Cat 3126

[bth9461]

I run a LTL/hotshot business, mostly flatbed freight and cars. I am considering buying a used 1999 FL70. IT has a 6 speed, 3.58 gear ratio, and a 300hp CAT 3126 in it. I was wondering what any of you thought of the CAT3126 as an engine? Is the Cummins 8.3 liter of that era a much better engine? The CAT is only a 7.3 liter. Which engine is better on MPG? What about Engine life? This truck has 280k on it, it has been used as a trailer puller most of its life, Injectors replaced at about 200k.

Brian

 

[Refer Hauler]

Suggest you do a search on this site about the 3126 engine. then make your decision.
For what it's worth I would run away ( at high speed ) from this unit as soon as I saw the yellow engine. The 8.3 ltr ( ISC ) engine is a much better choice IMO.

 

[Bruno]

The 3126 Cat is not a bad motor and gets better mpg than the 8.3 Cummins. I can stay that because I have 3 3126 Cats and 1 8.3 Cummins. We have had more problems with the Cummins than the Cats, also Cummins parts seem to be higher.

 

[P51bombay]

As I understood it, cat prices are generally higher than Cummins. Local dealer overcharging you perhaps? The 3126 in my M2 gets around 9.5 with the usual load 4-6K. It runs pretty nicely at speed but shakes like crazy at idle. Overall though its been a good reliable engine, never failed me despite a couple of times shops saying they found things (literally) falling off the engine, engine mount, starter motor, oil filter housing.

 

[EagleRiverWI]

I get 10 mpg with my 3126 and it is a 2003. I have read about the potential problems and would not consider getting an older one with too many miles on it. I am no mechanic so I need to play it safe.

 

[spudhead911]

A 1999 FL70 with just 280k on the clock just doesn't seem right. I would be very careful about buying this truck. I might wonder if the engine passed the million mile mark and was on the second time around, hence the 280k on the speedo. Those class 7 engines are only good for about 250k or so before most of them need a rebuild. I had 2 FL70's one had a Cat, the other a Cummins in it, both needed rebuilds at around 265k.

 

[greg334]

Well between the two engines, Cat 3126 and a Cummins ISC, the ISC wins on many points, one is it is far cheaper to fix and the parts are still being made.

When buying a truck, always get the oil analyzed, get the vin and run the vin, have the ECM dumped to verify the miles and get the engined dyno'ed. If you can, have an independent mechanic check things out.

With that low of miles with the age something does not seem right.

 

[bth9461]

I believe the truck was never used as an Expediter, The guy who has it now put 45k on as a tow vehicle for a 4 horse trailer, and the previous owner pulled a mini-float trailer pulling flat freight for the oil patch I think. I will try and get more history on the vehicle. So I think it might have seen short haul or recreational use mostly.

The main thing I was trying to find out is wether the Cat motor is a problem, I had heard some negative things in the past, but I have found that now that I am asking questions it might be better than I thought.

I understand that the motor is a throw away were the Cummins can have an inframe. I am calling both dealers and getting a ballpark figure, to see the cost difference.

Plus once I find THE TRUCK ( this is still a maybe), I think I will spend some money to have some tests done on the truck. I want to be real sure before I spend that money though.

I really appreciate the advice, thank you. Anyone else want to add something please do.

Brian

 

[greg334]

Brian,
All engines are a cr*p shoot, some will work great for one person and break down constantly for another.

The thing is, hauling has a different effect on it than say using is as a taco wagon. You as a buyer have to think about it as a tool and when you buy the tool that makes you money, then you spend some money to make sure it will work (OK I think I said that right). I tell everyone these are the most important things to do, Oil Analysis, Dyno, ECM dump and a VisCheck. the last item is not as well received but it tells you a lot about the chassis and the condition is it in. The ECM dump will tell you an awful lot about if the ECM is original, how many times the key was turned, Idle time in some of them and so on. The dyno will tell you the blow by (an indication of how the rings are) and the horse power (torque too). The OA will tell you the condition of inside the engine and so on.

