Do you know how to replace DP alternator & belt?

Anyone having alternator problems should ck the cables, both pos+/- where attached to alt, frame, panels, etc. loose connections can/will cause alt to overheat & seize up, break belts. Tendency is to blame the alt when it may be something as simple as a loose cable.

We went thru 5 alternators (24volt) on our MCI (6V92TA) in about 12 months due to a loose pos cable. All were R&R by Stewart Stephenson in Dallas to Newport News, etc. finally a bus buddy/mechanic was doing something else & pulled on the pos cable & it moved. He took it off, cleaned the end, etc. & reattached. He also found we had incorrect belts (4). I've forgotten what belt it takes but I carry a spare set. The SS mechanics never ck'd the belts or the cables.

These alt's are heavy & require a hoist. I seem to recall they weigh 200-300 lbs. not to mention, you just about can't get to the thing.

The loose cable was causing the alternator to kill itself when it lost contact, it would overheat & fry.

May not be your problem, but if this helps one person-----

James
MCI 8

I did the alternator on my rear-radiator Cummins B just last April. I had to work from the top. The alternator needed replaced as did the tensioner. The belt would have not been too difficult to change at the point, but it was still in good condition because the Alternator didn't sieze.

I agree with others that it wasn't too much fun holding the alternator into position while inserting the bolt. It was a minute, but felt like an hour. The tensioner was so badly rusted that spring didn't seem to return to its orginal posiiton. The tensioner was almost as much as the alternator.

Bring the old tensioner with you to the parts store, because I orginally got a Cummins tensioner that worked in the opposite direction. Sending the alternator out for a rebuild may take a while. My NAPA had the alternator in stock, but the (correct) tensioner was a special order. Hopefully your tensioner is still in good shape.

After freeing the alternator from the block, I didn't have to remove any other hoses. I was able to find a clear pathway out along the frame almost 3 feet back. Just remember how you got it out, so that you'll know the way back.

You probably already know this, but I didn't see it mentioned...

Ensure you disconnect the ground cable (or any other suitable battery disconnect) before you disconnect any wires from the alternator.

And, I have a question for anyone who looked at the photo in the thread with the OK and NOT OK to use a longer extension on the tensioner.

I just can't imagine that the tensioner bearing is so weak it can't handle the twisting load for a couple of seconds at most.

The photo seems to show a 1/2 ratchet, with a fairly short handle. Now, if it showed a 1/2 break-over bar and 24" handle I might tend to agree that is probably not a smart idea.

A tensioner tends to move in an arc, and a solid fitting extension isn't going to create much twisting if the operator of the handle places the pressure to create torque on the correct vector according to the angle of the handle in relation to the arc angle at that moment in time.

In short, I believe that if I really felt I needed to use an extension to get to the beast, I would do exactly that.

Both photos showed an image with extensions. As a general rule I don't an extension unless I have to; so I'm curious as to why this wasn't the default "good" picture, the short extension the "OK" picture, and the long extension the "bad" picture.

Sorry if this hijacks the thread.

I've tried this just to see if it is real. It is... but, I wouldn't try this with your coach....:B....Dennis

Belt change in 5 seconds

donsuefuggrwe wrote:
How do I find all this info for a 2001 3126B 300 HP rear radiator Cat engine. THANKS

Well Sir,

If you're asking about replacing the belt(s) and or any other items of wear on the front of that CAT, there's a couple of alternatives. You've got some explanation above this post. Another way is to "cut" a large access port, right on the top section of the shroud. Many have done that for a multitude of reasons. They've replaced the fan hub bearing, the serpentine belt, belt tensioner(bearing) and idler(bearing) etc. The final alternative is to R&R the radiator and the CAC. I did that.

I had ulterior reasons though. I had a leak in the radiator and, my CAC and radiator were both severely clogged due to blow by fumes/oil/dust/road debris etc. Now, while R&Ring that radiator and CAC is a fairly pain in a$$ job, it sure as heck makes getting at the rest of it, real easy. And, like stated, you can go to town on replacing all the drive bearings you can get your hands on too.

It's sort of a tossup. You stand on your head, arms twisted, blood rushing to your head, hands and arms going to sleep, all while TRYING to do all that kind of service. Or, you simply ( I say "simply" yeah sure it is) remove th radiator and the CAC and do all your work at one time.

Neither way is real fun. It took me about 6 hours to remove the radiator and CAC. But, I got a lot accomplished while it was off. So, it's your choice. Good luck.
Scott

My alternator (Leece Neville) did the same thing while I was traveling in Northern BC. Belt also snapped.

From reading around on the internet, this scenario does not seem to be uncommon with Leece Neville alternators. Not sure if they make them cheaper for RV's or what.


I have a Cat C9.

In my case, there was enough room to thread the belt around the fan fins between the shroud to get it on the pullies. I am sure this is the case with yours as well. You are going to need two people to put the belts on, one putting the belt on the pullies reached underneath, and one putting the belt onto the pullies on top.

Removing and replacing the alternator will take some hand strength. On my alternator, there are four bolts holding it to the engine. Loosened the top two from inside the RV and the bottom two underneath it.

In my case, the alternator would not come down from underneath the RV because there was no room. Had to come out the top. This being the case, had to remove some Turbo and Exhaust lines that were preventing the alternator from coming out. This part took the longest as these turbo and exhaust hoses were really wedged on there.


I would recommend that you have someone else do this job, unless you lift weights on the side. Holding that alternator with your fingers trying to get it lined up, while using the other hand to jam the bolts in, all the while standing on your head is exhausting. This ain't no car alternator!

In my case, the ONLY belt supplier that makes a belt the perfect size with the perfect amount of grooves was Caterpillar itself. Others make some "close" or with less grooves, but I would rather go to the dentist than do this job again. Goes without saying that I ordered a spare belt to carry from now on!

donsuefuggrwe wrote:
How do I find all this info for a 2001 3126B 300 HP rear radiator Cat engine. THANKS

That is really a "Two party" question.

Caterpillar fit the water pump belt. This is the inner belt and runs just the water pump. Goes from crank pulley to water pump to idler pulley. It is an old fashion slack adjusting idler pulley.

Your chassis maker speced and fit the other engine accessories like alternator and dash A/C compressor and you will need to check with them for the proper belt (serpentine belt) and it's routing. It is on an automatic belt tensioner.

Follow up---First and last time fan belt was changed 60000 miles ago I did this with a master mechanic and it took us 6 hours. It was his first time also.

How do I find all this info for a 2001 3126B 300 HP rear radiator Cat engine. THANKS

Not to throw salt on your wounds but that is why I love my side radiator. You will be able to fish the belt around the fan in between the shroud, I would have someone up top in the motorhome and someone down below to help if possible. As for unbolting the alternator, make sure that you mark the wires and disconnect both the house batteries as well as the coach batteries. Good luck to you.