M30 head bolt removal mystery--advice sought

[Dash01]

Engine is sitting on garage floor on its bottom and mount leg.

I un-threaded the head bolts to the point (~1" out) where their grip threads should now be disengaged from the block. However, 4 or 5 of the middle head bolts are still very stiff & tight and will not disengage for withdrawal. Side load on the head should be taken by the dowel pins and by the strap attached to the overhead hoist, so side load should not be binding on these bolts.

What am I doing wrong? Why won't these bolts just get looser and come out like the others did? Nothing of this sort happened with other M30 head removals. At the end of a long day, I thought it best to get some objective advice before monkeying further.

[632 Regal]

gaskety goop holding it sealed in there perhaps??

[Dash01]

gaskety goop holding it sealed in there perhaps??

Maybe, but I dunno how. It takes a fair effort on the 1/2" drive ratchet wrench to turn the bolts, yet they are already ~1" up out of the head so should be already disengaged or nearly so.

Besides, no gaskety goop should be down there at the head gasket, which supposedly has silicone impregnated so needs no goop. 8 or 9 of the bolts came out just fine and normal, only 4 or 5 seem unduly stiff.

Any more thoughts?

[Blitzkrieg Bob]

Did the head gasket fail?

if so there may be a little rust or custy stuff around those threads

[Dash01]

No evidence so far of HG failure--oil not contaminated, brown, or milky, although the alu. head itself is somewhat discolored or stained by the oil.

Normally (as with 7 or 8 of the head bolts), loosening gets easier as they come out. Somehow, the middle 4 or 5 bolts continue to be quite stiff regardless of the fact that they are ~1" out and should have little or no thread grip into the block. I thought perhaps since the engine sitting on a concrete floor is slanted and the head would naturally slide off to one side, the bolt problem would be due to side load binding on the bolts. However, to prevent such side load I left the upper corner bolts in, and attached straps to the overhead hoist to support the weight of the head and keep it centered. And, there are a couple of dowel pins to keep the head properly centered. So, there should be no side load to bind those bolts. Maybe slackening the straps will help.

[whiskychaser]

Long shot but maybe you have got some oxidation on the head bores and the bolts are binding in that. Only sure way to find out the cause is pull one out

[Dash01]

Long shot but maybe you have got some oxidation on the head bores and the bolts are binding in that. Only sure way to find out the cause is pull one out

The head bolts that came out had no oxidation, but were pretty goopy with oil. The ones that don't want to come out are quite stiff, despite being ~1" unscrewed. I'm gonna hoist the whole shebang from the engine block hoist points, then lower onto a wood space so as to keep the head level, to make sure there is no side load on those bolts.

[Ross]

It ain't side load. Corrosion, I'll bet. I hope you don't pull the threads out.
Also, all the head bolt holes on the M30 are blind if I remember correctly. It'll be interesting to see what comes out since they aren't in a coolant passage to promote rusting.

[Jeff in MN]

with a rubber hammer. Why are you stopping after 1" out? After the bolts are out, the head will still be held in alignment with two guide rings I think on the 4th and 9th bolt (diagonal), so just rap it firmly with rubber hammer. I finshed my head rebuild about 6 months ago and my M30 has been running flawlessly.
I'd be glad to share some pics. Even the one were I gouged head surface during the install. Arrrrrrgh.

[Dash01]

with a rubber hammer. Why are you stopping after 1" out? After the bolts are out, the head will still be held in alignment with two guide rings I think on the 4th and 9th bolt (diagonal), so just rap it firmly with rubber hammer. I finshed my head rebuild about 6 months ago and my M30 has been running flawlessly.
I'd be glad to share some pics. Even the one were I gouged head surface during the install. Arrrrrrgh.


I'm stopping ~1" out because at that point the bolts really get stiff, and I don't want to force them for fear of buggering the threads machined into the block.

So, rather than taking the chance of messing up the threads, I thought I'd ask advice from others more knowledgeable.

I've removed the head on an M30 a couple of times, but never had this sort of difficulty--normally the bolts just loosen to easily remove by finger after a turn or so with the wrench. Not these, though. What could be fouling them? I squirted some penetrating oil down each bolt shaft, so we'll see if that helped overnight.

