OM603 - engine. What is this part on the exhaust manifold? - PeachParts Mercedes-Benz Forum

ah-kay · #1 08-18-2014, 05:16 PM

What is this part with a vacuum line hooked up to it? When I rev the engine to about 2500rpm then release the throttle, it would make a relatively loud strange noise. If I remove the vacuum line then there is no noise. It seems to be open/closing a valve inside. What is wrong? Do I need a new one?

ichris93 · #2 08-18-2014, 05:19 PM

EGR valve.

Mxfrank · #3 08-18-2014, 07:56 PM

The EGR is usually closed at higher revs, so it's not abnormal.

If you put a gauge on the vacuum line, you'll find the vacuum signal is load sensitive. It's controlled by the EDS system. At higher speeds/loads, the valve is closed (zero vacuum). Otherwise the vacuum signal is proportional to load. It's also closed at idle. I've been giving some thought to installing the left gauge cluster from a 190E, and patching the economy gauge into the EGR feed.

scottmcphee · #4 08-18-2014, 08:41 PM

That there part is the manifold gunker valve. It opens to allow exhaust fumes to be breathed back in again. Like eating the same food twice...

ichris93 · #5 08-18-2014, 08:57 PM

Quote:

Originally Posted by Mxfrank

The EGR is usually closed at higher revs, so it's not abnormal.

If you put a gauge on the vacuum line, you'll find the vacuum signal is load sensitive. It's controlled by the EDS system. At higher speeds/loads, the valve is closed (zero vacuum). Otherwise the vacuum signal is proportional to load. It's also closed at idle. I've been giving some thought to installing the left gauge cluster from a 190E, and patching the economy gauge into the EGR feed.

You do not have your EGR blocked?

jay_bob · #6 08-18-2014, 10:10 PM

May I introduce you to our friend Roll Guy. He has something that will cure that.

http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html

Edit: forgot you are in Kalifornia. Never mind. You are going to have to fix that EGR valve, or move to a state that does not inspect like SC.

Shortsguy1 · #7 08-18-2014, 10:48 PM

Jay-bob: No inspection of older diesels in CA during ownership or during transfer of ownership. Also, Ah-kay and Rollguy know each other.

Shortsguy1 · #8 08-18-2014, 10:58 PM

For what its worth, EGR (exhaust gas recirculation) is a helpful way to reduce NOx emissions from many IC engines. By recirculating exhaust, some of the excess air in the engine is CO2 and H2O (both relatively inert), so less N2 is present. Having less N2 means that less NOx can form during combustion. Unfortunately, as most of us know, it can gunk up the intake with a diesel engine. Some have pointed out the gunk does not actually affect performance all that much, so I am not sure what MB engineers envisioned. Perhaps they thought it would stay perfectly clean because new engines have lower PM and lower oily blowby. Or perhaps they knew it would gunk up but figured it didn't matter much overall.

For the OP, it sounds like your EGR valve is functioning. If you don't want that to occur, the cheapest solution is to put a golf tee (or bb) in the vacuum line (and nothing else). A more elegant solution is a block off plate like Rollguy has made up.

ROLLGUY · #9 08-19-2014, 12:18 AM

Quote:

Originally Posted by scottmcphee

That there part is the manifold gunker valve. It opens to allow exhaust fumes to be breathed back in again. Like eating the same food twice...

I like your description, that is exactly what it does. Yes the golf tee (Bob is a golfer, so I am sure he has a few lying around) or the BB is the cheap way to go, or just remove all the vac lines completely. If you want the more elegant solution, I have EGR block-off plate kits available (as others have said).....Rich

ah-kay · #10 08-19-2014, 01:34 AM

I am curious as to why there is a sound from the EGR valve when I release the throttle. The EGR valve is shot? I have 3 other cars with the same OM603 engine in the yard and none of them make the sound.

mannys9130 · #11 08-19-2014, 02:54 AM

Did a PO install a blow off valve? Lol

Mxfrank · #12 08-19-2014, 07:53 AM

Quote:

Originally Posted by ichris93

You do not have your EGR blocked?

