Head bolt torque?

LibertyCRD · **Posted:** Wed Nov 03, 2010 9:41 pm

I have heard it's a good idea to check the torque on the head bolts. Anybody know what the proper torque spec is on them?

MrMopar64 · **Posted:** Wed Nov 03, 2010 10:49 pm

For the head bolts:
1st: tighten to 30 N-m
2nd: without loosening, tighten additional 75deg only the inner two rows in diagonal order
3rd: without loosening, tighten additional 50deg only the outer two rows in straight order (down one side, then back up the other)
4th: tighten all bolts additional 75deg, first the inner two rows in diagonal order then the outer two rows in straight order
This is only valid when starting from zero torque. The bolts are torque-to-yield, re-use them at your own risk. There isn't a torque spec for tightening them once they're already in service.

However, to get to the head bolts, you have to remove the intake manifold/cam carrier which would include removing timing belt, all injectors, fuel rail, wiring, etc. etc...

LibertyCRD · **Posted:** Thu Nov 04, 2010 7:54 am

OK I'll check them when I do my timing belt this Winter. I've heard that many of these head gasket failures are happening because the head studs are getting loose.

Joe Romas · **Posted:** Thu Nov 04, 2010 1:10 pm

LibertyCRD wrote:

OK I'll check them when I do my timing belt this Winter. I've heard that many of these head gasket failures are happening because the head studs are getting loose.

I've owned many VW diesel powered cars with torque to yeild bolts and have replaced some head gaskets. Did you read MrMopar's instructions? You'll need a 6 foot cheater pipe on a braker bar to get the last 75 degrees. It's real scarry hearing them creak :shock:

this might be a good thing to leave alone untill you know you have a problem.

litton · **Posted:** Thu Nov 04, 2010 4:22 pm

Head gasket failures???

Must have missed that problem. How do head bolts loosen??

warp2diesel · **Posted:** Thu Nov 04, 2010 4:41 pm

After owning and running a repair shop for 14 1/4 years, I learned not to mess with torque to yield bolts once they are properly torqued.
By yielding, they stretch and put a continuous tension and uniform tension on the head and head gasket as the head expands and contracts. With a cast iron head, block and steel bolts, where all expands at the same rate, the engine runs for a long time with out a problem. Install an aluminum head that expands twice as much as cast iron or steel with solid bolts, the head gasket has to do all of the yielding and will more or less wear out the head gasket causing it to fail resulting in a blown head gasket that has to be replaced. On aluminum head engines before torque to yield bolts, I would back off the head bolts 1/6th turn and retorque them. An engine with an aluminum head and torque to yield bolts will run much longer than one with conventional bolts. On aluminum head engines I have worked on, I found that the engines with torque to yield bolts would at least run two to three times longer with out a head gasket going bad.
Since our CRDs have torque to yield bolts you are best not to mess with them until you plan to pull the head to replace a head gasket, remove a broken glow plug, or service the valves.
On some engines with torque to yield you measure the bolt shank diameter and use that dimension to reuse or scrap the head bolt. Others tell you to replace them (I would do that on my CRD). One trick I did use on VW diesels was to replace any head bolts that did not feel right when I was doing the extra degrees of turn recommended. Since I have not done several CRD heads, I can't recommend the does not feel right trick.

LibertyCRD · **Posted:** Thu Nov 04, 2010 7:53 pm

litton wrote:

Head gasket failures???

Must have missed that problem. How do head bolts loosen??

I don't know, but if you do a 'Net search and read about VM engines (used all over the world in Jeeps, multiple other brands, boats, etc.) they always talk about the notorious head cracks, leaks, gasket failures, etc. And one site I stumbled upon talked about making sure the bolts are tight after a lot of miles are racked up. This is common on Cummins engines, especially when turning the power up, so I figured it makes sense for the VM too.

MrMopar64 · **Posted:** Thu Nov 04, 2010 8:41 pm

The early engines that you are referring were the old indirect-mechanical injection engines that had individual cast iron heads per cylinder. That was a whole different ball game, and yes they were prone to some issues.

The new engines I wouldn't touch unless you had a problem that was directly affected, they have been pretty trouble free in the grand scheme of it all.

Head bolt torque?

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