'98 5.9 Getting Hot

VaiFanatic · Jun 8, 2019

Recently I've noticed an issue with the truck getting hotter than usual, even in Spring time temps with the AC running.

I'd noticed my overflow bottle was dry, so I topped it back off and refilled the radiator which had dropped somewhat in coolant levels. It occurred to me that my radiator cap has been failing to hold pressure, so hot coolant was forcing its way into the overflow tank where it would effectively flash boil away (you could hear intense boil/bubbling in the tank after shutting the vehicle off).

Replaced the cap yesterday with one purchased from a local dealer, no more issues with bubbling expansion tanks, but the truck is still running hot sitting in the direct sun with AC on. Highest temps I saw with the TorquePro App was around 233°F, temps would drop if I pulled into the shade and shut the AC off; temps would further drop if I turned on the heat and allowed the coolant to pass through and lose some heat through the blower motor. I didn't get a chance to go for an extended drive to see if temps would return to normal while on the move, as recent construction has turned the streets around where I live into an almost constant gridlock, meaning the truck would be sitting in stop-and-go and getting toasty.

I know the 98-99 models were known to run hotter, and this contributed to an improvement in the fan system for the 2000 model year, but I've had this truck in both Texas and Florida, and never encountered this before.

I replaced the water pump and radiator (Mopar parts) two years ago, and did a reverse flush on the heater core to PUSH out any debris that had settled on the inlet side. I don't believe I'm dealing with a clogged radiator, and I certainly don't believe the water pump has failed. Thermostat was also replaced with an OEM Mopar part. Viscous fan clutch seems okay as can only spin the fan by hand just a short distance before it stops; fan spins when the truck is running, and quite fast too.

Think that covers just about everything, maybe it's always been like this, but I guess I'm hyper sensitive now about the temp gauge after having a failed cap allow the coolant to boil off.

Truck is at 89830 miles.

RXT · Jun 9, 2019

Ok, it sounds like you gone thru the obvious cooling system culprits. I can think of a couple of possibilities. It's possible you have an air pocket trapped in the system. Under normal situations, an air pocket would work itself out, but sometimes it doesn't and it can lead to overheating. Try purging the system

It's possible that your engine is running lean, and this can result in an engine that runs much hotter.

The problem could be transmission related. Most of these trucks have an automatic, so I'll assume yours has one too. Automatics are cooled by a heat exchanger in the bottom of the radiator. If the ATF level is low, or the trans is overheating, it will pump that heat to the radiator, which makes cooling the engine much harder. Make sure the ATF is at the proper level and clean. Also the trans isn't slipping, even a little.

Engine oil. Check to make sure the oil level is full, the oil is clean, and it's the correct type and weight of oil. The wrong type of oil can prevent proper lubrication which in turn creates more heat.

Incorrect timing. If the timing is retarded this could lead to overheating too.

Ed

VaiFanatic · Jun 9, 2019

Ed,

Trapped air is a possibility; I always pull any vehicle I do cooling work on up on the hilly section of my driveway with the nose up with the radiator cap off and heat on full blast for 15 minutes or so while squeezing the top hose to purge any bubbles.

I do get an occasional code P0463 (the ABS and Brake light seem to come on when this code pops) for the Fuel Level Sensor Circuit High Input, but the fuel gauge operates as normal, and the motor does not show any obvious signs of running lean. This code has been popping up intermittently for some time now, so I guess I need to hook up a pressure tester to test the fuel pressure. It could be pump related, causing a lean condition, but I won't know until I measure the fuel pressure. My gauges are at the shop, so I'll have to go grab them.

I haven't checked the ATF level in quite some time, but I hadn't considered that. I'll give that a look... Right now, I'm letting my dad drive that truck since he doesn't have a vehicle of his own; future plans when no one else but me is back to driving it is to swap in a manual out of a Dakota with a 5.2

I've changed the oil recently, and there's no sign of coolant milkshake; the oil cap and manual call for 10W30, but this truck has been running 5W30 its entire life (it was in Florida until 2015, serviced by the same dealer using 5W30 each time).

No work has been done to any timing components, and I don't believe it to have jumped timing without something being more noticeable. I'll grab the timing light from the shop and check as well.

tntoy · Jun 10, 2019

Wow. They’re really overcomplicating this.

You need to bite the bullet and get out of town so you can get it moving. If temps slowly drop when you’re lightly cruising over 50mph and then climb in traffic, your radiator fins are clogged with road dust and dirt (unlikely given what you’ve stated)... or your fan clutch is bad.

