garyreed Report post Posted September 11, 2017 Looking at this picture, you replaced the #6 tensioner at the same time? Were they exactly the same with the alignment tit in the same spot? I know it is a pain, but have you put the old one back one to see if that helps the alignment? that is the only thing besides the belt that is different. Gary Share this post Link to post Share on other sites
hermanmullins Report post Posted September 11, 2017 If you haven't started it how are you sure that it is not true? Not trying to smart just asking. Also all this time I had been thinking you had a "V" belt. Sorry if my questions sounded strange. Herman Share this post Link to post Share on other sites
wolfe10 Report post Posted September 11, 2017 His engine has one "V" belt driving only the engine water pump and a serpentine belt driving everything else (alternator and A/C compressor). The V belt/water pump belt is on a MANUAL ADJUSTER, not automatic adjuster. Share this post Link to post Share on other sites
hermanmullins Report post Posted September 11, 2017 10-4 my bad. Herman Share this post Link to post Share on other sites
kaypsmith Report post Posted September 12, 2017 6 hours ago, garyreed said: Looking at this picture, you replaced the #6 tensioner at the same time? Were they exactly the same with the alignment tit in the same spot? I know it is a pain, but have you put the old one back one to see if that helps the alignment? that is the only thing besides the belt that is different. Gary I agree with Gary, the tension idler would my prime suspect. I had a part replaced just a few months ago and the alignment dot was incorrectly placed and just not allowed to seat into the alignment hole, the mechanic was wanting to make all sorts modifications, I had him remove the part and showed him his mistake, he then put it back together correctly, with no modification and a perfect fit. Share this post Link to post Share on other sites
manholt Report post Posted September 12, 2017 Quote One looks as if it has about a 3 degree tilt compared to the outside belt...or is it my eye's? 1/64" off. Share this post Link to post Share on other sites
Losciuto Report post Posted September 12, 2017 The tensioner was bought from CAT, I brought the old one in, the old one was superseded by the one they gave me. The tit is in the same spot, I wire brushed the surface where the tensioner and the block meet and have rechecked the bolt tightness. Also the problem is almost identical as when the old tensioner was installed. I have sent a package with pictures to Prestolite, they are trying to help. Does anyone have a Beaver with a 3126 that could send a picture of the alternator in place. The one possible solution I would like to rule out is that the upper bracket that holds the ALT adjustment bolt is on the block side of the ALT, I do not think it can go on the other side but I want to rule out every possibility. Share this post Link to post Share on other sites
Losciuto Report post Posted September 12, 2017 I am from Alaska, but the RV is located in Plymouth MA at my sisters house. Share this post Link to post Share on other sites
garyreed Report post Posted September 12, 2017 The adjustment is usually on the pulley side of the ear that it bolts to. Unless the bottom mount ( the hole might be egg shaped) and bolt is worn out, I am not sure the adjuster arm can pull the alternator out of line. Is the A/C compressor mounting solid? Can you take a picture from the top looking down towards the crank? The reason I question the idler is that in most cases the leading pulley will push the belt to the next. one. In this case engine rotation would be crank, idler, A/C, atl. if it does not climb the alt then it has to be in the idler or A/C. Gary Share this post Link to post Share on other sites
Losciuto Report post Posted September 12, 2017 This CAT tensioner has one bolt and a nipple that inserts into the block, I do not believe it has a way to set the tension. When I start with the belt aligned in all pulleys, the belt is in the middle of the tensioner pulley. When it comes off the A/C inner pulley lip the belt has moved closer to the block on the tensioner. I have cleaned the fan pulley with a wire brush as well as the Crank Pulley each time I remove the belt. I will pull the tensioner again today and recheck that the nipple is in the exact location as the original tensioner, I believe it is but will double check. The belt I am using is a Napa Micro-V AT25-080702, as stated before I bought a new one and the problem continues. Share this post Link to post Share on other sites
wolfe10 Report post Posted September 12, 2017 6 hours ago, losciuto said: This CAT tensioner has one bolt and a nipple that inserts into the block, I do not believe it has a way to set the tension. Yup, Cat or Cummins, that is how they work. The tension is pre-determined by the spring. As long as you get the detent/dowel in the hole, tension is automatically set. Yes, they come with the detent in different positions/springs with different tensions. Share this post Link to post Share on other sites
garyreed Report post Posted September 12, 2017 I went back and looked at some engines out of RV's and they all have the alt. bracket on the back side of the ear. It lookes as if the tension idler may be hard to install incorrectly as long as the tit is in the hole and sits flush on the bracket. My concern now might be the A/C comp. After everything is put together and it is lined up, and you turn the motor, are the A/C comp. and tensioner the only pulleys to run the belt back? How about the stationary pulley beetween the alternator and fan hub? How many rounds do you have to turn the motor to start the belt moving back? Gary Share this post Link to post Share on other sites
