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Overheating 4.0

C

ctnsupra1

NAXJA Forum User
Location
MD
So I have been having issues with my 95 4.0 getting too warm. Lately we have had some extremely warm weather and the XJ has shown that it does not handle the heat well. This evening I took it out after replacing both coolant temp sender and sensor to make sure it wasn't them giving false readings and they showed it running right around 240 degrees on both highway and backroads. I have very warm air with heat on and set to high so that may rule out a blocked heater core. The system is less than a year, year and a half old and consists of:

- CSF 2-row radiator
- Triple Threat all electric fan setup
- New Cardone water pump
- Stant Premium 195 t-stat
- New upper and lower hoses
- New sensor and senders

The system had been working fine up until our 100+ degree days recently and all of a sudden has been going downhill. The motor gets up to operating temp within 5 miles of leaving the house, if that. Any suggestions on what to look for or test out? Thanks.
 
Whats the setup with the fans ???

Three on at a set startup temp ? .. or

Two on on at a set startup temp and the third replicating the original aux fan operation ?

Whats the initial start temp you have them set at ?
 
Change these out for the summer.(Triple Threat all electric fan setup).
Just helped a friend do this out here in the desert(CA) and his jeep now runs cool with his AC on.Our temps run around 105 to 115 every day here during the summer.

You'll pull more AIR with the STOCK setup.
 
Proper mix of anti-freeze/water?
 
Change these out for the summer.(Triple Threat all electric fan setup).
Just helped a friend do this out here in the desert(CA) and his jeep now runs cool with his AC on.Our temps run around 105 to 115 every day here during the summer.

You'll pull more AIR with the STOCK setup.
Click to expand...

X2. Go with the stock set up and add a ZJ fan clutch. Just put one of those on and it REALLY moves some air.
 
With your triple fan setup is it shrouded over the radiator properly? Fan shrouds are there for a reason, to help direct and pull air through the radiator. What are the fans rated at for air movement? Are they rated to pull enough air for your application?
 
electricfans.jpg



That seems to be a common theme..
 
Sounds kinda silly, but are your fans wired to pull? (I'm assuming you have them on the inside)
As embarrassing as it is, I had replace my stock electric fan with a newer 10 blade and I wired it backwards. It felt like it was pulling when you put your hand behind it, but I never check the front to see if it would pull a piece of paper or shop rag against the radiator. It took me several months, several frustrating trail runs where I was running warm and the aux fan wouldn't help cool it down, and some parts that I probably didn't need to realize the fan was just recycling hot air from the engine. I felt pretty dumb...reversed the wires and now it works like a champ.

Worth checking to make sure they are all wired to pull...
 
Also, testing engine temps with an infared temp gun really helped to be sure the engine was or wasnt operating at the temps my guage was showing...
 
Check for any exhaust leaks blowing exhaust on the block.
 
Fans are set to pull, infrared thermometer confirmed engine was up to operating temp and checked upper and lower radiator hoses and they were at proper temps as well.

Looks less like clogged heater core or t-stat issue and more like a headgasket issue. There's no antifreeze leaking so I'm thinking the heat from the cylinders is getting into the coolant and heating it up and thus the higher temp readings.
 
What is the temperature drop across the radiator at idle? Inlet and outlet temps on the metal radiator tank walls?
 
Another something to check, you said you replaced the upper and lower hoses, did you replace the lower hose with one that has the spring installed to help it from colapsing?
 
Ecomike said:
What is the temperature drop across the radiator at idle? Inlet and outlet temps on the metal radiator tank walls?
Click to expand...

I measured the radiator pipes exterior surfaces, they were 188 on the upper and 166 on the lower so the radiator was working when I checked.

I have only visually checked the lower to make sure it hasn't collapsed but every time I have been under there it has appeared normal when hot and running.
 
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