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BMW 7-Series 2006 and earlier

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  • F1Buick, your head bolts failed? How do head bolts fail? Bolts stretch, bolts fatigue, but bolts usually don't break. Were you in there retorquing a head and a couple broke off? Did someone not used Grade 8 head bolts?

    This is mind boggling.
  • f1buickf1buick Posts: 45
    Well, if you grew up with cast iron chevies and fords like i did, the mind indeed does boggle.

    Many all-aluminum engines, including the BMW M70 V12's, use a head bolt system known as "torque to yield." Do a google search if you want more detailed info. (I can talk about it for pages, but I'll pass). At the simplest conceptual level, the "stretch" in the bolts is an integral part of the clamping force used to seal the head/block/gasket. The bolts are stretched just short of the point of permanent deformation (the "yield point").

    One of the benefits of this system is that the bolts can be used as "circuit breakers" in case the block/head is overstressed, with the most obvious example being overhearting. It the bolts were extremely strong and held fast, the block and head would have to absorb the thermal expansion by warping. This would be very expensive with a V12. But with torque-to-yield the bolts already are stressed just short of permanent deformation, so when the block/head expand, the bolts just fail by stretching too far. This releaves expansion stress on the head/block, but leaves you having to install new bolts and head gasket. Way cheaper than new head/block castings, but still a pain in the [non-permissible content removed] (you can imagine how accessible the engine compartment is in a 750).

    Anyway, my V12 did not overheat. The bolts just failed in normal use. This is a rare occurance, but it appears that BMW just couldn't get the V12 bolts quite right. There were several iterations of bolt design. To analogize: they stuck a 19.5 amp fuse in a 20 amp circuit and it thus was possible to overload the bolts during normal use.

    Have I said enough?

    Many motors by BMW and others use torque to yield head bolts. I've been told that Honda had similar issues with some of its 4cyl motors in the late 80's and early 90's. I would imagine that others also have not got the bolt design correct at first. I believe that most BMW I6 and V8 motors use torque to yield but have not exhibited premature failures like on my V12.

    My other car is 2000 Buick Ultra. It has a CAST IRON BLOCK AND HEADS, which makes me feel very secure :). Now if they could just work on the chinzy interior . . . .
  • F1Buick, thanks for the well done bit on t-t-y bolts. Yeh, to people raised on flathead, indeed inline 6 cylinder flathead, cast iron blocks and heads, this is new stuff. Kind of like when capscrews replaced studs.

    BUT, you went opaque when you got to the good part. What do you mean by "The bolts just failed in normal use." How did you recognize this? A bolt just fell out? A blown head gasket?
  • f1buickf1buick Posts: 45
    when I started loosing coolant and then I got 9 quarts of fluid out of a 7 quart pan during an oil change. Uh oh! A compression check confirmed the worst--one cylinder about 40% low and several down about 20-30%. This on a motor that during a previous check had shown only 5lbs variation between cylinders.

    TTY bolts usually do not fail by "breaking." They are stretched until they permanently deform (yield point) and thus loose their ability to hold the deck/gasket/head seal. They seldom reach the modulus of rupture, ie., the point where they actually crack and break. None of my bolts broke, but when I removed them I check the torque with my click-stop wrench. None retained more than 50 ft/lbs and some were under 40. This will not hold compression very well! :(
  • Bmwseller, you posted a week or so ago that the warranty on a CPO wasn't the same as on a brand new BMW. Without asking you for an exact comparison, what are the big differences? Here I was all prepared to save 30 large (70-40=30) on a 745 AND still get a factory warranty.
  • bmwsellerbmwseller Posts: 200
    I recommend the cpo's. It is a BMW product and that's good.

    Maintenance is obviously not covered. Also, paint, glass, headlamps, mirrors,body seals, gaskets, iterior trim, exterior trim, moldings, fatsteners, upholstery, headliner, air/water leaks, wind/body noises, wheels, and "wear and tear". There is a big explanation for "wear and tear" and includes possible exceptions that may include piston rings, valves and valve guides, suspension bushings, ball joints, etc.....

    Add in the $50 deductible and it is a fair departure from a new car warranty. But, check on one of these 'free warranty quote sites and see how where non-BMW products are going for so, it's good, but it's not too good to be true. As you would expect.
  • Bmwseller, thanks for the outline. It seems to me to be a very good warranty, probably about the equal of a new car warranty of 10 years ago.

