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2008 CTS
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213 Posts
Discussion Starter #1
I have a 2008 rwd and a week a go a bearing noise started that sounded like a wheel bearing but the sound would not change if I turned right or left. I decided to let it get worse until I could determine which wheel it was. I also noticed what looked like the transmission cooler lines were leaking fluid. Today the transmission felt like it was slipping when going up a long hill on the highway. A few minutes later the checked engine light started flashing but it stopped after a few minutes. I thought the transmission fluid was probably low so I jacked the car up with a downward slant to the front. With the tranny up to temp and engine running I removed the plug from the pan. Too much fluid started to come out so back in went the plug.

I am confused, I looked up what I could on the net and it appears the plug in the middle of the pan is supposed to be a level check with a stand pipe that goes up a couple of inches so as not to drain the whole transmission. Is this correct? The fluid that came out appeared very clean. Any ideas? Is this transmission known to be trouble prone? The plug is near the rear of the pan, hence I kept the car on a downward slant. I hoped to squeeze some transmission fluid up out of a squeeze bottle into the trans but it appeared to be over full the way I was doing it. Am I servicing the trans correctly?
 

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08 CTS blk/blk
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383 Posts
Depending on the mileage I would drain the pan change the filter and install a measured amount. Prove out any leaking lines and change them as needed

Best of luck
 

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2008 CTS
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213 Posts
Discussion Starter #4 (Edited)
Thanks you for the information. I have determined the transmission has the correct amount of fluid if not a little over filled and the transmission does not appear to be the problem. The front left wheel bearing had one of the mount bolts missing and may be the source of the "bearing noise". This car has had 4 wheel bearings replaced over the years. I can't say gm makes good bearings and it was a gm dealer that neglected to install one of the mount bolts in this latest case.
This is my son's car and he was the one who diagnosed the transmission as "slipping". Turns out the engine is suffering multiple misfires under medium load. The mechanic suggest the replacement of 3 ignition coils and all of the sparkplugs but says it's only an educated guess.

This vehicle has over 135,000 miles and as far as I can tell it still has the original platinum spark plugs. I don't like a mechanic just "guessing" and I don't see how 3 ignition coils can fail so I'm going to replace the spark plugs for now and see what happens.

The leaking lines ended up being power steering lines. Topped up the fluid and I an now shopping for a new set. Should get some of this done on Saturday.
 

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2013 Black Diamond CTS4 Premium Coupe (sold-09 CTS4 DI Black Raven/Ebony)
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4,339 Posts
135K on the original plugs?!? Wow!! Check the gap when you pull them. You may be surprised at how far that gap opens as the ground electrode wears away over time.
 

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08 White Diamond CTS DI RWD FE2 all options
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2,541 Posts
Drunken Elvis said:
Thanks you for the information. I have determined the transmission has the correct amount of fluid if not a little over filled and the transmission does not appear to be the problem. The front left wheel bearing had one of the mount bolts missing and may be the source of the "bearing noise". This car has had 4 wheel bearings replaced over the years. I can't say gm makes good bearings and it was a gm dealer that neglected to install one of the mount bolts in this latest case. This is my son's car and he was the one who diagnosed the transmission as "slipping". Turns out the engine is suffering multiple misfires under medium load. The mechanic suggest the replacement of 3 ignition coils and all of the sparkplugs but says it's only an educated guess. This vehicle has over 135,000 miles and as far as I can tell it still has the original platinum spark plugs. I don't like a mechanic just "guessing" and I don't see how 3 ignition coils can fail so I'm going to replace the spark plugs for now and see what happens. The leaking lines ended up being power steering lines. Topped up the fluid and I an now shopping for a new set. Should get some of this done on Saturday.
I'm sure you need new plugs. I changed 3 coils already. The scanner will tell you which ones.
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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14,181 Posts
I'm sure you need new plugs. I changed 3 coils already. The scanner will tell you which ones.
I agree. Your mechanic was "guessing"?
 

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08 CTS blk/blk
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383 Posts
If you look at my threads on this, changing the three hardest coil packs and all the plugs with OEM plugs you have a good shot at eliminating your skip issue without a huge expense.

Best of luck!
 

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2008 CTS
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213 Posts
Discussion Starter #9 (Edited)
Changed all the plugs which was rather easy and the problem seems to be solved. No coils necessary. Still have a wheel bearing noise and a power steering leak. When the weather gets better, I'll have a go at those problems. Thank you to those who responded and if anything develops I'll keep you posted.

The plugs I removed were a little worn with a wider than spec gap and they also had black carbon on them. I guess this was from the misfire. All coils had both a Bosch number and a GM part number so it appears that bosh made the original coils? I installed ac delco platinum plugs as delco doesn't make an iridium plug for this car. I wanted to keep it as from the factory for easier troubleshooting. Torque for plugs 15 ft lbs and the coils 7.5 ft lbs. I purchased a wheel bearing from Primechoiceautoparts. They are cheaper than the gm part and gm wheel bearings don't impress me. The throttle body and air plenum had a little oil in/on them. This engine seems to ingest a little oil through the pcv line.

Still....an impressive car.
 

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CTS 2008 3.6DI Sport Luxury
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1,027 Posts
The throttle body and air plenum had a little oil in/on them. This engine seems to ingest a little oil through the pcv line.
Not even a little... Many users including me installed catch can which allows to significantly reduce the amount of oil entering intake manifold.
 

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2008 CTS
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213 Posts
Discussion Starter #11
I am aware that this can be a problem with these engines and I think it's a common problem with many other engines as well. My 4 cylinder Malibu consumes a little this way. Why this happens, I don't know, perhaps it's the design of new engines. I notice this 3.6 doesn't have the usual style pcv valve. It consumes about a quart every 3,500 miles; not enough to be a real problem yet. You want to make sure the air filter is clean [not restrictive] or it will apply more vacuum to the pcv line when the throttle opens up.
 
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