C15 TT cat issues

[corneileous]

I'm sorry, but this is freaking hilarious!

It actually is....lol. This guy actually is a pretty good mechanic but he's been known to do some pretty weird shit sometimes. lol.

At one point, they were waning to put a damn winter front on the front of my truck to make it get warmer but I told 'em, it don't get near enough cold around here to put one of those damn things on there.

But then again, their answer to getting colder air in the summer time is closing the damn heater core valves instead of actually fixing the blend door actuator so you don't have too.....

 

[Electric Chicken]

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.

I wanna see pics of this. Lol

 

[Electric Chicken]

I know what his thought process was. Get the sensor away from the coolant so it won't think it's hot and run the fan all the time.

 

[corneileous]

Monday morning update.... well, the mechanic did something this weekend, because I no longer have heating issues. I left my yard this morning and before I even got two miles down the road, my motor was already warmed up to 175°. It’s never done that that early. Matter of fact, just to refresh y’all’s memory, it didn’t matter if I was only going 30 miles away or 120 miles away, the motor would only warm up to barely 130°.

But anywhoo, when I checked the oil this morning, I noticed he had either put, or replaced the sensor indicated by the yellow arrow in the first pic. I’m sure if there ever was a sensor there, or if there was, and he changed it; I don’t know but there’s a new one there now.

Also, that sensor up on top that I told y’all about- that’s in the second pic, that had all the brass fittings between it and the top of the block, he didn’t do nothin with it, just left it alone which I thought was weird because I was under the impression that that sensor was the temp gauge sensor and the fan sensor. But either way, whatever he did, my problem seems to be cured.

 

[corneileous]

I know what his thought process was. Get the sensor away from the coolant so it won't think it's hot and run the fan all the time.

Well, it probably was, but however he wired it, he made it to where the fan didn’t stay on all the time.

 

[corneileous]

Well, now I’m having another problem… LOL. It turns out, down there by the alternator, where in that picture that I posted- the first one, apparently that’s not where the temp sensor is supposed to go… but I don’t understand, if the temp sensor goes in the same location as that other sensor with the wires screwed to it in the second pic, then where does the fan switch sensor go?? It’s actually fine that he put the temp sensor way down on the bottom but since it’s a lot warmer down there, it’s making my motor seem to be a lot hotter than it is and as a matter of fact, my motor just de-rated just a little bit when the temp gauge showed the temp to be over 225°. Turning the fan on manually fixed it so, he said he’s gonna have to find a new spot to put the temp sensor....

 

[corneileous]

I swear, I’m learning more and more about this engine and it ain’t even funny...lol.

Apparently since there is no actual sensor for the fan switch and that it’s all done from the computer or some shit, in order for him to get the fan to come on and off automatically like it’s supposed to, he had to add that sensor in the second pic I posted this morning because that’s all he could figure out how to make it all work so the reason there’s all those brass fittings plumbed into the hole where just the temp sensor goes, is so that he could essentially have two sensors in the same spot where only one is supposed to go....

So now, since my current setup with the temp sensor being all the way down on the block, he’s gonna remove all that brass and put the temp sensor where it goes, and put the new fan switch somewhere else because having the temp switch where he put it is causing the ECM to think the motor’s running hot causing it to de-rate.

The saga continues.............

 

[Electric Chicken]

This is becoming like a daytime soap opera.

 

[corneileous]

This is becoming like a daytime soap opera.

Well I guess when your new to you truck has problems that aren’t simply remedied with easy fixes, this is what happens. These old-ass trucks weren’t in the best of shape and the boss got 6 of them for fairly cheap considering they’re pre Kommiefornia-emissions trucks. I’m sure the right way to fix it would be to down the truck in an actual Peterbilt shop for a few days, spend a bunch of money while losing a bunch of money cuz the truck’s down and making me sit at home losing money since we don’t have any spare trucks right now, so the mechanic does what he can over the course of a weekend to keep the truck on the road. Lol. We got a small shop and a shit load of trucks and only three well-knowledged mechanics available.

