General engine question

[Whitaker717]

I just have a general engine question guys. Being new to these Comanches, so they always run hot? I have a new radiator, water pump, thermostat, and clutch fan. I also just had a flush and fill from the Jeep dealership. Whenever I am at idle, the temp starts creeping up. Also when I pull in my garage and pop the hood, the hood itself and the heat off the engine could cook an egg and it smells like burning coolant. Is this normal for these little trucks or am I panicking for nothing? Thanks guys!

[Eagle]

What's your idea of "hot"? I have owned and driven regularly seven Jeeps with the 4.0L engine -- four Cherokees and three Comanches. They all run with the temperature needle pointing straight up, right in the middle of the dial. I think that's 220 degrees.

 

If yours is overheating, it could be the radiator is clogged, or it could be that the viscous fan clutch is failing -- or a combination of both. If the temperature rises when idling in traffic and goes back down as soon as you start moving -- you need a fan clutch.

 

[Whitaker717]

22 minutes ago, Eagle said:

What's your idea of "hot"? I have owned and driven regularly seven Jeeps with the 4.0L engine -- four Cherokees and three Comanches. They all run with the temperature needle pointing straight up, right in the middle of the dial. I think that's 220 degrees.

 

If yours is overheating, it could be the radiator is clogged, or it could be that the viscous fan clutch is failing -- or a combination of both. If the temperature rises when idling in traffic and goes back down as soon as you start moving -- you need a fan clutch.

 

I typically run around the 190 range. It tends to creep up to that 210 range when idling. I try not to let it get any higher than that. I think it’s the smell for me that worries me. The burning coolant smell. I’m just not used to it. 

[Whitaker717]

4 minutes ago, saveevryjp1998 said:

Info on setup? Year,engine, closed or open coolant system? Did you test your tstat yet?

It’s an 87, 4.0 with a closed system. I’m not too interested in covering to open at this time. My thermostat isn’t even a year old so I haven’t checked it. 

[Whitaker717]

16 minutes ago, saveevryjp1998 said:

210 would be a happy setup for me where I'm located this time of year in Indianapolis. If it likes to keep climbing slowly though, something is still a miss. If it jumps really fast, I'd definitely work on getting it purged again of air. A slow increase is tougher to narrow down the issue. Those could be from small leaks, blocked passages, failing/faulty parts, a plastic cracked heater bypass valve, hoses, gaskets, cracked pressure expansion tank(it's not an overflow tank), bad pressure cap are all things I check first. 

I appreciate it. It definitely is slow. I haven’t allowed it to go past 210 yet to see if it keeps going. I just know the smell when I park it in my garage reeks of overheating coolant. Lol

[gogmorgo]

If there’s coolant coming out onto something hot (like the exhaust), it’ll smell. Doesn’t need to be much of a leak. If you pressurize the system you may be able to see it hitting the ground somewhere, or else give it a real good look over for signs of leakage. Check for rust staining on the block under and around the freeze plugs, and especially check any of the connections you’ve had apart to replace components. It’s not unusual to have to snug up a hose clamp or two shortly after installing new parts.

[ghetdjc320]

I think you’ve found your heating problem or at least a major contributor. If you can smell coolant, you need to track down where that is coming from. If the system can’t build pressure, it won’t effectively cool. Even a tiny leak can keep you running hot

[cruiser54]

THIS^^

[rokinn]

A leak in a closed system isn't just a leak like it would be in an open system where the open system leaks until there isn't enough coolant in it to sufficiently cool the engine.  It's a source for sucking in air from the leak source when the engine cools down instead of returning the coolant from the expansion tank to the engine as it's designed.  The more cycles it goes through the more air that is sucked in compromising the effectiveness of a closed system.  The smell is likely just this.  I had a pin hole leak in my newish closed radiator doing this.  I switched to an open system.

[ghetdjc320]

5 hours ago, rokinn said:

A leak in a closed system isn't just a leak like it would be in an open system where the open system leaks until there isn't enough coolant in it to sufficiently cool the engine.  It's a source for sucking in air from the leak source when the engine cools down instead of returning the coolant from the expansion tank to the engine as it's designed.  The more cycles it goes through the more air that is sucked in compromising the effectiveness of a closed system.  The smell is likely just this.  I had a pin hole leak in my newish closed radiator doing this.  I switched to an open system.

Very true. Even on open systems, a leak prevents pressure buildup which is essential to a properly functioning cooling system. So a leak in any part of the pressurized side of an open loop cooling system will cause on overheat as well

[rokinn]

20 hours ago, ghetdjc320 said:

Very true. Even on open systems, a leak prevents pressure buildup which is essential to a properly functioning cooling system. So a leak in any part of the pressurized side of an open loop cooling system will cause on overheat as well

Makes sense!  Thanks for adding that correction.