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Technical headgasket
- Thread starter trevor212
- Start date
Currently reading:
Technical headgasket
Markonee1
New member
I'm new here, but here's my method that I use on my VW diesels, but will apply to any engine with stretch head bolts:
Sequence not crucial as such, but start from middle two bolts, and nip them up, then go diagonally opposite first bolt, then jump diagonally across middle bolts to your next bolt, then the bolt on the same face but jumping back over the middle bolts, then diagonally over to the sixth bolt.
Then diagonally over to the other side of the head.. Then jump straight over other side same row, then diagonally, then straight back across.
Next go diagonally over to an outer bolt then across to the other distant corner then diagonally back and finally to the last bolt.
It sounds messy but your aim is to gradually tighten the bolts from the middle pair working your way out to the outer 4 corners, filling in the spaces as you proceed, but keeping tightenings apart from each other.
Important:
Use an accurate torque wrench [I have a snap-on, but a bar type is good].
Repeat sequence with a little more torque each time.
Keep repeating UNTIL you reach yield point on bolt. At this point you stop for that bolt and move on to the next. Forget so many 90 deg turns etc. This just weakens bolt.
After warming engine for 10 minutes or so torque each bolt a little further until yield point reached, and finally after so many miles, say 300, slacken each bolt in turn, just enough to break free the bolt, then retorque until yield point reached for each bolt, before moving on to the next bolt in the sequence. Not sure of value for petrol engines, perhaps it's 70 to 80lbft... A 12mm diesel bolt yields at about 115lbft, and then stretches in plastic mode at maybe 105lbft.
Interestingly a gently stretched bolt will regain some strength after being left for a while:idea:
If someone can give you the exact method/torque values, for your particular engine, then that is obviously fine. My method means that there is reserve 'stretch' left in the bolt, to allow their safe reuse once if neccessary.
Replacing with high tensile head studs is another option favoured by high-boosted diesel enthusiasts...
Sequence not crucial as such, but start from middle two bolts, and nip them up, then go diagonally opposite first bolt, then jump diagonally across middle bolts to your next bolt, then the bolt on the same face but jumping back over the middle bolts, then diagonally over to the sixth bolt.
Then diagonally over to the other side of the head.. Then jump straight over other side same row, then diagonally, then straight back across.
Next go diagonally over to an outer bolt then across to the other distant corner then diagonally back and finally to the last bolt.
It sounds messy but your aim is to gradually tighten the bolts from the middle pair working your way out to the outer 4 corners, filling in the spaces as you proceed, but keeping tightenings apart from each other.
Important:
Use an accurate torque wrench [I have a snap-on, but a bar type is good].
Repeat sequence with a little more torque each time.
Keep repeating UNTIL you reach yield point on bolt. At this point you stop for that bolt and move on to the next. Forget so many 90 deg turns etc. This just weakens bolt.
After warming engine for 10 minutes or so torque each bolt a little further until yield point reached, and finally after so many miles, say 300, slacken each bolt in turn, just enough to break free the bolt, then retorque until yield point reached for each bolt, before moving on to the next bolt in the sequence. Not sure of value for petrol engines, perhaps it's 70 to 80lbft... A 12mm diesel bolt yields at about 115lbft, and then stretches in plastic mode at maybe 105lbft.
Interestingly a gently stretched bolt will regain some strength after being left for a while:idea:
If someone can give you the exact method/torque values, for your particular engine, then that is obviously fine. My method means that there is reserve 'stretch' left in the bolt, to allow their safe reuse once if neccessary.
Replacing with high tensile head studs is another option favoured by high-boosted diesel enthusiasts...
Hi,
is this the mark 1, with the ohv, XM7 or XN1 engine?
It should be the same as the Peugeot 505 engine, I did mine from the Haynes manual for that.
If so
stage 1 50 Nm (37 lbf ft)
stage 2 loosen in sequence, then 20 Nm. (15 lbf ft)
further tighten M12 bolts angle tighten 90 degrees
M11 bolts angle tighten 180 degrees
(do this one bolt at a time, ie slack it off, tighten it, angle tighten it, then move onto the next one)
stage 3 warm up engine, to normal temp,
and now you have a choice, early Peugeot 505 engines you let cool for six hours, then repeat from step two, later ones you let cool then angle tighten further 35 degrees. I would hazard a guess to treat it as a late engine.
Sequence is
8 4 1 5 9
7 3 2 610
is this the mark 1, with the ohv, XM7 or XN1 engine?
It should be the same as the Peugeot 505 engine, I did mine from the Haynes manual for that.
If so
stage 1 50 Nm (37 lbf ft)
stage 2 loosen in sequence, then 20 Nm. (15 lbf ft)
further tighten M12 bolts angle tighten 90 degrees
M11 bolts angle tighten 180 degrees
(do this one bolt at a time, ie slack it off, tighten it, angle tighten it, then move onto the next one)
stage 3 warm up engine, to normal temp,
and now you have a choice, early Peugeot 505 engines you let cool for six hours, then repeat from step two, later ones you let cool then angle tighten further 35 degrees. I would hazard a guess to treat it as a late engine.
Sequence is
8 4 1 5 9
7 3 2 610
Hi,
is this the mark 1, with the ohv, XM7 or XN1 engine?
It should be the same as the Peugeot 505 engine, I did mine from the Haynes manual for that.
If so
stage 1 50 Nm (37 lbf ft)
stage 2 loosen in sequence, then 20 Nm. (15 lbf ft)
further tighten M12 bolts angle tighten 90 degrees
M11 bolts angle tighten 180 degrees
(do this one bolt at a time, ie slack it off, tighten it, angle tighten it, then move onto the next one)
stage 3 warm up engine, to normal temp,
and now you have a choice, early Peugeot 505 engines you let cool for six hours, then repeat from step two, later ones you let cool then angle tighten further 35 degrees. I would hazard a guess to treat it as a late engine.
Sequence is
8 4 1 5 9
7 3 2 610
is this the mark 1, with the ohv, XM7 or XN1 engine?
It should be the same as the Peugeot 505 engine, I did mine from the Haynes manual for that.
If so
stage 1 50 Nm (37 lbf ft)
stage 2 loosen in sequence, then 20 Nm. (15 lbf ft)
further tighten M12 bolts angle tighten 90 degrees
M11 bolts angle tighten 180 degrees
(do this one bolt at a time, ie slack it off, tighten it, angle tighten it, then move onto the next one)
stage 3 warm up engine, to normal temp,
and now you have a choice, early Peugeot 505 engines you let cool for six hours, then repeat from step two, later ones you let cool then angle tighten further 35 degrees. I would hazard a guess to treat it as a late engine.
Sequence is
8 4 1 5 9
7 3 2 610