2004 Cadillac SRX Rattling noise when starting cold

TANG3NT

MEMBER
2004 CADILLAC SRX
V8
2WD
AUTOMATIC
99,000 MILES

Yesterday I had the SES lite come on with codes P0430 and P0341.

Once the car warms up it runs and sounds fine. But when first starting cold for the first second or two it sounds like it will tear itself apart. Lots of mechanical noise and clanking. This is a new simptom.

One of the codes is for the catalyst. I am looking in to replacing that. But I am worried that its only a "downstream" problem. The other code is for "cam sensor performance". This one worries me more. If this sensor fails could that cause valve/piston interferance and damage?

I've reset the codes and so far they have not come back. But the cold start noise bothers me much.

George

7 Replies

FACTORYJACK

MECHANIC
4,159 POSTS

A faulty cam sensor will not cause valve/piston interference. A loss of mechanical timing, possibly. As far as the noise, have you checked your oil level lately. Low oil in these can cause misfires, noise, and check engine lights. It don't play well with the variable valve timing.

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Monday, February 8th, 2010 AT 9:23 PM

TANG3NT

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Thanks for the reply. I had that in mind since last night. The oil level is ok but I will be replacing the filter and oil in a few just the same. Just to take that out of the equation. If the noise is still there after the oil change would you consider that a cam sensor problem then?

On that note, there is a good amount of oil loss or consumption on this engine. Typically I have to add a full quart every month or so. In fact one of the places the oil leaks is from the top of the head in the front of the engine (I'm assuming this is where the cam phasers are). But there are other places. I'm considering if I should replace seals and gaskets.

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Monday, February 8th, 2010 AT 10:16 PM

FACTORYJACK

MECHANIC
4,159 POSTS

I would not address the cam sensor, if you have no reoccurring light. Thinking of it, that rattle and the fact you have a catalyst efficiency fault, could be an indication that the inside of the catalyst is coming apart. I am not sure, but you may have a 100k mile emissions warranty that may cover replacement of that converter, it may only be 80k. The code will have to come back, or it be diagnosed as the rattle, though. P0430 is for bank 2, which should be the left bank of cylinders. You might be able to produce a some noise by banging on it(converter), with rubber mallet. As far as the cam actuators leaking, they are just sealed with an engine assembly adhesive(gm p/n 12378521).

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Monday, February 8th, 2010 AT 10:37 PM

TANG3NT

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4 POSTS

Thanks again for the reply. I have an update.

I changed the oil and filter last night and now I'm thinking it is a lubrication problem. When I started then engine for the first time after filling with new oil, it clanked for over 5 seconds (instead of 1 or 2) until finallly settling down to a smooth humm. I gather this happened because the new oil took some time to work its way through all the areas.

The clanking is still there on cold starts but smoother and shorter than before the oil change. But it makes me wonder if there is a problem with the oil pump or if there is some sort of permanent damage or clog to some oil jet(s) and it takes a few moments for the oil to accumulate in enough quantity on cold start.

Am I on the right track or way off?

Btw, thinking back I think it all started a week or so after I added a can of RESTORE oil additive. :(

George

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Wednesday, February 10th, 2010 AT 12:07 AM

FACTORYJACK

MECHANIC
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I have yet to see a northstar with any kind of mechanical low end knock, and that goes back to when it came out in 93. I work at a dealer though, and often times the cars are in independant shops after a while. The only oil related problems were either caused by improper repair procedures, or 1 time I had a pump with a stuck regulator that caused max pressure when cranked, holding the valves open, and resulting in no compression. That was somewhere in the 2000 era. What oil are you running in it? This only happens 1 time a day, when the first cold start occurs? Have you taken the drive belt off, and see if it makes any changes, or listened to it from underneath? Have you tried banging on the converters?