Quote:
Originally Posted by caprirob
Mine seemed to get noisier after changing the oil and filter !
Before I changed it I just had the brrrrrrr-click over and over again, afterwards there were times when it was constantly rattling and sounded like a 1970's diesel !
Expensive to replace yes but worth doing - I couldnt put up with it like that for long.
Indy I went to recommended 0w30 fully synthetic for future changes - they have an S40 with over 200k on the clock as a courtesy car which is still on its original VVT thanks to regular oil changes with quality oil
|
VVT systems suffer from a number of lubrication related problems and if they get worse after you change the oil I would guess it could be blocked or restricted oil flow to the system. The increase in viscosity that occurs after the oil is changed can make the problem worse if the unit is already suffering from sludge or varnish deposits.
One trick that might work is to run an idle only flush just before you change the oil. That will help clean out the gunk in the narrow oil feeds to the unit. When you select the oil to use it must have a good amount of detergent AND not be a 10 or 15W, the Volvo recommended Castrol Edge 0/30 (It's almost into the 40 range) is perfect, although Mobil 0/40 (Nearly a top 30) would be my choice as it has more in the way of detergents and dispersant.
There are several different problems that can cause VVT related rattles, BUT for a cold start only rattle the important thing is to get the oil feed lines clean and use an 0W oil because it flows faster when cold.
Obviously the previous advice to help figure out if the problem is the actual unit or electrical is valid. This article gives a good description on how a VVT works:
http://youdiyauto.blogspot.de/2012/0...rtup-tick.html
I don't like them much because they are like turbocharges, rather too sensitive to poor lubrication issues. If you buy a car with a VVT and a dubious service history, the first thing to do is get the block clean by using a high detergent major brand oil and short oil change intervals. If things are really suspect, then try the Liqui Moly idle flush before each oil change. Once the block is clean, then pick a good oil, OEM filter and OCI. For a VVT in good condition an 0 or 5W (Down to minus 25C only) quality synthetic with lots of detergent is one real good idea to keep the vanes in the unit clear. Castrol Edge, Mobil 1, Shell Helix Ultra or Liqui Moly Synthoils will all clean well, most oil gurus use Mobil 0/40 or Shell Ultra 0/40 to help clean the block, although a good high mileage oil like Valvoline Maxlife will also do the job well in summer (It's a 10/40).
In general terms cold start rattles can be caused by poor oil flow or too thick an oil, for example using 15/40 in winter. Hot rattles are much more likely to be caused by thin oil, like using a cheap 5/30 in summer for too long an OCI.
The LM additive I suggested trying in a previous post makes no difference to the viscosity, it just contains a dose of Moly and other EP & AW additives to help protect the engine combined with a dollop of detergents and dispersants to try and clean out the gunk, BUT using an idle flush is more effective. If an engine has a high oil consumption or leaks, then using a flush can increase the leak rate due to the false oil seal effect, if that happens just switch to using a high mileage oil with seal conditioners. I would never use a drive around flush like MMO or the Liqui Moly oil scourer with a turbo charged engine due to the potential risk of damaging the turbo bearings if something goes wrong, like the oil filter of pump feed line blocks. The idle only flush additives made by Castrol, Amsoil or Liqui Moly are all similar and seem to produce good results in a safe manner.