 

[pushbroom]

Im not sure what was so wrong with just installing new sensors where they are supposed to go.

On top on the thermostat housing there is a sensor for the guage and a switch for the high temp light. Both of them should be threaded directly into the thermo housing. Both are single post style.

On the front of the thermostat housing near the bottom facing the fan there is a temp sensor for the ecm. It should be a 2 pin deutsch plug. Using the reading from that temp sensor the ecm will command the fan on and off.

 

[corneileous]

Im not sure what was so wrong with just installing new sensors where they are supposed to go.

On top on the thermostat housing there is a sensor for the guage and a switch for the high temp light. Both of them should be threaded directly into the thermo housing. Both are single post style.

On the front of the thermostat housing near the bottom facing the fan there is a temp sensor for the ecm. It should be a 2 pin deutsch plug. Using the reading from that temp sensor the ecm will command the fan on and off.

I’ll have to go out there and look at what you’re talking about because I only know what my mechanic tells me. I know nothing about these motors. All I know is it seems like there’s something wrong with the sensor or the wiring that goes from that sensor to the ECM that you talked about in your last paragraph; supposedly, that’s why he wired in a whole new switch that’s basically in the same place as the actual temp sensor for the gauge. I’ll have to talk to him about that and find out why that temp sensor that goes to the ECM isn’t doing it’s job, which probably goes all the way back to the original problem where he could turn the engine fan off himself with his computer but without it, the fan never would shut off. That’s why he added the new switch up on top where the gauge’s sensor goes and how he somehow wired it into the high-pressure switch on the AC.

 

[pushbroom]

There is no fan switch on this truck. That is pre ecm thinking. If your mechanic installed one, its time to take the truck somewhere else.

Engine fan solenoid is wired direct to the ecm.

Ecm decides if it wants the fan on or off based off coolant temp, intake temp, a/c pressure switch and manual fan switch.

 

[Duck]

There is no fan switch on this truck. That is pre ecm thinking. If your mechanic installed one, its time to take the truck somewhere else.

Engine fan solenoid is wired direct to the ecm.

Ecm decides if it wants the fan on or off based off coolant temp, intake temp, a/c pressure switch and manual fan switch.

As I recall, I think the fan on/off temperatures were a parameter you can set with a laptop, the last time someone was stupid enough to turn me loose with a laptop on a truck.

It was 6 years ago. I was just in there to de-fleet a former fleet truck. Delete the governor and un-stupidify the jake brake settings. Didn't mess with anything else. It was a 13 liter Cat.

 

[corneileous]

There is no fan switch on this truck. That is pre ecm thinking. If your mechanic installed one, its time to take the truck somewhere else.

Engine fan solenoid is wired direct to the ecm.

Ecm decides if it wants the fan on or off based off coolant temp, intake temp, a/c pressure switch and manual fan switch.

Yeah, I think I’m figuring that out now which is apparently why our mechanic added that fan switch in the threaded hole where the temp gauge’s sensor is supposed to go because leaving it as it all was before he started tinkering with it to keep the fan from being on all the time. That’s why he rewired it the way he did and added that fan switch because he thinks the problem lies in the ECM, not that little sensor on the front-bottom of the thermostat housing that you told me about that the ECM uses to control what the fan does.

Like I said, he was able to control the fan with prompts on his laptop but without the laptop, the fan was always on. He said he has another ECM that he could put on there that would totally fix the problem but the only other problem is, since the boss doesn’t subscribe to that high-dollar computer-programming network thing from Cat, he has no way to turn the horsepower up on that new ECM and he said they’re not set as high as the one on mine because I’m assuming it’s because they are probably either meant for, or are programmed to run little C13’s or C12’s and not a 475hp C15. That’s why he’s pretty much locked in to just putting the temp sensor for the gauge back in it’s original spot and relocating his new fan switch somewhere else.

