Can banging sound at front of engine.....what could it be? - Page 2 - PeachParts Mercedes-Benz Forum

Hatterasguy · #16 07-20-2008, 01:14 AM

Having been in a similer spot, IE needing the car and having the cash...shot gun away. It does work, just isn't cheap.

Thats why I spent a fortune on the SDL's oil cooler, I needed the car. I had a spare for 4 days, I had to get it fixed in 4 days with school and no time. Cash can do that. If I had time I could have done it for much less...

pawoSD · #17 07-20-2008, 01:44 AM

I don't have a job, so there is very little cash available right now....

However, if it needs a pump it will get a pump....I'm not going to make a dumb decision that destroys the engine...

How can you physically tell if the vacuum pump is the culprit? Tomorrow I am going to pull the pump from our dead engine and see what it looks like inside....then maybe I could compare it to mine if I pull that one too.

Does the rebuild kit for $43 replace the critical components? Or do you need a whole new pump to be extra safe?

On a side note, I still think it may be the fan clutch/fan because it goes away when the engine warms up a bit.....we'll see, I'll do diagnosis tomorrow.

Beagle · #18 07-20-2008, 03:45 AM

I still think it may be the fan clutch/fan because it goes away when the engine warms up a bit

The noise from a worn fan thermo is more of an irregular tinny clatter only at idle. To check, pull the fan hard forward and back. If there is play jam a piece of string in the gap and see if the noise goes away.

How can you physically tell if the vacuum pump is the culprit?

When you hear mechanical noise from the vac pump at least one of the bearings has already failed. While the pump may continue to function for some time the cam is now rubbing on the rocker arm instead of the roller and the mechanism will soon disintegrate.

The noise is louder and more of a regular ‘hammer on steel’ noise that will also disappear after about 5 min. Once the pump has drawn full vacuum the cam follower is held away from the cam by the vacuum and hence the noise will cease – contacting cam again as vac falls.

If you catch it in time you will only need to replace the two $5 bearings. They are No. 626 (6x6x19mm Dia) available at any specialist bearing store. The complete rocker replacement kit from MB is over $400. The $43 kit you refer to is either the diaphragm or poppet valve kit.

There are two types of vac pump on the 617’s. The diaphragm type has two pipe connections and the piston type fitted to most later 123’s has only one.

.Have a nice day

Hatterasguy · #19 07-20-2008, 05:01 PM

If you have a spare one on your dead engine, and it looks good swap it over. A gasket is like $2 and since you don't have a job you have more time than money...

elkman · #20 07-20-2008, 07:09 PM

Couple things, I just went through a similar noise and the alternator was not my problem either, rather the tensioner bracket holding the alternator. If the 17 bolt that mounts in the side closest to the block is loosened the tensioner plate can be elevated up to give more clearance to the alternator fan blade. Look at the blade of your alternator, is there shiny metal where it may have rubbed on the belt or bracket? Is your belt worn or frayed next to fan? Also check to make sue you actually got your front 17 bolt through the spacer. If not the alternator will shift towards tension causing the belt to contact the fan blade.Also if you suspect any bending of your bracket switch it out. If you really want to locate the problem remove your belts and see if the sound goes away.

pawoSD · #21 07-20-2008, 10:12 PM

Today I ran it and tried to pinpoint the sound using a piece of wood to my ear touching various engine parts....I am 100% sure its not coming from the vac pump.....I also disconnected the vacuum lines from it and plugged....unplugged....plugged....unplugged......the opening....and the sound on the engine did not change.....I listened by the hole where it sucks in the air and it sounded normal + it has strong vacuum.

Its not the alternator or mounting bolts/bracket for it....I just swapped that out friday night and all bolts are nice and tight and the bracket is straight....the belts are only about 1.5 years old and are in excellent shape still. (Conti Belts)

The fan has some play in it, when I push forward and back on it it wobbles a bit and there's probably close to 7mm of play......and if I wobble it fast it makes an eerily similar sound to the noise I am hearing. I checked the fan on our 300D for comparison and it is not as loose.

The water pump seems to be/work fine....so I doubt its that either. When listening closely the sound seems to come from the area right around the fan/thermostat......its not by the vac pump. Its not a hammering sound either....more of a rattle...if you tap a screwdriver along the blades of the aluminum engine fan it sounds very similar.

