C15 TT cat issues


corneileous

corneileous

Well-Known Member
Morning fellas, boss got me a new truck… 2004 Pete 379 long wheelbase, 15 speed deep reduction trans… Supposedly the truck’s been sitting for around five years when they were just bought.

We’ve got most of the bugs worked out of it, I’ve been running a lot of fuel additive in it just clean it up but the only real major problem I’m having now is the motor doesn’t wanna warm up… which, let me rephrase that, it’ll warm up once I get to wherever it is I’m going but the whole way there, the needle on the water temp gauge barely moves over 125°. Now once I get there and idle for a little bit, the temp gauge will go all the way up to about 175° but almost certainly every time, when I get back out on the highway- doesn’t matter if I’m loaded or empty, engine water temp goes back down to 125, 130ish.
Mechanic said they changed out both thermostats which I guess in a way does kind of make sense because last week, I was running up the interstate with a load on and I looked down and low and behold, the motor was running 200° which it’s never done that since I’ve had it but that was the only day that it’s ever ran that hot.

Far as I know, the fan is staying off and, it’s really not that cold around here in southern Oklahoma and here lately, it’s only been getting down to about 27, 28° which I don’t think is nowhere near cold enough to warrant the installation of a winter front, which is what they’re wanting to do.

What’s y’all’s thoughts, opinions? Thanks
 

Hammer166 said:
If they've replaced the thermostats, try changing the sending unit. Or you might get a thermometer and make sure what the temp actually is.
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I think they’ve changed that too but next week, I’ll be sure to bring along my infared temp gun that I use to tune the motor up on my nitro rc car.

But here’s a little update; I stopped up here to get some coffee and a snack and before I walked to the store, I shut the truck off and pulled the hood. At that time, temp was showing 125, 130 and the lower radiator hose was definitely cooler than the upper hose. Upper hose was actually pretty hot. Now that the truck has idled for a little bit, the temp is up to almost 175 but I’m pretty sure that as I get going, that gauge is gonna go down......
 
Snowman_w900 said:
Do you have any heat coming outta the vents? Obviously when its showing 125° the heat won't be hot, but still be warm enough to tell if your coolant is circulating. When its reached 200° you should really have some hot heat coming outta the vents if the coolant is circulating right.

Just curious if its circulating. I've had Caterpillar water pump impellers slip on the shaft causing false readings on the gauge. No circulating coolant might be hot in the block, but not in the head or vise versa and the thermostats might not open because they aren't seeing enough heat. Also, make sure you have a good tight seal on the radiator cap. 3406 and C15 need atleast 7 lbs of coolant pressure inorder for the coolant to circulate correctly.
Click to expand...
I’ve got heat but it’s definitely not as hot as it was that one and only day since I’ve been driving this truck where my motor temp hit 200° which is after they supposedly replaced both my thermostats. And it’s even worse on a cold, wet muggy day when I have to use my defrost because since the defrost kicks on the AC compressor to dry the air, the cold air from the evaporator actually overrides the hot air that passes through the heater core which means that while I’m driving down the road and my defrost is on, it’ll actually blow ice cold air out the vents until I turn the defrost off and then I get my hot air back. Or well, warm air.

But yeah, I’ll have to talk to my mechanics about that possible slipping impeller on the water pump because just like this morning when I started my truck up, eventually as the motor kind of started to warm up, the lower radiator hose was definitely a lot warmer than the upper radiator hose which if I’m not mistaken, the coolant exits the motor from the bottom and comes back in on the top, correct?

I wish I had my little infrared temp gun along with me so I could check it myself but how would you tell if the water pump is actually circulating the coolant? Because yeah, that makes a lot of sense that even though the coolant inside the block is possibly a lot warmer than it is up on the top part of the engine which would make the thermostats, even if there’s nothing wrong with them, not open because the water is not hot enough to tell them to open.
Regarding the radiator cap, they replaced that with a new one because I noticed one day while adding coolant to the upper reservoir, the little rubber seal that’s on the inside of that cap was all dry rotted away so they did replace it.
 
corneileous said:
I’ve got heat but it’s definitely not as hot as it was that one and only day since I’ve been driving this truck where my motor temp hit 200° which is after they supposedly replaced both my thermostats. And it’s even worse on a cold, wet muggy day when I have to use my defrost because since the defrost kicks on the AC compressor to dry the air, the cold air from the evaporator actually overrides the hot air that passes through the heater core which means that while I’m driving down the road and my defrost is on, it’ll actually blow ice cold air out the vents until I turn the defrost off and then I get my hot air back. Or well, warm air.

