[W126 Coupe] 560SEC top-end rebuild

[Gerry Van Zandt]

Hi Steve,

It's not so much how the bolts come out, it's when they go back in that you find the need for heli-coiling. 

Most all the head bolts have come out just fine. One side I soaked overnight with penetrating oil and the other side I didn't. I'd say that the soaked side came out about 30-40% easier than the non-soaked ones. That said, even with the non-soaked ones, they were pretty easy to do with just a modest breaker bar.

The two rear-most bolts on the sides of the heads nearest the firewall are the worst, just because of the lack of room to get at them. Chet recommends in his write-up removing the inner firewall sections, but I found that I didn't need to do this at least for removing them. The factory procedure didn't mention this either. However, for torquedown, I probably will need to so that I can get a better angle on them with the torque wrench.

For the toasted cam, I'm getting my hands on a good used 560 cam, and I will replace all of the 8 rocker arms on that side. I will keep and use the lifters becuase they appeared to be just fine. It looks like the cam issue was caused by a lubrication problem, so I will closely examine the oiler tube on that side for cracked oilers or caps that supply oil to the holes where it flows down onto the cam lobes and into the cam bearings. These caps and oilers are very cheap and easy to replace when it's all apart.

ALso, my chain rails, tensioner rail and timing chain all have 60K miles on them, but I'm just going to replace all of them out of hand because they'll never be as accessible as they are right now. Also the two rear heater hoses into the firewall - they've got to be original and their rubber isn't getting any fresher....

I cracked the vacuum hose that goes from the brake booster to the intake manifold (a $95 hose) so will have to replace that, and I saw some outside surface cracks in the two fuel lines that go to the fuel cooler, so those are getting replaced too. The idle slide valve-to-intake hose cracked in my hand, so obviously that's getting replaced; the idle air injection hoses are around 60K miles old as well, but I will replace those too becuase the injectors are out and everything is right there for the reassembly.

Basically a top-end rebuild is an excellent opportunity to replace all soft parts, hoses and vacuum lines. Hell, even the motor mounts are easily accessible with the manifolds off the heads !! If I'm motivated, I may even do those although I know my current ones are good. Unlike the 500E, which has hydraulically-damped motor mounts, the 560's mounts are simple & cheap.

There is no better way to learn about how the 560SEC works than to just carefully and patiently take it apart, and put it together. Really gives you a feel for the engineering of the cars and their complexity, even 25 years ago ! Much nicer to work on than modern cars. Makes you feel like you're really doing something instead of sitting at a computer screen or pulling codes. No handheld-testers or Star Diagnostic Systems in sight when doing head work !!!

Cheers,
Gerry

 
On Tuesday, March 16, 2010, at 11:15AM, <mbcoupes-request at mbcoupes.com> wrote:

>

>Hi, Gerry, nice to hear from you again. Looks like a great project that you are on - great write-up and photos in Espot, too.

>

>How have the head bolts been coming out? Any problems and do you foresee having to put inserts into the block?

>

>Steve