Mailbag: CTS rocker arm knock

[Bruce Nunnally]

Mailbag question:

 

Email author said: I have a 2003 Cadillac cts luxury sport 3.2L engine and it has a rocker arm knock how can I stop or fix this

[Bruce Nunnally]

The 2003 CTS had the 3.2L V6.  First, thanks for asking the question.  Second, how did you diagnose & determine that the issue is rocker arm knock?

[Bruce Nunnally]

Author writes: 

1. I did a oil change put in a oil helper the knock didn't go away and it sounds like its 2 knocks on the drives side

[BodybyFisher]

I saw the REPORT that the oil was changed and an 'oil helper' was used.  

What kind of OIL was used?

When did this start?, gradually or was it caused by a hard acceleration?, or wind out of the RPMs?

How many miles?

Is the check engine light on?

Does the engine idle and accelerate smoothly?

Have you had your timing belt replaced?

Does it sound like this?

 

[Logan]

Yikes.....the 2003 CTS uses the Opel designed GM V6 engine. That engine was also used in the Cadillac Catera and Saturn VUE.

It does not use rocker arms. It is a direct cam lobe...to lifter...to valve stem set up.

It does use a rubber timing belt and requires J-42069 tool to change the belt. The belt is required to be replaced every 100k.

If the belt breaks or jumps time....the valves will get bent. It is a interference engine.

On any of these engines. A known warning sign of a failing belt or tensioner is...noise. If it starts making noises. Stop driving it...stop running it...stop starting it....leave it where it is...tow it to the shop to verify the timing belt or tensioners are not going into failure mode.

It is very easy to go from a $700 timing belt / tensioner change to a $4000 heads off engine repair....or worse....scrapping of the car.

Do not crank or attempt to start the car until the timing belt and tensioners are inspected.

Picture shows a cylinder head from a Saturn VUE...same engine....all intake valves bent due to a slipped timing belt.

 

 

[Cadillac Jim]

If the car has over 60,000 miles on it, particularly in-town miles or other hard driving (cruising miles on flat highways don't wear an engine much), you can take Logan's warning to heart.  At any mileage, Logan's warning must be taken seriously - examine the cam drive belts before you start the engine again.  Logan has huge hands-on experience with many things, quite apparently including your engine, and he does not speak out without due prudence.

The sound is a bit like a flat lifter (near-zero oil pressure at the valve lifter).  A check of oil pressure on the left head can verify if that's a problem.

I have seen flat lifters on OHC engines, which can give a sound like this, in an engine that had 20W-40 oil in it and was run hard.  After sitting for a few hours, the flat lifters re-inflated and the sound went away.  Using manufacturer-recommended (10W-30 or similar rating) oil avoids this particular problem.