OK! head gasket replacement on this my mother in laws car. 2 sets of head bolts so far and at 50 quid a set I don't want any more outlay!! she loves it and doesn't want to replace the thing!! I have followed the instructions that came with the gasket set. and at the 3rd round of torq settings the bolts shear always before I reach the indicated 62 lb.ft. I have used 2 torque wrenches (one a brand new one!) both tested on a analyser and the Engine number corresponds.
Any ideas/help would be so greatly appreciated!!!!!
Kirklander
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There can only be two posibilities, either the bolts are u/s or you are tightening them up to much. Are you sure that the torque figures you have are correct? What does the bolt supplier have to say?
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Might you be greasing the bolts, but not supposed to? Some cars you do and some you don't.
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for a 97 proton, why not stick the original ones back in?, surely we are not talking high tec here.
Could the torque setting have changed since the data was produced that you are using?
Years ago , we just tightened heads bolts up as tight as possible using a reasonable tommy bar. Never had problems, bu the cars did wear out faster then
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Are they click stop torque wrenches by any chance.....I always liked the pointer type (they are cheap too), less chance of over torquing. They can have handles 2 ft long and it really requires very little force to get to 62 ft lbs....much less than people often think.
62 ft lbs is not very much, try with a 7 inch long ring spanner and tighten hard, that will be more than 62 ft lbs and I bet you can't snap easily, then check em with a pointer type torque wrench...the Draper ones are only about a tenner.
Edited by davecuk on 07/10/2009 at 23:51
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Are you confusing ft lbs and Nm?
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Fullchat is on the money. A proton spec is most likely to be metric so Nm not Ft Lbs. 61 Nm is 45 ft lbs. Regards Peter
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Head bolt new
33nm
53nm
73nm
if less than 103.2 mm ( old bolts)
49NM
slacken off
20NM
+90 degrees
+90 degrees
Ensure no oil or water down bolt holes in block as this will hydraulic bolts & shear
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>>There can only be two posibilities
I think there are more than two.
One of the more likely possibilities is that the threads and more critically, the under bolt head area are being oiled / greased if the spec calls for them to be installed dry, as mentioned above.
One point of interest here is that the used bolt spec, which uses angles is *much* less sensitive to this problem of varying friction level.
It's possible that here, we are seeing in a very graphic way just how poor a method of installing high performance fasteners torque tightening is.
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Head bolts are normally M10 or bigger - they should be almost impossible to shear! If they are letting go at less than 65lb ft (which is less than road wheel torque!) I would be thinking along the lines of a batch of duff bolts... Especially as the tightening method for the old bolts is +180° which is pretty brutal.
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Thanks everyone! first time the problem was "all of the above" but everyday is a school day!
Thanks again appreciate it!!
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And the solution was ??? Regards Peter
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