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  #1  
Old 10-14-2004, 02:39 PM
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Trap Catalyst breaking up, '85 300D

Last year, the turbo developed a hole in the top of it. I made a bracket with a piece of gasket material for a wood stove, for a temporary fix.

This worked ok for awhile. Recently, the car became very underpowered and sluggish. I found the hose going to the wastegate valve was torn. replacing it made no difference. With the hose pinched shut, I was getting only 4Lbs of boost.

I replaced the old turbo with a good used one the other day. The car runs great, probably better than it ever has Boost is around 10Lb max.

Now the fun part. I just noticed a chunk of ceramic like material (2X3") jammed in the rectangualr exhaust input of the old turbo. Evidently this came from the trap catylist (I verified awhile back that the car had the retrofit to the catylist). I have not heard of this happening. I suppose the torn hose may have caused the wastegate to always be closed, diverting all exhaust thru the turbo, putting more stress on the catylist, causing the piece to break off.

Of course now the question and delimma is....is another piece going to break off? I did take a look at the inside of the 'cat' with the turbo off and saw nothing loose in there. Has anybody else observed this problem?

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Old 10-14-2004, 03:00 PM
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I am not sure on the pre 86 cars but the traps on the 86 and 87 cars were recalled and replaced for free by the dealer. Their replaced with something smaller thats not a trap I'm not sure what it is. If I read your post correctly you should have taken the car to the dealer they would give you a nice new turbo and replace the trap with some exhaust parts to. The best part is it is all free!
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  #3  
Old 10-15-2004, 07:15 PM
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Yes, This car already has the catylist retrofit. A chunk of the interior ceramic broke loose. I need to decide whether to drive as is, or to park it until finding the earlier (non Calif) part to bolt the turbo to. I've driven it about 25 miles since installing the newer turbo.
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Old 10-15-2004, 07:59 PM
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Trap catalyst cannot clog the turbo since it's downstream under the car. Trap oxidizer is replaced with a plain insulated pipe on the 603, and I assume on the 617 was well. Trap oxidizer is sliver plated ceramic honeycomb, and I would guess that is what you found in the turbo. Probably been there a while, and equally probably the cause of the turbo bearing failure due to imbalance.

Check for exhaust restriction -- the trap catalyst is prone to plugging with age and/or oil burning, and will greaty reduce power when it does, along with boost.

Peter
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Old 10-15-2004, 11:01 PM
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Peter -

On the 617 engine the catalyst replaced the trapox in the same location, so it is upstream of the turbo. Definately different than the 603. I presume there was no space to locate it under the car. I've not heard of one of these breaking up, but it happens on modern gasoline cars all the time, so why not on a diesel.

- JimY
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Old 10-16-2004, 11:51 AM
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Actually, the turbo bearings appear tight, and the rotors look ok. If the hole on the top (.020" X 0.200") could be welded over I think it would work.

The Catylist is upstream from the turbo. I think what happened is:

Wastegate hose fails, killing boost, and not allowing the wastegate to open.

All exhaust now has to exit thru the turbo. AT higher speeds at least, the engines are designed to operate with the wastegate at least partially open.
Perhaps this caused excessive heat in the catylist..breaking off the piece.

The broken piece jams in the rectangular tubo input, reducing flow thru the turbo and bypass port....maybe 50%.

The moral is, inspect the wastegate hose regularly. If you notice boost is lost, park the car and fix the problem.
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Old 10-16-2004, 11:59 AM
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Wastegate is normally closed until boost pressure on the servo opens it, so a broken line gives you too much boost -- if the overboost protection switchover valve is working, it will dump the boost signal to the ALDA and you will only notice it if you get surging as the overboost opens and closes. You won't ever get low boost unless something is wrong with the turbo.

Catalyst supports are very tough, they usually only break up from serious impact damage or severe overheating/rapid cooling -- this could happen, I suppose, if the overboost protection cycled a lot a full throttle, but is more likely to be from other causes the produce lots of soot or unburned fuel in the exhaust.

Your turbo should be OK if there are no marks on the turbine from flying ceramic chunks. The restriction in the exhaust would cause low boost and power loss by itself, the turbo wasn't getting decent flow and couldn't produce any boost that way.

You need to replace or remove the catalyst, though -- if one chunk came out, more will follow until the whole support is gone.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #8  
Old 10-16-2004, 02:12 PM
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If the wastevalve hose is broken, there is no boost because the intake manifold is then open to the atmosphere, the way I see it.
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Old 10-16-2004, 02:19 PM
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Nope, the hole the hose makes it much smaller than the intake manifold. You will loose a bit of pressure, but the turbo will just speed up and deliver more air...

I would guess the chunk of support material in the tubine inlet had a lot more to do with low boost than the broken servo hose.

You need to inspect the turbine blades for damage, as I'm sure at least a few bits of support blew through the turbine when it failed. Damage to the tubgime blades, even seemingly minor, will slow the turbo down and drop boost.

I would also contact Mercedes concerning trap catalyst failures -- you may have an emissions warrenty claim, althought it's unlikely.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #10  
Old 10-19-2004, 02:24 PM
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Hmm, perhaps it works much like the vacuum system orifices. Could be. The impellers look ok on the old turbo, but I'll look more closely. The catylist 'chunk' was wedged in there...needed a screwdriver to get it out. I exaggerated the size. It is more like 1" X 2" X 3/8"

Meanwhile, the new turbo is on there and working, and my son has made off with the car. So I hope for the best. I'll keep my eye open for the 49 state non-catylist part. If anyone knows of one, please let me know.

Thanks,

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