Engine/Transmission (1994 - 1998) high exhaust temps

[SWashabaugh]

I have a 1995 ctd 2500 5 spd. when we got the truck about a year and a half ago we thought it ran really good and it still does. it is suposed to have about 310 hp. (I know not quite enough) Anyway when we pulled the trailer with it on the high we never seemed to have a problem with exhaust temps. The other day towing the trailer (stock trailer with pigs not that heavy) it seemed that u never wanted to get on it or take your eyes off the pyrometer gauge. On the level or pulling a slight grade it would heat right to about 1,000-1200 degrees. It never used to do this. The only thing that has changed is the tire size (285/75/r16)they were 265/75/r16, and i have a different air filter geting a little better air flow. Any suggestions i'm all ears. The truck still creates horsepower u just can't use it cause of the heat. Thanks for your replys.

 

[Todd T]

At lower RPMS it will run hotter when under a load. since you raised the tire height you lowered your cruising RPM's for a given speed. try to speed up a few hundred rpms or unlock the converter and see if it cools down.



I was going to suggest you clean you air filter but sounds like it is new.

 

[LRamey]

Sounds to me like you may have a boost leak. Do you have a gauge? The same thing happened to me a couple years ago, I could still develop the HP but my egt's were through the roof. I found the boost leak & everything was just peachy!

 

[JGheen]

since you raised the tire height you lowered your cruising RPM's for a given speed. .

Tire height is the same(75), but a bit wider than the 265s.



My bet would be some kind of boost leak as well, less boost, same fuel, hotter EGTs. Your running a boost gauge right? Then again, you said it has the same power, so maybe something else. For EGTs to go up considerably, it would have to be a pretty good leak and you would feel a power drop and probably would have more smoke.



Joe

 

[JPittinger]

Tire height is the same(75), but a bit wider than the 265s.

Don't think so... LT265/75R16=31. 5" and LT285/75R16=33", which is enough to make a small difference in cruising rpms.

 

[SWashabaugh]

yes i do have a boast gauge. It can make upwards of 30 PSI if u keep ur foot it it. Where is the most common place for leaks and i can check. There might be a slight power difference but not very noticeble if there is. The air filter is clean and new. NAPA 6478 gets a good bit better flow.

 

[RJPotts]

I'd say do all of the above. Check for boost leaks. If I had to venture a guess though, I'd say its the larger tires. Do what Todd T said and run it at a slightly higher rpm.

1000-1200 really isn't dangerous though so if you can't find any leaks, and raising rpm a little doesn't help, but you still have good power and everything else seems ok, don't worry about it.

-R. J.

 

[biggy238]

Metric tires work like this. XXX is tire width XX if aspect ratio R is rim diameter

The aspect ratio is a percentage. If the aspect ratio is 75 then that number is 75 percent of the tire width. 75 percent of 285 is a larger number than 75 percent of 265. that makes a 285 75 taller than a 265 75. Overall tire diameter is the percentage of width, doubled, converted to inches, and added to rim diameter.

 

[RJPotts]

Excellent, you couldn't have explained that better. And again, I think the bigger tires are what's causing the increase in EGTs.

-R. J.