've seen where the metal impellar pumps wear/rust down to almost nothing, but I'd think you would have to severaly neglect your cooling system for that to happen.

I have no clue if it is the MOPAR water pump or an aftermarket one. I remember the original owner I bought it from telling me he had the water pump and the timing belt replaced and I think he mentioned the thermostat as well, but the thermostat I pulled out today is the OEM from 1998, I guarantee that.

 

[Tigerman]

I had a similar problem, I noticed mine was always to the right side of 210, When I was doing an oil change I decided to take a peak in the radiator, rusted out completely, coolant looked like literal shit... literally. I took out the thermostat and added blue devil radiator flush in distilled water, no coolant to try and flush everything, radiator, heater core etc. I drove my daily routine for 4 days, flushed and refilled with the cleaner and water. Did that entire cycle about 3 times and finally replaced my radiator (with an OEM), thermostat and a new water pump. Now my temp gauge is to the left and just barely touching 210. Hope this helps

I was thinking about this radiator...
https://www.amazon.com/gp/product/B07TC1YDX9/?tag=wranglerorg-20

 

[D M]

I was thinking about this radiator...
https://www.amazon.com/gp/product/B07TC1YDX9/?tag=wranglerorg-20

Personally I wouldn't use anything other than an oem mopar radiator, if it lasted nearly 20 years I really cant complain and see no need getting one that would last longer. Plus, you cant go wrong with oem

 

[DaYooperTransplant]

When you say distilled water, you mean it’s straight, no antifreeze? I wonder if it would run cooler with the proper mix? When you said it always ran a little below 210, was that with antifreeze mix? Curious.

 

[Tigerman]

When you say distilled water, you mean it’s straight, no antifreeze? I wonder if it would run cooler with the proper mix? When you said it always ran a little below 210, was that with antifreeze mix? Curious.

I mean straight, without antifreeze.
I thought it could possibly run cooler with the proper mix, but I now have the proper mix and runs the same.
No, it ran at below 210 with water as well, when I just rebuilt the Jeep about a month ago or so. This problem appears to have developed recently.

 

[Flivver250]

Cooling issues can be all traced to one big fault, or many little issues all over the place. The clutch fan is an often overlooked source of concern that is easy and inexpensive to replace. Some radiators are partially plugged or were cheap knock-offs with inferior cooling capacity. If age, quality and performance of the cooling components are questionable, don't be afraid to replace them. As my Jeep is my primary toy, I do not mind lavishing it with new parts and mechanical love. I rarely change broken parts, but I do change parts every week. A fail on the trail is a sign of weakness.

 

[CodaMan]

I wouldn't recommend and radiator except Mopar parts.

I just replaced my radiator, pump and fan clutch with all Mopar parts and it runs left of 210. And BTW, you should never run straight distilled water. The coolant raises the boiling point of the water. It also has a water tension release in it so it runs closer to all the parts.

 

[Tigerman]

Personally I wouldn't use anything other than an oem mopar radiator, if it lasted nearly 20 years I really cant complain and see no need getting one that would last longer. Plus, you cant go wrong with oem

Normally I would agree with you on OEM vs aftermarket. For example, I am certainly ordering a MOPAR water pump. In case of a radiator, I respectfully disagree. Let me explain:
The radiator is a very simple part (in terms of possible mechanical points of failure). An all aluminum radiator (if well made) will certainly outlast a composite one due to its simplicity and "one" piece design. So, it is an upgrade. Not only that, but it is also cheaper to upgrade than to buy the OEM one in this case, so the logical thing to do is to go with the upgrade.

Cheers

 

[Tigerman]

I just replaced my radiator, pump and fan clutch with all Mopar parts and it runs left of 210. I wouldn't recommend and radiator except Mopar. And BTW, you should never run straight distilled water. The coolant raises the boiling point of the water. It also has a water tension release in it so it runs closer to all the parts.

Thanks CodaMan. I do realize that the boiling temperature of the coolant is higher that of straight water and hence less bubbles and more contact with the surfaces (better heat exchange). it was never my intention to run water for prolonged time. I put the water temporarily to finish the rebuild process and give it a test run for a few weeks before doing a flush.

 

[D M]

Normally I would agree with you on OEM vs aftermarket. For example, I am certainly ordering a MOPAR water pump. In case of a radiator, I respectfully disagree. Let me explain:
The radiator is a very simple part (in terms of possible mechanical points of failure). An all aluminum radiator (if well made) will certainly outlast a composite one due to its simplicity and "one" piece design. So, it is an upgrade. Not only that, but it is also cheaper to upgrade than to buy the OEM one in this case, so the logical thing to do is to go with the upgrade.

Cheers

To each their own, I understand where you are coming from, I just like using OEM mopar because I know from experience how the piece will perform, but hey, thats why theres a dial on the radio.

 

[Chris]

An all aluminum radiator (if well made) will certainly outlast a composite one due to its simplicity and "one" piece design. So, it is an upgrade.

