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CAT 3126

MattMO

Expert Expediter
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I heard some things about staying away from the CAT 3126 ??
I always thought CAT in general made great motors ?
What are the problems with the 3126??
 

Doggie Daddy

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matt mo, go to the bottom right corner of this page and click on other pages and get into the archives of this forum. there you will find dozens of posts about this engine. be sure and pay particular attention to the posts by weave,he knows what he's talking about. DD
 

RichM

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One of the main drawbacks to the Cat 3126 is that it is not a rebuilable engine. It is a dry sleeve engine meaning that the pistons go up and down on the cylinder walls similar to a car engine. The larger Cat engines and the medium Cummins C 8.3 liter have a liner between the pistons and the block. When a problem occurrs or for a general overhaul the ASCE (lol) mechanic will just disconnet the pistons from the crankshaft and remove the pistons and liners and then install new ones. This can be done without removing the engine from the truck. Usually a new cylinder head and valves are also put in.
The Cat engine also seems to be very picky about low and dirty oil.It is probably a fine engine for a local delivery truck that goes 40-50,000 miles a year.But in expediting you can easily rack up 125,000 or more miles in a year.
Somewhere in the archives there is a comparison of all of the engines you will find in a class 7 truck.This was posted by our EO resident truck genius WEAVE. You should look for it as it will give you a lot more info.
 

Left Turn

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We had the 3126 in a Freightliner FL70. It was a motorhome conversion, pulling a 32' stacker trailer. That is a enclosed trailer, triple axle, hauling two ARCA race cars, one above the other. The truck was equipped with a 6 speed manual transmission. With two cars, spare engines, tool cart, and extras, we were very heavy. Never took it over a scale, so don't actually know how heavy we were, but felt real heavy. Two problems turned up, with one being CAT's problem, and the other being a mechanic's fault. The CAT problem was the Turbo blew, blowing oil all over the side of the engine. We had a mechanic turn up the engine, and when he tried, he flashed the computer. Destroyed everything, in the computer, and had to have a new ECM. Very costly mistake. Truck never did run right again. When it was at stock horsepower of 225, it seemed to pull everything well, just don't get into a great big hurry. Couldn't anyways, darn thing felt like it was going to turn over at anytime, since the truck, and trailer were both air ride. We also had a new T400 Kenworth with the same engine, with an automatic, and same motorhome conversion. It ran like a dream, hauling the race cars, but it came with 275 horse from the factory, and was 3 years newer. The Freightliner was a 1999, and the Kenworth a 2002. Hope this helps you out.
 

Left Turn

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In case you were wondering why we didn't go over any scales, is because the truck was classified as a motorhome. We would just go right on by the scales, and never were chased down. I just spent the last few minutes looking for a picture, so you could see what the rig looked like, but cannot find it right now. When I do, I will post it here.
 

Left Turn

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I found the pictures of the Freightliner. Hopefully they download ok. I did make a mistake. I said the trailer was a triaxle, but it is only a tandem axle trailer. Any how you can see just how heavy this truck, and trailer was for the 3126.
 

Larry

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As an owner of a FL70 with a Cat 3126 engine, I have paid close attention to the comments and discussion about this engine. There are probably other owners out there that very anxious about the the engine and its anticipated short life. I have heard of one person that was able to go over 600,000 miles with their engine. With 415,000 miles on my truck, I have begun to investigate the options.
There is an ad from Midwest Diesel Service (Minn. MN) in American Trucker Magazine, for brand new, factory warrantied 3126 engines/250 HP. Apparently these engines are complete (less fly wheel and electrical). ECM is included, along with turbo, etc. The engine sells for @ $8500 plus trade. Buyer pays for shipping new engine, and Midwest Diesel will pick up cost of shipping trade-in. My mechanic tells me that he can swap the engine out for @ $2,000 + a few parts. That may keep the cost of the change out to around $11,000.

Most of the drivers I have spoken to said that the problems with the engine were developed over a short time, rather than suddenly loosing the use of the truck. The engine sounded or acted differently; or oil leaks were observed (cracks in block began to develop). Those of you that have experienced problems with the engine may want to comment.

Midwest Diesel representative says that they have limited availability of very low milage used engines.

