dudeinthepnw

Hey guys - I just replaced the fan clutch on my 95 because that's what I thought to be the issue. It likes to get warm at idle/stoplights etc like so many of these rigs do, as soon as I bring up the rpms or begin driving again, the temp will go down to right around 210 where it's supposed to be. Hence why I thought it was an issue with the fan clutch. The Jeep also has a new radiator, coolant levels etc are all good and clean. I'm pretty sure the previous owner said he recently replaced the thermostat as well, but I can't recall for sure so that will probably be the next thing I replace.

The ac compressor also makes a grinding noise when turned off, which tells me it's probably the pulley bearing. AC doesn't blow cold so I'm not sure if I'm going to spend the time/money to go through the ac system or delete/bypass it. I live in the PNW where AC isn't necessary all too often, but it's still nice to have. When I first bought the Jeep, the compressor made the noise, I lubed it up and it went away until I replaced the fan clutch today. I played with the belt tension etc, and it didn't seem to make a difference. Just odd that the noise would resume after I did the fan clutch today after being silent for a stretch of time.

Anyways, as long as I have the AC turned on, the compressor is quiet and this also turns the electric fan on and the temp will sit at appx 215-220 while at idle and while driving it's right at 210, maybe a smidge below. When I turn the AC off, the compressor grinds again and the temperature will rise. Do you think the compressor pulley bearing being shot is making the belt spin slower or something when I disengage the compressor and in turn making the temp rise? This is the best I can come up with, but I would love other opinions as well. I come from Arizona and have always watching my engine temps like a hawk and I get a bit OCD about cooling systems working properly.

BlueRidgeMark

It makes a big difference when trying to defrost a window in a humid climate. On the defrost setting, the AC runs which chills the air, drying it out, then the air flows oer the heater core to warm it up. Warm dry air will clear your windows a lot faster than warm humid air.


Hmmm. Possible, but you really should hear the belt slipping if that's the case.

Have you considered the water pump? Unlike most vehicles, these things will go south without showing any external sign. The fins corrode away, so they aren't moving nearly as much coolant. Could be your problem.


This was mine a while back:

dudeinthepnw

I had thought about the defrost etc regarding the AC. I would prefer to keep the AC system functional, it's just a matter of priority at this point..So there's no weep holes on the 4.0 water pump? I imagine that could be a possible culprit seeing as how when the revs go up the pump spins faster. Hadn't considered that until now to be honest. Thanks.

BlueRidgeMark

Hmmm. Come to think of it, I don't know if it's got a weep hole or not. But it's a different failure mode than a bad bearing or seal. It's just the Amazing Evaporating Impeller Fin!

You'll find it distributed throughout your coolant as RUST!

TwistedWrench

This definitely sounds like either a bad water pump as stated above, or an airflow problem. Simply put, sitting at idle the waterpump is turning it's slowest, and the fans are the only thing moving air through the radiator.

Make sure the fan clutch is working properly(new doesn't mean squat unfortunately). Engine off, you should be able to turn it, but there should be pretty good resistance.

Make sure you have a fan shroud, and that its mounted properly. Its not there to protect your fingers, lol, it creates a vacuum that lets the fan pull air through the radiator. Without it you're just swirling hot air around.

When you do the thermostat, make sure to use the right temp(195). A lower temp thermostat wont help it run cooler. The coolant needs enough time to cool down in the radiator before it cycles back into the engine.

As stated above, you really wont know for sure about the water pump till you pull it, so just get a new one. Once the pump is done, put the thermostat housing on without the thermostat and flush the bejesus outta that engine.

The noisy AC... no idea bud.

4.3L XJ

Are all the shrouds in place?

dudeinthepnw

Yeah, shroud is there and in great shape. Fan clutch does just as you say, turns but with resistance. I will probably grab a water pump and thermostat and tackle those this weekend. Thanks

dudeinthepnw

Sure are!

Basslicks

Make sure you get a QUALITY 195* thermostat. Many people will try to "cheat" by getting a lower temp thermostat which is ill-advised and will make your Jeep stay in open-loop mode, thereby making your fuel economy plummet. Don't get a cheap one either as it can also cause problems.

Stant is a good brand, MOPAR is too of course. Just stay away from ValuCraft or the parts house brands.... except Napa... their stuff is usually good too.

JeepingDan

The entire shroud is there? Not just the left over top piece?

dudeinthepnw

Yep, just had the entire shroud pulled out yesterday when I did the fan clutch. It was in really good shape.

4.3L XJ

Then it sounds like you need to pull more air at idle. I would suggest a ZJ fan clutch. It is stronger and will make the fan spin faster at idle

BlueRidgeMark

If everything is working properly, no upgrades are needed. If it's not keeping cool, something is in need of replacement.

cruiser54

Yes, it has a weep hole.