I am a new member. I have lurked here for years and now would like to take advantage of the combined wisdom of the members. I have a new to me D7E 48A series dozer that is in very good shape. I was pushing cedar last month and the forward fan belt and alternator belt were lost. In the process the blade on the fan (one) was bent as well. I was able to get a pair of new belts, but the alternator belt was too short. I replaced the drive belts , and got an auto belt that was the right length, but too narrow. I put it on anyway , thinkg I would get the correct from Holt Cat on the next trip to town. I straightened the bent blade while it was off of the unit and put all together and fired it up. After 20 minutes or so while observing at idle the alternator belt was rolling in the groove and then kaboom. Alternator, and forward drive belt come off and get cut up by fan. Now, I looked over the old drive belt and it appears that the belt is wearing unevenly, in that one side had worn more taper to it. My manuel shows a different setup than my engine has for the fan. I have a fan pulley attached to the block with pressure oil lubrication, and the idler is adjusted with one bolt to raise, and only one to lock the the bracket down. My first assumption is that the bearings in either the idler or the fan pulley are bad or loose allowing the misalignment. Which do you think is most likely? The alternator belt doesn't use the idler, and this makes me think it is the fan pulley. Is this something that is field repairable? The front of the pulley has a cap with three bolts that looks like a bearing would be behind it. Also the fan is a two piece blower fan setup. The machine had a out of frame rebuild about a 1000 hours ago. thank you in advance rick in texas
While your belts are off grab all the sheaves and push and pull and wiggle them to see if there is any slack. Also make sure all turn freely and dont have any large chunks broke off. If every thing looks good there, look real close and see if they are all on the same plane. The wrong width belts will flip over and tear up if they are too narrow. Look at the inside of the sheavs and see if they are grooved out. A good check is to take a new proper width belt, lay it in the sheave and see if it is slightly above to flush with the outside diameter of the sheave. A properly running belt contacts the sides of the "V" not the bottom. At the same time too wide of belt wont work properly either.
Sounds like the pulleys are not lined up in the same plane. If there's room, check alignment with a straight edge. The alternator may not be in there with the right bolts, washers etc...just a shot in the dark.
thanks, That may be the case. I will be at the location on thuesday with new belts but I will check the alighnment with a straight edge, as I think with the fan out I can do that. I should have the correct belt for the alternator this time. I appreciate the help.
Pullys may be worn out. Often the case with older Cat models. If so, new belts last only a short time, then tend to whip out. Standard automotive belts will not work with most Cats, usually being thinner in both dimensions. They tend to bottom out in the pullys and quickly wear or turn over as you found. When they come off, they often remove other belts on the way. Cat has dimension tools to check pully grooves for wear. But quite often it is very visable to eye. Remember too, that Cat pullys also have extra height to grooves. This is a feature designed to help prevent belts from being thrown off. It also means that Cat belts sit down in the pully groove a ways. They usually do not sit flush with the top or extend over it. Cat has used alternator pully bracket as a belt tensioner for many years on many models. Yours may be one. A close look at the parts book for your serial number and arrangement will tell the story. Good Luck!
You said alternator. Cat D7E's were built with generators for at least part of the series. Was yours changed over and someone built a bracket to support the alternator which is not aligned properly with the fan and the sheave on the crankshaft?
mine is a very late model, but it may indeed have had a gen on it, However it has a large cat alteranator on it and it appears like it is properly mounted. 160 amp I think the PO said. The alternator belt only runs on the front sheave of the fan pulley and the alternator itself. the wear is onesided on both drive belts. leading me to think it is a fan pulley out of alignment. The idler pulley has no relation to the alternator belt in this case.
Could be the bearings are starting to go out on the fan drive hub .
I've seen a tensioner idler undo a intermittent seizure. It would shred belts routinely, but would spin just fine when checked. Not sure if that applies to you.
I think you are correct on the fan hub bearings. I can get a bit of play on the hub, even though it spins smoothly and no roughness.