A new one is $50.
They fail on dodges all the time.
They’re easy to replace.

They still feel okayish when you test them, until you put a new one on, get the motor hot, and feel the difference in how stiff it is.

I just went through this exact same conundrum with my 2000 Durango.

Be aware that highway air will only help a little bit; it would seem that 70mph would be better than any fan, but it only cooled down to perhaps 200-210 on the highway. I was running 220+ at red lights in traffic, like yours is.

I replaced the fan clutch and I can tow a twin axle trailer in the 98* Tennessee heat with the A/C on high and it holds 180-185 no matter what. ?

VaiFanatic · Jun 10, 2019

I purged some more air but there wasn't much. It's only about 78° today, so not as hot as it will be in a few days. Temps never broke 210°, ran up to just a tick before it. Haven't had a chance to do any higher speed driving today. Fan clutch spun about a quarter of a turn when attempting to do so.

The ATF level is low, and it's quite possible that's been the culprit all along; I wish it was easier to drain and flush the transmission beyond dropping the entire pan!

I'll order up a replacement clutch anyway, just to get it swapped since the original is now 21 years old.

So the part number 52029767AA is no longer available; does the clutch from the 2000+ model years work to? I've also noticed the later models have an option for a clutch for vehicles equipped with Max Cooling and without.

VaiFanatic · Jun 11, 2019

ATF level is now good, but I was getting temps creeping above 220°F again, this time I got the truck up to speed and sure enough, temps began dropping. I also don't seem to hear the fan spooling faster anymore as I used to, so I'm positive the fan clutch is toast.

Now I just need someone to confirm for me if the '00+ part will work for the older trucks.

VaiFanatic · Jun 11, 2019

Called a dealer, gave me part number 52029276AB, $202, and they aren't even sure if it fits. There's also a week or so shipping.

I really, really don't want to cheap out and use an AutoZone or similar branded part. I also can't wait that long to get the truck in running order either.

VaiFanatic · Jun 12, 2019

Springing for the AutoZone part, since I can't wait a week nor am I willing to pay $200+ for something that's non-returnable.

We'll see what tomorrow holds after I pick it up and replace it.

RXT · Jun 12, 2019

The problem I find with "cheap" auto parts store, parts is all of it is now made in China, and that will mean low quality parts. Sometimes the quality is so bad that some parts won't actually fit without work. I replaced a water pump years ago and had to re drill the mounting holes, because they were off by a millimeter in the casting. I'd now consider any auto part store part as an option of last resort… BTW check Rockauto and Amazon

Ed

VaiFanatic · Jun 12, 2019

Ed,

Yeah, I'm weary of any auto parts store parts for those exact reasons... I did look on Amazon, and found even cheaper options (not a good sign) with no guarantee that it'll actually fit.

RockAuto and I are not on speaking terms, currently. They've messed up a few times in recent years and I'm still stewing over it.

I guess after the AZ part is installed and hopefully resolves the issue, I will buy the later model Mopar part and be a guinea pig to test it out. It's only money, right? Worst case scenario I'll just pass it on to someone here with a later model truck that needs it.

VaiFanatic · Jun 12, 2019

Much to my surprise, the unit is a TorqFlo, with the box stamped Made in the USA. Haven't opened the box itself yet to look at the actual clutch, been a rather terrible day for me.

VaiFanatic · Jun 13, 2019

Well, here's the verdict... clutch is smaller/lighter but it fits, very stiff when cold.

Drove the truck, got it up to temps, seemed to stay happy when moving, not a lot of stopping or traffic at this time of night. Toward the end up my quick drive, the temps started to creep up eventually shooting passed the 210 mark and settling around 220°F.

Pulled into the driveway, shut the truck off, and went to spin the fan to find it spins freely with little effort.

Normally the clutch should turn freely when cold, and there be drag evident when hot; it's completely reversed in my case.

VaiFanatic · Jun 13, 2019

It also turns out upon looking up the TorqFlo part number, that the clutch itself is a heavy duty clutch, and my truck uses the severe duty clutch; that explains the size/weight difference.

I've ordered something else off of Amazon and will be returning the TorqFlo unit tomorrow.

VaiFanatic · Jun 16, 2019

Just an update... got the clutch off Amazon, definitely the right size this time. Got it installed and tested, seems to be working, but the truck is still overheating. No sign of coolant in the oil, but I did notice I puddle under the truck of ATF, that looks like it's coming from where the transfer case and the transmission meet.

