I consider myself a pretty decent weekend mechanic, with a better than average understanding of things mechanical, BUT, these dang camshaft cover bolts are driving me insane.
I'm attempting to replace my gaskets, plugs, inspect tensioners and such. All done and now the simple task of replacing the cover, EXCEPT I've now torqued off 4 cover bolts.
After the 1st, I rented a torque wrench thinking mine from Harbor freight was not valid. Wrenched off 2 more. OH, 1 was even a brand new bolt of the 10 I ordered as replacements.
I then decided to just back down to a more modest 4 NM, and dang it did it again. This is absurd and only Jaguar could come up with a system that should be so simple and make it difficult.
Am I wrong that the stem the bolt goes through will only allow the cover to go so tight onto the head anyway? What good is it to torque it so tight, as the stems will not allow the cover to
compress tighter anyway. It basically needs to be tight enough as to not back out from engine heat and vibration, correct?
I'd like anyones thoughts and experience with this problem.

 

I just today completed the valve cover gaskets set replacement. I torqued my bolts to 9.60 Nm, according to my torque wrench, and had no issues.

When you say you torqued off the bolts, do you mean you are stripping them or breaking them? I would pay close attention to the threads on the bolts and the engine head. Are the bolt threads corroded, dirty, or stretched? Are the threads on the head stretched? If they don't want to be driven in, consider that you may need to retap the threads. Also, some anti-seize is advisable to avoid problems in the future. Do not mindlessly attempt to force the bolts in. You may be in luck that only the bolts are giving you problems, but there's always a possibility that you could end up breaking the bolt holes on the heads.

Almost forgot, do not exceed 11 Nm of torque. If you do, it is very likely that you will end up micro-cracking the camshaft cover bolt holes.

 

+1

I have done this operation (admittedly only on one side) without mishap, torqued to 9 Nm. One member did have this issue recently - the only one I've heard of - but it was down to a faulty wrench. Something is definitely wrong - 4Nm isn't much more than finger tight.

I'd suggest taking one of the spacer/bolt combinations out of the cover and experimenting with a suitable nut held in a vice rather than risk damaging the head.

Yes, you're correct. The bolt has only to nip the spacer to the head. The clamping force for the cover is provided by the rubber isolators.

 

Thanks for response. I mean the bolt snapped off in the engine head on 3 of them and 1 did strip out of the hole. No, they went in very easily to snug the cover down onto the head and I encountered no resistance prior to tightening the bolt. I did not use anti seize and now wondering if that is my problem?? After stripping the one, I purchased 4 new bolts and of course ended up using all 4 now. I DID NOT use anti seize and now wondering if that is my problem?? Now I am feeling sort of snake bit and afraid to continue this process. I am getting good with the Easyout Bit. I was actually leaning more towards the 9NM , but do not believe I have achieved that torque yet as the bolts have snapped prior to that level.

 

Michaelh, I like your idea about experimenting with a bolt. I'll try that as well to test torque.

 

Using anti-seize makes it more likely that the bolt will snap as the theory is that the reduced thread friction means that the tension will be higher for the same torque figure. Having said that, I do so, except on bolts that either need locking compound or have nyloc nuts, and then wind the torque back ~10%.

Note that the upper rearmost bolt on each cover (should be the only one that isn't captive in its spacer) is 'special'* and should be replaced with one of the same type.

Good luck!

Here's the thread I mentioned:
https://www.jaguarforums.com/forum/x...2/#post2310435

*AFAIK its magnetic characteristics are different so it doesn't affect the adjacent cam position sensor

 

Yes, what Michael said is correct. The purpose of the anti-seize is to prevent corrosion of the bolt so that it can be easily removed at a future time. However, it will not prevent over-torquing and breaking of the bolt at the present time. I should have been more clear when I suggested it. It makes no difference to you at the present time or not. What you should do is slowly clean the threads of the heads with a tap. Also, I have to wonder if the bolts you possess have lower tensile strength and modulus of elasticity than is required, thus leading to their failure?

Are you positive you have not cross-threaded your bolts?

