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Discussion Starter #1
Good day all,
I have been assembling a Scenic 2 f9q 812 engine. I thought I would spend a few euros more on the new head bolts so I bought Elring bolts because I have always thought their products were of superior quality. I searched around for head bolt torque information and decided to follow the following proceedure.
step 1: torque in proper order all bolts to 3 N.m
step 2: angle torque all bolts another 100 degrees
step 3 loosen bolts 1&2 180 degrees and then tighten them to 2.5 N.m plus another 213 degrees.
Continue tightening bolts 3&4, 5&6, 7&8, 9&10 in the same manner.

I lubricated the threads and the bolt head bottom faces with a proper lubricant. Things were going along fine but I noticed that some of the bolts did not reach the "yield" state until they were almost all the way tightened. Most of the bolts started to yield by the time they were 3/4 of the way tightened.
However, the 8th and the 10th bolt never reached the "yield" state. I feel that they are actually excerting more fource and will not have the elasticity over the engine temperature range that the other bolts have and therefore the cylinder head is not evenly tightened down and could have problems in the future. I am wondering if anyone else has had this problem and what you all think. I suppose for another 18 euros I might as well get another set of bolts but maybe I will go for the lowest price this time. Thanks for your thoughts;
Papy
 

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Super fantastic Mod Technical Supremo Nice Guy
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You did clean the holes in the block where the bolts went in with pieces of cloth and a screwdriver..
Just asking
What Gasket as two types fitted..






Cylinder head(Gasket should be replaced with a gasket of the same material (metal/non-metallic gaskets
are fitted))
Renew the bolts
Cylinder head (bolts)(Non-metallic gasket only)
Stage 1 30(Nm)
Stage 2 100 ± 4(°)
Stage 3(Wait for 3 minutes)
Stage 4(Loosen bolts 1 and 2)
Stage 5 25(Nm)
Stage 6 213 ± 7(°)
Repeat stages 4, 5 and 6 for bolts: 3-4, 5-6, 7-8, 9-10
Cylinder head (bolts)(Metal cylinder head gasket only)
Stage 1 30(Nm)
Stage 2 230 ± 6(°)

ELRING are very good bolts, and will have been tested..
If all tightened up now leave alone, DONT get doubting your workmanship..
 

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Premium Member
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If it was done right the first time I would agree:iagree:


Torque settings are seriously affected by lubricating threads ................. I was taught to always torque on dry holes and surfaces only and its been sound advice - never had an issue with a stretch bolt in yonks.


Once you exceed the elastic phase of the bolt material (over torquing) it enters a plastic phase where it stretches/deforms rendering it useless for the job.


I have seen people overdoing it and ending up with a shank on a bolt looking like a corkscrew.......................


I would spend the money on a new set and start a fresh and dry
 

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Super Moderator Technical Supremo Platinum Member
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Two questions ??

How did you work out they had reached the yield state ?

Second is why are you doubting if you got good bolts and followed procedure?

The whole point of angular tightening is that it removes inconsistencies from dirt, lubrication or whatever.
A simple torque reading simply measures the force used.
Can be fooled by dirt resulting in too low a clamp force or lube...too high.
Angular simply tightens the bolt a set distance (that has been calculated by the pitch of the thread) to give the right clamp force.
The only issue is if the initial pre load torque is being fooled...dirt if the worry here... so the bolts are starting from an unclamped position.
Which is what the tighten then loosen bit is all about... to squish the gasket, settle the head and get the threads summat like clean before the final tighten.


If you followed procedure then as Ourkid says, trust in your workmanship and leave well alone.

And don't ever buy cheap (as in may be poor quality) bolts for cylinder heads
 

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Discussion Starter #5
Thank you ours for more good information.
Yes, I cleaned the bolt holes very well - ran the old bolts to the bottom and cleaned them again. However, I messed up. I bought a high quality head gasket (Victor Rienz) but believed the specs of a Renault workshop manual instead of what was included with the gas:forehead:ket ! I had not come across mention of different torque procedures for different gaskets. All the gaskets I looked at were all metal. Anyway, my torque procedure was bad and that is why the bolts did not behave properly. It would be nice if there was a section on the forum with accurate, up to date torque specs. I looked through the forum several times and found much misinformation but never the proper spec for this application. Looks like I will buy another set of Elring bolts.