I suggested to Midwest Diesel that they check out this web site and let us know more about what they can do for truck drivers.
 

davekc

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We have put several posts on here regarding this engine. We have a old fl70 with about 900000 and it is still running. But it does smoke a little. In addition, we have a kw300 and it currently has 285000 on it. As of late we have not had to put any money or repairs into the kw. Maybe we are just lucky. On the other side of that many people like the cummins. We had one in a 98 fl70 and it was the biggest piece of junk imaginable. With milage in the 250000 range we had to replace numerous a/c parts, turbo, fuel pump, water pump, injectors just to name a few. With all the repairs and down time you would be looking at 15 to $20,000 in costs. Yes the cummins are a better bet as far as rebuilding but overall I wouldn't spend a dime on one. If you want rebuilding capabilities, get a larger cat and then you can do that. One other piece of advise is to use a block heater if you are in a cold climate to eliminate dry starts. Just my two cents worth. As far as replacement, $10,500. and that is in Jacksonville FL. Add another $2,000 if you want it turned up with larger turbo, pump ect.
 

Weave

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Aside from just being too small a displacement engine in the opinion of many for the highway, the CAT 3126 has a few more things going against it. As Rich mentioned, it is a parent bore engine that is not rebuildable in the frame of the truck. It costs too much to rebuild out of the truck, so when it dies a replacement is usually the way to go. From people I know this has been ranging anywhere from $12-15k, which is usually more than what the truck itself is worth at the time the engine is needed, making it somewhat impractical to do. The 3126 uses a fuel system called HEUI, which has fuel injectors that are powered by engine oil pressure. This makes clean oil at all times in the 3126 a must, or it eats the injector seals and sends engine oil into the fuel system and vice versa. Very ugly! Valve adjustments cannot be overlooked on the 3126 either. They are very critical, and if not done right the engine will shread its cam lobes, sending the metal into the engine and killing the rest of it.
There are a lot of trucks for sale out there dirt cheap with 3126 engines. These are some of the reasons why. (Professional opinion- the thing basically sucks and should be avoided. It's something you have slim odds of winning with financially on the highway.)
I have heard a few horror stories on the Cummins 8.3's but nowhere near as many as the tales of the 3126. I know there are some on this forum who have had good luck with it, so not everyone has been burned by it. I'm just stating that if you are someone who is shopping for a used truck, there are many better finds on the market than a job with the 3126.
-Weave-
 

MattMO

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Thanks for the info, sort of sounds similar to the old CAT 3408 v-8 which was basicly a throw away engine once its 1st milage/hours lifespan was reached.
 

Weave

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You are right on with the idea. The 3116 CAT is another throwaway.
-Weave-
 

davekc

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I don't know, I think I will take my 900000 miles on a 3126. I will agree they are not what one would call a rebuildable engine. But easy figuring tells me the "$12 to 15,000 to buy new beats the same amount over a shorter period of time for countless repairs and considerable downtime on a cummins. Pretty easy figuring if you ask me. Referencing a earlier post, the 900,000 is a fl70 flatbed used to haul lumber. Has had some minor work but no rebuild or replacement. I have however heard some good things about the Detroit engines if you can live with the oil leaks. We know a few friends that have the 50 series and seem to like them. Not sure on their milage though.
 

Weave

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The Cummins on my old FL70 had 465k miles on it at trade time. It was one of the little disposable B5.9's. Out of ordinary maintenace costs during ownership were a tad under $1000. That to fix a front cover oil leak, replace a starter, and an air conditioner bracket. The thing still ran great at trade in time, and I got good money for the 1995 truck, traded a year and a half ago. The place I traded it at would not even take newer FL70 trucks with 3126's on trade. I know a lot of people have different opinions, but the class 7 trucks with Cummins engines have considerably higher resale value, just a fact. The C8.3/ISC's have the highest- 3126 or 3116 trucks, basically zippo.
My new Freightshaker has the Detroit series 60, 470 HP derated to 360 HP. It now has 215k miles on it, had 54k on it when I bought it. This is an AWESOME engine, but it is a class 8 job in a Columbia tractor based truck. Short of regular scheduled maintenance items, not one penny has been spent on it yet, and it does not leak or consume any fluids. Starts in a heartbeat in the coldest of temps, and has not skipped a beat. Quiet at speed, a bit noisey at idle. The smaller 4 cylinder Series 50 is in layman's terms a series 60 minus two cylinders with a balance shaft. The drawback with it has been availability- is has only been put into Freightliner FL106's. As is is an overhead cam engine like the S60, it needs a setup with a tall hood, and would not fit into FL70's or the little KW's and Petes.
-Weave-
 

