HI fellows!
Little story - I've lost compression on #4 cylinder on my '96 850 turbo due to broken exhaust valve. So obvoiusly I have to replace a head gasket. When I was removing the head bolts, it looks to me that torque they fastened far more that manual remommended 20, 60nm and 120degrees.(I even broke a craftsman '14 socket)
The bolts are yield to torgue, so I have to replace them with new ones, right? What it would be if torque is exceeded the specifications?
Just want to get some feedback how you guys did your head fastening, how hard it feels when you do bolts (damn question)
Any feedback would be appreciated.

P.S Searched forums for similar threads, found nothing. Is there is a good thread about head removal-installation?

 

The head bolts always come off tough. Sometimes you can "wake the bolts up" buy giving them a rap with a hammer. Be gentle, as in not going after them with a impact wrench, they will break easily. Steady pressure works better than big yanks on the break over bar. If you can't get them loose get a bigger pipe to extend the handle.

Several guys say that you can get a second use out of the head bolts but my rule is that anything that gets angle torqued gets replaced and the head bolts fall into that category.

...Lee

 

Impact socket and a long breaker bar. Pull and cringe...they will release. They are not to expensive to replace and I am sure you wont want to pull the head a second time due to a blown head gasket so why risk it. Replace them.

 

Thanks for answers
I've got new bolts, will install the head tomorrow. Is the torque settings right
1 stage - 20Hm (15Foot pounds) - I have SAE wrench
2 stage - 60nm (45 Foot pounds)
3 stage - 120 degrees

It seems to me that 45ft-lbs + 120 degrees is not enought for fastening that king of thing. Am I wrong? What if to go a little extra than 120 degrees?
Thanks

 

120 degrees? no... it's 130 degrees. And yes... 130 degrees is a LOT of extra torque above 45. It should end up over 100 ft/lb. Make sure to lube the threads of the bolts, and chase the threads in the block with one of the old bolts, cleaning it after each hole, and use an angle torque gauge of some kind, even the el cheapo type sold at AutoZone for $10... Torque- to- yield head bolts are precision parts, and the reason for the angle torquing is because you're tightening the bolt to EXACTLY the point where it just starts to stretch. This is where the bolt is giving the absolute maximum clamping force it can... it's acting as a sort of spring, applying hundreds of thousands of pounds of pressure. If you undertighten, even by a little bit, it won't have the spring- action, and clamping forces are reduced by a factor of 10 or more. If you overtighten, even a bit, you will stretch the bolt beyond its "yield" point, and it will lose strength. Precision is VERY important here. If they were to go with a ft/ lb spec of such high forces, you could actually reach that spec before the bolt gets to its yield point due to debris and friction. An angle torque specification avoids this by being a precise distance, no matter what amount of friction is encountered in the threads.

And yes, the head bolts on these cars are a bitch and a half to take off. Don't even think of putting anything short of a high- quality, 6- point socket on them to remove... it WILL break otherwise. Huge breaker bar and a piece of pipe- a hydraulic jack handle works great- with steady pressure, and you'll get them free. Remove them in the reverse order of the installation tightening pattern, about 1/4 turn each at first, then remove... this will help prevent warping of the head.

 

Thanks for a good explanation!!! It really opened my eyes on what is going on with these bolts)))) I have everything ready - bolts, wrenches, gaskets, angle gauge, so, now is the time to do stuff
Will update post to share how everything went through.