Absolutely not. EGR has almost no impact on performance or fuel economy. The manifold may not have to be cleaned out every 150K miles, but that's not a big deal either. If you manifold is dirty, it's that much less that you're forcing people to breathe. EGR does reduce nitrogen oxides significantly, so keeping it in place is the responsible thing to do.

HOWEVER, removing it is illegal, an carries a $3500 civil penalty. While there may be no inspections at the moment, the more idiots there are removing pollution equipment, the sooner it that will end. If you for some reason think it's inconvenient to have EGR, think about how much less convenient it would be to be scrounging around for expensive parts to get past inspection. So keep your EGR, it's really no problem.

tjts1 · #13 08-19-2014, 10:32 AM

Quote:

Originally Posted by ah-kay

I am curious as to why there is a sound from the EGR valve when I release the throttle. The EGR valve is shot? I have 3 other cars with the same OM603 engine in the yard and none of them make the sound.

Either theres a vacuum leak in the valve or a clogged valve. Without a hand vacuum pump or removing it its hard to tell.

Quote:

Originally Posted by Shortsguy1

Some have pointed out the gunk does not actually affect performance all that much, so I am not sure what MB engineers envisioned. Perhaps they thought it would stay perfectly clean because new engines have lower PM and lower oily blowby. Or perhaps they knew it would gunk up but figured it didn't matter much overall.

Removing the black tar like substance from the manifold and intake ports makes a very noticeable performance difference. The Mercedes engineers correctly calculated that EGR buildup wouldn't be a problem until after the car was out of warranty when it would no longer be their problem. In most markets these engines were sold without it. EGR was a bandaid to meet US emissions.

No performance difference? HA

Also keep in mind that the more you restrict the intake with the EGR/crankcase vent tar, the more smoke your engine will produce under acceleration. Its a self defeating system that eventually increases HC emissions. Whether or not you believe in keeping the EGR functional (I'm not going to argue either way), its worthwhile to clean the manifold and intake ports for lower emissions and improved economy.

Parting shot: Whatever happens to a Mercedes diesel engine, its 10 times worse on a VW TDI.

Mxfrank · #14 08-19-2014, 02:25 PM

If you let it go, it can get bad, I suppose. But cleaning out a manifold every 150K miles isn't so awful. Shouldn't affect performance much, either way. I won't even address the technical arguments, it should be sufficient to know that removing it is illegal, and can get you a hefty fine.

To test, apply a vacuum directly to the valve with a Mityvac. It should hold without having to continuously pump. When you release, you should hear the valve click closed. There's not a whole lot inside, if the diaphragm holds vacuum, just take the valve off and clean out deposits.

A better test is to add a y fitting at the valve, and run a vacuum gauge into the car. Watch it as you drive. Vacuum should be zero at idle. Just off idle, it will peak at around 15 inhg. Then it will move smoothly in proportion to speed and load. The vacuum will return to zero in high speed/high load conditions. If it doesn't, then replace all the rubber elbows involved in EGR (it's actually a good idea to replace all the rubber elbows throughout the engine compartment every so often).

If the valve always shuts at a particular load condition, a likely cause is a problem with the air mass sensor, which is located in the air cleaner. It's a flap that opens against spring pressure: the wider it opens, the more air is going in. The sensor part is a coil of resistance wire, which may have a dirty or broken coil.

tjts1 · #15 08-19-2014, 02:38 PM

Quote:

Originally Posted by Mxfrank

If you let it go, it can get bad, I suppose. But cleaning out a manifold every 150K miles isn't so awful. Shouldn't affect performance much, either way

I've cleaned out the intake on 3 diesels (OM603T, OM606na OM602T) so far and the performance improvement was dramatic as well is the reduction in smoke at high load. A dirty intake will increase your hydrocarbon pollution (smoke) under load. These engines were designed without EGR then it was tacked on as an afterthought to get it to meet an arbitrary NOx limit set by CARB and the EPA.