Just recently @LittleredMPS and Myself prepared for and completed a timing chain/ VVT replacement on an interstate (QLD) members @auscer MPS6 that had been experiencing the good old rattle on start up and the more concerning erratic idle also complimented by an inconsistant, consistant rattle from the timing case area of the engine. So basically in need of some pretty serious repairs!
Vehical details:
Model- MPS6
Year- 11/05
KLM- 128588
Confirming there was an issue with the timing train was very simple, the noises were loud and clear! After turning the car off a quick check of the timing chain slack through the extremely hot oil cap only further confirmed that the repair was to go ahead!
Before getting to excited it was important to for me to check some minor details. I started by removing the valve cover to visually inspect the timing chain slack where the engine came to a rest. In the following pics you will see I stupidly used a clear rule across the top of the gears to demonstrate the amount of sag in the chain at rest and secondly the free upward slack in the chain.
1 [img]http://www.ozmpsclub.com/forum/attac...ment-image.jpg [/img]
2[img]http://www.ozmpsclub.com/forum/attac...ment-image.jpg[/img]
I then proceeded to remove the HPFP and housing to access the camshaft alignment slots, I then turned the engine crankshaft clockwise stopping short of TDC at which point I installed the crank stop pin into location, I then turned the engine crankshaft clockwise the remaining distance until I felt contact between the pin and crankshaft counter weight. This process removed all timing chain slack to the tensioner/guide. At this stage I checked that the crank angle sensor was aligned to the crankshaft pulley and that the crankshaft was aligned to the crankshaft, these relationships where all OK which means the crankshaft pulley and lower timing chain gear had not moved since initial fitting.
3 [img]http://www.ozmpsclub.com/forum/attac...ment-image.jpg[/img]
Next I attempted to install the camshaft alignment tool, this was only to check how much the camshaft timing had changed with the stretch in the timing chain. The following pic clearly shows the inlet cam is retarded slightly enough to prevent the alignment tool from slotting in, the exhaust cam was aligned enough for the alignment tool to slot in.
4 [img]http://www.ozmpsclub.com/forum/attac...ment-image.jpg[/img]
I only checked this as I was curious but its just 1 step in many to help find the actual cause of the noise. I then removed the camshaft alignment tool, if you remember I turned the engine clockwise and this removed the slack from the timing chain to the side where timing chain slack is automatically controlled by the guide and tensioner, I pushed my finger down on the timing chain between the 2 camshaft gears and observed any movement in the timing train, I found that the timing chain tensioner in this instance was allowing alot of movement and not clicking out to the next increment. It was time to open up the front of the engine and have a good look at the timing train components and identify the actual cause. The engine remained in a timed position while I removed all associated external parts and the timing cover, once removed there is plenty of viewing room, the following pic shows the route of the timing chain and just how long the timing chain is.
5 [img]http://www.ozmpsclub.com/forum/attac...ment-image.jpg[/img]
6 [img]http://www.ozmpsclub.com/forum/attac...ment-image.jpg[/img]
I marked the current position of the tensioner, fitted camshaft alignment tool and removed all timing train components including the camshaft gear, VVT and oil pump drive chain and components for further inspection and cleaning. I focused my attention to the timing chain tensioner and its condition, in particular the ratcheting device. The teeth didnt seem to be badly worn or damaged, had plenty of available adjustment and the ratchet was ok. Given those mentions I can only guess that the timing chain was stretched to an awkward length not allowing that extra click required to remove the slack from the timing chain resulting in obvious noises and in this case erratic idle/rpm signal from the inconsistant relationship between the crankshaft and camshaft.
The reality is that at any point this could have turned extremely expensive repair had the chain decided to exit the show!
This repair included the replacement of the following parts;
All friction washers, VVT unit, tensioner, guides, timing chain and front seal.
During the repair and fittment of new parts the engine timing was checked 3 times to ensure nothing had been disturbed during the tenioning procedures and once before engine was to be started.
This thread isnt intended as a "how to" and there is alot of detail left out of whats actually involved to complete this task.
At this point Littleredmps and I would like to thank @auscer to travel so far and give us the opportunity to carry out this work on his much loved MPS6!!!