This is a replacement engine from a wreck, so I don't know its history. Any chance such engine could be so warped as to foul the middle headbolts?

[Ferret]

I'm stopping ~1" out because at that point the bolts really get stiff, and I don't want to force them for fear of buggering the threads machined into the block.

So, rather than taking the chance of messing up the threads, I thought I'd ask advice from others more knowledgeable.

I've removed the head on an M30 a couple of times, but never had this sort of difficulty--normally the bolts just loosen to easily remove by finger after a turn or so with the wrench. Not these, though. What could be fouling them? I squirted some penetrating oil down each bolt shaft, so we'll see if that helped overnight.

This is a replacement engine from a wreck, so I don't know its history. Any chance such engine could be so warped as to foul the middle headbolts?

The first M30 I played with did this - I have no idea what caused it, though I suspect it was oil on the threads creating an airlock/etc. Wind them back in and out several times - see if you can get them to loosen up? The one I had I just got a bigger bar to wind them out, no damage just very clean threads.

There's always the possiblity that they've been stretched and the threads are a bit shot on them

[Jeff in MN]

Seems a stiff 20 to 30 ftlbs would be ok. Any higher and I might be scratching my head too. Keep us posted after you let'm soak for a while.

[632 Regal]

as mentioned tighten and loosen. For whatever reason the last few threads are binding up. did you start loosening these on a warm engine?


I'm stopping ~1" out because at that point the bolts really get stiff, and I don't want to force them for fear of buggering the threads machined into the block.

So, rather than taking the chance of messing up the threads, I thought I'd ask advice from others more knowledgeable.

I've removed the head on an M30 a couple of times, but never had this sort of difficulty--normally the bolts just loosen to easily remove by finger after a turn or so with the wrench. Not these, though. What could be fouling them? I squirted some penetrating oil down each bolt shaft, so we'll see if that helped overnight.

This is a replacement engine from a wreck, so I don't know its history. Any chance such engine could be so warped as to foul the middle headbolts?

[genphreak]

*** WHATEVER YOU DO... don't force them out.***

The holes are tapered towards the top of the head. The gunk builds up like tar around the bolts in the cavity, and when you want to pull/push them out (only way out is up) it just has nowhere to go, forcing them may CRACK the head. Another example of Frederick's bastardry.

M30 parts are strong, but don't risk it. Happened on mine, only a few bolts were really hard to get out though. I did force mine with a rubber hammer (screw Frederick!), as it turned out I was lucky. Only worked out Frederick's tapered hole trick was fooling us, after we got them out, so was worried until the outcome of the tank test put me at ease.

Just use some carb cleaner/degreaser to soak the gunk away and/or break it up. It should just ooze out when you push them, instead of jamming up solid- if you leave it long enough.

:) Nick

[632 Regal]

Claimed into a blind hole so nothing should corrode or otherwise cause malfunction... mechanical error perhaps?


*** WHATEVER YOU DO... don't force them out.***

The holes are tapered towards the top of the head. The gunk builds up around the bolts in teh cavity, and when you want to pull/push them out (only way out is up) it up has nowhere to go, forcing it may CRACK the head. Another example of Frederick's bastardry. M30 parts are strong, but don't risk it. Happened on mine, only a few were really hard- I was lucky, but was worried until the tank test put me at ease. Only wokred it out after we got them out.

Just use some carb cleaner/degreaser to soak the gunk away and/or break it up. Shoudl just ooze out when you puch them, instead of jamming up if you leave it long enough.

:) Nick

[Dash01]

So far, I've let the sticky bolts soak in penetrating oil and carburetor cleaner, and this seems to help.

The gunk on them is like tar, and the prior suggestion about working them a bit in and out helps with loosening, as it seems to allow the penetrating oil/carburetor cleaner to seep further down. Actually, given that the thread grip on the bolt ends is only ~1", it seems the tar is the only thing holding them in.

Perhaps I'm being too gentle with these bolts, but better safe than sorry.

What would cause the oil to become so tar-like? Would such cause also damage the engine? (Again, this engine is from a junker, so I don't know its history.)

[genphreak]

Old oil and short trips causes it I think, good to hear you are taking it easy. That is the only way with these things, the hammer never wins much progress on a BMW- in fact it usually screws things up Royally.