    Certainly, more of the trim maintenance (mirrors, headlights,headliners, etc.) is now being shifted to the owner. The 7 series CPO owner can possibly expect some $500 service bills in exchange for a 30K reduction in purchase price and a $1500 reduction in sales tax (5% of 30K). for a gently used 7 series. Thats OK and more than fair. Sign me up.
  • sysadbsysadb Posts: 83
    As BMWseller mentioned, you might want to check out other warranty plans. I paid Warranty Gold $1650 for their Diamond Plus plan on my used 740i a month before the factory warranty expired. (The price is different depending on whether you buy it before the fac. warranty expires). In comparing the available plans I found WG to be the most comprehensive and flexible (especially good on the wear-and-tear issue).

     For example, the best part of the WG plan for me was that their coverage period does not start until the date you buy the plan; not from the in-service date of the car. In other words, if you buy a 5-year 100k plan from WG a month before the fac. warranty expires you'll get close to NINE years of protection, assuming you don't hit the 100k mile limit before the 9 years are up. Most other plans advertise a maximum of 7 years/100k miles, but the 7 year period starts on the in-service date of the car. You're really only getting 3 additional years of coverage over and above the factory part.

    This doesn't matter if you get to 100k miles on the car quickly, of course. I only have 44k on my 1998, so the extra 4 years (and 75k limit) that I bought suited my driving needs. WG will also quote you customized plans, even over 100k miles, but the price rises quickly on those. I think the quote I got for 5 extra years (limit 100k) was around $2200-$2300, IIRC. Once you get an online quote from WG they send you email "sale" notices regularly on their plans, and I was able to negotiate an extra few hundred off as well. Also keep in mind that if the CPO car is still in factory warranty you're paying for additional coverage up front. If you decide to get rid of the car early you've wasted a lot of money..

    The only problem with WG (and other competitors) is that they use Chilton (or similar)rates to determine their claims reimbursements. This is fine for most shops, but your BMW dealer service department might get Bitter Beer Face over the claims "process". If you know you'll want to use a BMW dealer for repairs you might want to ask them whether they'll honor the rates before you decide.

    DB
  • bmwsellerbmwseller Posts: 200
    I'm thinking that the $1650 figure from warranty gold seems a little too good to be true. That company might go out of business, who knows? But, wouldn't you expect to pay MUCH more than that for service on a 98 model seven series in that higher mileage range?
    I'd want the BMW product that I know any BMW center will honor without question.
  • patpat Posts: 10,421
    Read about other TH members' experiences with Warranty Gold by inputting that phrase into the Keyword Search box on the left side of the page.

    And scan through the list of the active discussions here at this link for further scoop on other companies: Finance, Warranty & Insurance board
  • sysadbsysadb Posts: 83
    I've used the WG plan at my BMW dealer.
  • I'm going to buy a 2001 740iL. Will I need snow tires to keep move in the Northeast this year? I assume yes. I just want to factor in the $1K when making a decision.

    Thanks
  • If you want to get to work every morning and home at night you'll need $1100 worth of tires, wheels, mounting, balancing and shipping. This $1100 will get you through only three seasons if you choose Blizzak and don't put on more than say 4K between 1 Dec and 1 April.
  • Earlier this year, I replaced my OEM Michelins w/ Dunlop 16" all-season Sport A2's. I'm in Boston and they're fine in the snow. Consumer Reports rates these the #1 all season tire. You will probably want to switch tires for the winter if you are currently runnin the M-Parallel tire and wheel sport package.
  • Thanks for the responses.

    I'm zeroing on a 2001 740iL with sport so I'll need to replace the tires/wheels for the winter. I'll check out what TIRERACK has to offer.

    Thanks again,

    Jay
  • on my 750. They seemed great for the first 5000 miles but were disappointing over 30,000. They were vulnerable to road hazards, had difficulty sealing to my rims, and lost a lot of traction as they wore down. The handling deteriorated so markedly that I finally ditched them even though they weren't down to the wear bars.

    I now have had Firestone SH30's for 20,000 and it is a vastly superior tire, especially in the rain. Unfortunately, it is out of production!
  • The car I'm buying is being prep'ed now. Anything particular I should look for in the final inspection? Has 39K and just came in off a lease. It will be Certified when I pick it up.

    Thanks again for the help,

    -Jay
  • I've been asking some what some may consider "stupid" questions. I appreciate the tolerance of the board.
    =====================================
    I was looking at custom wheels for the snows I'm going to buy. The wheels will end up costing $400-$600. Are the rest of you that put snows on for the winter going through this?? or do people just buy steel rims and wheel covers for the the few months that the snows are on the car?

    Thanks again,

    -Jay
  • did somebody pull the plug??
  • rowlandjrowlandj Posts: 254
    They have packages with wheels and snows that you can likely find in a more reasonable price range. You can find wheels not quite as plain as steel with covers. I am sure they have something in the less than $400 to $600 range as above.

    They'll ship the goods ready to install so there's not a lot of hassle.

    JR
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