Hello all,

I recently changed the injection pump on my 87 300sdl and the car runs much better, great power. However, now there is a rattle noise at the front of the engine. With the hood closed it sounds like a loose peice of sheetmetal vibrating right behind the grill. When I open the hood I just can't seem to nail it down exaactly where it is coming from. It makes me
weak in the knees to think that there is something wrong with the timing chain after the IP was changed. I had to remove the chain tensioner to do the pump. I accidentaly dissassembled the unit istead of removing it. I located another and copied the internal parts setup so I am confident I recovered that to its original configuration. The only other idea I had was the sheetmetal chain keeper that is installed around the IP drivegear. Could that possibly be causing this noise? The noise is very annoying, Ireally need to get rid of it.

Thank you for your thoughts

Eddie E.
87 300SDL

Thats a tough call, its hard to figure a noise out without hearing it.

But if it started since you changed the IP, I bet it has something to do with what you just did.

Do have the new style vacuum pump?

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I don't know the difference between new and old.

With the car running it sounds like it is coming from the right front of the grill. I loosened the belt tensioner and found the pulley spins freely with a very small amount of lateral freeplay. The rocker seems to move without resistance. I plan on pulling the timing cover to have a look at the timing chain for any kind of marks to the chain.

Any suggestionsare greatly appreciated.

Eddie E.

87 300SDL

Does it just rattle at idle?

Take your hand and push the top of the little damper shock towards the car. The bushings get some slop in them and will cause a racket. Carefull not to chop your fingers off in the fan.

The new pump has 4 screw heads on the cover, if you don't see those its the old one and needs to be changed.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I only hear the rattle when at idle or a few hundred rpm above idle. No difference if the car is rolling or stopped.

Push the belt tensoner towards the engine and see if it goes away.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Well I think I found the source of all the noise. I took the car around the block. Heard a chunk under the hood and the instrument cluster lit up. When I opened the hood the belt was a birds nest. When I tried to remove it the alternator pulley fell to the ground. The pulley was all marked up from bouncing on the shaft. The woodruff key pulled through it, plenty of stress cracks. The alternator still spins freely and the cooling fan is still in place. I will have to look further and see if any other parts were damaged in the system as a result of this. I suspect that I lost more than one pulley. Of course I shut down immediately to avoid an overheat. I have a #22 casting cylinder head so I should be ok there....I hope.

Thank you for your suggestions, they are greatly appreciated.

This is the one that got away.

Eddie E.
87 300SDL
316k miles and limping home.

Happens, at least it failed at a good time.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200