OM603 stuck at 5 psi boost - PeachParts Mercedes-Benz Forum

87tdwagen · #1 04-15-2015, 09:19 AM

Hello all,
I'm scratching my head on this one. I noticed a few days ago that the OM603 was a little sluggish and sure enough, I realized that my boost gauge would not go higher than 5psi. I have a manual boost controller and normally I would see 14psi max. I adjusted the manual boost controller to no avail, still only 5 psi. I checked for leaks in the IC plumbing, but could not find any although I hear a lot of air escaping (hissing) which I assume is from the wastegate. I also disconnected the boost controller and ran the wastegate to the turbo pressure port like stock, and still only 5psi

What gives? I could understand possibly a weak actuator spring, but I am surprised that it would have "just gone" weak, as a sprig I would expect the weakening to be progressive rather than sudden.

I also disconnected the manifold pressure switch and again, no change, so I think I can rule out the overboost solenoid as a cause.

I also tested the wastegate with compressed air, and the assembly starts to open at around 10psi, which seems that the actuator spring is within spec.

Ideas? What to check next?
TIA

87tdwagen · #2 04-15-2015, 12:30 PM

OK a little more testing, this time I hooked up my gauge to the pressure outlet on the turbo and still am only reading 5psi there, so it seems as if the turbo is not putting out more boost than that. I had also tested without the wastegate actuator connected, and still only 5psi.

Any thoughts?

CarpeDiem51392 · #3 04-15-2015, 01:00 PM

Try removing the alda?

Hit Man X · #4 04-15-2015, 02:46 PM

How about that cat under the car? I have fixed more than one 603 where it was plugged up and the car was a slug. Just remove the downpipe and hollow it out, then reinstall.

87tdwagen · #5 04-15-2015, 02:51 PM

Hi CD, thanks, removed the ALDA, no change still 5 psi.

Hitman, good suggestion, I was worried about possible backpressure in the exhaust, my cat is in the middle section of the car, big oval looking thing, is that the one you are talking about? If so I'll see if I can remove it although it seems welded to the pipe and I may have to hack it off.

Hit Man X · #6 04-15-2015, 03:11 PM

I have experienced a few plugged catalysts on turbo gassers too. Gutless wonders even at WOT, had a Turbo Buick blow the downpipe gasket out it was so bad!

Seem to recall the catalyst on my SDL about 12-15" in body length, I have not been under a 603 powered W124 in about a decade so I am not the best person to ask on its location

Also I ran into a plugged electric switch over valve at one point, was it for the ALDA I am not sure. It has been a while but I seem to recall it ran from the intake manifold to the solenoid to the IP somewhere. If for ALDA, then disregard.

87tdwagen · #7 04-18-2015, 09:43 AM

OK a few more updates:
Removed ALDA, no change still 5 psi boost
Removed CAT was pretty clogged up, thought that was it, nope spins faster to 5psi but wont go over.
I had removed the crossover pipe to check for obstructions, found none, noticed a Turbo mounting bolt (right at the wastegate) was all the way backed out and covered in soot. Ah-ha!, tightened and sealed but nope, still 5psi.
Disconnected the actuator pressure line, still 5psi
Closed boost controller completely, but no effect on the boost still 5psi.

What's left to check? I have no visible leaks on the turbo compressor housing, or in the plumbing. I hear hissing when under load so I assume that the wastegate is dumping prematurely regardless of the signal it gets. Is that possible/reasonable? Am I missing something else? Can the turbo leak internally with no external signs? Is this a wastegate spring issue? I would have thought that the boost controller would override the wastegate, but it's not, so can the turbo simply dump boost due to a weak wastegate spring?

What is the range of motion for the wastegate? Mine moves about 3/4 in from one side to another when applying compressed air, is it possibly stuck open? I would imagine the diaphragm can only move <1"

TIA

Hit Man X · #8 04-18-2015, 07:37 PM

Try another boost gauge?

Intake manifold gasket and crossover gasket good?

renaissanceman · #9 04-18-2015, 10:27 PM

How about the air recirculation valve?

mytmousemalibu · #10 04-18-2015, 10:31 PM

Could have a damaged wastegate valve and its bypassing exhaust. If you have a hiss that you didn't hear before, money says finding that will be the problem. All your induction gaskets & O-rings good? Is the turbo inlet restricted? If you still have the air flow meter, make sure the vane is free, or delete the thing and all the EGR garbage. One other idea is seeing if a local shop with a smoke machine can hook up to it and test it for leaks. The shop I used to work at had one and it was the cats meow for finding induction system leaks. Sucks those machines cost so much.

87tdwagen · #11 04-19-2015, 07:29 PM

I'll keep checking but at this point I hate to assume, but it seems as the wastegate, possibly the spring broke. This would explain the "all of a suddeness" of the problems occurrence and the lack of boost. If a ring or two on the spring broke, the wastegate would always be open. the louder turbo whine/whistle could be from the wastegate being "just" open enough.

I ran compressed air through the manifold to check for leaks in the plumbing and found none. I long ago deleted the EGR and associated plumbing, so at this point I'm left with the turbo assembly as my most likely source.

I guess the only way to find out is to disassemble the wastegate. I hear that the Garrett ones are a PIA, any links or tips from those who have done one?

Also with respect to source for parts, where can I get a replacement spring? Would a generic wastegate spring from Summit work in a retrofit? Would a different wastegate actuator work in this application?

TIA

mytmousemalibu · #12 04-19-2015, 09:20 PM

I'm sure that spring has a part specific size and pound rating. Not to say you can't find a usable substitute. You will need to see the old one to measure it. If it is a broken spring, there are many turbocharger companies you could give a call to source a new one. I would recommend getting some Kroil penetrating oil for this job and soak the fasteners and bolt heads in advance. A good hot torch is helpful too to heat up nuts or the threaded area a bolt shank goes into. I don't know anything about the Garrett 603 turbo, my car had a Triple K but either way, it may or may not be a serviceable item.

flainn · #13 04-20-2015, 03:32 PM

Have you inspected the turbo itself? Vanes, shaft play, etc?

87tdwagen · #14 04-22-2015, 02:13 PM

Quote:

Originally Posted by flainn

Have you inspected the turbo itself? Vanes, shaft play, etc?

About a month ago I swapped cylinder heads and checked the turbo then, no play, free spin on the vanes. Will look again when I tear into the actuator. I have not heard any unusual turbo noises, whine or grind since the loss in boost.

Other than physically not working, are there any internal gaskets that could blow in the turbo causing this and not showing any external signs?

winmutt · #15 04-22-2015, 02:20 PM

Quote:

Originally Posted by 87tdwagen

About a month ago I swapped cylinder heads and checked the turbo then, no play, free spin on the vanes. Will look again when I tear into the actuator. I have not heard any unusual turbo noises, whine or grind since the loss in boost.

Other than physically not working, are there any internal gaskets that could blow in the turbo causing this and not showing any external signs?

How are you testing boost? How did you test it and listen to it?