Mercedes-Benz Forum banner

1 - 11 of 11 Posts

·
Registered
'91 300SEL W126
Joined
·
25 Posts
Discussion Starter #1
Hey All,
I will be rebuilding my ’91 300 SEL with a 103 engine type, but the procedure Mercedes uses to reinstall the bolts on these engines is different than what I have used before (on rice burners). So I need to be absolutely clear on my understanding of the way Mercedes uses for torquing down cylinder head/flywheel stretch/bearing caps/etc bolts.

How I read the instructions are that I torque the bolts, for example using the tech manual ‘01-4050 Checking/tightening cylinder head bolts’ for the 1st stage to 55Nm. Then 2nd stage I just tighten them all following their diagram to 90 degrees from the initial torque valve point and again the same 90 degrees for the 3rd stage for a total of 180 degrees from the initial torque valve?
I am assuming that its similar to other engine rebuilds where you would torque the 1st pass say @ 55Nm, then the 2nd pass @ say 75Nm and the 3rd pass @ say 100Nm?

Any help will be appreciated.

Again thanks,

Rick L.
 

·
Registered
92 190E 2.3 SOLD, 91 420SEL, 95 C280
Joined
·
488 Posts
You understand it correctly, there is no torque specs for 2nd & third passes, just the 90 degree turns of the wrench. I highly recommend a long breaker bar for these passes as you want to make the full 90 degrees in one motion.

Don't worry you'll be fine. :D
 

·
Banned
2007 E350 4Matic P2; 2008 GL320 CDI P2
Joined
·
20,153 Posts
There are multiple ways to insure a threaded fastener creates the desired/engineered clamping force.

Some rely only on torque to be an accurate indicator of stretch, but some use others methods to create the desired/engineered amount of stretch, such as a specific amount of turn, knowing the thread pitch.

http://www.boltscience.com/pages/tighten.htm
 

·
Registered
92 190E 2.3 SOLD, 91 420SEL, 95 C280
Joined
·
488 Posts
And if you are reusing old bolts you need to check the neck diameter
Actually it is the length of the bolts that you need to measure with a caliper to see if they are still within spec, if this is the first head gasket replacement they should be fine, I don't have the exact specs but if you search the W201 forum there is a great online repair manual that covers the m103 engine and gives you all the specs needed.
 

·
Banned
a device that is designed or used to transport people or cargo.
Joined
·
14,116 Posts
Actually it is the length of the bolts that you need to measure with a caliper to see if they are still within spec, if this is the first head gasket replacement they should be fine, I don't have the exact specs but if you search the W201 forum there is a great online repair manual that covers the m103 engine and gives you all the specs needed.
how much could new bolts cost?
 

·
Registered
1987 420SEL
Joined
·
1,133 Posts
$130 in the case of the V8.

Measuring the neck diameter seems to be a more plausible method than measuring the actual length of the bolt.

Genuinely curious: does the M103 manual actually state to measure the overall length?
 

·
Banned
2007 E350 4Matic P2; 2008 GL320 CDI P2
Joined
·
20,153 Posts
Actually it is the length of the bolts that you need to measure with a caliper to see if they are still within spec, if this is the first head gasket replacement they should be fine, I don't have the exact specs but if you search the W201 forum there is a great online repair manual that covers the m103 engine and gives you all the specs needed.
Either length or diameter will indicate if they have been stretched beyond the allowed tolerances.
 

·
Registered
92 190E 2.3 SOLD, 91 420SEL, 95 C280
Joined
·
488 Posts
$130 in the case of the V8.

Measuring the neck diameter seems to be a more plausible method than measuring the actual length of the bolt.

Genuinely curious: does the M103 manual actually state to measure the overall length?
YES the manual actually ONLY mentions measuring the length as that is what is the true indicator of the allowable stretch of the bolts. See the attached.

91 1991 Mercedes 300E Head Bolt - Engine Mechanical - Victor Reinz - PartsGeek Looks like about $56 for the set.
 

Attachments

1 - 11 of 11 Posts
Top