Zel's Fleet Blog - BX, Jag XJ-S, Sinclair C5, Mercedes 208D & 230TE, AC Model 70.

[Gibbo2286]

I do like a bit of Pi .

[myglaren]

I do like a bit of Pi .

That one is extra clever as it knows Pi without a dedicated Pi button.

[myglaren]

[Zelandeth]

I do have one which does...think it's a TI branded one. Apparently they used an identical core for several models and simply changed which buttons were populated on the case. The actual membrane and keypad contacts were still there though for several scientific functions it notionally didn't have.

[Zelandeth]

This afternoon has been frustrating.

On the plus side, Motorserv reckon I should have a head gasket and inlet manifold gasket ready to collect tomorrow. Hopefully they'll have more luck than Mercedes themselves or the specialist I was trying to order from before.

Fat lot of good it will do me though as the head is still attached to the car.

I've just wasted the best part of two hours trying to get the pin that holds the timing chain guide out.

This pin, which is helpfully drilled and tapped with an M6 thread.



Should in theory just pull out, using a nut and bolt as an improvised puller seems to be a popular method.



Yeah...even using the best quality M6 nut and bolt I could find (the ones in the photo were purely to show how things fit together) just ended up mangling the threads on the bolt in one case and shearing off in another.

Basically I need to resort to a slide hammer. Unsurprisingly given this engine's history it's well glued in place. Unfortunately there's not enough space to get in with one.



So to get in there I'll need to pull out the radiator. Which means I need to disconnect the very crusty looking transmission fluid lines (the oil cooler is integrated into the bottom radiator tank). Oh, and I need to buy a slide hammer as I don't own one.

...Or just buy a new timing chain which comes with a split link...oh...but then I'd need to get the whole timing cover off. To get that off you need to remove the sump...which we've already found is a non trivial process. So I guess we keep messing around with this.

Oh, in case there was any question over whether the head needs to come off... here's a random selection of the journals the camshaft sits in...







Yep...that's had it! Has been for a long time too given the scored out areas have had time to get varnished deposits on them.

[xantia_v6]

I am not sure that a slide hammer is the best tool for that job. They are best for breaking away a taper joint, but not ideal for a tight friction fit. It is not clear what you were pressing against with the nut, a spacer or socket?

[white exec]

Could you try a length of steel, with a hole for your bolt, and lever (knock) outwards, pivoting on the metal bits below?
Get some PlusGas in there, too?

[NewcastleFalcon]

Bit slow to watch and I presume this is the method you have already tried. Probably not your exact engine but a similar arrangement I would think. The pin when it did come out was much longer than I expected

Regards Neil

[Zelandeth]

There was a spacer in there (10mm socket) when I was actually trying to remove it to ensure I was actually pushing against the head rather than the surface of the pin.

Will see if I get a chance to look at that video later...though I have to confess that I have an unreasonable aversion to the whole "everything has to be a video" approach to how to guides these days. Sure, augment them with videos if it's hard to describe something in words, but I'll always take a written guide over a video any day of the week. Especially as 80% of them - especially the first few Google will suggest - seem to be blurry dark disasters created by people who have absolutely no idea how to use their cameras.

Seems that the art of writing a step by step guide on how to do anything is dying out...

Edit: I should add here, I'm not grumbling about you linking to that video, it's useful and I appreciate it...more just a general rant about a growing trend on the web over the last few years that bugs me.

[mickthemaverick]

I actually think this video is a clear visual message as to how to do this particular job. If I were doing it I would use a ratchet spanner on the tightening nut to speed up the process but it would seem the 'designed for the job' high tensile bolt used is a must. Having said that I do agree Zel that the video has become too obvious a substitute for a traditional Workshop Manual type description but they do have a place if produced properly and ideally endowed with a decent commentary.

[Zelandeth]

Having left the timing chain guide pins stewing in Plusgas for a few days I went back for another shot today. Armed with a few high tensile bolts and an assortment of spacers I figured this was the last chance saloon before I get more tools involved and strip things down further.

After far more torque than I would have liked was applied, the pin started to move with a terrifyingly loud crack.



It was tight all the way out (as expected given it's purely a friction fit), but didn't require stupid amounts of force once it was moving. One removed pin.



At this point I figured I would be able to withdraw the chain tensioner. Err... apparently not.

A quick consultation with the spare head showed there were actually TWO of these pins. I'd missed this one entirely.



Partly because I'd just unbolted the thermostat housing from the head and left it otherwise in situ, partly because...well...would you have spotted it under all that slime?



About 3/4 of a can of carb cleaner and some scrubbing later...hey look, there it is!



Same process as before...another pin out.



Which *finally* allowed me to get the chain guide out.

It defied all attempts to usefully photograph it, but there's hardly any visible wear on this, I'd not be surprised if it's been replaced at some point.



Before pulling that out (which would let the chain go slack) I put a cable tie on it to maintain enough tension to hopefully keep the timing where it should be. I'll obviously rotate things to cyl 1 TDC and check everything anyway before attempting to start it again...but I figure minimising the opportunities for things to move in the meantime can only be a good thing.

