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  1. #1
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    Broken Belt Tensioner

    Several years ago, at about 80K miles, when I first replaced the drive belts in my 2002 330cic, I broke off a bolt that passes through the automatic main belt tensioner. Apparently, this is common, as the Bentley manual inaccurately appears to point to this bolt as the tensioner "release." That is, the point where one puts the wrench to lever the tensioner so as to release the tension on the belt. Anyways, postings on the web seemed to indicate that this bolt isn't necessary unless one needs to remove the timing chain cover, and folks who made this mistake were leaving the broken bolt in place.

    This turns out to not be true. Yes, the bolt is unthreaded where it passes through the tensioner body. However, after several years in this condition, the tensioner managed to rotate around it's remaining mounting bolt. This brought part of the body into contact with the water pump pulley. The force of that contact against the rotating pulley broke the tensioner body. It also damaged the water pump pulley, and eventually, broke the main drive belt.

    The main drive belt disintegrated, and the reinforcement wires inside it wrapped themselves around the crankshaft. Talk about a bloody mess. Anyways, I've got all of the aforementioned removed, and tomorrow morning will schlep down to the dealer's parts counter for replacement.

    The only tricky part will be removing the broken mounting bolt. It is broken off flush with the timing chain cover surface. There isn't alot of room to work. I've never done this before, but I think I need to drill a small hole in that bolt, and use a screw extractor to back it out. I might need to remove the radiator so that I have room to get a drill into position.

    Wish me luck. And, of course, I'll be figuring all this out while going to 3 job interviews in as many days, plus a holiday party.


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    PS: Mileage is now 129K


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    Yikes! You do have your work cut out for yourself!

    As you say----Good Luck!
    I know there are few left hand thread bolts lurking around in there. Make sure this is not one of them.
    And are you changing from a mechanical tensioner to the replacement hydraulic unit?
    Sorry you have to go thru all this just to get back to normal. Hindsight probably teaches that we should not ignore a broken bolt in such a critical area.

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    all that sounds confusing to me - this might help?



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    Re: Broken Belt Tensioner

    You can also use a -right angle drill attachment- to lessen the distance you need to work in there. Also consider -left hand drill bits- which will back out the remaining bolt as you drill. Good Luck!

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    Re: all that sounds confusing to me - this might help?

    Thanks, c.d.iesel. Your diagrams helped alot, as Bentley doesn't show the tensioner in detail.

    The bolt that I broke a couple of years back is the 5" long one numbered as #6 in your fourth diagram. The backing plate (body) of the whole (hydraulic) tensioner assembly is what broke recently. It didn't rotate around the remaining bolt as I originally thought. There are still two bolts mounting the tensioner. But both of the remaining bolts are on the drivers side end of the assembly, so the years of stress caused the cast aluminum plate to fracture.

    Here's a picture of the broken tensioner as well as the new replacement parts.

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    Good tips - thanks!!

    Thanks for suggesting those tools. I went right out and bought them. Man, browsing the aisles of Harbor Freight at this time of year is dangerous to the wallet!!


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    Yeah, it's turned into a belt system overall

    Thanks, Stinger. My model year (2002) is recent enough that I already had the hydraulic tensioner from the get-go. I've almost got the new tensioner re-assembled. I had to replace the body or backing plate, as the part is officially called.

    And since I have to move all the parts, I elected to replace the pulley and it's star head mounting bolt. For years, the pulley has been giving off a slight high pitched squeal that it's famous for. And after two major cooling system services, and multiple attempts to make the new Stewart water pump leak-proof, that star head bolt was pretty chewed up.

    So I'll come out of this with those components also in better shape. And as long as I have it all apart, I'm going to have another go at fixing that coolant leak around the water pump. I've been living with the seepage since I replaced it a year ago, and it's really annoying me. I picked up a new O-ring seal and a BMW water pump while I was at the dealer. If the seal fits the Stewart pump and fixes the leak, I'll return the BMW pump. Otherwise, the Stewart pump is going back to the manufacturer.