I double dog dare you to ask @mrblaine if he has found a single aluminum radiator that is "well made" and will will outlast the OEM radiator.

If it was just anyone else, I'd disregard that. But considering Blaine builds these things day-in-and-day-out, I have to say that his opinion on this matter holds more weight than most.

To my knowledge, Blaine has tested almost every aluminum radiator for the TJ out there, and found issues with every single one of them.

So unless you have found something he doesn't know about, I think you're wrong about this one.

I hope Blaine chimes in, as things may have changed since I last heard from him on this matter.

 

[CodaMan]

Normally I would agree with you on OEM vs aftermarket. For example, I am certainly ordering a MOPAR water pump. In case of a radiator, I respectfully disagree. Let me explain:
The radiator is a very simple part (in terms of possible mechanical points of failure). An all aluminum radiator (if well made) will certainly outlast a composite one due to its simplicity and "one" piece design. So, it is an upgrade. Not only that, but it is also cheaper to upgrade than to buy the OEM one in this case, so the logical thing to do is to go with the upgrade.

Cheers

My last Mopar radiator lasted 17 years and 150,000. Find an aftermarket one that will do that and you're golden.

 

[Tigerman]

Cooling issues can be all traced to one big fault, or many little issues all over the place. The clutch fan is an often overlooked source of concern that is easy and inexpensive to replace. Some radiators are partially plugged or were cheap knock-offs with inferior cooling capacity. If age, quality and performance of the cooling components are questionable, don't be afraid to replace them. As my Jeep is my primary toy, I do not mind lavishing it with new parts and mechanical love. I rarely change broken parts, but I do change parts every week. A fail on the trail is a sign of weakness.

Hi Flivver250,

Thanks for the clutch tip. It was replaced during the rebuild, so it is about a month old. I think that part is still good. The reason why I don't want to just replace all the components and call it done is because I really want to find out the cause, reasons and learn Swapping parts is easy, correctly diagnosing the problems is still hard for me. I am learning.

 

[Tigerman]

I double dog dare you to ask @mrblaine if he has found a single aluminum radiator that is "well made" and will will outlast the OEM radiator.

If it was just anyone else, I'd disregard that. But considering Blaine builds these things day-in-and-day-out, I have to say that his opinion on this matter holds more weight than most.

To my knowledge, Blaine has tested almost every aluminum radiator for the TJ out there, and found issues with every single one of them.

So unless you have found something he doesn't know about, I think you're wrong about this one.

I hope Blaine chimes in, as things may have changed since I last heard from him on this matter.

I have full trust in Blaine and you for that matter, so if you say they are not well made, I will go with OEM. That is settled then.

 

[Chris]

I have full trust in Blaine and you for that matter, so if you say they are not well made, I will go with OEM. That is settled then.

I went down this route once with a Griffin aluminum radiator. GenRight uses them, and they are made in the U.S. Everything seemed to point to them being good, but Blaine mentioned that he's had issues even with the Griffin radiators.

What I don't understand (and maybe @mrblaine can educate me on this) is why it's so hard to make a full aluminum radiator (end caps and all) that doesn't have issues. Is it the welds that continuously fail? Because if so, that seems like it would be a relatively easy thing to fix.

I'm missing something, no doubt, but Blaine knows more than I do on this matter. I just feel like it should be a pretty easy thing to make a quality aluminum radiator, yet no one seems to offer one that will outlast the OE unit last I heard from Blaine.

This of course sucks, because once the OE Mopar radiator stock drys up, we'll have no choice but to use crappy radiators.

 

[Tigerman]

I went down this route once with a Griffin aluminum radiator. GenRight uses them, and they are made in the U.S. Everything seemed to point to them being good, but Blaine mentioned that he's had issues even with the Griffin radiators.

What I don't understand (and maybe @mrblaine can educate me on this) is why it's so hard to make a full aluminum radiator (end caps and all) that doesn't have issues. Is it the welds that continuously fail? Because if so, that seems like it would be a relatively easy thing to fix.

I'm missing something, no doubt, but Blaine knows more than I do on this matter. I just feel like it should be a pretty easy thing to make a quality aluminum radiator, yet no one seems to offer one that will outlast the OE unit last I heard from Blaine.

This of course sucks, because once the OE Mopar radiator stock drys up, we'll have no choice but to use crappy radiators.

Interesting point...

It would be great to hear from him on what exactly fails and why! Also, I am curious if it is cheaper to make the composite one or a welded one. If it is cheaper to make the welded one, then there is definitely issues with the welds, otherwise FCA or others would switch to a "better", cheaper alternative. If, on the other hand, it is cheaper to make the composite one, then the question remains open as to why and what exactly goes wrong with all aluminum.

 

[Tigerman]

So the consensus is that water pump is probably the problem? The radiator's tiny leak at the top probably would go unnoticed if not for the pump I am guessing, but we are replacing it anyway...

What do you guys think caused the water pump failure? Usage of water plus age? other factors?