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Old 12-01-2011, 10:46 AM
Autohead Autohead is offline
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Location: Moody
 
Join Date: Nov 2011
Posts: 9
Mein Auto: 1992 BMW 325
I've been reading all the responses to the posts above and it's not uncommon for these cars to crack the heads. Reason being because the cooling system fails at close to 95k miles. The heads are made of an impure aluminum that doesn't withstand the heat as much as a purer aluminum would. That's just the reason why it's so common to see these heads crack. If the cooling system is kept in tip-top shape, these heads will run forever.
That said, and here comes a shameless plug, we have a machine shop that deals specifically in BMW and we would be happy to give any advice that may be needed.
My primary reason for mentioning this here is because it's sad how often a machine shop gets a BMW head to recondition and they end up junking it. Why? Apart from the common mistake of resurfacing before having pressure tested only to find it's cracked and now too thin to resurface again, not every machine shop realizes that BMW is the ONLY car in the world whose heads have a very fine tolerance for how much can be machined off of them. They can only have .012" machined before they become undersized and in need of a thicker gasket. From there, they only have another 0.012" before they're junk. Shops don't realize this and machine too much to begin with (without having straightened the heads prior to skimming) and go from an original thickness head to a junk head in under 5 minutes.
So, please, if it ever does turn out to be a cracked head, be sure you know the shop you're dealing with is aware of what kind of tolerances these heads need to remain within.
If you want advice, you can check out www.autoheadperformance.com and call with questions. We're happy to answer questions before you take your head to a machine shop.
Do your research beforehand and ask the shop you're using questions, you won't regret it

Sheldon
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