 

[Oxbow]

Yeah, I think I’m figuring that out now which is apparently why our mechanic added that fan switch in the threaded hole where the temp gauge’s sensor is supposed to go because leaving it as it all was before he started tinkering with it to keep the fan from being on all the time. That’s why he rewired it the way he did and added that fan switch because he thinks the problem lies in the ECM, not that little sensor on the front-bottom of the thermostat housing that you told me about that the ECM uses to control what the fan does.

Like I said, he was able to control the fan with prompts on his laptop but without the laptop, the fan was always on. He said he has another ECM that he could put on there that would totally fix the problem but the only other problem is, since the boss doesn’t subscribe to that high-dollar computer-programming network thing from Cat, he has no way to turn the horsepower up on that new ECM and he said they’re not set as high as the one on mine because I’m assuming it’s because they are probably either meant for, or are programmed to run little C13’s or C12’s and not a 475hp C15. That’s why he’s pretty much locked in to just putting the temp sensor for the gauge back in it’s original spot and relocating his new fan switch somewhere else.

Big boy toys aren't cheap, but I would guess that your boss would be money ahead to get it on CAT's software, diagnose the problem, and have them program the new ECM if it needs it. Fixing one problem that causes another, especially with engine temps, could wind up costing a lot more than a new ECM.

Just my way of looking at it.

 

[corneileous]

Big boy toys aren't cheap, but I would guess that your boss would be money ahead to get it on CAT's software, diagnose the problem, and have them program the new ECM if it needs it. Fixing one problem that causes another, especially with engine temps, could wind up costing a lot more than a new ECM.

Just my way of looking at it.

And you would be exactly, 100% right but these aren’t my trucks. It’s all at the decision of the guy that owns them and unfortunately, it’s like he doesn’t wanna realize that with the majority of our trucks being over 20 years old, it’s like he doesn’t want to make the connection that yeah, your repair and maintenance bill is always going to be high because that’s where the trade-off is from buying much newer trucks is that yeah, you’re going to save money on the older trucks, but you’re going to spend a lot of time and a lot of money keeping the older ones up and running.

But AnyWho, I guess now that I know a lot more of what my problem is and why he wired the truck the way he did was done for a purpose that’s out of my control so, I think he’s going to stick with trying to find some other spot to plumb that switch that he added for the fan, to another place so that he can put the temp sensor for the gauge back in its original spot. But thanks to everybody who helped out in this thread with trying to give pointers, advice and suggestions. It’s highly appreciated.

 

[Oxbow]

Trust me, as the owner of two 31 year old trucks and a 20 year old truck (our new one!), I understand.

 

[corneileous]

I wonder if someone rigged and hacked into the fan solenoid and tried installing a thermal switch that kicks the fan on at a certain temp (old horton, kysor style) so either #1 didn't wire it correctly, or #2 its bad.

It might explain that big brass fitting chimney. LMAO

Lol, our mechanic added that big, brass fitting chimney because now that I know a lot more of what’s going on, he did that on purpose because he had to add an old school fan switch to make the fan work because for some reason, the ECM isn’t controlling the fan the way it should; so he added those fittings so that he could put his new fan switch on the bullhead side of the T, and the temp gauge sensor on top of the T.

As I was tellin everybody else, the problem at hand is what he thinks is a bad ECM and this is the cheaper fix.

 

[corneileous]

Whoa whoa whoa, not so fast there hero.

Now, you owe us a little something for the moral support we all chipped in and gave you. I think its bout time to pay up. So is it too much to ask,

I WANT A DAMN PICTURE OF THAT BRASS FITTING CHIMNEY!!! NOW!!

Lol, look at the second picture in post 29. All the way down where that little 1/4inch blue hose is, all the way up to where that brass hex plug is with the visible blue pipe tape is the part you’re wanting to see.

 

[tony97905]

3406E and C15 are set in the ECM at around 217°

To my knowledge, you cannot change that thru ET.

You would be correct