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MG MGF Technical - Knocking noise or Paranoia
|I've got a 97 VVC with 49k, A week before it was due it's 48k service, I noticed a knocking noise coming from the engine bay. This seems to only have started since the weather has been getting colder. I took it in for it's service & they couldn't find anything wrong or even hear the knocking noise.|
Any ideas? or am I just being paranoid?
|I may have similar|
I have recently started to notice a tapping kind of sound.
normally when cold, I always warm car up before driving. Even when warmed, oil temp above 65 degC I noticed it once after running up to 5500 in 1,2 and 3. Then after I backed off, found that I could not accelarate even moderately without sound. So took it easy for a while and no more sound.
Never had an oil level problem, is it the valve seats?
(I think on the older cars they used to say this noise was coming from the tappets)
|I have seen on other threads that the vvc can be noisy and a tapping sound is usually the tappets and the VVC mechanism! tapping as in a light ticking noise!|
If you have a Knocking noise - heavy knock - iWOULD PURSUE THIS FURTHER!
Your tappets are hydraulic and work on oil pressure - as the engine wears, tappets get noisy because oil pressure reduces
Oil takes a while to get to correct operating temp - so this is when tappet noise is heard most - as oil gets warmer it fills up all the galleries in the engine easier and flows through the pump with more efficiency
There has been some discussion on using semi/fully synthetic oils - in my opinion you shouldnt be using fully synth in the F ?? do u know what oil is being used?
Has the engine been serviced regularly - may need oil flushing out (sludge in oil galleries)
May just be wear n tear
tHE ROVER ENGINE IS AN EXCEPTIONALLY QUITE BEAST when new -so NORMAL ENGINE WEAR WILL CREATE noises after 30-40,000 miles and they will be more noticiable than in an engine that was noisy from day one!
|>>>may need oil flushing out (sludge in oil galleries)|
The problem is common with many engine sthat use hydraulic tappets. Essentially there is only a small hole that controls oil flow in and out of the tappet. Infrequenmt oil changes or an engine that is subject to short and urban use will see a significant increase in deposits building up. This always shows first in the valve gear with the characteristic ticking, usually on a cold to warming engine, but sometimes it is more persistent.
It is often a variable sound, fluctuating with engine revs or comiung and going on a warm engine. In some cases the blockage can be removed simply through a more frequent oil and filter change with as many long journeys as possible in between to get the engine hot and keep it hot for at least an hour. Changing oil when hot is also helpful in removing more deposits which will be more fluid.
In some cases you can overcome the problem with the use of a flushing agent in the oil immediately before the oil is changed. Running on a fast idel for 15 minutes or so with this added to the old oil turns it into 'water' and so it flushes much from the inside of the engine. Using a flushing oil offers similar advanatges.
I would normally have some reservations on flushing oils as they may not only dislodge the deposits you want to move, but can also dislodge them elsewhere and not fully clear them out. However in these circumstances I feel the potential advantages are greater than the potential losses.
In the most persistent cases you end up renewing the noisy tappet.
|Here is an alternative source of noise I found in a customers engine, on removing the cam belt cover the VVC cam gear appeared to be wobbling, the bolt was tight and on further investigation we found that the bearing in the end of the VVC unit had failed, to rectify involved removing the cam carrier and dismantling the VVC unit and replacing, needless to say it added a few extra hours to the sevice we were doing! after examining the unit closer we found that the bearing had been assembled from new with some swarfe beteween the bearing and the housing , no wonder the owner thought it sounded like a diesel!!He was very lucky not to have thrown the cam belt off and caused serious damage.|
|Roger you are of course right with your comments on hyd tappets ,however from some of my observations with the VVC followers there has been excessive wear combined with these higher noise levels, although my investigations are not complete there might be a link with excessive clearance between the followers and the cam on the VVC engines.I am looking at a way of correcting this ;} all donations welcome.|
This thread was discussed between 15/11/2001 and 23/11/2001
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