Tested fuel pressure too, and I'm sitting right about 50PSI, which is well within the 44-54PSI parameter.

I'm going to try and investigate further where that leak is coming from.

WestCoastKevin · Jun 17, 2019

Get one of those Infra red thermometers. Start pointing it at the engine and cooling system and figure out where the heat is. Specifically pay attention to the radiator.

1. it is probably a crossflow radiator. You might have blocked passages. If so, you will have hot spots and cold spots on the radiator. (New radiator fixes that)
2. Make sure you do not have a bunch of insect debris blocking the fins. (or that the fins are not flattened).
3. Make sure you have an air gap between the transmission cooler or a/c condenser and the main radiator.
4. The sensor might be reporting wrong. Be sure to check the temp where the sensor plugs in.

VaiFanatic · Jun 17, 2019

WestCoastKevin said:
Get one of those Infra red thermometers. Start pointing it at the engine and cooling system and figure out where the heat is. Specifically pay attention to the radiator.

1. it is probably a crossflow radiator. You might have blocked passages. If so, you will have hot spots and cold spots on the radiator. (New radiator fixes that)
2. Make sure you do not have a bunch of insect debris blocking the fins. (or that the fins are not flattened).
3. Make sure you have an air gap between the transmission cooler or a/c condenser and the main radiator.
4. The sensor might be reporting wrong. Be sure to check the temp where the sensor plugs in.

The radiator in it is a Mopar replacement I installed two years ago, I was sure to reverse flush the heater core before installing the new radiator so as to not contaminate it and block it up. Before that, I flushed the entire system using the Prestone flush solution. While it's possible some debris has somehow remained, I doubt that new debris has accumulated in such a short time. I don't live in a dusty environment, and the vehicle doesn't see any kind of mudding or anything like that. As such, fins still look great, and there isn't much in the way of insect bodies. There is a gap between the condenser and the radiator, and I don't have an aux. transmission cooler.

It's possible the sender is toast, but I'm not going to check that until after I've replaced the rear seal of my transmission. Getting that transfer case out of the way is pain getting to those top three bolts.

WestCoastKevin · Jun 18, 2019

Fair enough.
I was thinking about it more.
A infra red thermometer can help either way.
Check that the thermostat is not broken in the housing.
Take the thermostat out and do the boiling water test. See if it is opening at the expected temperature.

Good luck with it, and the transmission seal.

VaiFanatic · Jun 19, 2019

My plan is to check the temps with my infrared thermometer once I get it up and running and assuming I'm still dealing with this issue.

I'm having the worst time trying to drop the transfer case. I have two nuts left up at the top that I simply can't reach. The slip joints for my exhaust are tight, so getting the catalytic converter out of the way has proved to be difficult, even beating on it with a rubber mallet after dropping the rest of the exhaust from the hangers.

Factor in that the secondary center crossmember that's underneath the transfer case is welded to the frame, so there's no dropping that either. I was hoping to be able to simple disconnect the transfer case from the trans and move it back on my transmission jack just to get enough room to get the seal out and replaced without having to drop the actually transmission crossmember, but that doesn't seem possible either.

This is not an easy job, lol.

tntoy · Jun 20, 2019

I was trying to figure out why you’re having such a hard time with those. The I remembered I have a body lift!

VaiFanatic · Jun 20, 2019

tntoy said:
I was trying to figure out why you’re having such a hard time with those. The I remembered I have a body lift!

Oh man, it's a pain. I'm still struggling to get the exhaust apart at the slip joints so I can drop the last two bolts from the trans crossmember and gently let everything down 2-3". The reassembly process will go by so quickly...

My grandfather purchased this truck brand new way back, had it built to his specifications; even says it was built for him on the window sticker. I remember fond trips to Pensacola Beach and just cruising around town in it as a kid. I always knew someday it would become mine, and it did some time back.

As much as a pain in the ass this thing is to work on, it's one of the few things I have left to remind me of my grandfather, and I've no intention of letting it go or fall into disrepair.

ETA: How do you like the body lift? What height did you use? Any concerns with overall stability or change in ride?

'98 5.9 Getting Hot

VaiFanatic

RXT

VaiFanatic

tntoy

VaiFanatic

VaiFanatic

VaiFanatic

VaiFanatic

RXT

VaiFanatic

VaiFanatic

VaiFanatic

VaiFanatic

VaiFanatic

WestCoastKevin

VaiFanatic

WestCoastKevin

VaiFanatic

tntoy

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