But yeah, I’ll have to talk to my mechanics about that possible slipping impeller on the water pump because just like this morning when I started my truck up, eventually as the motor kind of started to warm up, the lower radiator hose was definitely a lot warmer than the upper radiator hose which if I’m not mistaken, the coolant exits the motor from the bottom and comes back in on the top, correct?

I wish I had my little infrared temp gun along with me so I could check it myself but how would you tell if the water pump is actually circulating the coolant? Because yeah, that makes a lot of sense that even though the coolant inside the block is possibly a lot warmer than it is up on the top part of the engine which would make the thermostats, even if there’s nothing wrong with them, not open because the water is not hot enough to tell them to open.
Regarding the radiator cap, they replaced that with a new one because I noticed one day while adding coolant to the upper reservoir, the little rubber seal that’s on the inside of that cap was all dry rotted away so they did replace it.
Click to expand...
If you have proper water flow, the temp of the upper part of the block and head should be consistent from front to back.

It really sounds like the stats aren't working, though. Does the temp climb a bit under heavier load?
 
Hammer166 said:
If you have proper water flow, the temp of the upper part of the block and head should be consistent from front to back.

It really sounds like the stats aren't working, though. Does the temp climb a bit under heavier load?
Click to expand...
Either that, or maybe something might be in there that made one of the thermostats stick open like something got lodged in there holding it open.

It’s just really weird that only for that one day, haulin ass loaded up the interstate that it actually ran at 200°.

But as of now and this way all week, it doesn’t matter if I’m loaded or empty, the temperature always goes back down to 130° when I get on the road.

But now the weird thing is, it’s almost 55° outside and while I was sitting there idling waiting to get loaded, my temp came up to 175° as usual… Got loaded, took off down the dirt road to the highway and it might’ve cooled off to about 150 to 160° and now that I’ve been on the highway for the last 20 minutes, the temperature has warmed up to 175° and is actually staying there now.
 
Genuine Cat t-stats?
Were the t-stat seals actually changed?
Any erosion in the t-stat housing?

Just had a customer put 3 sets of t-stats in an ISX and it would still run cold. Seals were worn out and coolant was slipping by. New seals and it would actually warm up. You could see on the outside of the thermostats there was no rubbing where the seal was bad.
 
Snowman_w900 said:
That just brought a funny story to my mind.

When I worked at the international dealership a long time ago, at the time we were doing ALOT of warranty work on the DT466E engines. Fuel rails, HPOP, oil pumps, rear main seals alot of front covers. For some reason, Navistar decided to start using factory extended life orange coolant instead of the red stuff. The orange (can't remember the name) was very corrosive to the oring seals around the water pump and front cover, so warranty was paying for a front cover reseal, water pump and red coolant back in. Then you'd take them out side and let them run on high idle about 1000 rpm for about an hour and then check everything over for leaks and proper temps etc.

On those trucks, you really had to bleed them good to get the air out of the cooling system or they absolutely wouldn't circulate. Pain in the ass sometimes depending on the model of truck.

Well, one day a mechanic named Rob got one to do. He gets it apart, flushed and back together. He parks it outside on this beautiful summer day. He started on another truck while that one was running. Bout 45 mins goes by and I see alot of smog coming from where the truck was running high idle. I go over and the truck is pouring out blow by. I jump in and shut it down, but as I did I saw the coolant temp gauge was buried on 250°f. I checked the oil and it was coal black! It smelled completely burnt. The engine had less than 10k on it. It was a new truck.

