can i remove and re-torque cylinder head bolts on a newly rebuilt engine?

Question

can i remove and re-torque cylinder head bolts on a newly rebuilt engine?

Answer 1

As said but make sure you do them in the correct sequential order / tightening torque/ progresively, as per the service / repair manual or you'll screw it even more.

No manual, try



www.carlsalter.com might be a free bee there.



or go buy one.

Answer 2

Hopefully your in luck, but over tightening bolts to damage them is not seen just as damaged thread but you initially start to stretch the bolt.

You can undo and re do to the specified torque again not problem tho.

The 90 degree bit after the torque setting means, when the torque wrench clicks that you have reached your specified torque you must carry on with tightening by moving the torque bar another 90degrees

ie think of the torque bar as a hand on a clock, when you get to the specified torque, think to yourself your at 12o'clock then carry on tightening till you would get to 3o'clock

Answer 3

Hope this helps!

Answer 4

The main reason for torquing down a cylinder head is so that it is pulled down equally over its full area and doesn't allow it to warp when it gets hot.Just slacken em off and starting at the centre and moving out in a spiral take em down to 30 nm then start at the centre again and turn em 90 degrees then repeat.Leave 2 minutes between each circuit to allow the gasket to "relax".Don't slacken just one at a time and then re-torque as the head gasket will not be able to realign itself if all the rest of the bolts are tight and do it when the engine is stone cold.The reason they replace stretch bolts is to stop them bottoming in the block bolt holes and they would have to stretch some to do that.But it sure as hell makes somebody a lot of money.

Answer 5

well they are stretch bolts,but I'd doubt very much if you achieved the correct torque doing it with a breaker bar.

Most manufacturers manuals state maximum stretch length, and don't say always renew all bolts!

and a fair number of head tightening sequences state: tighten all to 58Nm,slacken all back off 1 complete turn and "then" follow the torque sequence..for example.

Slacken them off 1 at a time and torque to correct loading before moving on to the next one.

90 then 90 degrees is a great deal more tightening than you'd think.

Answer 6

Head bolts are designed to S T R E T C H to accomodate the hots and colds of engine running. Go to the dealership and buy NEW bolts and install them correctly! You have already ruined the first set of them. Use ONLY genuine BMW coolant in there with engine oil that meets European standards, not American ones!! This means Mobil One 0W-40 , Total, Pentosin, or AMSOIL. Pennzoil European Ul;tra is also good!

Answer 7

You cant re use the head gasket now you have crushed it so you will need a new one.

It means tighten using a torque wrench to 30nm, then tighten 90 degree's then another 90 degree's, this implies that the head bolts are of the stretch variety so you should also fit new bolts as they have now been stretched and thus are useless now.

There should be a set time delay between the torque meter tighten and the two 90 degree turns, this is to allow the stretch bolts to settle at each position before moving to the next-this is vital.

Also as i suspect you are doing this without a manual there is also a specific order in which you need to tighten the head bolts, doing them in the incorrect order risks warping the cylinder head and/or not compressing the head gasket evenly leading to premature failure.

Answer 8

I'd remove them 1 at a time and re-torque them to stage 1... repeat this for all bolts a couple of times following the pattern the makers or manual recommends. Then re-torque to stage 2, then stage 3.



You *may* have crushed the head gasket too far by over-torquing so it may develop leaks over time... it depends what sort of gasket you fitted (metal edged or not... rubber in the metal edge or not... It's not likely but it is possible. Only time will tell.



Tighten initially to 30nm torque... this is stage 1.



Then for stage 2 tighten all the bolts a further 90 degree



The for stage 3 tighten all te bolts a FURTHER 90 degree... so the final torque is to 30mn and then another 1/2 turn. You must do it in stages to prevent warping the head. You must do it in the right order, again to prevent warping the head.

Answer 9

You should be ok. Just when you reuse the headgasket, which Is ok to reuse, just get some copper spray and put a thin even layer on the block and head. That should seal up good.

If you are uncertain about the torque specs, get a second opinion. I don't know nm so I use foot pounds or even inch pounds.

Two or three stages of tightening is also a good idea. On my honda I first tighen to 22 foot pounds then 50, and finally 70 or 80 pounds depending on which motor.

And with the 90, like the other guys said: torque to specification, then do an additional 90 degree turn. So one quarter of a full circle with the tool.

Answer 10

Lets hope you didn't go past that final torque spec with the power bar. If you didn't then all is not lost, just follow the pattern and start torquing. The 90 means you need to turn the bolt another 90 degrees (three sides of the bolt) in the torque pattern and then do another 90 degrees for the final torque. These bolts are torque to stretch which means you don't use then again or you risk the possibility of breaking one. Not worth the cost. Running the engine has me worried, you didn't have to run it to temp to do the damage as the cylinders would have got up to temp on the first minute. Lets hope your still good, if not you need to replace the head gasket and any bolts that were torqued to spec or over. You will need a tool to do the 90 degree turns to be sure it is right, do a final torque on one bolt and read the torque on the torque wrench and check that all the other bolts are at a lower torque to see that none are over the final reading , if not I think your good to re-torque and go driving.