Valve adjustment as per factory manual

EuroIron · Post by **EuroIron** » Mon Sep 10, 2007 1:54 pm

ummmm St,

I think somebody said the procedure was that every bolt was backed off and retorqued before every valve adjustment

maybe that was you?

is that the same as re-torque?

don't think so

EuroIron · Post by **EuroIron** » Mon Sep 10, 2007 2:58 pm

Every 4000 miles (6000 km) with the engine cold and before adjusting valves clearances, the cylinder flange fixing nuts and the cylinder head bolts must be checked for tightness to a torque of 24 ft/lb (3.5 mkp). This work should be left to the (hahahhhaa) BMW service workshop.

Note........... nowhere does it specify backing off, removing, or loosening any of the fasteners .........

btw.......... that is from a factory manual

saintclair2703 · Post by **saintclair2703** » Mon Sep 10, 2007 3:16 pm

Backed of about a half turn before re-torquing- yes. Isn't that the best way to get a proper reading?

EuroIron · Post by **EuroIron** » Mon Sep 10, 2007 3:26 pm

you'll have to prove that to me...........

I've read, understood, and performed many similar torquing and retorquing procedures while working for more than one factory dealer and nowhere in the BMW manual does it say backing off at all

much less about a half a turn

however, I can give you very valid and logical arguments why loosening a head bolt on a BMW prior to retorquing?, isn't a good idea

schrader7032 · Post by **schrader7032** » Mon Sep 10, 2007 7:32 pm

however, I can give you very valid and logical arguments why loosening a head bolt on a BMW prior to retorquing?, isn't a good idea

EI -

I'd sure like to hear some... I've heard completely the opposite. You won't get the right torque reading unless the nut/threads are actively sliding...otherwise you're trying to overcome static friction which won't be the correct value. When applying the torque, don't you watch the torque value as the nut is continually tightened (OK, it's usually done in stages, but it's an example)? Once you reach the appropriate value, don't you stop? The book doesn't say to reach the torque value, stop, and then confirm the torque by trying to continue tightening. You get the right torque by measuring the value while things are in motion, not while stopped. The only way to simulate the same thing is to slightly loosen and then retighten. I've heard to only loosen maybe 1/4 of a turn.

Also, I wouldn't do this process EVERY valve adjustment. Once the valves are bedded in, I might only check the torque maybe every 10K miles...possibly longer...

Kurt in S.A.

EuroIron · Post by **EuroIron** » Mon Sep 10, 2007 10:14 pm

Argument 1) such a procedure is not specified in the service manual

in fact, I'm digging right now to see if I can find any factory's specified "checking for tightness" procedure that calls for backing off the bolts about any fraction or whole number of a turn........... for head bolts or nuts/studs

so far.......... zilch but there are many manuals of which I do not own and plenty of engines of which I know nothing

Argument 2) show me a such a specified procedure from any valid source

Argument 3) your method specified and reasons therefore are only valid if the fastener was over-tightened to begin with

I could type here for days telling you all the things I've heard but they may not all be valid or factual

schrader7032 · Post by **schrader7032** » Mon Sep 10, 2007 10:57 pm

I think we should focus on the basic process of torquing a nut....let's not worry about the "checking for tightness" at first. I contend that the process of torquing a nut from a state of zero torque is to do so while the nut is sliding on the threads. My guess is that BMW won't have specificed it this way. In fact, if you look at their manuals, they're written for mechanics who already had a required level of skill as a mechanic and the manual is written more as a reminder of specific steps or processes.

Once we've agreed on this process of torquing a nut, then we can define another process which best simulates this and might be used to "check for tightness" in a manner consistent with proper application of torque.

Kurt in S.A.

EuroIron · Post by **EuroIron** » Tue Sep 11, 2007 2:09 pm

well even without coming to the fact that loosening the head fasteners........... about some unspecified amount......... how much seems to be anyone's guess........ does indeed bring about the highly undesirable possibility of the microscopic seal surfaces of the head gasket being broken or shifted slightly.......

in fact, everything you specify is not what is written in the factory book......... even your interval is greater by 150% and it clearly demonstrates you do not grasp why the factory specifies checking for proper tightness PRIOR to checking and adjusting clearances........ it has NOTHING to do with how well the valve has "bedded in" on it's seat

we have reached the wall

I certainly disagree that BMW specific instructions are less than concise and I also maintain they are indeed written for anyone with eyes to read......... not certified black magic wrenches possessing great mystical wrenching prowess never to be known by mere purchasers of motorcycles........ btw......... what I posted was taken directly out of an "INSTRUCTION MANUAL" that was sold with the bike and in the hand of the bike's owner

it is however amusing that in the same paragraph it specifies valve adjustment should only be performed by a BMW service center

and I can certainly show you BMW, even Porsche procedures that are extremely concise and clear, even when they are seemingly questionable or convoluted........ and nowhere in any BMW or Porsche repair or service procedures have I ever read the words "about, a cunt hair, just get it tight enough, back off some.... yada yada" or even "do this if some old blue hair says he fixed one this way and they all should be done this way"

for proper torquing procedures and why the very foundation of your recommended backing off procedure is invalid

check out the Society of Automotive Engineers

or go bend the ear of your local VoTech Mechanics shop class teacher and ask........ and then specify next you would like to discuss head fasteners in specific

if you really want to know

otherwise, feel free to continue to interpret what are actually, very concise and direct instructions handed by the factory, to all owners of these machines

schrader7032 · Post by **schrader7032** » Tue Sep 11, 2007 7:04 pm

in fact, everything you specify is not what is written in the factory book......... even your interval is greater by 150% and it clearly demonstrates you do not grasp why the factory specifies checking for proper tightness PRIOR to checking and adjusting clearances........ it has NOTHING to do with how well the valve has "bedded in" on it's seat

Wow, you sure can read a lot between the lines...

OK, let's get ot the basics since you say it's very clearly written and/or well known. What is the exact procedure "for checking for proper tightness"?

Kurt in S.A.

saintclair2703 · Post by **saintclair2703** » Tue Sep 11, 2007 9:10 pm

Hey UE!
If the manufacturer says to retorque the headbolts at a given interval, DO IT!! Who would know better than the those that engineer and produce them?
Early Mazdas(pre-'88 626 for example) required headbolt retorque every valve adjustment. Was a normal part of my job.
The headbolt was backed off 1/4 turn--to eliminate false torque readings from the underside of the bolt head sticking), then retorqued to spec.
This weekend I did a major service to my '81 CB750, and I did retorque the headbolts--to lessen the headgasket oil seep that was common on that series engine. I marked the socket to a fixed point, backed off the bolt, and retorqued. I noted that the final socket position was 10--20 degrees beyond the intial setting, so SOMETHING changed.
It also depends on the headbolt design--torque-to-yield or stretch bolts do not require retorqueing and should not be disturbed. Torque to yield bolts must be replaced after each use, and stretch bolts must be measured and if beyond specified length, replaced.
Terry"

Got this from a mechanicalesque friend who has little experience with BMW. Makes sense to me.