The real problem with the 3126 is;
Parts are getting harder to find, which means that you may be stuck with the engine at a shop trying to find parts for it.

It uses in-cast cylinders which means that the cost to do a proper rebuild may be too much, the cylinders are part of the block, not like the Cummins ISC where you can replace them.

outside of that, it carrys the cat name and quality.

Hope that helps a bit more.

 

[Bruno]

The 3126 Cat has been a great motor for me. My one truck got 720,000 miles on a 3126 before we had to do an Inframe at R & R engine in Akron, Ohio. Now the 8.3 Cummins we have had more things go wrong with it. The fuel pump was $2700 to replace. A fuel pump in a Cat is less than $300.00. Now if it had a 5.9 Cummins I would say go for it, those are great motors and you can get great MPG with them.

You can always ask to take the truck to the dealer to have them pull an ECM report and it will tell you how many miles are on the truck.

 

[P51bombay]

Brian,
The dyno will tell you the blow by (an indication of how the rings are) and the horse power (torque too). .

How do you get an indication of blow by from a dyno?

 

[greg334]

How do you get an indication of blow by from a dyno?

When the truck is on the dyno, there is a sensor that is attached to the engine that measures the flow of air out of the crankcase. The flow comes from the compressed air that is in the cylinders and with worn rings, the flow is greater. The engine has to be running and under load to produce a proper reading.

Dave, many have great luck with the 3126, it is a good engine but like I said it is a cr*p shoot, the same goes with Cummins where I can have sister engines (meaning came right off the same line built next to each other), one lasts a million miles while the other lasts 250k.

 

[Bruno]

Gregg is telling you the truth. Get the ECM checked. Gregg I don't have a hard time finding parts for our 3 Cats. Just call up Ohio Engine Power and they always have the parts we need.

 

[davekc]

Lots of good advice. Biggest one is have the thing tested. That engine will be around for quite some time. New ones are still being built for marine and construction so parts shouldn't be too much of an issue.
These engines are awesome in a marine application.
ISC is cheaper to rebuild but we have run the 3126 up over 800,000 with no problem. We currently have one at 500,000 and only major repair was a shorted wire to one of the injectors.
The other issue is price and how service is performed. Many Cat dealers charge by the job rather than by the hour. Quite a bit of savings if you have the option to shop a little.
On the truck with a rough idle, that can be adjusted through the ECM at a minimal cost unless there is another issue on it.

 

[ericmoss37]

My advice is not to buy it. I bought one with 380K miles on it back in Febuary and on my first load it broke down and I had to put 3K worth of work in to replace the o-rings heiun pump, injectors and seals. Well I was about to trade it in tomarrow and the truck is sitting in a truck stop waiting to be towed to a dealer because it has internal engine problems. It's smoking black and white smoke and dumping fuel. I will never go class 7 again. I am going to stick to class 8 trucks.

 

[Bruno]

Sorry for Your bad luck on your motor. I would have the ECM checked to see if that is the real mileage on the truck. I swear by lucas, I use it in all of our trucks.

 

[bth9461]

Thanks for all the advice, many of the comments seem well reasoned, and agree with what I was told by some friends that have experience with these motors.

I priced a REMAN engine from CAT it was ballparked at 15-18k, the rebuild on the Cummins was 6-7k. If the egine goes down, I am sure it will be away from home and with freight on the trailer.

Seems to me that the CAT motor is a good engine if taken care of, seems that many get well over 500k on the motor. The question seems to be how well it is taken care of and a little luck seems to help (with any engine).

I will let you know how this turns out, think I am going to go with the used Cummins, because of the rebuild cost, I can absorb that much easier, at an unexpected time, I have never been a very lucky guy either. I am also cosidering class 8's with the 11-12 liter Cummins/CAT/Detroit's.

Brian