head removal m180 help?

[Neubie]

Ok, So Ive got gobs of sticky white goo in the oil filler cap, indicating a head gasket/cracked head. Ive started the disassembly process and gotten stuck at the timing chain. The Haynes manual says:
"From the front upper edge of the cylinder head remove the the chain tensioner bolt. Screw in a suitable bolt into the sprocket shaft and extract the shaft and the sprocket."

Ive got the tensioner bolt off, but I am not understanding the whole shaft bit. What would be a suitable bolt? obviously not the one that came out, it the shaft threaded to accept a bolt?

If someone could explain this process I would be most thankful!

Marc

[300SDog]

Dunno the Haynes method, but I've always just unbolted the sprocket (with chain in place) and rapped it evenly around with rubber hammer to disconnect both it and the chain from the camshaft. Be careful not to loose the woodruff key in the process. And reassembly is the reverse.

Also first paintmarked the chain to sprocket, used bungie cords to keep chain tension tight and set the engine at TDC before pulling the head. And dont forget a couple of small 8mm(?) allens securing the head down in the front channel on the m180.

[Tomguy]

If it's like the m116/m117 (and it sounds like it is):

You removed the "cap bolt" - the actual bolt/shaft itself is threaded on the inside to be pulled out. Be CAREFUL to screw whatever you're using in far enough so that you do NOT strip the threads out! On the m116 and m117, the thread is the same as the valve cover bolts, and those work well for that purpose with a socket and washer for spacers...

[senorunimog]

The shaft it is referring to acts as a pivot for the tensioner assembly. Its basically a pin about 3 inches long, driven in from the front of the block. You should be able to look down the opening in the head and see where the shaft is. The shaft will have the tensioner assembly on it, and then a spring. Find a long M5 (I think) bolt, and screw it into the hole in the front of the block. The hole is probably covered with crud. There might be engine accessories, or other bolts over the hole that has this pin in it. I know in my 280se the bracket that holds the injection lines and the A/C bracket use the same hole.

Once you have the bolt screwed in try and pop the whole assembly out with a slide hammer. The tensioner should stay in place without the pin because of the spring. Get a magnet on the spring, or run some wire through it, then pull out the tensionder. Pulling out the tensioner is a bit frustrating, but eventually you'll get it out. After the tensioner is off the rest is fairly easy. Unbolt the cam sprocket, put a wire around the chain, and gently bop off the sprocket. I wouldnt worry too much about the key, I've never had one pop off, but just be aware that it might happen.

Hope that wasnt too confusing,
-Eric

[senorunimog]

Here is a pic of an m180 from a unimog, so the accesories wont be the same, however the shaft or pin should be in the same place. To access the pin on the mog engine, I first had to remove the large bolt. If your puller bolt is long enough you might be able to thred it in through the hole and pull it right out, otherwise if you have a plate in the way you will have to pull it off.

let me know if you want a better version of the picture

-Eric

[Neubie]

Ok, thanks for the help, it's kinda what I thought but it helps to have some reassurance and to know the shaft is threaded, thats what wasn't clear.

the adventure continues!

Marc

[300SDog]

Hmmm, have pulled more then one m180 cyl head and dont remember messing with the chain tensioner at all........ I wonder what makes Haynes think the head caint be pulled w/out ditching the tensioner first.

[Neubie]

Sure will try that first, less apart the better.

[cth350]

The things to be careful with are the little bolts that hold the metal bypass tube (U-shaped thingy) from the water pump housing to the head.

The pipe is replacable, as are the bolts. However, the bolts are hollow and subject to corrosion. Which means not only do they get stuck, but they can break easily.

Once you've drained the coolant (you did drain the coolant, right?) You can heat the bolt heads with a torch to loosen the corrosion.

Then again, you might have removed them already, in which case, throw the bolts away and buy new ones along with new aluminum crush seals. The new ones are cad plated and will last a while.

-CTH