Engine rattle at certain revs??? Only just started!!????

clayton · Post by **clayton** » Thu Jun 16, 2005 12:32 pm

Hi there. I've had a search through this forum to see if anyone else has had this problem but can't seem to find anything.

I have a '95 1.3 MKIV Polo (is the 1.3 engine from the MKIII I think just before they started using the 1.4) - I have posted this in the MK4 forum aswell but I think the MK3 people may know more as it's the 1.3 engine they were using from around '85.

Anyway...just recently I've started getting this very strange and very noticeable rattle - almost grinding type noise - which you can only hear at certain revs (about 1500) when whatever it is starts to resonate. With a mate keeping the revs constant so it makes the noise i've stuck my head under the hood. Is definately coming from the left hand side down around the cam-belt. The cam-belt was changed 6000 miles ago and has been fine.

I'm thinking it could be somewhere around the alternater or maybe a knackered bearing in something? or maybe the cam-belt tentioner wheel?

Is definately not the clutch release bearings.

Has anyone got any ideas or had this before? Any suggestions are very much appreciated! I hope it's not serious!!

Tahrey1043 · Post by **Tahrey1043** » Thu Jun 16, 2005 7:16 pm

how many miles does the car/engine have, and how has it generally been treated?

hope it's not your big end..... O_o... if it is i can order you a set of bearings when i get mine, but good luck with the replacement!
nor your water or oil pumps - they're in a similar location to the alternator, distributed round the engine at the belt end.

the "cam belt tensioner wheel" is actually the water pump.... so if you suspect that... get it sorted.

might be a small gasket leak with combustion/exhaust gases blowing through, that can sound very much like what it's NOT if you know what i mean.

maybe just a loose fitting of something, eg with my hot air feed pipe removed, its halfway bracket resonates something chronic at certain rpms.

Karl_CLCoupe · Post by **Karl_CLCoupe** » Fri Jun 17, 2005 11:52 am

It is common on most of the earlier Polo engines to have a rattle that comes in at higher revs (though 1500 rpm sounds a bit low to be that).

As Tahreys covered really.

Karl.

Tahrey1043 · Post by **Tahrey1043** » Sat Jun 18, 2005 12:25 am

so there's nothing else it could be??

clayton · Post by **clayton** » Thu Jun 23, 2005 11:31 am

Thanks for all your suggestions. It's scary to think how many possible things it could have been!

As I went to loosen the alternator to take off the belt I found the problem. I undid the bolt on the bottom bracket holding the alternator on and it fell into 2 pieces in my hand. The solid metal bracket had snapped in half. Probably because it was old and brittle. So took it off, welded it back together and bob's your uncle, fanny's yer aunt. Quiet as a mouse (well...almost) once again.

Thanks

Matt

GroovyCarrot · Post by **GroovyCarrot** » Thu Jun 23, 2005 12:20 pm

Ah, that alternator bracket is the source of my engine rattles 9 times out of 10. It's just impossible to tighten it up properly, such an awkward position.

amstrange1 · Post by **amstrange1** » Thu Jun 23, 2005 4:08 pm

Tahrey1043 wrote:the "cam belt tensioner wheel" is actually the water pump...

It's a Mk4/6N Polo he's talking about, which do have cambelt tensioners in addition to the water pump!

Glad you got it sorted though, the alternator brackets are a pain in the arse - at least on my G40 it's a solid bracket, the belt tensioning's done by moving the supercharger.