Cat Diesel Engines

[Swamp_Man]

Been looking at the used MDT market and see a ton of trucks with CAT 3126, C-7, etc engines for sale. During my research it seems these engines allegedly have a lot of problems. I say allegedly as with any research on the net, you have to be careful. Any have one of these engines and how does/did it work out for you? I am aware that there are engines with failures that occur due to manufacturing defects in every brand. Some of the trucks listed have a good price but the old saying about if it sounds too good to be truth, it is.

[rowekmr]

I went through some of those problems in the link provided. It seems to be a lot of problems with the DPF system and the heads. Were the pre emission engines as problematic? I'm no strander to engine issues but those owners spent big $$$ and still had unresolved problems.

Turtle n Peeps wrote:

Swamp Man wrote:
Been looking at the used MDT market and see a ton of trucks with CAT 3126, C-7, etc engines for sale. During my research it seems these engines allegedly have a lot of problems. I say allegedly as with any research on the net, you have to be careful. Any have one of these engines and how does/did it work out for you? I am aware that there are engines with failures that occur due to manufacturing defects in every brand. Some of the trucks listed have a good price but the old saying about if it sounds too good to be truth, it is.

All right, now that all the fan boys of the Cat can do no wrong have checked in, lets talk about some of the common problems with the C-7. :B

Before all the fan boys get all froggy on me let me first say that Cat makes some damn fine engines. Most of their stuff is anvil reliable and built like a brick,,,,,,,well you know. Unfortunately the C-7 isn't one of them.

Problem #1 is the HEUI. Back in time this was thought by Cat to be a good system. Years later Cat saw the error of their ways and dropped the whole oil pressure injector deal like a hot potato much like International did.

Problem #2 is injector cup leaks. My friend worked on diesels for over 35 yeas said they were a nightmare. He said the early ones with the copper cups were a bad deal. He said they came out with stainless steel later and that helped things a lot.

Problem #3 is the HEUI and injectors are very expensive and like I said above, have a bad habit of going out.

Problem #4 is when the HEUI goes out it is much like the CP4 pump. The HEUI have a bad habit of taking a dump and when they do it takes the WHOLE fuel system out with metal everywhere. Can you say, BIG BUCKS!

Here is a little reading about the C-7 common problems.

If you want the real story about the C-7 go to a Cat dealer and talk to a gray hair tech about common problems with this engine. Most will give you the true story.............both the good and the bad.

[Jarlaxle]

Swamp Man wrote:
Been looking at the used MDT market and see a ton of trucks with CAT 3126, C-7, etc engines for sale. During my research it seems these engines allegedly have a lot of problems. I say allegedly as with any research on the net, you have to be careful. Any have one of these engines and how does/did it work out for you? I am aware that there are engines with failures that occur due to manufacturing defects in every brand. Some of the trucks listed have a good price but the old saying about if it sounds too good to be truth, it is.

Going by our experience where I work, I would not own a C7. We had four...three failed, one catastrophically (threw a rod). My truck (2007 Freightliner, 250HP) was our last C7...it has ~170,000 miles, and before Ryder sells it off, the service manager at the facility said will have to put a motor in it! It has excessive blowby, flat wont start below 25 degrees (though every C7 I have seen was a bad cold starter), and holds about 30psi of oil pressure at 2200RPM.

It's also less than a year removed from an almost-$5000 HPOP and injector job. According to the manager, that's typical for a C7 at ~150K.

I'd much rather have a Cummins!

[Ric_Flair]

My cat leaks. That's why I won't let the wife bring the thing inside any more. Ruined a good pair of my Johnson and Murphy dress shoes!

And don't get me started on the hair balls

[UsualSuspect]

Big Katuna wrote:
Mine either.

x3, no leaks. Only issue with mine is every once in a while the wastegate sticks for a second, and one day I will replace it, but otherwise it runs like a top.

[Hank85713]

I drive a school bus and we have cat and cummings engines. The cats by far are the better running engines but they do leak just like the cummins do. Most drivers like the cats because they run way better and acceleration is positive. Even the same size buses with the different engines, the cats perform better. We even have some john deere cng buses and talk about dogs!

The one thing with the cat that I have been told is that they are higher cost to repair vs the cummings, the one I currently drive has about 157000 on it and it runs very well. Only engine issue I have is the dash AC system but thats not the engines fault!

[FishOnOne]

Mandalay Parr wrote:
My C7 does not leak a drop.

Jerry Parr

Interesting...

[Big_Katuna]

Mine either.

[Mandalay_Parr]

My C7 does not leak a drop.

