08-03-07, 10:37 PM
My 07 V8 SRX now has 4200 miles. I have a engine start-up noise that I don't know if it is normal. The sound occurs only at start-up - and only if the car has been turned off for several minutes. Cold starts are worse (longer duration of noise) - but it still happens with a warm engine as well. It does not sound like piston slap or rod knock. The sound is totally gone within 3 to 5 seconds of engine start. No performance issues either. It almost sounds like a old Chevy engine with shot hydraulic lifters. It is as if the oil has totally bled out of the hydraulic lifters - but as soon as pressure is up - all is good. (I assume this engine does not have lifters?) Any Northstar techs out there with advice? I did take it to the dealer just to document the issue, but can't take it to the dealer for a few weeks (unless something is truely broken) I love this thing - and hate to have it in the shop if this is "normal" for a northstar engine. Maybe this relates to the VVT operation? I also can't say the noise is new as I almost always have the radio on (louder than it should be :tisk:). Now I am sensitive to the noise so I turn everything off before I crank.
08-03-07, 11:19 PM
The Northstar has what are called lifters by GM but are in fact hydraulic lash adjusters. They can bleed down. I would rather have lifters that have some clearance and can leak down because they are not as likely to stick and result in a burned valve.
08-04-07, 04:22 PM
hey there have been many other threads on this. I suffered this too only after 35K miles.
It sounds like the Cams - this thing has 4 - and there are Phasers that go out see : http://autospeed.drive.com.au/cms/A_1569/article.html
The noise is the sound of a "dry" start. GM assures me that no damage is done - however the sound made me nuts! They diagnosed it quickly but lots of stuff can go wrong during the repair. I was in the shop 8 days..............
This is info copied directly from that site referenced: Because the control valve is internal to the phaser, only one pressure oil feed is required to both advance and retard the camshaft. A locking pin holds the vanes in their "parked" position during engine start-up to ensure quiet starts. The pin is automatically disengaged when oil pressure reaches a level to assure quiet operation. The camshaft position sensors are mounted in the VVT housing, one per camshaft.
There are four camshaft position sensors, one for each camshaft, located in the VVT housings, which determine the movement and position of the cam target wheels located on each of the four phasers. The outputs from the cam position sensors to the ECM are used to determine camshaft positions for comparison to commanded positions. This information enables rationality checks for crankshaft and camshaft position fault diagnostics, and provides backup engine position data for limp-home operation in the case of crankshaft position sensor failure.
08-06-07, 12:48 AM
There is a tsb on this and it should be fixed under warranty. I had mine done at 48,000 miles on an 04 N*awd.
08-08-07, 08:50 PM
Thanks for the info - now off to the dealer. Any good web sites to search for TSB#'s so I have it in hand when I take it in?
08-10-07, 12:34 AM
Edmonds.com or search google for cadillac tsb's
08-10-07, 07:37 AM
Thanks, found a good site. The TSB I am looking for I assume can be used on my 07, as there was only 1 TSB I could find for 07's. The TSB I found was for 04 SRX, #01454 - basically a cam phasor issue... The description is exactly what I am expiriencing...