Was reading over the itemized bill from the mechanic at the mercedes dealer who did and awesome job fixing my tranny shift problems. I did not get a chance to speak with him personally, since he had left for the day.

It says - and I need help to know what he may have done - he tested vac controls, replaced 2-3way valve on valve cover, adjust accel. and trans linkages and cables, adjust modulator pressure and valve o injection pump, test boost control circuit, clean lines and by pass restricted switch-over valve C3.0P
Wonder what he bypassed? Any guesses?

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1982 300SD Light Blue
2002 Honda Accord SE
1974 Toro Wheel Horse Tractor
2000 Toyota Tundra Pickup

Not sure exactly what C3.0P is but look around in front of the brake master cylinder area. You should see a solenoid valve with a couple pressure lines attached. If the lines are not attached then this is what he bypassed.

Not exactly sure this is what it is referring to though.

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Jim

Maybe he's talking about the "overboost protection" valve.

If the intake manifold pressure rises too high (e.g., failure of wastegate to open), then this valve disconnects the "pressure signal" going from the intake manifold to the ALDA on the injection pump. The IP then no longer increases fuel delivery as a function of intake pressure, dramatically reducing available horsepower (and preventing a meltdown).

A search of the forum would turn up more and better descriptions than I've given.

Edit: this is the same valve Engatwork described.

He may have meant to say "Bypass Restrictor in switch-over valve"

Vacuum restrictors, (I just bought one yesterday cost $3.00) are basically in-line little plastic tubes that hook-up into a rubber vacuum line. They are smaller in diameter than the original line. This effectively reduces the overall dimension of that line, and consequently decreases the available vacuum. Some of these restrictors also have a little filter inside.

I assume that yours was either partially or totally plugged, and that he did not have another one in stock, or that he removed it because he needed to increase the amount of vacuum in that line for some reason.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

A switchover valve is not the color coded orifice that you all are refering too.
I can't remember which one is technicaly called a switchover valve by MB, someone with a FSM and time look it up. I'm guessing he disabled the EGR.

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

This is what I thought of as soon as I saw "switchover valve"

I would find out what he actually did and get it corrected right away. You don't want to leave it unprotected like that for too long.

Danny

My factory manual calls it the switchover valve, it's *probibly* not a problem, but I'd fix that, it's there for a reason. I'm sure I have some at work Will..

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

Should look somewhat like this.
It's screwed to the firewall behind
the brake booster.


Louis.

Attached Thumbnails

 

Yes, I have confirmed that the mechanic did bypass the overboost protection vavle. Apparently is was a source of a bad vacuum leak. He simply joined the two vacuum hoses together.

Will this cause any damage? I trust this guy since he's at the dealer and is highly reccomended.

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1982 300SD Light Blue
2002 Honda Accord SE
1974 Toro Wheel Horse Tractor
2000 Toyota Tundra Pickup

I just did the same thing myself. I bypassed the overboost protection and it made a huge difference. I can now go up hills. Drove it like that from Middle Georgia to DC.
I also ordered a new switchover valve and a new boost pressure sensor from Phil and got it the next day. I haven't installed them yet since I haven't driven the car since, but I will not drive it again until they are replaced.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

Opinions vary. It's there for a reason, but whether that reason is still valid depends on the particular car.

Remember, something has to go wrong (to cause too high a boost pressure) for it to come into play anyway. Also, if memory serves me (someone please correct me if I'm wrong here), at least one forum member (gsxr) determined that for one of his cars, it was essentially impossible to create an overboost condition even with the turbo wastegate disabled.

IF one really does run the engine with too high a boost pressure without having the overboost protection to tell the IP to cease and desist, I am given to believe that very bad things can happen.

That said, my car currently does not have overboost protection, but it's on my list. This thread is a good reminder for me.

Do any of you have the part numbers for this part?

What is the boost sensor? What does it do?

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1982 300SD Light Blue
2002 Honda Accord SE
1974 Toro Wheel Horse Tractor
2000 Toyota Tundra Pickup

I don't, but I'll bet d.delano does (see his post in this thread).

It's a pressure switch (on the intake manifold) that controls the switchover valve. See my post earlier in this thread for a brief description of what the valve does, or search the forum for more and better information. It's a common problem, and as such has been discussed often.

A spare one of these also allows my remote starter to function..


I'd replace the switch Will..

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

If you just look around on the Fastlane parts site you'll find what you need no problem. Alternatively, Phil knows. I like ordering from Phil because the parts always arrive the next day. The part # on my original unit and the used spare engatwork gave me is different from the one I got from Phil, the obvious difference between the two is the one I got from Phil doesn't have the cap on the top vent nipple. I suppose it doesn't matter, that cap is just there to prevent misc dirt and stuff from getting in there and blocking it because that's where the boost pressure vents out.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)