Cat c12 engine . Starter motor still runs after key is released. The drive releases but the starter motor does not. Have to disconnect the battery to stop it . Have checked starter relay and other related relays and circuit breakers. After tapping on starter solenoid the problem ceased. Is the solenoid the problem?
Yes, the solenoid terminals have welded themselves together. Time for a new solenoid, or maybe even a new starter.
I've put 4 Caterpillar reman starters on my 95E tractors in the last 7 years. The tractors have a 3196, which is the same engine as a C12. The solenoids are complete ****. Mine stop making connection after about a year. I disassembled one last week, just to see *** was going on, and they have burn spots on the cable terminals, the contact disc looked pretty good. At $575 a pop for a complete starter, I'm going to replace the solenoid with one from Napa for about $150. I would guess your problem is similar, the contact disc is welding itself to the terminals. Are your batteries good? Cranking speed good? Low voltage from bad batteries/cables will make the problem worse.
Thanks for your replies. The batteries are fine and the cranking speed is great. The engine starts quick. I forgot to mention in my original post that the starter was rebuilt a few months ago. Makes me think that the new solenoid is junk but I am looking for your opinions since the starter is a bear to remove. Likely I should replace the solenoid then.
IF you can get the solenoid off easily with the starter in place, that is where I would go.
You will probably not get the solenoid off without removing the starter. The stem is attached to the shifter for the starter drive with a locknut, that you have to access through the cover that faces the flywheel housing. If you can get in there to remove the nut, I doubt you will be able to get the new one back in and the nut started.
that's good to know. I changed out the solenoid on the 3406 without much problem. The starter looked like a heavy bear behind the frame rail to deal with. I have two repaired shoulders that don't do "up" very well.
Yes , the starter must be removed to change the solenoid on that c12 because of what Shimmy 1 said. But I know that we have changed one on a 3406 without removing the starter.
39MT-replacement, count drive teeth.
Since the starter was recently rebuilt should I assume that i just got a bad solenoid and just change that?
Who rebuilt it/what brand?
That's your suggestion? Are the 39s better? It would be nice if it cranked faster, I want to add a box and give my tractors 4 batts instead of two, but haven't gotten around to it.
Almost everything has gone to the MT 39. The MT 40 & 42 are a thing of the past. The 39 has a smaller field case will fit most anywhere. Mitsubishi makes a 39MT also/plus one that's clock-able. It's a good starter but a little hard to find, Delco is the norm. I gave up on reman electrical years ago. About the time you really need it the train is coming down the track and getting close.
Thanks for your replies. The starter was rebuilt by a local shop. I don't know the model number of that starter. I know that we have other trucks with a MT 39 though. Are you saying that a MT 39 will fit if it has the correct number of teeth on the starter drive?
Standard count is 11 there are some different brands of engines that require 12 tooth. Unless a starter rebuilder has a torque bench to test load for amp draw it's a crap shoot.
The 39MT is a gear reduction starter and this is the way all the new starter designs are going because a smaller motor spinning faster means less high-torque damage on startup to the motor and connections. Starter Delco 39MT 24V 9.0kW 11T CW 56mm Suits Caterpillar C12/13/15 Detroit S60 Mack E7 The Delco Remy 39MT Heavy Duty Starter is a gear reduction starter ideal for heavy duty truck and off highway applications. The drive has an electrical soft start that rotates the pinion for proper ring gear engagement before cranking, minimizing tooth a www.baxters.com.au Interestingly, there's a heavy duty dual-earth 39MT which is popular in mining here. It's been found that poor earthing (related to corrosion, oil and moisture buildup) is the cause of a lot of starter problems - and it can also lead to cooling system electrolysis problems, believe it or not! Starter Delco Dual Earth 39MT 24V 9.5kW 11T CW 56mm Suits Mining The Dual Earth is built with a long lifecycle in mind and not just that of the starter motor.Whilst a decreased resistance from the get go allows for a higher cranking power and therefore more reliable starts (even at lower battery voltages), it's over th www.baxters.com.au
That is interesting, I would like to learn more on that . . .
The description in the link above gives you the information ....
It's why allot of radiators have a ground cable, which in some cases doesn't get re-installed. Very few clean the bell mating surface. But in some cases electrolysis is caused by a bad cooling system design, like early Freightliners. The top tanks trapped bubbles, didn't matter the engine brand.
I am under the impression that there is less electrolysis issues with the newer ELC coolants, is this the case?
I suppose, haven't really noticed. But cooling systems have improved also. When crossflow radiators came on the scene combined with a surge tank a lot of that went away. IMO