Jerry Parr

[FishOnOne]

Turtle n Peeps wrote:

Swamp Man wrote:
Been looking at the used MDT market and see a ton of trucks with CAT 3126, C-7, etc engines for sale. During my research it seems these engines allegedly have a lot of problems. I say allegedly as with any research on the net, you have to be careful. Any have one of these engines and how does/did it work out for you? I am aware that there are engines with failures that occur due to manufacturing defects in every brand. Some of the trucks listed have a good price but the old saying about if it sounds too good to be truth, it is.

All right, now that all the fan boys of the Cat can do no wrong have checked in, lets talk about some of the common problems with the C-7. :B

Before all the fan boys get all froggy on me let me first say that Cat makes some damn fine engines. Most of their stuff is anvil reliable and built like a brick,,,,,,,well you know. Unfortunately the C-7 isn't one of them.

Problem #1 is the HEUI. Back in time this was thought by Cat to be a good system. Years later Cat saw the error of their ways and dropped the whole oil pressure injector deal like a hot potato much like International did.

Problem #2 is injector cup leaks. My friend worked on diesels for over 35 yeas said they were a nightmare. He said the early ones with the copper cups were a bad deal. He said they came out with stainless steel later and that helped things a lot.

Problem #3 is the HEUI and injectors are very expensive and like I said above, have a bad habit of going out.

Problem #4 is when the HEUI goes out it is much like the CP4 pump. The HEUI have a bad habit of taking a dump and when they do it takes the WHOLE fuel system out with metal everywhere. Can you say, BIG BUCKS!

Here is a little reading about the C-7 common problems.

If you want the real story about the C-7 go to a Cat dealer and talk to a gray hair tech about common problems with this engine. Most will give you the true story.............both the good and the bad.

I thought the HEUI system on the CAT was the same system used on the 7.3 PSD. I know the 7.3 PSD HEUI fuel system can tolerate just about any diesel fuel contaminant known to man kind and keep on truckin.

I will say the the C-7 leaks oil like a sift. :E

[bobx2]

lj2654 wrote:
Mine has a 3126 B with 40,000 miles and not a single issue. Oil and filter changes yearly, valve lash adjustment done at 32,000 miles. Keep an eye on the belts and it runs,runs,runs!

I would certainly hope you could get 40,000 miles out of it without any problems. Not sure I would be overly impressed by that. You can do that with a high revving little 1.8 liter engine in a rental car with no problem...

[wirenutz]

Jezz I feel like I'm driving on borrowed time, another thing to worry about

[lj2654]

Mine has a 3126 B with 40,000 miles and not a single issue. Oil and filter changes yearly, valve lash adjustment done at 32,000 miles. Keep an eye on the belts and it runs,runs,runs!

[Turtle_n_Peeps]

Swamp Man wrote:
Been looking at the used MDT market and see a ton of trucks with CAT 3126, C-7, etc engines for sale. During my research it seems these engines allegedly have a lot of problems. I say allegedly as with any research on the net, you have to be careful. Any have one of these engines and how does/did it work out for you? I am aware that there are engines with failures that occur due to manufacturing defects in every brand. Some of the trucks listed have a good price but the old saying about if it sounds too good to be truth, it is.

All right, now that all the fan boys of the Cat can do no wrong have checked in, lets talk about some of the common problems with the C-7. :B

Before all the fan boys get all froggy on me let me first say that Cat makes some damn fine engines. Most of their stuff is anvil reliable and built like a brick,,,,,,,well you know. Unfortunately the C-7 isn't one of them.

Problem #1 is the HEUI. Back in time this was thought by Cat to be a good system. Years later Cat saw the error of their ways and dropped the whole oil pressure injector deal like a hot potato much like International did.

Problem #2 is injector cup leaks. My friend worked on diesels for over 35 yeas said they were a nightmare. He said the early ones with the copper cups were a bad deal. He said they came out with stainless steel later and that helped things a lot.

Problem #3 is the HEUI and injectors are very expensive and like I said above, have a bad habit of going out.

Problem #4 is when the HEUI goes out it is much like the CP4 pump. The HEUI have a bad habit of taking a dump and when they do it takes the WHOLE fuel system out with metal everywhere. Can you say, BIG BUCKS!

Here is a little reading about the C-7 common problems.

If you want the real story about the C-7 go to a Cat dealer and talk to a gray hair tech about common problems with this engine. Most will give you the true story.............both the good and the bad.

[Ivylog]

The 3126 is one of the few Cat's that does NOT have replaceable sleeves. Comparing it to a C15 or even 3406 is night and day. A 3126 is a great engine for a MH that will never see 200K miles BUT this post was about MDT trucks converted to tow vehicle service. I would stay away from a high mileage truck with a 3126/C7.