My bets are the fan. Any risk in leaving it be? I could check/swap fans with the dead engine from our project car....but it may be no better with 313k on it...

Hatterasguy · #22 07-20-2008, 11:37 PM

Yank the fan and run it, see if it goes away.

I wouldn't let it get to much worse, if it lets go its going to take some other stuff with it.

vstech · #23 07-20-2008, 11:45 PM

yeah, really easy to remove the fan, put the bolts back on the pulley, and start her up. see how it sounds with the fan off...
wiggle the fan on the donor motor and see how much play there is... if none, swap it.
if some... now might be the time to follow DG's electric fan mod...

pawoSD · #24 07-21-2008, 02:01 AM

Tomorrow I will look into taking off the fan and running it to see what it sounds like.....hopefully that is the issue, I'd like to solve it!

leonard-929 · #25 07-21-2008, 02:04 AM

I think I have the same problem with my 78 240D. I put a steth on the vacuum pump and it was very noisey, but not the sound I was looking for(lots of moving parts in there!). The sound is loudest where the trans and motor meet. Could it be the clutch, If so why would this problem all but disappear when warmed up. The clutch works great.

I could hear this noise throughout the engine with slightly varying volumes...... I'm stuck

jt20 · #26 07-21-2008, 03:13 AM

Quote:

Originally Posted by Beagle

I still think it may be the fan clutch/fan because it goes away when the engine warms up a bit

The noise from a worn fan thermo is more of an irregular tinny clatter only at idle. To check, pull the fan hard forward and back. If there is play jam a piece of string in the gap and see if the noise goes away.

How can you physically tell if the vacuum pump is the culprit?

When you hear mechanical noise from the vac pump at least one of the bearings has already failed. While the pump may continue to function for some time the cam is now rubbing on the rocker arm instead of the roller and the mechanism will soon disintegrate.

The noise is louder and more of a regular ‘hammer on steel’ noise that will also disappear after about 5 min. Once the pump has drawn full vacuum the cam follower is held away from the cam by the vacuum and hence the noise will cease – contacting cam again as vac falls.

If you catch it in time you will only need to replace the two $5 bearings. They are No. 626 (6x6x19mm Dia) available at any specialist bearing store. The complete rocker replacement kit from MB is over $400. The $43 kit you refer to is either the diaphragm or poppet valve kit.

There are two types of vac pump on the 617’s. The diaphragm type has two pipe connections and the piston type fitted to most later 123’s has only one.

.Have a nice day

this guy is onto something. That housing that goes over the water pump makes a very can-like sound when hit. and there are many ways it can get hit if those 4 wimpy bolts that hold the fan and pulley to the pump are loose. I just discovered mine were all loose!!

Like he is saying... when the engine warms up the force from the blades on air is now transferred to the bolts / pulley / pump holding them in place and minimizing rattling.

a theory worth investigating

pawoSD · #27 07-21-2008, 08:58 AM

My fan has significant play in it, so that is likely the issue....in fact this morning after I had messed with it last night (pulling it back and forth) it didn't make the noise much....

I am going to check our inventory of parts and see if I have a better fan assembly....if worst comes to worst I'll just replace the fan/clutch with a new updated one....my dad's SD has the newer 9 blade nylon fan, it moves WAY more air!

Johnhef · #28 07-21-2008, 09:18 PM

I know it sounds crazy but (with thick padding) slow the fan and hang on to it with the engine running (and cold!) and see if the noise stops.

pawoSD · #29 07-21-2008, 10:34 PM

I will try this tomorrow morning when I start her up...

Since I have time tomorrow I may just swap fans. Turns out the dead engine from the project car actually has a plastic fan/newer clutch!

(I hadn't remembered this till I went out and looked at it today) So that will be going on there....

vstech · #30 07-21-2008, 10:45 PM

Quote:

Originally Posted by Johnhef

I know it sounds crazy but (with thick padding) slow the fan and hang on to it with the engine running (and cold!) and see if the noise stops.

um. dead readers are not good for this forum... recommending holding on to a fan with a possible damaged viscus fan clutch does not sound wise to me.
I envision the "heavy padding" getting caught in the belt, or the fan locking up, and sucking the unfortunate diagnostician's arm or entire body into the motor... decapitation... ensues...