As we all should know, we all make mistakes. I began as a mechanic in 1975 and have installed well over 1000 head gaskets. When angle torquing started I received training in which they explained what angle torquing was all about. They described it as "Torque to yield". This means that the bolt has been tightened to the point where it begins to stretch. When you tighten the bolt you can feel when this happens because the bolt suddenly becomes easier to turn. It was explained to me that with the bolts in this state they maintain the same clamping force throughout the engines operating temperatures. To get to the point where the bolt yields it has to be tightened much tighter than the old style head bolts but one they yield the clamping force is reduced to a level that is similar to the old style head torque. The reason you cannot reuse the bolts is because they have been stretched already and there is no reliable way to retighten them to the proper torque. I suppose some members will think I am a very confused old man and I would have to agree but as I said - I have installed many, many head gaskets and this was the first time I questioned if things were done right. It turns out that I was not torquing it properly and the head is not evenly tightened down. I do try to pay attention to that old nag when it tells me something is amiss.
As for lubricating the threads and bolt heads of the head bolts the instructions with the head gasket said to do it. I have always lubricated the threads of head bolts. Working at Porche and BMW, as well as at Jaguar, the shop manuals specified that the head bolts should be lubricated with a moly grease or in the case of Jaguar the threads on the studs. Everyone has their own ideas that get put in their head some way or another. Here's to diversity:toast:
Papy
 

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Premium Member
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Papy I think you may find we all come from about the same era with roughly the same experience:x
On the lube of head bolts .................. sound advise and what I also practice but on non-stretch bolts only............. purpose is to prevent the thread drag /resistance influence the torque MEASURED on the wrench - iow you need the torque applied to the rotating bolt material to ensure you apply an axial force directly related to the torque you applied and not end up with a force equal to that minus some unknown drag/resistance induced force - iow something not clamped properly.


On a stretch bolt the angled torque approach guarantees consistent results as long as the same starting point is used - imo applying lubes with different friction properties basically changes the starting point and THAT may be what you bumped into
 

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Super Moderator Technical Supremo Platinum Member
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If your concern is that you did not feel the yield but all else is correct, I would not worry.
Bit of tightness between threads or shoulder and head could easily fool you.
Can't say I've ever felt the yield point and done plenty.
But admit never something I've been looking for
 

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Super fantastic Mod Technical Supremo Nice Guy
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Just leave alone, ..
It will be fine..
There is at least a 3rd more these bolts will go, before any damage.
As in, if 300nm, it will go to 400nm before damage..
Only thing you have done is gone in stages, with a metal gasket its not needed....

But still the same results overall ..
Drive and enjoy,,

Stop worrying, If you now change the head bolts, its a new gasket needed.
 

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Discussion Starter #9
Papy I think you may find we all come from about the same era with roughly the same experience:x
On the lube of head bolts .................. sound advise and what I also practice but on non-stretch bolts only............. purpose is to prevent the thread drag /resistance influence the torque MEASURED on the wrench - iow you need the torque applied to the rotating bolt material to ensure you apply an axial force directly related to the torque you applied and not end up with a force equal to that minus some unknown drag/resistance induced force - iow something not clamped properly.


On a stretch bolt the angled torque approach guarantees consistent results as long as the same starting point is used - imo applying lubes with different friction properties basically changes the starting point and THAT may be what you bumped into
I can see your point but why was it writen on the instalation instructions with the Victor head gasket to lubricate the threads and the head of the bolt? They emphasize the point to replace the head bolts. Also, how can the dry friction of used block threads be predicted more exactly than lubricated ones? If they are all dry I suppose it would be the same as if they were all lubricated, no?
Papy
Papy
 

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Super Moderator Technical Supremo Platinum Member
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I can see your point but why was it writen on the instalation instructions with the Victor head gasket to lubricate the threads and the head of the bolt? ..........
Cos with angular setting, lube is probably more favourable then dry where a tight thread of bit of dirt could (could) affect initial set down (low torque value) adversely.
 

