220D vacuum pump repair - Mercedes-Benz Forum

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post #1 of 16 (permalink) Old 06-12-2012, 09:17 PM Thread Starter
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220D vacuum pump repair

Brakes on my 71 220D are all good but brake pedal very hard and it is not stopping - I am getting no vacuum from the hose which leads to the brake booster. there is good vacuum at the manifold but after removing pipe from what I believe is the vacuum pump there is no 'suck' there.

I imagine the vacuum pump is not working even though it looks like a newer part which has been put on - does this sound right? Also I did some research and found that it is possible to replace diaphragm on this?

Thank you


Lee
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post #2 of 16 (permalink) Old 06-12-2012, 11:23 PM
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The vacuum pump is at the front of the engine. It has two hoses attached to it, one runs to the brake booster, the other runs to the intake manifold. The vacuum pump sucks air out of the brake booster and pumps the air into the intake manifold.

There is also a hose running from the intake manifold to the diesel pump, that is the (venturi and butterfly valve-created) vacuum to control the diesel pump.

You can replace the diaphragm of the vacuum pump, but you have to take the vacuum pump off to examine if that is the problem. If the diaphragm is broken, the hoses turn black because of the engine oil. The valves of the vacuum pump can also fail or the lever inside the vacuum pump.
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post #3 of 16 (permalink) Old 06-12-2012, 11:32 PM
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Slightly OT: There are repair kits for the vacuum pump I know but when does one determine if the vacuum pump is still "fixable" using a repair kit and when it already needs replacement?

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post #4 of 16 (permalink) Old 06-13-2012, 12:23 AM
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There are two repair kits for the diaphragm vacuum pump: 1. diaphragm and valves; 2. rocker arm.

If there is no vacuum and hoses are black, probably only the the diaphragm has failed.

If the engine makes a horrible noise or if there is some heavy ticking, than you need a new rocker arm. If the rocker arm is still in one piece, you can replace the roller bearings of the rocker arm, that is the only items which wears down. If the rocker arm or the bearings fail, it is not uncommon that it will lead to severe engine damage as parts of it will come between the timing chain and some or all of the sprockets.

You can buy a second-hand vacuum pump and prepare that one, so that you can exchange them if one pump fails. If you have the time, simply take off the vacuum pump and diagnose.
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post #5 of 16 (permalink) Old 06-13-2012, 03:12 AM
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Originally Posted by Govert70227 View Post
There are two repair kits for the diaphragm vacuum pump: 1. diaphragm and valves; 2. rocker arm.

If there is no vacuum and hoses are black, probably only the the diaphragm has failed.

If the engine makes a horrible noise or if there is some heavy ticking, than you need a new rocker arm. If the rocker arm is still in one piece, you can replace the roller bearings of the rocker arm, that is the only items which wears down. If the rocker arm or the bearings fail, it is not uncommon that it will lead to severe engine damage as parts of it will come between the timing chain and some or all of the sprockets.

You can buy a second-hand vacuum pump and prepare that one, so that you can exchange them if one pump fails. If you have the time, simply take off the vacuum pump and diagnose.
You could have not said it any better. Thanks!

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post #6 of 16 (permalink) Old 06-13-2012, 08:43 AM Thread Starter
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Quote:
Originally Posted by Govert70227 View Post
There are two repair kits for the diaphragm vacuum pump: 1. diaphragm and valves; 2. rocker arm.

If there is no vacuum and hoses are black, probably only the the diaphragm has failed.

If the engine makes a horrible noise or if there is some heavy ticking, than you need a new rocker arm. If the rocker arm is still in one piece, you can replace the roller bearings of the rocker arm, that is the only items which wears down. If the rocker arm or the bearings fail, it is not uncommon that it will lead to severe engine damage as parts of it will come between the timing chain and some or all of the sprockets.

You can buy a second-hand vacuum pump and prepare that one, so that you can exchange them if one pump fails. If you have the time, simply take off the vacuum pump and diagnose.
Thank you, I removed the hose to the brake booster and put finger over end and there is no suction - the pipes are black but the vacuum pump itself looks much newer than the rest of the engine which leads me to believe that this has been replaced once already - however this might have been done over 10 years ago or more as the car is 1971. I think I am going to have to rebuild it with a kit - both kits are available from Napa - might do both at the same time - there is a good video on rebuild on you tube which is helpful.
I am assuming that it is not unusual for these pumps to fail?