 

I'm sure the 4.0 litre cam cover bolt set up is the same as my 4.2.
You probably already know some of this, and others may have had a different experience but here are some hints below of what I found worked for me:
The shims in the bolt shafts are designed to make it virtually impossible to overtighten (crack) the plastic cam covers, so no problem there. This is a pretty good Ford design, I don't think Jaguar. Probably also cheaper to buy the bolts from Ford as well.
However shims or no shims doesn't mean you can't overtighten and snap the bolts!
They're only M6 so cant take much torque.
Don't use anything bigger than a small 1/4" socket drive and stop when it just feels tight on the 1/4". Anything bigger makes it too easy to snap a bolt.
Need a deep 10mm socket and standard 10mm socket with the usual extensions/wobble bars.
If you have the correct SMALL 1/4" socket drive no need for a U/V joint.
A U/V joint makes it harder to 'feel' the torque, so try not to use one.
Remember the top corner, RH on LH head and top LH on RH bolts are not attached to and remove from the shims. Probably something to do with the sensor nearby within the head.
Some of the bolts have the adjoining studs on top.
Don't use silicone or any type of gasket former, otherwise you'll never get the covers back off. Only apply in the 4 areas where the timing case cover meets the head, as per workshop manual. This took me a few goes to stop oil weeping out of there.
I found all the rubber O rings within the shims of my bolts to be in excellent condition and didn't leak when re applied but each case different.
I couldn't get any of my torque wrenches in there effectively in my S Type R. Just relied on feel in the end.
I actually did snap the top corner RH head bolt (with the loose shim). I have bolt removal tools but fortunately there was enough broken bolt protrusion. Just gripped it with my cordless drill head, selected low speed and reverse. It slowly came out! From this I learnt some of the above!


Photo of small 1/4" socket drive I used on another job; EGR valley hose.

 

Great tips, thanks. The only torque wrench I have is a 3/8 and I think you are correct, its easy to snap one. I like your idea with the 1/4 drive, which
is what I was using in the difficult places, but not everywhere. Gonna use that with the right "feel's tight" method.

 

Yes, use it all round.
That 1/4" drive I use is 5 1/2" long (length a bit deceptive in the photo). So unless you go nuts on it, hard to overtighten an M6 bolt. Just use your thumb to tighten and not push with the wrist.
Forgot to mention I have a 1/4" breaker bar as well that's about the same length, same principle as above and I think I interchanged both depending on which head and socket combo I could get in the engine bay clearances.
It's a cute little breaker bar (if you could call it that, and it wouldn't break much LOL). I use it a lot on the car.
Good luck.

 

Based on my recent debacle with a faulty torque wrench, it appears that the 'old bolts' (i.e. the ones in the car when I took the cam cover off of unknown vintage) will take qualitatively more torque than the 'new bolts' (fresh from jagclassicparts). That is actually a blessing in my case since it didn't take but drilling and fishing several broken bolts back out of the engine to try pitting my torque wrench against the 'rental' autozone one. Unfortunately, my torque wrench 'won' with much higher actual torque per indicated torque than the 'rental' or the new one hastily ordered.

Against all of my 'precise torque' instincts, at this torque level, your decision to go with 'feels tight' is probably wise. Beats the stress of digging the broken bolts out...

 

So I am almost to embarrassed to post this and I'm sure most of you will say "What an Idiot" that guy is. Unfortunately I would probably agree. I am posting only because I fear it happened to me, then potentially it could also happen to someone else. I've rarely used a torque wrench, but have borrowed and used one on several occasions. Up until this project I had always been told the settings in Ft. Lbs. Of course being European, Jaguar uses Newton Meters. So the two settings on the Torque wrench I bought are Ft. Lbs. and (what I thought) was NM. Well after gone through my problems outlined above, I went online and converted NM to FtLbs. To my amazement its about 7-8 Ft Lbs. That is supremely lower than what my tool was indicating using the scale on the tool. So after some reading, I discover the other scale on the torque wrench is Metric Kgs. DAMN!. Now there is some writing above that scale that says
(da) NM, which I later find means 10x NM. It's so small how would I make that distinction? Anyway, No wonder these bolts were snapping off. Probably a safety precaution for guys like me that are too stupid to know how to use a torque wrench. Anyway, back on course with my Cam Cover Replacement. Thanks for your input and I'm happy to provide you with a chuckle.

 

I was thinking that was you problem, but did not know of a way to mention it without the possibility of your taking offense, as others have done. You are not the first, and won't be the last. I always work with a torque wrench calibrated in in.lbs for these fastenings.

 

Thanks for sharing.
I've never encountered the Decanewton metre [daNm] either, so I've learned something new.

As RJ says, not the first and won't be the last...