HELP! '85 300D Turbo blow-off valve diaphragm source - PeachParts Mercedes-Benz Forum

85chedeng300D · #1 05-10-2006, 01:25 AM

does anyone out there knows where can i get a replacement blow-off valve diaphragm for an '85 300D turbo??? on california models, i am referring to the vacuum element/diaphragm that is located on the forward side of the intake body of the turbocharger that is usually connected to a blue/light-blue vacuum hose. it is secured by (3) 10 mm bolts almost looks like a thermostat housing. i think it is important because i'm guessing, what it really does is, if the wastegate lets go of the HOT EXHAUST AIR to prevent turbo from overspeeding, on the other hand, this blow-off valve lets go of the COLD INTAKE AIR and recirculates it to prevent the turbo from lagging. therfore air intake is regulated and prevents too much or too high intake manifold pressure when the engine don't need that much amount air to burn with diesel.
for some reason, mine was puctured and tried everything to vulcanize it but it keeps leeking and my vacuum system, especially transmission shift is affected. i already tried to install a diaphragm out of a dodge neon SRT4, which is a little bigger and shallow but i'm not happy with it. it fixed the vacuum leak but i'm not sure if its really working right and not doing what it supposed to do. it doesn't have that high-pitched humming sound like it used to do before it broke.
can anyoune tell me where can i buy one of this or any domestic car that will match this particular part???

85chedeng300D · #2 05-13-2006, 07:59 PM

Quote:

Originally Posted by 85chedeng300D

does anyone out there knows where can i get a replacement blow-off valve diaphragm for an '85 300D turbo??? on california models, i am referring to the vacuum element/diaphragm that is located on the forward side of the intake body of the turbocharger that is usually connected to a blue/light-blue vacuum hose. it is secured by (3) 10 mm bolts almost looks like a thermostat housing. i think it is important because i'm guessing, what it really does is, if the wastegate lets go of the HOT EXHAUST AIR to prevent turbo from overspeeding, on the other hand, this blow-off valve lets go of the COLD INTAKE AIR and recirculates it to prevent the turbo from lagging. therfore air intake is regulated and prevents too much or too high intake manifold pressure when the engine don't need that much amount air to burn with diesel.
for some reason, mine was puctured and tried everything to vulcanize it but it keeps leeking and my vacuum system, especially transmission shift is affected. i already tried to install a diaphragm out of a dodge neon SRT4, which is a little bigger and shallow but i'm not happy with it. it fixed the vacuum leak but i'm not sure if its really working right and not doing what it supposed to do. it doesn't have that high-pitched humming sound like it used to do before it broke.
can anyoune tell me where can i buy one of this or any domestic car that will match this particular part???

Anyone?!? I'm just hoping that somebody might be able to help me this weekend? I think it is also called AIR RECIRCULATNG VALVE. I just need the black rubber diaphragm inside it. Once again, my car is a 1985 300D Turbo with California version emmision system without a trap oxidizer. Thanks!

#3 05-13-2006, 09:49 PM

No idea where you can get the diaphram. If you do a search for "ARV" in diesel discussion, there are several threads on how to disable it.

Your idea of how it works is a bit off. It's only for emissions, it has 0 performance benefit. More specifically the EGR function. They want more exhaust gas flow into the intake but the intake pressure is too high to flow engough. The ARV lowers intake pressure to a point much lower than the exhaust manifold pressure. This allows greater flow of exhaust gasses into the intake than before (non-ARV). Higher flow results in less NOx. Current EGR diesels use VNT turbos (increase exhaust backpressure) and intake flaps (lower intake pressure) to achieve this. A notable exception to this is the Cummins ISX, they use a VNT turbo and a very restrictive venturi tube after the intercooler.

TheDon · #4 05-13-2006, 09:56 PM

also my friend this diesel didnt come stock with a blow off valve nor do many diesels unless they are high performance and need one like a twin turbo cummins engine featured in Diesel power mag

85chedeng300D · #5 05-14-2006, 01:50 AM

ForcedInduction; The Don,

Thanks for your reply, and for all the infos. I know the Germans overengineered this car too much and I know that this is not much of a necessity to have this Air Recirculating Valve, Federal versions doesn't have it, but, I just wanted to restore this car back to on how it was, just like how the Germans designed and built it. They put that part in this car for a reason. They didn't just put "$#1t" in it. If not for performance, for longevity, maybe, who knows. It has been disabled for a while now since it last broke and the car , I guess, I'm the one driving it every single day, has not been the same like it used to be. So, I just don't want to repair it but I want to fix it right. I dont want to "half-a$$" it. Whats the sense of driving a gorgeous car like this if it has a "band-aid" on it? You know what I mean? I hope you all understand. This is what this forum is, right? "To take good care of our Benzes" Thanks again!

TheDon · #6 05-14-2006, 08:41 AM

if i could give yu my ARV i would but its attached to my triple K...

tjohn · #7 05-14-2006, 09:22 AM

Quote:

Originally Posted by 85chedeng300D

ForcedInduction; The Don,

Thanks for your reply, and for all the infos. I know the Germans overengineered this car too much and I know that this is not much of a necessity to have this Air Recirculating Valve, Federal versions doesn't have it, but, I just wanted to restore this car back to on how it was, just like how the Germans designed and built it. They put that part in this car for a reason. They didn't just put "$#1t" in it. If not for performance, for longevity, maybe, who knows. It has been disabled for a while now since it last broke and the car , I guess, I'm the one driving it every single day, has not been the same like it used to be. So, I just don't want to repair it but I want to fix it right. I dont want to "half-a$$" it. Whats the sense of driving a gorgeous car like this if it has a "band-aid" on it? You know what I mean? I hope you all understand. This is what this forum is, right? "To take good care of our Benzes" Thanks again!

We understand, but I think what ForcedInduction was saying is that "the engineers" did not place the ARV there because it was necessary for the safe, efficient, reliable and durable operation of the OM617. Instead, it was placed there solely to meet state emissions standards. It does so by working as part of a system that takes your engines waste gases, and forcing them to be burned a second time through your engine. This provides a benefit as far as your emissions, at the cost of sooty build up in your intake.

No one will fault you for restoring your vehicle to stock, but many feel that the way "the engineers" truly intended the car to be, is without the egr/arv.

85chedeng300D · #8 05-14-2006, 03:52 PM

Quote:

Originally Posted by TheDon

if i could give yu my ARV i would but its attached to my triple K...

Thanks The Don, I really appreciate it! You dont really have to do it, so don't worry about it, I'll figure it out to get it squared away! '85 CA version is rare but I'll just try my luck in the salvage yard.