how to detect eta engine hexagon head bolts - BMW Forum - BimmerWerkz.com
3-Series (E21, E30) Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.

 
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#1 (permalink) Old 10-05-2005, 02:08 AM
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how to detect eta engine hexagon head bolts

my car is a 325e and want to know if the engine has torx or hex head bolts.i was told to open the engine oil filler cap and illuminate with a light and check visually the head of the bolts. i have attempted to tell the difference to no avail is there anyother method to detect hex head bolts. i want to change them as soon as possible if i have them. thanks
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#2 (permalink) Old 10-05-2005, 11:14 AM
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You may have to remove the rocker cover to she the heads of the bolts I have a drawing showing the difference but since the site has changed I can't work out how to attact it email me through the site if you need it
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#3 (permalink) Old 10-05-2005, 12:26 PM
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Take the oil fillter cap off and look inside. If you see a bolt with a head like this, you have the hex head bolt. If the head of the bolts look like this you have the torx ones.
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#4 (permalink) Old 10-05-2005, 03:08 PM
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Red face head bolt nonsense!

Hi,
Why are you concerned about the head bolts? The current mania about changing the 17mm factory bolts for hex-head is in my opinion, patent nonsense. First of all unless you have a need to repair a valve or gain access to the block for some reason, you should never remove head bolts, even one at a time, as you run the risk of unseating the head gasket. I just did a valve job on my 325IC at 200,000 miles, and following the advice of my machine shop, (thirty years of experience with BMW engines) I measured the original 17mm head bolts for length, making sure none had stretched, (they had not ) cleaned and oiled them, and put them right back in. The car runs fine! I also find the tightening sequence for hex bolts confusing; The torque instilled by turning them an "extra 90 degrees is vague. I'd rather use a conventional bolt with a reliable torque wrench. Instead of forking over $70.00 to the hex bolt people, give it to your favorite charity instead. My opinion. Good luck!

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#5 (permalink) Old 10-05-2005, 08:04 PM
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There have been issues in the past of the hex head bolts having the head of the bolt come off due to a design flaw. There is a TSB from BMW stating this issue and advising using the updated torx head bolts. The later production M20's came with the updated torx head bolts. I work at an independant BMW shop and we replace the hex head bolts for the torx head ones all the time just doing one bolt at a time with no problems. When I got my E30 the first thing I checked when I went to look at it was the head bolts. Personaly I'd rather spend $40 on a full set of head bolts than $250 to get my head rebuilt, but thats just me. Turning the bolt an extra 90* is not vauge, its called a torque to yeald spec. You will find this a lot in engine building and it actually produces and more accurate tightening of the part. I hope you didn't use oil to lube your bolts, if you did your torque is going to be off. Its best to install bolts dry or at most with a very light coating of machine oil.
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