Dust Caps. Why do they keep coming off?

Discussion in 'Tires / Brakes / Bearings / Axles' started by Matt O, Jul 17, 2010.

  1. Matt O

    Matt O Strangers are friends who have not yet met

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    I have owned my 1992 coleman Seneca popup for 3 months now. I have just put my 5th dust cap on and have the 6th one in the TV. Why do they keep coming off???

    Here is my theory. Tell me if I am wrong. Metal expands when it heats up. Not having the cap on all the way the hub opens up an loses its grip on the cap and it fell out. Many times. By me putting it on while warm, it went in easier and as it cools it should crimp the cap and lock it in place and never ever fall out. Right?

    When I bought it I knew it was missing. I went to the auto parts store close to home and bought a Ford dust cap that seemed to fit. It was 1 31/32. I left for the first camping trip and it was gone by the time I got to the campground. I must not have tapped it on hard enough. I bought a 2nd dust cap and banged it on there. I saw it roll off in the middle of the highway. Darn. I do some research online and call an RV store. For a trailer I need a dust cap that is 1.98 inches. The ford 1 31/32 works out to be 1.96 inches. OK, two one hundreths of an inch was the problem. They are cheaper too, $5 for two -vs- $4 for one Ford dust cap. I put 3rd one on. It was a bitch to put on, I had to really bang it. I go to the Spring Gulch Rally. It's gone when I get there. WTF?

    Now I know this problem is beyond me and I call the RV place to get a quote to repack the bearings and for THEM to put the dust cap on. $150. DW and I talk about it as we are going through the mail and what do we see??? A coupon for Stolfzus RV $99 per axle. I dropped it off last weekend.

    I picked it up on Thursday night. I checked the 4th dust cap. It is really on there good. This is not going to come off. Of course, by the time I got home it did. I went back this morning and watched as the guy put the 5th one on in the parking lot. I talked with him as he did it. He was really banging it and it was not going on any farther. It was not on down to the little lip. He said it was tapered so that it would get a better bite as it goes in and that was it. OK, makes sense.

    I leave and I am smart this time. I pull into the first parking lot I can get into. Good timing. It was just about to fall off. Hmmm. The hub was at warm operating temperature. I can basically put it on and off for a little bit, not like I have to bang it on like when I first put it on and it is cold. Is this the issue????????


    I bang it on while it is warm. I get it on down to the lip. I check it again. It's still on good. I check it another time. It's still there when I get to my destination finally :) Will it fall of again? [MOD]
     
  2. Twisty

    Twisty New Member

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    The hub may be out of tolerance from the factory if it has always dropped caps.
    If it was mine I would use a hammer and punch to "fold in" three "tabs" on the inner edge of the opening, equally spaced.
    Replace it and it will save you time, money and grief in the long run!
     
  3. Flyfisherman

    Flyfisherman New Member

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    Of course, getting the correct sized dust cap for the hub is the first thing. I've always replaced, when I had to, with one that was specified by Dexter Axle in that is the axle/hub that's on the pup. Sometimes when having the hubs serviced, as in re-packing and replacement of the seals, they dust caps are not replaced securely and the first rest stop on a trip you'll note one is missing. - So, having the correct size to begin with, then making sure it is "banged" home securely (I use a rubber mallet), and a trick I picked-up from an oldtime service manager as those dust caps are taken on and off serveral times, was to take a hammer and give a light hit on one side right at the edge that goes into the hub to make the once round hole now ever so slightly egg shaped ... not too much though as it won't go on!
     
  4. Matt O

    Matt O Strangers are friends who have not yet met

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    I don't know if the tabs or the egg shape would go on. It was very difficult when I put the 1.98 one on myself and even witnessed the service guy having to play with it a bit to get it on perfectly. I don't know what brand axle is on the popup, it is a coleman. That would be the next thing I will do. Find out what axle I have and get that specific brand dust cap. If that doesn't work, I may just have to buy a whole new popup [:D]
     
  5. Flyfisherman

    Flyfisherman New Member

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    If it's a Coleman I'm quite sure the axle would be a Dexter.

    To find out for sure ... you'll have to crawl under the pup from the rear ... might lower the front jack to make it easier ... and on the back side of the axle there should be a metallic label telling the manufacturer, the date the axle was made, the axle capacity and the model number. With that information you can log onto the Dexter website and find whatever you need to know about that axle assembly.
     
  6. Raycfe

    Raycfe Waterford Ct.

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    An easy repair would be to drill a hole in the center of the cap and spindle, and hold the cap on with a small sheet metal screw.
     
  7. phipps

    phipps Member

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    Won't work. The cap spins with the wheel and the spindle is stationary.
     
  8. Matt O

    Matt O Strangers are friends who have not yet met

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    A screw can't go into the spindle but a hole in the side of the hub at the end would work like a set screw. I don't have the skill or tools to accomplish that. I am half tempted to just drive around in a circle just to see what will happen if it will fall of again.
     
  9. Raycfe

    Raycfe Waterford Ct.

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    Didn't think about that ..... thanks for bringing that up.
     
  10. Sharpie

    Sharpie Member

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    I had the same problem til replaced the caps with bearing buddies. Now no more lost caps.
     
  11. Raycfe

    Raycfe Waterford Ct.

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    The bearing buddies are stronger and don't collapse. But don't grease the brakes with them. I know my screw idea would not work, but how about a heavy wire over the top of the cap and held on to the hub with a zip tie or hose clamp??
     
  12. justinwy

    justinwy New Member

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    Had the same problem more than once on my boat trailer.
    The first time I used blue loctite, just be sure to use the blue, not the red.
    Have also used a small dab of rtv gasket maker.
    Make sure the cotter pin is not out to far and pushing the cap off as the hub spins.
     
  13. Matt O

    Matt O Strangers are friends who have not yet met

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    the cotter pin is clear of everything so that isn't an issue. I am afraid to put bearing buddies on due to the cost. If the caps won't stay on, why or how will the bearing buddy stay on? And they cost more then the caps. There is something I saw that is basically a big rubber boot that goes over the hub and on the studs before you put the wheel on. I don't know what it was truly for but I thought it would at least catch the cap when it falls off. But they are $20 each. That may be a next step. I thought about a little tether on the cap and onto one of the studs but I don't know how that will exactly work with a wire whipping around with the tire at 65mph.
     
  14. Retired Alex

    Retired Alex New Member

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    Just ran into the same problem this week. A friend came home from a trip and had a bearing failure on the road. The hub had expanded and when it cooled it did not return to specs in size and he kept loosing his dust cap. He was able to keep one on to get home by wraping it in electrical tape. The solution, buy a new hub. Much cheaper than a new trailer.

    Possibly the former owner had overheated the hub and never told you about it.
     

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