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  #1  
Old 01-01-2012, 11:42 AM
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I need help identifying a part on a 1992 300SD

Happy new year folks.
I would appreciate it if someone can identify the silver canister very near the turbo on a 603.971 as installed on a 1992 300SD.

What does it do? And where is the vacuum line connected? (I am assuming it's a vacuum line).

And why do I see quite a few cars with it disconnected!?

This item can be seen in pictures 9 and 10 of post # 13 in this thread:
92 300SD W140 engine head

Thank you.

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  #2  
Old 01-01-2012, 11:52 AM
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EGR valve vacuum motor. Opens EGR at certain EC temperatures and mostly at part throttle to reduce NOX tail pipe pollutants.

Many folk disconnect it if it fails or to stop EGR valve from sticking open. Will cause a slight drop in power when operating .

On some engines it plugs up the intake tract with oily soot and reduces air flow due to restriction.

Late TDi's... VW, SEAT and Audi have this problem a lot. Not so much on the Mercedes.


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  #3  
Old 01-01-2012, 12:01 PM
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Quote:
Originally Posted by dkveuro View Post
EGR valve vacuum motor. Opens EGR at certain EC temperatures and mostly at part throttle to reduce NOX tail pipe pollutants.

Many folk disconnect it if it fails or to stop EGR valve from sticking open. Will cause a slight drop in power when operating .

On some engines it plugs up the intake tract with oily soot and reduces air flow due to restriction.

Late TDi's... VW, SEAT and Audi have this problem a lot. Not so much on the Mercedes.


.
So it is closed when the vacuum line is disconnected!?
When it's closed there is a slight power increase?

Any other advantages/disadvantages to having it disconnected (closed)!?

Thank you.
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  #4  
Old 01-01-2012, 12:04 PM
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Quote:
Originally Posted by kayooh View Post
So it is open when the vacuum line is disconnected!?
When it's open there is a slight power increase?

Any other advantages/disadvantages to having it disconnected (open)!?

Thank you.
The vacuum signal is supplied to the vacuum motor to open the EGR valve at part throttle positions mostly. When vac' supplied to EGR and it opens it causes very slight power loss.

This is due to the exhaust gas entering displacing some fresh air for combustion reducing combustion temperatures.

Disconnecting or disabling a emissions system component is against the law.

Inspection & Maintenance - Tampering and Warranty | Cars and Light Trucks | US EPA



.
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  #5  
Old 01-01-2012, 02:14 PM
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Legality aside, you shouldn't just disconnect it in your car because the ECU will detect the EGR system inoperative and effectively disable the turbo.

To clarify the negative effect of EGR, exhaust gas bakes into a stubborn tar oil and oil vapor that flow along the air intake system from crankcase ventilation and aging turbo seals. Oil through the EGR valve means big problems with the engine.

Sixto
87 300D
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  #6  
Old 01-01-2012, 02:28 PM
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Quote:
Originally Posted by sixto View Post
Legality aside, you shouldn't just disconnect it in your car because the ECU will detect the EGR system inoperative and effectively disable the turbo.

To clarify the negative effect of EGR, exhaust gas bakes into a stubborn tar oil and oil vapor that flow along the air intake system from crankcase ventilation and aging turbo seals. Oil through the EGR valve means big problems with the engine.

Sixto
87 300D
How can the ECU disable the turbo (being purely a mechanical device)!
Moreover, how and where can I reconnect the vacuum line?
I bought this car in July and this is how I got it (without a vacuum line to begin with).

As far as performance is concerned, which should be impacted by an inoperative turbo, the car does not seem too slow to respond even though I am used to driving a 1992 600SEL.
Actually it is much peppier than my 1995 E300D.

Any comments, especially on how and where to reconnect the vacuum line?

Thank you.
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  #7  
Old 01-01-2012, 02:46 PM
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The turbo in a '92 SD has a vacuum actuator that closes the wastegate, which is normally open, to enable boost. This is unlike older turbos which have a pressure actuator which opens the wastegate which is normally closed. There are a couple of vacuum amplifiers behind the air cleaner. One is for the EGR actuator, the other is for the wastegate actuator. I don't have a vacuum diagram for your car but that's how you'd trace where the line connects. IIRC there's a fitting through an engine compartment divider as shown in the picture you referenced. Maybe the line remains connected on the other side of the divider.

