Vacuum pump mechanical wheel & drive track questions. ORIGINAL TOPIC! - PeachParts Mercedes-Benz Forum

Matt Petty · #1 07-12-2003, 06:33 PM

Hello,
I have looked at all 625 posts found on searching "vacuum pump" and still have some specific questions. This is in regards to my '79 300td.

1. How big is the wheel in the vacuum pump which rides on the "hill and valley" track. My motor appears to to have had a previous vacuum pump lose its bearings in the past (I found them in my oil pump). The "hill and valley" confirms this because of the marks worn into it. My current pump is intact but the wheel is almost the same size as the bearing carriers on either side of the wheel. I am concerned that the worn track from the previous pump failure is now causing premature wear of my current pump's little wheel. My little wheel only protrudes a millimeter or two from its carrier and has a rounded profile. So... how far out of the bearing carriers should the wheel protrude?

2. If indeed the wheel has worn out due to scrubbing on the rough "hill and valley" track, is the track easily replaced or do I have to remove the injection pump and drive?

Thanks in advance!

ricali · #2 07-12-2003, 09:12 PM

Some of the gears with the wobble track were two piece. It's a nightmare as you must remove the pump and you might as well replace the chain while your at it

Stevo · #3 07-12-2003, 09:36 PM

Matt

I will comment on the timing device because I just finished taking it out and putting it back to get to an oil leak. I could do it faster the second time but it was rather a bugger of a job. Getting it out past the timing chain was tough but getting it back in was the bugger. Had to remove the lower chain (lower half) guide then there is no room to put it back.... anyway maybe someone else will have a better way. Heres hopping you dont have to replace it.

Stevo · #4 07-13-2003, 12:01 AM

"Sure would be nice to just bolt on a face plate!"

No such luck. I dont think the track part comes off. How bad is it scored?

Steve

Matt Petty · #5 07-13-2003, 12:05 AM

If the ramp piece is a separate piece, how is it removed? It appears that there is a large center nut and 2 x 15mm bolts outside of the track. Sure would be nice to just bolt on a face plate!

Matt Petty · #6 07-13-2003, 02:55 AM

The surface of the track is smooth but instead the ramps have little jumps on the uphill sides. Basically one side of either bump is convex and one is concave. These are pretty slight.

It appears that the wobble track is on a separate plate on the front of the driven hub part. This may be wishful thinking but maybe it is possible to remove just this plate.

Thanks in advance!

Stevo · #7 07-13-2003, 10:44 AM

Matt

Seems like what you need to do is get your hands on a new timing device, compare the two and determine if your "rollercoaster" track is good or not. If bad have a couple beers and post us in the morning. Like ricali said you could do your chain which would mean the timing device would come out, no problem but you would of course have to retime the pump. I THINK you would need to pull the IP which may mean pulling your oil filter housing (change the gasket there as it may be leaking now). I know you don't want to hear all this but if its time to do the T chain and your oil filter gasket hasn't been done you might be able to "kill a few birds with one stone" Also ricali said some tracks did come off so you may luck out there.

Steve

psfred · #8 07-13-2003, 03:00 PM

To change the pump timer on a 617, you need to mark the chain and timer with a paint marker. Make SURE the marks are wipe-proof, you don't want to loose them. I assumer you still have the vac pump off. Collapse the chain tensioner (large rail on the right side) completely to get some slack in the chain. Transfer the slack to the IP side by rotating the cam sprocket with the bolt.

Hold cam timer against engine rotation and loosen the nut in the center, the slip a piece of sheet metal between the timer and the chain. As noted, you may need to remove another slide rail to get enough slack, but probably only on a new chain. Pull timer gently out, making sure you don't disturb the IP shaft too much.

On the bench, transfer the paint mark to the new timer by locating the Woodruff key slot and counting sprocket teeth so that the mark is in exactly the same relative position on the new timer.

Slide new timer onto the pump drive (have a care not to push the key out and into the chain case!) using the pit of sheet metal to hold the chain away from the sprocket. Align marks and pull the sheet metal out to drop chain onto the sprocket and pull the chain tight with the cam sprocket.

You should return the IP timing to exactly where ti was with this procedure, but it may not be a bad idea to check anyway.

Check the chain stretch, too, and if it is more than 8 degrees, pull a new chain after replacing the timer, THEN check IP timing.

Peter

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