I broke part and that fixed downshift clunk - PeachParts Mercedes-Benz Forum

angst · #1 03-08-2006, 07:32 PM

Well not completly fixed, but I had a downshift into first clunk that is almost imperceptable compared to before.
The change happened when I broke the part in the picture a day ago while in there running some coolant hoses for my veggie project.
The part has been long overdue for replacement. You can see all the gasket maker and similar sealants Ive had on it limping it along.
Well, what is the part called? Im trying to describe to the dealer and to Phil at FL what Im after.
Perhaps Im better off without it? Well maybee not buy why would the downshift clunk be less?

westkill · #2 03-08-2006, 07:37 PM

That is your overbooost protection valve.

H-townbenzoboy · #3 03-08-2006, 07:40 PM

Quote:

Originally Posted by angst

Perhaps Im better off without it?

No you're not. I'd get it reconnected. This has been a sort of hot topic of discussion lately.

dieseldiehard · #4 03-08-2006, 07:55 PM

Don't lose any sleep if you're without a two way valve there, as long as the boost sense hose is in good condition you are probably ok. For a while, or at least until you can get a replacement valve.
I ran a 300TD for two years without a valve. I plumbed the alda directly to the nipple on the back of the intake manifold. I finally found a cheap valve at a wrecking yard and put it in. Its a safety device true, but in reality how often has the wastegate valve failed on the turbo? I know of one case, the boost sense hose ruptured somehow. Its supposed to be silicone rubber Oh say, that reminds me I have a temporary one in place on my 603 engine, using a section of rubber hose I grabbed to get running. tsk

angst · #5 03-08-2006, 08:23 PM

Quote:

as long as the boost sense hose is in good condition you are probably ok

oops. Maybee Im not ok. Are you talking about the hose on the passenger side that goes from the exhaust side of the turbo to the intake side of the turbo? Thats broken too.

P.S. what is the official name for the broken vacuum thingy?

Diesel Giant · #6 03-09-2006, 05:50 AM

You should not plumb the boost line directly into the ALDA. You can get overfueling. Mercedes put that in the system to keep the engine alive if there was a malfunction. Yes it rare, but why take a chance?

willrev · #7 03-09-2006, 06:02 AM

My MB mechanic at the dealership disconnected and bypassed mine because it was leaking and giving rough shifts. He has been there 25 years and has a huge following with the older cars. He is tops in his reputation and knowhow. I don't think bypassing it will harm a thing. I've been running my car for 30k with it bypassed and no problems.

Brian Carlton · #8 03-09-2006, 09:35 AM

Quote:

Originally Posted by willrev

My MB mechanic at the dealership disconnected and bypassed mine because it was leaking and giving rough shifts. He has been there 25 years and has a huge following with the older cars. He is tops in his reputation and knowhow. I don't think bypassing it will harm a thing. I've been running my car for 30k with it bypassed and no problems.

There is no problem with bypassing that valve and tossing the valve away.

However, if you lose the wastegate hose.........it slips off.......or cracks........there is no wastegate to bleed off boost pressure.

Under such a condition, the turbo will offer some very high boost numbers............maybe up to 23 psi or so.

The overboost protection valve is designed to protect the engine under such a condition and dump the boost. If you don't dump the boost, you have a good possibility of blowing the head gasket or melting a piston.

So, run without it.........but understand the risk.

boneheaddoctor · #9 03-09-2006, 09:41 AM

Quote:

Originally Posted by Brian Carlton

There is no problem with bypassing that valve and tossing the valve away.

However, if you lose the wastegate hose.........it slips off.......or cracks........there is no wastegate to bleed off boost pressure.

Under such a condition, the turbo will offer some very high boost numbers............maybe up to 23 psi or so.

The overboost protection valve is designed to protect the engine under such a condition and dump the boost. If you don't dump the boost, you have a good possibility of blowing the head gasket or melting a piston.

So, run without it.........but understand the risk.

The overboost protection solenoid doesn't really dump boost...what it does is reduce fueling via killing boost signal to the ALDA which in turn will reduce the fuel and in turn the volume of exhaust gas slowing the turbo and thus reducing boost.

A blowoff valve would actually dump boost...something Benz and most diesels are not equiped with.

Since few of us run boost guages you will not know you have a wastegate hose failure until damage has been done. Therefore its wise to keep it working....How many people here still have original 20+ year old wastegate hoses on your car? I'll bet most people. Like radiator hoses they don't last forever.

H-townbenzoboy · #10 03-09-2006, 09:49 AM

Quote:

Originally Posted by willrev

My MB mechanic at the dealership disconnected and bypassed mine because it was leaking and giving rough shifts. He has been there 25 years and has a huge following with the older cars. He is tops in his reputation and knowhow. I don't think bypassing it will harm a thing. I've been running my car for 30k with it bypassed and no problems.

It's not like a new one costs very much. They're only $31, a small price to pay for engine protection. Like BHD said, you never know when your wastegate hose may decide to fail. It's happened before.

Brian Carlton · #11 03-09-2006, 10:05 AM

Quote:

Originally Posted by boneheaddoctor

The overboost protection solenoid doesn't really dump boost...what it does is reduce fueling via killing boost signal to the ALDA which in turn will reduce the fuel and in turn the volume of exhaust gas slowing the turbo and thus reducing boost.

........a matter of semantics. It dumps the boost in the line from the valve to the ALDA and simultaneously blocks the boost signal from the manifold.