It's unusual that the turbo produces boost with the EGR system disabled. Either someone converted to a pressure actuator (as I did in picture 5 of the same reference), or the vacuum actuator has a continuous vacuum signal. I'd check on this ASAP to be sure there is some level of overboost protection.

Sixto
87 300D
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  #8  
Old 01-01-2012, 06:02 PM
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On a parallel thought, what would be the best aftermarket coolant suitable (read safe) for the cooling system of this car (1992 300SD).

The nearest MB dealer is 100 miles away and visiting him is not something I can do whenever I need to.

Thank you.
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  #9  
Old 01-01-2012, 06:26 PM
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Zerex G-05 is is believed to be the same as you find in a MB label jug. How is that a parallel thought?

Check the Buy Parts link at the top of the page. I'm sure Phil or Pelican will be happy to mail coolant to you.

Sixto
87 300D
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  #10  
Old 01-01-2012, 09:29 PM
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Quote:
Originally Posted by sixto View Post
Zerex G-05 is is believed to be the same as you find in a MB label jug. How is that a parallel thought?

Check the Buy Parts link at the top of the page. I'm sure Phil or Pelican will be happy to mail coolant to you.

Sixto
87 300D
How does Zerex G-05 compare to the Pentofrost NF (Pentosin) sold by O'reilly, among others I am sure.

O'reilly's web site claims that this product is made in Germany and is MB specific.

Any thoughts on this subject?

Thanks.
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  #11  
Old 01-01-2012, 11:03 PM
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Here are the spec sheets I found online. I can't make comparative sense of them other than Pentofrost NF references a MB spec. Pentofrost has a slightly lower freezing point, G-05 has a considerably higher boiling point. pH is comparable and I believe that's a key aspect of MB approved coolants:

http://www.crpindustries.com/pentosin/pressreleases/CRP-116_Pentofrost_NF_2.pdf

http://www.valvoline.com/pdf/zerex_g05.pdf

I couldn't find any reference to Pentofrost in this forum.

Sixto
87 300D
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  #12  
Old 01-02-2012, 12:49 AM
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Quote:
Originally Posted by sixto View Post
The turbo in a '92 SD has a vacuum actuator that closes the wastegate, which is normally open, to enable boost. This is unlike older turbos which have a pressure actuator which opens the wastegate which is normally closed. There are a couple of vacuum amplifiers behind the air cleaner. One is for the EGR actuator, the other is for the wastegate actuator. I don't have a vacuum diagram for your car but that's how you'd trace where the line connects. IIRC there's a fitting through an engine compartment divider as shown in the picture you referenced. Maybe the line remains connected on the other side of the divider.

It's unusual that the turbo produces boost with the EGR system disabled. Either someone converted to a pressure actuator (as I did in picture 5 of the same reference), or the vacuum actuator has a continuous vacuum signal. I'd check on this ASAP to be sure there is some level of overboost protection.

Sixto
87 300D
Going back to my original inquiry, would it be possible for you to visually confirm whether or not this modification was performed on this car if I post a picture of this location on the car!?

Thank you.
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  #13  
Old 01-02-2012, 03:00 PM
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I can't tell a vacuum actuator from pressure actuator by looking. The basic check is to apply vacuum to the actuator canister and see if it draws the actuator rod. If it does, it's a vacuum actuator. If it doesn't, apply pressure on the order of 15 psi to the actuator canister. If the actuator rod extends, it's a pressure actuator. If it still doesn't move, it could be either kind with a ruptured diaphragm. Sadly, the business end of your car's vacuum actuator is under the exhaust manifold.

There could be a shortcut. Follow the hose from the wastegate acutator canister. Does it lead to a vacuum or pressure source? A pressure source would tap into somewhere from the turbo compressor outlet (wouldn't be a factory installed fitting) to the intake manifold.

Sixto
87 300D

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