Self-made tool: Timing Chain loader - PeachParts Mercedes-Benz Forum

donbryce · #1 04-12-2008, 12:49 PM

Thanks to the threads and pictures posted by several great people here, especially Alkraut and Roncallo, I'm nearly ready to finish my timing chain guides replacement and put in a new chain. By 'ready', I mean getting up the nerve to remove the distributor and do the driver side upper guides. The passenger side guide was easy, but I'm a bit worried about removing the chain sprocket to do the left side.
Anyway, I decided to make my own chain loader tool, dimensions copied/estimated from pictures of the actual unit available from U.S. sources for about $52.00 + about $30.00 more for shipping and duty/taxes etc. to Canada.
Besides the high price for a one-time use tool, I didn't like the way it mounts to the front camshaft bearing carrier bolts. I was worried about disturbing the torque settings and/or mis-alignment of the bearing to the cam when replacing the bolts after finishing doing the chain job. I suspect it is designed to be used on either the left or right head, but all the threads on putting on a new chain have it used on the right one only, so I thought I'd just custom make it to use there.
I took my best guess as to the actual sizing of the 'covering' piece that goes over the chain/sprocket and did up a cardboard pattern. I taped cardboard on the inside of the curved top to get a little over 1/16" clearance from the chain/sprocket, checked for fitment, then disassembled and traced the pattern on some steel scrap, just over 1/16" thick.
After tackwelding the cover piece together, I transferred the spacing cardboard from the mockup to the steel piece, then set it on the sprocket. I made a piece of angle with 2 holes to mount to the alternator bracket holes in the head, then did the uprights to connect them together.

donbryce · #2 04-12-2008, 12:57 PM

....continuing, after tack welding the unit together, it seemed a bit unstable, so I made a brace to support it from the backside. The brace rod is secured to the valve cover mounting hole.
I cut the opening for the chain access after welding it together. Painting wasn't necessary, but it looks nice. Hopefully, it'll do the job of keeping the chain on the sprocket when I get up the balls to put in the new chain.
I still have to replace the driver's side guides, so the chain job will likely be in a few days, at which time I'll post a follow-up on how it went.....

BTW, if anyone wants the dimensions to make one of these, just ask

TOPGUN · #3 04-12-2008, 10:48 PM

Very commendable. I used the vice grip method with one exception. I covered the jaws with aluminum so as to not mark up the chain or gear. (TOMGUY post). It was slow but sure.I really like what you made. The idea of removing 19 year old cam tower bolts did not seem like a good idea. Would like to hear back how it works. Good luck

Strife · #4 04-13-2008, 12:17 AM

No question, there is a big advantage in NOT removing the cam tower bolts- - this is a good idea. I have one of these (original design) tools, and I didn't realize just how sensitive the cam tower positioning is until I actually replaced a cam. Then, there is the small, but real possibility of getting a big surprise while retorquing these bolts - losing torque on them would be a head-off nightmare.

whunter · #5 04-13-2008, 02:56 AM

Quote:

Originally Posted by donbryce

BTW, if anyone wants the dimensions to make one of these, just ask

Please post the dimensions here.

donbryce · #6 04-14-2008, 08:03 PM

I snagged my son for some 'quality time' this afternoon, and we did the chain replacement together, using my new tool. More on that in a moment. As promised, here are the dimensions for making one. Referring to the drawing, and the earlier shots of the unit, I'll add a few notes on how it was designed.

I first cut out the pieces from thick cardboard, the stuff picture framers use as 'mat board', to make the cresent shaped top part. After verifying the fit, the cardboard was used as a template to mark and cut the steel, which was scrap about 1/16" thick. This was tack-welded together.
The objective is to get a nice tight clearance, absolute minimum, between the top of the chain on the gear and the inside of the loader tool's curved top. I taped 1/16" cardboard inside the steel top piece to establish this clearance, as it sat on the chain/gear.

After making up the lower bracket pieces, I marked the position of the uprights relative to the top piece sitting on the chain/gear. With the spacers inside, that meant that the finished piece would have just enough clearance to allow the chain to ride inside, but impossible for the links to leave the gear teeth.

The rear support rod may have been overkill, but in use, the chain definitely smacks the inside of the top piece as it tries to jump out while the valve springs jerk the camshafts forward. Thicker metal would have made this rod unnecessary, but then the cutting would've been harder. I cut this out on my bandsaw and using a jigsaw BTW.

So, as my boy and I found out, it would be easy to jump a tooth or 2 if not for something like this tool, or very tedious using visegrips or tie-wraps. I maintained constant upward pulling pressure on the old chain as it rolled out, and even pushed down on the new chain as it entered the tool top piece as he slowly turned the engine crank. I left the rocker arms in, sparkplugs and tensioner were out. We finished the load in about 20 minutes. All my timing marks line up and the balancer pointer is at '0'. I'm ecstatic!

One more piece to replace (tensioning rail) and the oiler plastic thingies and it's button up time.

Last pictures are of my modified vice grips, for holding the cam solid while undoing/torquing those big bolts (100nm). I couldn't find a picture of the MB tool for gripping those nubbins. All my books show a square block and large end wrench.

myanoch · #7 04-15-2008, 02:02 PM

Nice job,like what I see
thanks for the great idea

bbeberness · #8 04-21-2008, 02:52 PM

What a great bunch of guys here. I can't wait to get back to Portland, OR and get started replacing my chain and tensioners. More questions! Being a newbe to the MBZ I could use more details about what all do I need to change out. Tensioners, guides, gears,etc etc. Is there a special tool for removing the tensioner pins? are they threaded or just a tight push/pull fit? Should I replace all the tensioners and guides or just the guides or just the tensioners? I have about 80,000 miles on a rebuilt replacement motor and a bit nervous about throwing a chain on it. Total mileage on the car is about 151,000 and I want to be able to take it out of town without a worry about at least the chain. Any and all ideas and information is appreciated. Thanks a million.