KV6 bad engine noise & vibration - looks like I may need to take my car to a garage

[Bolin]

I think I may have found the problem, or at least part of it.

If you have a look HERE my tensioner pulley looks like the one on the right. The allen key bolt definitely tightened up as I rotated the bolt clockwise to release the tension from the tensioner body.

I'll replace both tensioner body and tensioner pulley for peace of mind and set the pulley using INA's guidence, which is linked to on a couple of other thrads on the forum.

Originally Posted by SD1too

I thought so. Have you considered opening your own garage?

Well now, if it is not the tensioner or the big ends, do you have any suggestions which I have not already dismissed I have been trying to work with a process of elimination

[Bolin]

Ok. Not good.

I have replaced both the hydraulic tensioner and the tensioner pulley, correctly adjusted the tensioner pulley (checked many times) and reset the camshaft timing with the special tools (again checked it many times). The old tensioner pulley had not been adjusted and there were some tiny marks on the cambelt which I believe are a result of this.

The noise is now WORSE! It is lounder, more like a 'tapping' and can definitely be heard when revving up to 3.5k (didn't rev higher than that).

One point is that the engine did sit for 2 and a half weeks with hardly any oil in it.

Any ideas?

Looks like something really major is wrong

[SD1too]

Originally Posted by Bolin

... more like a 'tapping' ...

Does its frequency increase in proportion to engine speed?

One point is that the engine did sit for 2 and a half weeks with hardly any oil in it.

So you had to add engine oil before starting the engine? Check the dipstick reading with a warm engine according to MGR's special instructions for the KV6 of which I'm sure you're familiar. If it's underfilled, your hydraulic tappets may well be noisy.

Simon

[Bolin]

Originally Posted by SD1too

Does its frequency increase in proportion to engine speed?

Yes, very clearly, whereas before it wasn't clear that it did and indeed seem to be drowned out whn revving, whereas now it isn't.

I put the old oil back in, as it was new on 31 May and had done hardly any mileage. I put it through a strainer and past a magnet to ensure it was clean.

There was a little bit left that I didn't put back, as it had quite a few bits in it (appear to be organic matter from surrounding bushes, trees etc, yes the driveway needs a good sweep, perhaps it was windy as the oil was draining out). But I looked at the dipstick before starting the engine and it was at least half full.

I'll run the car to full temperature and read it again and top if needed - see another thread of mine, it appears that the oil level reading is different if taken from warming the car up on the drive than if stopped after a run.

[SD1too]

Originally Posted by Bolin

But I looked at the dipstick before starting the engine and it was at least half full.

If I read my dipstick before starting the engine the level appears to be way over the max line. If I then follow MGR's advice and read it at normal operating temperature (and after removing the dipstick for 5 minutes), the level is lower, within the min-max range and consistent with the amount I put in at the last oil change.

So, if your dipstick showed half full with a cold engine, the actual level is probably below the minimum and the noise you are hearing is the hydraulic tappets complaining.

Simon

[Bolin]

Could be. Usually when I read the dipstick cold I get an unreadable mess that extends way above the max, whereas this was a neat line for once. But given the hot oil readings before draining (at max), the amount lost/not put back in I doubt that the level is low.

But perhaps the oil has drained out of the tapets due to not being started for 2 and a half weeks and the car needs a bit of a run to get everything back to nromal (I had only run it on the drive for a few minutes).

So maybe it's a new noise altogether - which leaves the vibration.

I'll go for a drive tomorrow to get it fully warmed up and see what happens. Hopefully the car won't explode.

[Bolin]

Update - I started the car today and the worse noise was not present from the moment it fired up :-D So as Zeb of the Enthausiasts suggested it was probably just oil not getting up into the tappets.

I didn't go for a drive, but let the engine idle to full working temperature. Oil level is fine.

The engine does appear to be quieter, I can't really make out the specific bad noise that I had heard before, but instead I can hear a few competeing bad noises. I think perhaps the bad noise I originally complained about has gone (and was probably due to an incorrectly adjusted cambelt tensioner pulley, which did also leave tiny tiny marks on the belt) but maybe it had been masking some other noises, now that I am being critical of the sounds I can hear those as well. That's my theory.

I think that there are at least three untoward sounds - two are the aux idler and inlet manifold, so I'll replace those as they should be replaced anyway.

That leaves another noise, plus the vibration.

The fact that the vibration gets worse as the revs drop back at idle and stop falling makes me think it could be a damper pulley, as perhaps the outer part of a damper pulley is coming away at the rubber and so the relatively sudden change of speed of rev movement (sorry can't think of a better way to put it!) means that it almost starts to 'get away' from the rest of the pulley - does that make sense?

There are 3 damper pullies - on the secondary belt end of the exhaust camshafts, plus the crankshaft damper pulley.

Some of the noise I can hear at the moment does sound like it's coming from the general area of the crankshaft pulley, so I wonder if it's that? However, I can't find a single confirmed case of one of these failing on any KV6. It does have some cracking to it, but that has been reported by SD1too, so may be normal. The exhaust camshaft pullies have been known to fail but the rubber on ine looked as good as new.

Perhaps I should replace the crankshaft pulley with a known good one and see what happens?

[SD1too]

Originally Posted by Bolin

So as Zeb of the Enthausiasts suggested it was probably just oil not getting up into the tappets.

Simon of the 75 and ZT Owners' Club also suggested this:

Originally Posted by SD1too

... the noise you are hearing is the hydraulic tappets complaining.

We're doing our very best for you here Colin.

Simon

[Bolin]

Well yes, but in my defence your suggestion was linked to the oil level which I knew to be about right, rather than the need for it to be pumped up due to the car having sat for a while with the oil drained - hence I wasn't sure that you were right, even though it was that type of noise. Zeb's experience matched with what I had thankfully, with the problem not being the oil level itself but rather the fact the oil just needed to work it's way up there. But the root cause of that (very very worrying!) noise was the same, so essentially you were both right

P.S. many thanks for your help and suggestions, it is greatly appreciated

[SD1too]

Originally Posted by Bolin

... with the problem not being the oil level itself but rather the fact the oil just needed to work it's way up there.

I think you may be getting a bit bogged down with minutiae Colin. I do know from practical experience (quite recently actually) that low oil level can cause noisy hydraulic tappets, which is why I suggested it to you. I also know from personal experience that it is easy to misread the dipstick on the KV6. Anyway I'm pleased that you've sorted out that issue, and good luck with the other things upon which you're still pondering.

Simon