davekc

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you seem to have as much luck with cummins as I have with cats. With the maintenance I spent on our old cummins I could have bought a new truck. They make a good rebuildable block but the rest of it is junk. Our local kenworth dealer won't sell the smaller ones for this reason. They say it is because of computer and fuel related problems, not to mention a/c problems. Talked to several other drivers with this engine and they are less than thrilled. To many pump and injector problems and way to noisy. On the upside, they said their fuel milage wasn't bad after repairs were made. The other guy had a 99, and was on his third set of injectors? Not exactly sure why 3 sets in that period of time?
 

Weave

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The early 1999 ISC Cummins had a lot of fuel system problems, including defective pumps and injectors. I don't really care for the ISC's fuel system, it is computer controlled, but still uses a mechanical pump-line-injector setup that I think is outdated. From what I know Cummins got the problems with the system ironed out, but not until recently. Jeff Jones at Kenworth of Fort Wayne, who builds the legendary KW HDX expediters will not build them with the 3126 anymore. The issues with it were far more serious ones than issues that have come up with the ISC. To be honest, now having the luxury of a class 8 engine I wouldn't really bother with any of the little engines again.
-Weave-
 

Weave

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I think Davekc is under the impression I don't like CAT engines, which is simply not true! The C10,12, and 15's are bulletproof, and owners love them. I haven't heard of too many complaints with the bigger CAT's, just the little ones. CAT is coming out with a new medium sizer, the C9. It is only available for the marine market now, but a truck version is on its way. http://www.batborsen.no/news/2003/08/06152835.html
I still don't think their HEUI system is great guns, but it is used on the big CAT engines too now. Reason there haven't been problems with is there is they hold a lot more oil than the 3126's and it stays cleaner longer.
-Weave-
 

davekc

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Any idea on when they are going to make this available? I wonder how much different they will make it for the truck market. They did say they can make alot of computer changes, which may or may not be a good thing. It will be interesting to see what happens.
 

simon says

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Expediter engines

Problem (as Weave alluded to): Longevity vs. initial price! Cat 3126/C7 is meant to be used (viz. Cat itself ) as a short to medium haul motor. If you keep clean oil (I ran 12K on short sump Pete, using 10W40 SB Rotella) and have proper gearing and hsp/torque (275 min. with 860 torque), you can do well for a period. If you run west of Mississippi, I wouldn't have one again. New C7 doesn't hit peak torque now until 1600 rpm- which is ridiculous! just to meet emmissions, and has catalytic and muffler.
I have priced and searched for C9 extensively, and only Freightshakers,& Sterlings offer them in the L7500 - 9500 range. This is where you first run into higher cost. Pete,KW only offers in baby 8 mode, 800 and 385 trucks. At Sterling, in L8500, additional cost for C9 over base 6.4 MBE (04 will be 7.2L above 250 hsp + EGR), is $5000! Out of my range, = difference of almost $200 in mthly payments. 2004 MBE 926 280-300 hsp starting to look real good.
New ISC/ISL will have common rail fuel delivery (finally) and improvements. However, If you see a truck with a P + C= lemon sign on the back door, it's me. I have had so much downtime with my 2000 ISC
with over-cooling, engine shut-off at speed, rebuilt Horton after 190K and new water pump- I wouldn't have another if you gave it to me.
x(
 

davekc

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RE: Expediter engines

sorry to hear about your isc cummins. Many of your problems have been experienced by others. You are right, that if the C9 is a $5,000 option, I would have serious thoughts myself. As far as the 3126, yes, if you are a west coast runner, a 3126 is not the motor you want to do serious mountain climbing with. You need the larger engines. The smaller mercedes engine I would think will have the same climbing issues that the cat does in that regard.
 
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