Can plugged cat lead to overheating? - PeachParts Mercedes-Benz Forum

Rob124 · #1 06-30-2011, 12:52 AM

Following a conversation with a mechanic friend, I'm wondering if the cat on my OM603 might be clogged enough to affect the coolant temp on long, uphill runs. He thought this could happen. I'm seeing up to 95 degrees on occasion on warm, but not necessarily hot, days, and I've kind of run out of ideas. Is this a possibility?

speednjay · #2 06-30-2011, 01:03 AM

im had an experience on a gas car with plugged cat.. will definaltely cause the temp to raise alot..as well as have huge power loss. id imagine the same would apply for a diesel

sixto · #3 06-30-2011, 01:37 AM

Long uphill runs without a cat can cause engine temp to rise to 95*C. Sounds normal to me.

The cat probably isn't clogged if you can maintain a decent speed uphill. In fact I'll guess lack or power is a more obvious symptom of a clogged cat than overheating.

Sixto
87 300D

Rob124 · #4 06-30-2011, 09:31 AM

I might not take notice except that it didn't behave this way in the past. It used to run at 80 most of the time, and now starts out at about 83. And I never saw it hit 95 at all. With a new radiator, thermostat, head gasket, fan clutch, and hoses, I thought things might improve, but they didn't.

scottmcphee · #5 06-30-2011, 09:40 AM

New head gasket I see, how's the head? And did you do anything with it while it was off?

vstech · #6 06-30-2011, 09:52 AM

... often, the #14 head cracks... a gasket won't fix that.

WINGAS · #7 06-30-2011, 11:06 AM

Can the cat then. Or replace it with a diesel specific one from Magnaflow. I think I used the 2.5" one.

The mechanic would have checekd for bubles int the collant, and the machine shop should have zyglo'd ( whatever they use today for Al) the head for cracks.

Rob124 · #8 06-30-2011, 11:17 AM

Head was tested. I replaced the gasket to eliminate coolant seepage into the oil, which it did. Had the valve stem seals replaced--that was all. The only other anomaly found was a warped exhaust manifold, which, after planing, quieted the car considerably. I'm still a little suspicious of an air bubble, so I'll probably look at that again. The water pump was replaced several years ago--might the impeller have corroded away again?

sixto · #9 06-30-2011, 01:15 PM

Quote:

Originally Posted by Rob124

I might not take notice except that it didn't behave this way in the past. It used to run at 80 most of the time, and now starts out at about 83. And I never saw it hit 95 at all. With a new radiator, thermostat, head gasket, fan clutch, and hoses, I thought things might improve, but they didn't.

It used to run at 80*C and you expected an improvement? 603s run a tick hotter than 617s or so the gauge says. If it gets to 95*C and sits there, it's fine. If it gets to 95*C and concern causes you to back of, you should investigate further.

There's something about MB temp gauges. They reflect how hard you drive. Other cars' temp gauges don't move until steam pours from the engine bay then they pop straight to red.

Sixto
87 300D

winmutt · #10 06-30-2011, 01:32 PM

If you can get away with it, remove or hollow out the cat. Its 30hp!!!!!

sixto · #11 06-30-2011, 01:39 PM

30hp over the rated 143hp or 30hp over a clogged cat?

Sixto
87 300D

scottmcphee · #12 06-30-2011, 01:56 PM

Quote:

Originally Posted by Rob124

Head was tested. I replaced the gasket to eliminate coolant seepage into the oil, which it did. Had the valve stem seals replaced--that was all. The only other anomaly found was a warped exhaust manifold, which, after planing, quieted the car considerably. I'm still a little suspicious of an air bubble, so I'll probably look at that again. The water pump was replaced several years ago--might the impeller have corroded away again?

Corroded, ...again? Radiator, Therm, head gasket, hey wait! You know about running MBenz or Zerex G5 coolant only in your w124, right?

No shelf brand stuff...

winmutt · #13 06-30-2011, 02:13 PM

Quote:

Originally Posted by sixto

30hp over the rated 143hp or 30hp over a clogged cat?

Sixto
87 300D

30hp over stock. I recently found factory specs on a euro turbo 603 and it was 170hp. Not sure where it was otherwise I'd send you the link. Pretty sure I dug it up looking for exhaust specs....

gsxr · #14 06-30-2011, 03:13 PM

Quote:

Originally Posted by winmutt

30hp over stock. I recently found factory specs on a euro turbo 603 and it was 170hp. Not sure where it was otherwise I'd send you the link. Pretty sure I dug it up looking for exhaust specs....

No OM603, Euro or otherwise, was factory rated at 170hp. The most was 148hp (SAE). It was the OM606 that was rated at over 170hp.

winmutt · #15 06-30-2011, 03:49 PM

Challenge accepted. Let me figure out where I saw that.

[edit]

Bleh I could be at it for hours and never find it. The number did not sound right to me either.