Another running hot thread

So my 97 XJ has been plagued with a running hot issue since 2011. I had a CSF 3 row brass radiator for 7 years up until 2011 before temps began to creep up and I discovered it leaking. I made the mistake of trying an all aluminum "performance" 3 row radiator from Champion. Went through 5 of those before they said they were not going to give me anymore replacements and just gave me my money back. Stupidly I bought 2 more from Ebay and 1 swamped out under warranty. They all sprung leaks from fractures where the tube met the tanks. Horrible experience over a nearly 5 year period. Decided to go back to what I knew worked, CSF. Well the CSF doesn't cool well at all. I consistently have 220-230 temps in the summer. And before you go down that road, I have had the problem after replacing literally everything in the cooling system including heater core and the engine itself, nothing has helped. Here is a list of what I replaced:

- Engine
- radiator (first new CSF replaced under warranty with no change)
- radiator hoses
- thermostat (tried 180 and 195)
- radiator cap
- heater core
- electric cooling fan
- fan clutch (twice)
- converted to all electric fans
- coolant temp sensor (Mopar)
- water pump (twice, before and after the engine swamp)

Nothing keeps the temps down. At this point I am either thinking the CSF radiator isn't what it used to be since the one I bought the first time was back in 2006 so maybe they changed something. Or maybe the condenser is clogged. Visual inspection of the front of the condenser has no signs of clogging but it is the original 20 year old unit.

If the CSF is the problem, if there a OE grade that is thicker than 1-1/4"? Mopar HD radiator is 1-5/8" thick, thicker than even 1-1/2", but I can't shell out another $260 for a stock radiator. Most other OE radiators don't go past 1-1/4"

There have been many complaints about the 3-row CSF radiators. I also don't see a water pump on your list. My Hesco pump has dramatically improved my cooling performance even after installing a Griffin radiator.

RCP Phx said:

There have been many complaints about the 3-row CSF radiators. I also don't see a water pump on your list. My Hesco pump has dramatically improved my cooling performance even after installing a Griffin radiator.

Click to expand...

Thanks for catching that, forgot to add water pump to the list. Did a stock replacement pump before and after the new engine went in. I have considered an upgraded pump but heard conflicting info. Some say it helps, some say it pump fluid through the radiator too fast and the fluid doesn't spend enough time in the radiator to effectively cool the fluid before going back in the engine.

The AW4 gets hot (all automatics do), could be source of your heat. Check the trans pan temp vs the oil pan temp.

ehall said:

The AW4 gets hot (all automatics do), could be source of your heat. Check the trans pan temp vs the oil pan temp.

Click to expand...

I ditched the in-radiator trans cooler for an external auxiliary cooler that is quite large for adequate cooling. I also installed a trans temp gauge on the A-pillar to monitor the transmission. It typically stays 160-185 on most summer days.

Have you looked for things that can make it run lean, O2 sensor, ECU, sensor issues, drifted off calibration making it run lean, clogged Cat....leaking exhaust blowing on the block, leaking/cracked manifold....

Tried going back to stock fans?

Checked fuel trims with a scanner, and closed loop operation. Does run cool with out AC on, or sitting in park (thus testing the AC or transmission for excess heat).

Is air bypassing the radiator that goes through the fans?

Have you checked the AC HP side pressure to see if it is getting too high?

Where and how are you testing the temps???

Ecomike said:

Have you looked for things that can make it run lean, O2 sensor, ECU, sensor issues, drifted off calibration making it run lean, clogged Cat....leaking exhaust blowing on the block, leaking/cracked manifold....

Tried going back to stock fans?

Checked fuel trims with a scanner, and closed loop operation. Does run cool with out AC on, or sitting in park (thus testing the AC or transmission for excess heat).

Is air bypassing the radiator that goes through the fans?

Have you checked the AC HP side pressure to see if it is getting too high?

Where and how are you testing the temps???

Click to expand...

All great questions! Lets see how much of that I can address.

All current issues I am experiencing have remained the same since they began with the old engine and now the new engine.

So when I put the new engine in it got a brand new Banks header because the old one had a crack that I discovered (but I knew about because I could hear it back when the old engine was running) so no exhaust leak heating up the engine block.

O2 sensors are new so no problems there. I was working in sales at a Jeep dealer for a while and I had a tech hook up a scanner to make sure things were running right and he confirmed that they were.

I have a spare ECU laying on the shelf so I popped that in and saw zero change.

I was running electric fans before the engine blew. Worried that cooling was inadequate from lack of enough air flow I swapped back to the mechanical fan and OE electric fan setup to make sure I didn't run the new engine too hot during the break-in period. Both dual electric fan setup and OE Mech fan + OE E-fan setup exhibit the same running hot instance to the exact same levels.

So finally, the only thing related to the cooling system outside the cooling system that could affect it that I haven't addressed is the AC system. The same technician that worked at the dealer that I spoke about earlier helped me recharge my AC after doing the heater core. He added dye to the system to test for leaks when he was telling me that the system was nearly empty. When he informed me of this I was a little shocked because my AC was always ice cold yet he was saying there was just about nothing left of refrigerant in the system. Well the dye confirmed I have several leaks in the AC hoses, but it still blows ice cold!