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post #7 of 16 (permalink) Old 06-13-2012, 08:54 AM
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No, it is not unusual that vacuum pumps fail over time. Diaphragm pumps usually don't last as long as the later style piston pumps. It is difficult to say exactly how long the pumps last, but 200,000 km / 125,000 miles for sure.

The diaphragm should ideally be installed under pre tension and adhere to the torque requirements described in the FSM:

43 Brake Booster

and there 43.610, 43.620, 43.630 and 43.660

The screws holding the cap of the pump are often corroded, so you might need to drill them out, after the head of the screw has broken off. That can be a good reason to overhaul a second-hand vacuum pump first and install that one.
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post #8 of 16 (permalink) Old 06-13-2012, 09:28 AM Thread Starter
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Originally Posted by Govert70227 View Post
No, it is not unusual that vacuum pumps fail over time. Diaphragm pumps usually don't last as long as the later style piston pumps. It is difficult to say exactly how long the pumps last, but 200,000 km / 125,000 miles for sure.

The diaphragm should ideally be installed under pre tension and adhere to the torque requirements described in the FSM:

43 Brake Booster

and there 43.610, 43.620, 43.630 and 43.660

The screws holding the cap of the pump are often corroded, so you might need to drill them out, after the head of the screw has broken off. That can be a good reason to overhaul a second-hand vacuum pump first and install that one.

OK thanks is one is in California and has been stored well - little or no corrosion on the vacuum pump (sure looks like already replaced once) - I am going to replace all parts however have question regarding this:
NAPA AUTO PARTS - says without rocker arm - my vechicle is 1971 220D - not sure if has rocker arm or not?


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post #9 of 16 (permalink) Old 06-13-2012, 12:22 PM
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That set doesn't contain the diaphragm.

Your vacuum pump does have a rocker arm.

Here you can see the inside of a vacuum pump:



another shot:



the wheel in the middle of the two bearings rolls over a wavy flange of the timing device:



Here you can see the rocker arm again, the threaded part is connected to the diaphragm and pushes it up and down, sucking and pushing air.



Here you can see the vacuum pump with the cover removed. You can see the diaphragm. It is leaking, as there is oil on top.



If it is not leaking, it should be dry.

Under the small cover with the two screws are the valves.

You can make something like this to put the diaphragm under pre tension:



MB has a special tool, but that is probably expensive/unobtainable:



You can also use the wavy flange to put the diaphragm under pre tension, simply install the vacuum pump minus the top cover. Turn the engine until the rocker arm is fully extended. Than install the cover.
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post #10 of 16 (permalink) Old 06-13-2012, 01:05 PM Thread Starter
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Quote:
Originally Posted by Govert70227 View Post
That set doesn't contain the diaphragm.

Your vacuum pump does have a rocker arm.

Here you can see the inside of a vacuum pump:



another shot:



the wheel in the middle of the two bearings rolls over a wavy flange of the timing device:



Here you can see the rocker arm again, the threaded part is connected to the diaphragm and pushes it up and down, sucking and pushing air.



Here you can see the vacuum pump with the cover removed. You can see the diaphragm. It is leaking, as there is oil on top.



If it is not leaking, it should be dry.

Under the small cover with the two screws are the valves.

You can make something like this to put the diaphragm under pre tension:



MB has a special tool, but that is probably expensive/unobtainable:



You can also use the wavy flange to put the diaphragm under pre tension, simply install the vacuum pump minus the top cover. Turn the engine until the rocker arm is fully extended. Than install the cover.
Thank you - very useful i bought both the smaller top kit and the main diaphragm - (can return if not needed) if the main diaphragm is split but the rest looks ok will it be ok to just clean and put back together? I doubt I will be able to construct something like that to pre-tension so will have to put on vehicle and do as you say.

Do I need to clean out the vacuum pipes with anything? They appear to have black stuff in them.

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