garyreed Report post Posted September 12, 2017 Do all of the pulleys spin smoothly without the belt? Gary Share this post Link to post Share on other sites
abyrd Report post Posted September 12, 2017 I assume the part that you a calling the nipple on the tensioner is a dowel that established the tensioner position. Have you checked to determine that dowel is not bottoming out in hole. I would check hole for debris and also check the length of the dowel pin. Jim Share this post Link to post Share on other sites
garyreed Report post Posted September 12, 2017 That is what I had originally thought that the dowel might not be aligned with the hole. When I looked at the bracket and it's position, it looks hard to get wrong. Gary Share this post Link to post Share on other sites
Losciuto Report post Posted September 12, 2017 I checked all pulleys , they turn freely. The belt starts to move off the A/c fairly quickly when turned over with the key, usually second short crank. ( although a couple times it took 4-5 attempts before it came off) I need to check the idler pulley. I have not kept a log book of each attempt because I did not think it would take this long. I do recall that the wear mark on the idler and the belt were not lined up, maybe 3mm movement on earlier attempts. Share this post Link to post Share on other sites
Losciuto Report post Posted September 12, 2017 One other question, I looked on line and could not find any information on turning a CAT 3126 over by hand. Is there a jacking port someplace? I know on the big ALCO's I used to work on there was a fitting to turn it over. Share this post Link to post Share on other sites
wildebill308 Report post Posted September 12, 2017 Did you happen to take the mount off the block? Could it be turned 180 from original position? Bill Share this post Link to post Share on other sites
garyreed Report post Posted September 12, 2017 I have two different tools. One resembles a pipe wrench with smooth jaws so it will not damage the balancer and it grips the edge of the balancer. The other is a homeade one that uses a 1 1/4 inch flat strap metal about 3/16 thick with a 12 point socket welded on the end that is barely long enough to clear the balancer and uses the crank bolts. There may be a plug on the bell housing that will take the turning tool but that is really slow. Does the A/C pulley look in line with the others? Is the belt the right length? The tensioner pulley should be level with the mounting bolt if not a little lower when the belt is on.You could also carefully tug un the fan blade or maybe grab the fan on the alternator and if you can turn either one it is to loose. Gary Share this post Link to post Share on other sites
desertdeals69 Report post Posted September 13, 2017 If you use a remote start switch you can watch the belt and bump the switch as little or as much as you need to rotate the crank. Share this post Link to post Share on other sites
Losciuto Report post Posted September 14, 2017 I am going to buy the laser alignment checking too, I need to eliminate that as a cause or find the problem pulley. Share this post Link to post Share on other sites
garyreed Report post Posted September 14, 2017 I feel your pain. These are not built for ease of service. On mine I can see all of the pulleys if I open the bed and lay down on top of the motor, I can't do anything there but I can make sure my belt is in line when I change it, then I have to get my wife to pull me out by my feet. Gary Share this post Link to post Share on other sites
Losciuto Report post Posted September 14, 2017 I was able to put the laser on to the a/c pulley. I put the other piece onto the ALT, looks like its lined up. I then removed the idler pulley and ran it to the fan, looks like it lined up. Then I went down to the crank from the A/C with the tensioner removed. It looks like there crank pulley is off by one ridge on the pulley. It looks like the pulley needs to come ways from the block by one ridge. The DAYCO belt alignment kit is what I am using. I cannot get it to work on the fan or crank pulley because it looks like the ridges are not high enough to allow the laser on switch to be activated. I checked the tension between the Alt and idler pulley and it was 160 pounds. The other thing I did notice as I was working with the crank pulley, there looks like a lot of built up rubber in the grooves of the crank pulley, much more than the fan pulley. I am going to be limited on how much tear down I can do as I will need to go back to Alaska for a couple weeks soon. Share this post Link to post Share on other sites
wolfe10 Report post Posted September 14, 2017 Be sure to check your vibration dampener (on the crankshaft, inboard of the pulley). If it is OK, shimming out the pulleys from the vibration dampener should be pretty easy. Share this post Link to post Share on other sites
garyreed Report post Posted September 14, 2017 How bad was the old belt? Were the ribs gone. If there is rubber in the pulleys of the crank and the fan it almost has to have been slipping. Can you get s screwdriver around and check the end play on the crank? Can you pry on the crank pulley and see if it is loose? There should only be a few thousandths of end play not a whole grove worth.Does the waterpump belt look ok and the pulley aligned? Is it a v-belt or serpentine? The crank pulley should be both the main belt and the water pump, so in theory if the water pump belt should be tracking off also. Gary Share this post Link to post Share on other sites