My theories or questions at this point are, is the condenser clogged and I just can't see it? It is the original 20 year old unit but visual inspection doesn't appear to have any concerning sign that it is clogged. Or, the refrigerant is so low that while it may be cooling, it is super heated when it comes back to the condenser and preheating the air before going through the radiator.

The second option however, would make sense if it only ran hot while the AC was on but it runs hot with the AC on or off only slightly hotter while the AC if running which the amount it runs hotter by over the AC off condition would be normal in normal operating temperatures.

Like I said I have addressed most other areas other than the AC condenser and the cat. The cat was replaced in 2008 with a Magnaflow high flow mini cat so there is the chance that it could be clogged but it is a high quality unit that I would expect to outlast an OE cat and OE cats do last a long time these days so 10 years is the bare minimum I would expect from this cat and I am good about running fuel cleaner and maintenance products through the Jeep to keep everything in top condition. In addition, if the cat was a problem I would assume the downstream O2 sensor would throw a code since that is it't job.

Might have a problem with coolant flow rate--too slow and it will heat up in the engine before shedding at the radiator. You can get a feel for the temperature of the coolant in the engine by monitoring the temperature of the water pump inlet and the thermostat housing and heater bypass. Maybe a pinched hose or a piece of crud in the radiator

Exhaust pipe into or very near the oil pan will heat the oil, raising the engine core temperature. I think this is a contributing factor to mine.

One of the key questions from Ecomike you didn't answwer...how/where are you testing temps?

FWIW, I used to run warm at idle even after a new water pump and t stat, got a new condenser to fix my AC, no more issues. Started getting warm again at idle, new fan clutch and radiator cap solved it. Even in 97 deg heat in traffic with the AC on full blast, never goes above 210. I'd replace the condenser. Not expensive compared to what you've been through!

He should put a set of gauges on the AC first to see if the high pressure side is too high (above 230 psi I would think is an issue, 280 I know is an issue), and use an infrared tester on the high pressure line from the AC to the condenser to see how hot it is getting. I could grab the temps off of mine.

Are all the fan guards in place?

I still think he may be reading the wrong temp from a bad temp sensor or drifted dash gauge???

One last thing, at some point you need to consider that any new part or engine, or manifold part could be the problem even if it is new. You could have fix one problem and replaced the problem with a new one when swapping more than one thing at a time.

Also OBD-II is not very good at finding things like bad O2 sensors, or wires / connections to them that have a bias error making the engine run a little lean while the computer things everything is OK. Best thing to do is test it!!

http://www.naxja.org/forum/showthread.php?t=1012701&highlight=oxygen+sensor+test

elwoodblues said:

FWIW, I used to run warm at idle even after a new water pump and t stat, got a new condenser to fix my AC, no more issues. Started getting warm again at idle, new fan clutch and radiator cap solved it. Even in 97 deg heat in traffic with the AC on full blast, never goes above 210. I'd replace the condenser. Not expensive compared to what you've been through!

Click to expand...

OP didn't say anything about idle or cruising, would be useful bit of info

Ben824 said:

So my 97 XJ has been plagued with a running hot issue since 2011. I had a CSF 3 row brass radiator for 7 years up until 2011 before temps began to creep up and I discovered it leaking. I made the mistake of trying an all aluminum "performance" 3 row radiator from Champion. Went through 5 of those before they said they were not going to give me anymore replacements and just gave me my money back. Stupidly I bought 2 more from Ebay and 1 swamped out under warranty. They all sprung leaks from fractures where the tube met the tanks. Horrible experience over a nearly 5 year period. Decided to go back to what I knew worked, CSF. Well the CSF doesn't cool well at all. I consistently have 220-230 temps in the summer. And before you go down that road, I have had the problem after replacing literally everything in the cooling system including heater core and the engine itself, nothing has helped. Here is a list of what I replaced:

- Engine
- radiator (first new CSF replaced under warranty with no change)
- radiator hoses
- thermostat (tried 180 and 195)
- radiator cap
- heater core
- electric cooling fan
- fan clutch (twice)
- converted to all electric fans
- coolant temp sensor (Mopar)
- water pump (twice, before and after the engine swamp)

Nothing keeps the temps down. At this point I am either thinking the CSF radiator isn't what it used to be since the one I bought the first time was back in 2006 so maybe they changed something. Or maybe the condenser is clogged. Visual inspection of the front of the condenser has no signs of clogging but it is the original 20 year old unit.

If the CSF is the problem, if there a OE grade that is thicker than 1-1/4"? Mopar HD radiator is 1-5/8" thick, thicker than even 1-1/2", but I can't shell out another $260 for a stock radiator. Most other OE radiators don't go past 1-1/4"

Click to expand...

You've really been through the mill over this heating issue. Find a smog station and ask them to run their sniffer 1/2" above your radiator opening with the radiator cap removed. If there is even a tiny bit of emissions in the cooling system that smog machine will pick it up. Way more sensitive than those liquid tests. Combustion leaks don't mean there is water in the oil or any obvious signs. A long time ago I bought an ancient BAR84 smog machine off of Craigslist so I could do this one test correctly. It saved my bacon a couple of times. Good Luck !