Then the swearing really started...as this was when I started to try in earnest to get the head off. Naturally I eventually found a couple of things I'd missed.

The first of these didn't take me long to spot. As well as being secured to one of the rocker cover studs, the transmission fluid dipstick is bolted to the back of the head.



Yes, that is a crowbar wedged in an exhaust port being used to lift the head... knowing it's scrap metal meant I was a bit less careful of damaging it than I otherwise would have been!

The ones which took me FAR longer to find than they should have though we're the two bolts which attach the inlet manifold to a brace underneath it.





Once they were out it just lifted off. Well...nearly. it resisted for a moment before I heard something ping off, whizz over my shoulder and bounce off the side of the van.

Oops...I also missed the throttle return spring.



Guess I'll need a new one of those then. Though if that's the only casualty, I'll take it!

Finally it's off the car.







It's worth noting that the head was initially cracked from the block about a week ago, so I was expecting a bit of water contamination to be present in the cylinders, and I think that's why the carbon that was present has sort of peeled away. Quite a bit of carb cleaner probably found its way in while I was blasting crud off the outside too.



After a bit of a wipe down news isn't looking bad. Cross hatching is still clearly visible on the walls of all cylinders.



I originally thought that was a huge wear ridge at the top...but given the presence of the hone marks I think it's just how this was originally machined.

This is the worst looking bore by a long shot.



The vast majority of that is above the swept area of the rings, but I'll see if we can clean it up a bit before putting things back together. Looking at the head gasket itself it looks like we might have just been seeing the very early stages of failure between the water jacket and cylinder on the rearmost one - which would tie in with the appearance of moisture having spent time in that bore.

Looking more closely at the head, it's astonishing that there's really no visible difference between number 3 which has had vastly impaired breathing compared to the rest!



I'm no expert, nor do I play one on TV (or even YouTube), but my gut feeling is that this head hasn't been off before.

Hopefully I should have a new head and inlet manifold gasket set waiting for me tomorrow. That will allow me to swap all the known good injection hardware over to the spare head. Given I know it's working fine I just don't see any reason to disturb it more than necessary
...just transferring the whole manifold with it all attached seems the least likely to introduce gremlins.

Then it will be a matter of lots and lots of cleaning of both the head and the block before we start putting things back together. Then praying it's solved our issues!

In reality this head is about as easy to pull as they get in OHC form...the only reason it's taken me a while to get to this stage is lack of knowledge of this particular engine. If I needed to pull it off again in the future I could do it in half the time.

Yes if I'd read the manual beforehand I'd probably have done it quicker, but I'd not have learned half as much. The one thing I did look up though was the correct sequence for tightening/loosening the head bolts. Good thing as I'd otherwise never have spotted that sneaky one by the warm up regulator.

Before I shut up shop today I made sure to absolutely mist everything (especially the bores) with oil, so no further surface rust can think about forming on things.



Hopefully you'll soon see me putting that mess back together...Taking bets now on how many bits are left over...

Goes without saying I'll be doing the rebuild more by-the-book though as I don't want to damage the replacement head, whereas the one I was taking off was scrap metal.

[Zelandeth]

Let's do a quick side by side comparison of the new and old camshaft journals...

From the front...

Ignore any blocked looking oilways, it's just grease from when I had things in and out a bunch.

1.





2.





3.





4.





5.





Think it's fair to say the new one is a bit healthier. Rear coolant line elbow is rather crusty on the old head too.



New one is in "considerably" better shape thankfully.



After a bit of deliberation I decided to leave the inlet manifold gasket alone and just swap the fuel distributor over. Not a big job really, only took about an hour to transfer everything over from one head to the other.



Not forgetting one of the most ridiculously overcomplicated throttle linkages I've seen in a long while.



Next steps:

[] Remove and reset timing chain tensioner.

[] Remove the remaining studs which are trapped in the exhaust manifold so they match what's present/missing on the new head.

[] Rotate engine to cyl 1 TDC so I can set the timing properly, reset distributor as necessary.

[] Clean up block and head surfaces.

[] Reassemble.

[] Flush sump out with copious amounts of diesel to get as much gunk out from there as possible.

[] Pray I've made things better than worse!

Feels like we're making progress at least...

I do at least have a head gasket in my hand now.



In other news...well there isn't any really! Just business as usual.



Hopefully we'll manage to keep up a bit of momentum on getting the Merc back together.

[white exec]

Looks like the coolant was neglected too, judging by that coolant line elbow.
The throttle linkage is unbelievable. Reminds me, I think, of the one on Domomite twin carb, where there was a slot/roller arrangement to alter the lever motion.

[Gibbo2286]

I think that if you were in a less prosperous country e.g. Cuba there would be a workshop with the ability to re-machine that head and put it to use for another 100k miles.

[white exec]

...or Spain...or Malta...