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Super fantastic Mod Technical Supremo Nice Guy
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Part most people miss, is the part that the bolt head touches the head itself..
Some head bolts have washers, or just the bolt head..
But all need one or the other. These always need a smear of grease or oil.. If going to a cast iron head, then copper slip under the head of the head bolt.
Never yet put a head bolt in dry, on any engine I have replaced gaskets on..
Dont ever think I would be brave enough..

The old head gaskets, pre 2000, if a diesel engine, then the gasket itself I would cover both surfaces in oil, ..
Never had an issue..

Very rare head gaskets fail now on a modern engine..
 

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Discussion Starter #12
Part most people miss, is the part that the bolt head touches the head itself..
Some head bolts have washers, or just the bolt head..
But all need one or the other. These always need a smear of grease or oil.. If going to a cast iron head, then copper slip under the head of the head bolt.
Never yet put a head bolt in dry, on any engine I have replaced gaskets on..
Dont ever think I would be brave enough..

The old head gaskets, pre 2000, if a diesel engine, then the gasket itself I would cover both surfaces in oil, ..
Never had an issue..

Very rare head gaskets fail now on a modern engine..
I totally agree:wink2:. Very few people take this into consideration.
Papy
 

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Papy - would you say you "felt" the same about the same head positions/locations with the new bolts?
 

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Discussion Starter #15
Yes. The bolts felt more or less the same. I used a different brand of bolts and I felt some reach the point of "yielding" and some did not. It does not match my description of torque to yield and also my previous experience but I will not try a third set of bolts.
Papy
 

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Just me ................. and please I am not trying to split hairs or start an argument.

I noticed that some of the bolts did not reach the "yield" state
Maybe I am misinterpreting your description so if that's the case then please everybody ignore my ramblings, but one thing is for sure (even though we may differ in the approach of the lube of threads/heads ................) - you definitely do NOT want the torqued bolt material to yield at all - the elastic phase/property of the material is intended to be used to allow the bolt material to accommodate the thermal range of expansion of the head/bolt/washer materials and thereby retain a known clamping force at that position - soon as the material yields (starts to non-elastically deform/stretch) it no longer exerts a known and spec'd force on the clamped area.


Did you perhaps have the head "surfaced"/skimmed?
 

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Discussion Starter #17
Just me ................. and please I am not trying to split hairs or start an argument.

Maybe I am misinterpreting your description so if that's the case then please everybody ignore my ramblings, but one thing is for sure (even though we may differ in the approach of the lube of threads/heads ................) - you definitely do NOT want the torqued bolt material to yield at all - the elastic phase/property of the material is intended to be used to allow the bolt material to accommodate the thermal range of expansion of the head/bolt/washer materials and thereby retain a known clamping force at that position - soon as the material yields (starts to non-elastically deform/stretch) it no longer exerts a known and spec'd force on the clamped area.


Did you perhaps have the head "surfaced"/skimmed?
No, I did not have the surface skimmed. It is flat and the manuals say not to.
It seems there is much misunderstanding about torque to yield bolts. I am not saying that I am an expert but I have worked long in the mechanic trade. As I mentioned I was given training when torque to yield bolts came to the automotive scene. The reason I have been uneasy with the results of the head torquing is that it would seem to me that there is not an even clamping force being excerted on the head with some of the bolts having yielded and others not. When torquing crank pully bolts I have felt them yield also. Just to check myself I looked up "torque to yield fasteners" on Wikipedia and they confirm what I have said.

I appreciate being able to discuss problems like this on this forum. I will not get into an argument because there are better things to do in life. :beer:
Papy
 

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Discussion Starter #19 (Edited)
Anyone who is interested might want to look at this link. It gives a much better explination than I did.
wbtools.com.au/how-to-understand-angular-torque-and-torque-to-yield/
Sorry, I don't know how to properly insert a link but if you copy what I wrote and paste it it should work:confused:

Papy
 
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