Engine knock

[Bikergonebald]

Hi, I'm after some second opinions on engine noise.
I bought a 2004 1.4 petrol with only 30,000 miles last September but it had been unused for 7 years before i got it. It had a noise that i thought was tappets and it was worse when cold. I did a full service with good quality VW spec oil and i did a timing belt change at the end of last year. It hasn't done many miles since, probably 1000 to 1500 but i'm sure the noise has got worse, it's more than just a ticking sound but based on the frequency it's probably only one or two cylinders and it doesn't seem to get better as it heats up although it's rare for us to drive it more than 20 minutes on any journey at the moment. Also it seems to get louder with load.

What i've previously been told about engine noises.

* Tappets, ticking sound that might get better as it heats up. The frequency of the sound depends on how many tappets are bad.
* Little ends are heard at higher revs as you come off the throttle and the engine has no load.
* Big ends and main bearings are a heavy knock heard under load at lower revs, they would have to be bad to be heard at tick-over. If it's minor wear it might be heard as a low rumble.

Does anyone agree / disagree with the three statements above?
Any suggestions on what the noise might be or how i might be able to better diagnose it?

On this engine i think i have to remove the cam belt to get the cam cover off because the cams are held in the cover not the head?

Thanks.
Kevin

[littlepolo]

From my own experience in a decade of ownership of a 1.4 16v tappets are noisy at start up and particularly in lower temps. Once the engine is warmed up they should be fairly quiet, especially at that mileage. However, unless it has had proper oil and filter changes excessive wear can occur. Do you know what oil was in it? What condition was it when you drained? It might be worth considering a lightweight flush using Comma and replacing the oil, drive a few hundred miles the replacing oil and filter again. If it has some minor gumming up due to lack of use a few oil changes (a decent oil with a good detergent) might do the trick. Make sure you are using a decent filter.

What oil is in it now? Is it using any oil? Have you noticed any changes in mpg? Given that you've said it has got worse after changing the oil, another possibility is the that old oil was damping it to some extent. Tappet noise would be half engine speed, and it tends both to quieten as the engine warms up and then gets harder to hear at speed. Also, it would quieten when you lift off (remove load). With that mileage I'd be surprised if it's the bearings, unless a poor maintenance history can explain it. The other thing that plagues the Polo is piston slap, caused by wear of the teflon coatings - again likely to be accelerated by poor maintenance.

Edit:

Yes, you need to remove the belt.

I've heard people say that fuel injectors can be noisy. Easy to diagnose with a screwdriver and your ear.

[Bikergonebald]

Thanks for replying.
When I bought it the back street dealer had “serviced” it. It had new plugs air filter and oil, he hadn’t changed the oil filter.
I put an additive in the oil and drove it for about 500 miles then used an oil flush and replaced the oil and filter. I don’t remember what brand it was, possibly comma and it was the correct VW spec. I also put another additive for tappets in. It wasn’t any worse to start with, it might have been slightly better but it probably only did 1000 miles before lock down and it was sorned for 4 months.

Since using it again I’m sure it’s worse than it was last year.

The service book has one stamp at about 5000 miles and nothing since. The next 24000 miles were done over 6 years, it’s possible it wasn’t serviced at all but I think it must have been reasonably well looked after by the elderly couple.

I don’t know what mpg it’s does, I’ve never checked. It’s doesn’t use any oil, there’s no smoke from the exhaust and the breathers are all clear so I think the pistons and bores must be ok.

It’s interesting that you say the tappet noise would quieten with less load. I wasn’t expecting load to have an effect on tappet noise, if it does then I’m more confident that’s what it is.

I’ve ordered a cheap stethoscope, I’ll see whether it works any better than a screwdriver.

[littlepolo]

Be careful what additives you put in. Do not put anything that significantly changes your oil viscosity for any length of time. The Polo only holds about 3.3l oil. If you put in 300ml of anything that's 10% - sure to change the viscosity. Then you'll have oil dilution by petrol, especially on cold starts (was there any odour from the old oil?). I purchased my Polo at 27k on the clock. It had not been particularly well maintained (or well built - I suspect a Friday afternoon job). I followed up with regular oil and filter changes with Castrol Edge (and by regular I mean every 6 months due to 75% short journeys). Despite that, eventually I had to replace the camshaft, hydraulic lifters, etc at 90k miles. I replaced the head and everything up because I had a 25k miles one at hand. It's still noisier than I would like.

To clean up dirty internals some recommend just to use oil and change 2-3 times each after a couple of hundred miles. I would only use a light cleaner like Comma and leave it in for a short period. I've found Shell Helix (syn) particularly good for this. Just a thought, if you have changed from a semi-synthetic oil to a full synthetic that might also explain a change in noise levels. The main thing is that the oil is circulating and reaching all parts as, despite a bit of noise (they are not quiet engines) less wear is taking place and this bodes well for the long term.

An old couple going to the shops, etc. short trips, cold starts... could equal wear. 24,000 miles over 6 years can mean a lot of oil dilution and bore wash with petrol, leading to wear.

As long as the oil is the correct VW spec it will be fine. At that low mileage 5W30 should be good (use 5W40 in higher mileage engines). Some filters do not have the anti-drain back valve which means oil returns to the sump when the engine is off, leading to more noise and wear on startup. I fit a new filter at 6 monthly intervals when I change the oil (it's cheap insurance).

Warmed up your tappets should be pretty quiet at idle. Rev up slowly (a bit of tapping), lift off, let it idle, quiet(ish). Rev up and turn off the engine - if there's a knocking noise with the engine off load that is possibly bearings or piston slap (the latter can happen in low mileage engines if the teflon coating has worn - annoying but not a show stopper).

I asked about oil consumption because that is a useful metric. They're known to drink, so well worth monitoring your mileage vs consumption to check that it is within spec. If you are doing short journeys do take into account fuel dilution (which can mask oil consumption and lead to wear).

It might be worthwhile going for a good motorway run and listening to the engine at idle after.

Could you confirm the engine code (e.g. BBY)?