M30 rebuild

[joshmc2]

My headgasket went out on me today. I already have the gasket kit for the engine. Initially thought that I had to replace the headbolts but I was told by a bmw dismantler that the M30 and M10 do not have to have the headbolts replaced. Just wondering if anyone can verify this. Also wondering if anyone has any experience with this. I have a bently manual, but sometimes they miss things. Also if there are any specific things I should be looking for.

[Bill R.]

you remove it. However its still a good idea to carefully inspect each bolt and replace and that look questionable. Clean and lightly oil the bolts when installing. Just wipe a film of oil on them in other words.










My headgasket went out on me today. I already have the gasket kit for the engine. Initially thought that I had to replace the headbolts but I was told by a bmw dismantler that the M30 and M10 do not have to have the headbolts replaced. Just wondering if anyone can verify this. Also wondering if anyone has any experience with this. I have a bently manual, but sometimes they miss things. Also if there are any specific things I should be looking for.

[shogun]

It's from Jon Evans, I have a link to Jon's page on my site.

click here (http://evansweb.info/index.php?topic=Repairs&page=2)

[callen]

Bill:

I know that the Lbs are really low compared to typical head bolts but wouldn't the threads stretch a bit anyhow? I've been cautious and replaced the bolts in both my M30 head repairs.

Callen

[Bill R.]

quite specific on m50's it says replace since they are tty torque to yield bolts , on the m30 it says to clean,oil and reuse..I myself would definitely replace any that looked like any stretching of the threads had taken place..easy enough to check with a thread pitch gauge and by measuring overall length. If your in the least doubt then by all means go and ahead and replace them. Better to err on the side of caution










Bill:

I know that the Lbs are really low compared to typical head bolts but wouldn't the threads stretch a bit anyhow? I've been cautious and replaced the bolts in both my M30 head repairs.

Callen

[Bill'93Touring]

When you take the head off coolant and oil will get into the head bolt holes. I think this is mentioned in Bentley's, but it's not just fussy, unecessary step. It's a tight fit for those head bolts, they nearly bottom out in the block. So any residual liquid in the hole will be put under hydrolic pressure when the bolts are tightened. Ask me how I know (my 745i had cracks eminating from almost every bolt hole when I removed the head).

Others may disagree, but once the head is off it's convenient to replace some ancillary stuff. The timing chain and tensioner rails can be done, along with at least the upper timing chain sprocket. If the engine stays in the car, then the oil pan is not coming off (but lower timing cover can), so the lower timing chain sprocket can't be replaced (it's a bear even with engine out). So, the new timing chain must have a split link, allowing it to be opened and threaded through and around lower sprocket. (Any comments on wisdom of this? I have no problems on this yet). Then there's the other obvious stuff - water pump, thermostat, even the A-housing if it's munged up, and every coolant and vacuum hose. Again, ask me how I know. Imagine my despair when I got the 745i running again, only to have a leaky coolant hose that runs under intake manifold. (Oh yeah, gasket kit comes with intake manifold gaskets? If not, get some and replace them).