Another "guess that engine noise" question

[ugli-stix]

Over the last few weeks my Rev2 tubby has developed an incredibly embarrassing noise somewhere in the engine bay. It sounds like a repetitive metallic scrapping noise that:

1) increases/speeds up with engine speed (revs).

2) occurs regardless of gear or clutch engaging.

3) is incredibly loud - easily audible above the exhaust/engine/stereo!

4) sounds like its coming from the cambelt/intercooler side of the engine.

5) occurs on EVERY car journey, but comes and goes randomly enough that I'm never able to pull over and have a look in the engine bay whilst it's happening.

Any thoughts? It's very frustrating. This noise, combined with an intermittant clutch pedal squeak, is making for very embarrassing driving!!

[Ian Geary]

I know engine sounds are tricky to diagnose, but here's a couple of thoughts:

Something easy: air con/alt belt too tight (would be a squeal not scrape though).

Something not so easy: I'd be tempted to take of the top timing belt cover and have a look at the cam belt and see if all is well. Look for marks, scores, generally anything that is not how it should be.

I don't think you'll be able to see the idlers though - these would need the lower cover off, which is pretty worse case.



Taking the cam cover off isn't hard (cross braces, air pipes, HT leads and a bit of the throttle body). You can then see if there's anything a miss with the cam shafts, but it's likely the gasket won't be oil tight afterwards.

All in all, because its rev related, it has to be something in the engine (unless it only occurs when moving, in which case have a look at drive shaft and bearing bracket, hubs, brakes etc).

From personal experience, I'd get noises looked at sooner rather than later - it's better to sort a small problem than a big problem. Toyota will charge a lot, but a non main dealer Toyota specialist might be able to have a nose about for a reasonable fee.

hth

Ian

[greglebon]

Water pump, perhaps...?

[Turbo-G]

check all the bolts and double washers that hold the driveshaft in. Failing that also check the shield isnt catching the shaft as it rotates. Easy way is to jack rear up on axle stands, wheels off drive so shafts are rotating and get right under and have a good look. I woudn't e suprised if it isnt what I have just mentioned. I had exactly the same problem a few weeks back.

[ugli-stix]

Cheers for the suggestions! I'm pretty sure it isn't a belt-related problem as its definitely not the normal squealing noise I'd associate with that...

I'll have a look at the waterpump and driveshaft this weekend, but in the meantime I have some more info if it helps. I was stuck in a traffic jam this morning (complete standstill) and the noise suddenly started up. I had the air-con on and tried turning that off and it didn't change. But then I turned the air-con back on and I heard the usual relay click and the noise immeadiately stopped.

In the end I noticed that with the air-con on auto and not econ mode, there is a relay click every few minutes. The noise comes on and off with that relay click.

I'm not sure if the air-con part is a bit of a red herring though - because I'm also wondering if it is something to do with the car getting hot whilst in standstill traffic and something is coming on and off to cool it down?

[jont]

Air con idler pulley bearing would be my suggestion.

I've got a similar noise on my car (although not quite as loud as in your case). The a/c belt is driven off the crankshaft so will change speed with engine revs, and a knackered bearing would sound like metallic rasping. I'm guessing as the compressor kicks in and out it changes the load on the belt which may make the noise worse. I know that's the problem on mine because when I changed the aircon belt I couldn't get enough access to do the nut up properly, so I think the idler spindle is now at a slight angle - thus casuing the bearing to wear. It also is present/quiet depending on whether I've had the aircon on or not.