He had forgotten to bleed the coolant system after he refilled it and toasted that 466 in less than 45 mins. I cant imagine how long that damn thing was buried on 250°f, but it roasted it, bad. Our dealership had to buy a brand new engine. They were not happy LOL
Click to expand...
Dexcool I think. GM was using it with bad results too.
 
Snowman_w900 said:
That just brought a funny story to my mind.

When I worked at the international dealership a long time ago, at the time we were doing ALOT of warranty work on the DT466E engines. Fuel rails, HPOP, oil pumps, rear main seals alot of front covers. For some reason, Navistar decided to start using factory extended life orange coolant instead of the red stuff. The orange (can't remember the name) was very corrosive to the oring seals around the water pump and front cover, so warranty was paying for a front cover reseal, water pump and red coolant back in. Then you'd take them out side and let them run on high idle about 1000 rpm for about an hour and then check everything over for leaks and proper temps etc.

On those trucks, you really had to bleed them good to get the air out of the cooling system or they absolutely wouldn't circulate. Pain in the ass sometimes depending on the model of truck.

Well, one day a mechanic named Rob got one to do. He gets it apart, flushed and back together. He parks it outside on this beautiful summer day. He started on another truck while that one was running. Bout 45 mins goes by and I see alot of smog coming from where the truck was running high idle. I go over and the truck is pouring out blow by. I jump in and shut it down, but as I did I saw the coolant temp gauge was buried on 250°f. I checked the oil and it was coal black! It smelled completely burnt. The engine had less than 10k on it. It was a new truck.

He had forgotten to bleed the coolant system after he refilled it and toasted that 466 in less than 45 mins. I cant imagine how long that damn thing was buried on 250°f, but it roasted it, bad. Our dealership had to buy a brand new engine. They were not happy LOL
Click to expand...
Dang, that aint good....
 
Well guys, the truck was back to its old ways today. But, I found out something new from the mechanic that might be another possibility of why my temp gauge has been reading all funky-like, when I got back to the shop this afternoon....

Apparently when my boss got the truck and the mechanics did their shit to it to get the truck all ready to be put into service, the engine fan would stay on all the time and never shut off. He tinkered with it and tinkered with it, replaced the little air actuator on the firewall that engages the fan clutch and replaced the temp/fan cut on sensor but the fan still wouldn't turn off. He got that part figured out but for some reason, where the temp sensor goes on top of the right front corner of the engine, he put all kinds of brass plumbing fittings between the engine and the sensor, to where the sensor looks like its on top of a chimney on a house.... Don't know why he did that but now he thinks that since the temp sensor isn't in the top of the motor and way above it, he thinks that maybe there's an air pocket between the motor and the sensor within all that plumbing that might be making the temp gauge give false readings since the sensor probably isn't making contact with the coolant.

Again, I don't know why he plumbed in the new sensor that way but he's gonna take all that junk off tomorrow and plumb the sensor in the top of the motor how its supposed to be so we'll see I guess.
 
corneileous said:
Well guys, the truck was back to its old ways today. But, I found out something new from the mechanic that might be another possibility of why my temp gauge has been reading all funky-like, when I got back to the shop this afternoon....

Apparently when my boss got the truck and the mechanics did their shit to it to get the truck all ready to be put into service, the engine fan would stay on all the time and never shut off. He tinkered with it and tinkered with it, replaced the little air actuator on the firewall that engages the fan clutch and replaced the temp/fan cut on sensor but the fan still wouldn't turn off. He got that part figured out but for some reason, where the temp sensor goes on top of the right front corner of the engine, he put all kinds of brass plumbing fittings between the engine and the sensor, to where the sensor looks like its on top of a chimney on a house.... Don't know why he did that but now he thinks that since the temp sensor isn't in the top of the motor and way above it, he thinks that maybe there's an air pocket between the motor and the sensor within all that plumbing that might be making the temp gauge give false readings since the sensor probably isn't making contact with the coolant.

Again, I don't know why he plumbed in the new sensor that way but he's gonna take all that junk off tomorrow and plumb the sensor in the top of the motor how its supposed to be so we'll see I guess.
Click to expand...
I'm sorry, but this is freaking hilarious!
 

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