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    Progress - Tensioner Replaced

    Well, the belt tensioner is back in with the new backing plate. The hardest part was getting the broken upper mounting bolt out. I combined a right angle drill attachment with left handed bits, but the left handed bits kept breaking. Once I was out of bits, I switched to right handed bits. I thought I must be applying too much pressure, but I pressed just as hard with the right hand bits. So, Drill Master left hand bits from Harbor Freight are just cheesy crap, especially since my regular cheapo Black and Decker bits got the job done.

    Anyways, once I had a hole drilled into the bolt stub, I tapped an extractor into the hole, and used a wrench to turn the bolt. It took some fussing, but I eventually got the broken bolt backed out. I was mighty gentle with the hammer, because I didn't want to swing back and punch a hole in the radiator. There just wasn't room to really seat the extractor in the hole, so I kept having to re-seat it every quarter turn. But eventually, the bolt started to wiggle, and then it was out. Victory!!

    Once that was done, I assembled the tensioner and mounted it, along with the pulley next to the alternator.

    My back and neck are sore from leaning over the engine compartment, so I'm going to finish the job tomorrow. I need to jack up the car, drain the coolant, and pull the Stewart water pump, and see if the BMW seal fits it.

  10. #10
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    When you need HS steel drill bits, do not skimp

    on quality. But you already said you learned!
    I lost your train of thought; what do you mean "see if the BMW seal fits in"?

  11. #11
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    Trying to fix a leak at the Stewart Water Pump

    I have a Stewart water pump that I've removed twice, but it still leaks. I have a theory that the O-ring went bad in the year that the pump sat on my shelf before I installed it. I assume the O-ring from a BMW water pump is the same size, but I won't actually know without removing the pump once again. I picked up the BMW water pump O-ring as long as I was at the dealer.


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    have the stewart water pump in place for

    at least 5 years, maybe 7--good part. Much better built than the BMW. No plastic inside of it like the BMW. Never leaked. But, I have no idea how long the life of a water pump should be on E46. Prior to the stewart, I use to change the water pumps on my E30 about every 4 years, the same time I changed the timing belt (60k)

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    At least it's an easy out. Preparation to get to

    that place is the pain. I'd bet the O ring is the right fit.
    Let us know how you make out on that one too!

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    Lest I forget to add; I always read to lube


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    Lest I forget to add: I always read to lube

    O rings and gaskets before assembly, but then strong admonitions against using oil on some rubber parts as it attacks the rubber.
    So for this and other O-rings in the cooling system, etc. I went to my local photography store and found s small tube of silicone lube sold for O-rings on underwater camera enclosures. Pain in the neck to find, but once you have it, it lasts forever as you only use a speck of the stuff each time.
    I mention this as lubing the O-ring on the water pump is essential given the potential to get twisted wrong during the long squeeze you gotta make when assembling.

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    Supplier?

    So where would one find high quality, high strength, left handed drill bits? At my level of DIY-ness, Harbor Freight, Sears, and PepBoys are my typical tool retailers.

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    Try the King

    They have EVERYTHING, with a really smart online catalog. Ship same day if early enough, and don't have high S&H as a separate profit center. Their product line is deep enough so you can buy a variety of mil spec bolts or teflon tape for instance.


    Try Here

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    All Back Together

    Stewart water pump back in with BMW O-ring. The BMW O-ring is definitely just a tiny bit larger in diameter, both inside and outside diameter. So it's not snug on the Stewart pump, but will probably be pressed more firmly against the pump housing. I lubed it with coolant before slipping it onto the pump.

    Everything is now back together, and at idle, things seem to be all good. The rebuilt tensioner appears to be working fine. No obvious leaks, but a bit of a whine from somewhere in the belt system that I hope is just slippage due to coolant on the pulleys. Gonna drive it a few miles next.


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    Suggest you try the black & gold oxide left-handed

    drill bit designed to resist breaking.

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