Technical 750 Top end rattle

[VmanC]

Hi all. Spent alot of time today exploring the forum, getting to know how things work etc, posted a couple of wanted's, and now i'd like to ask if anyone can shed some light on a niggle I have with my 750L.
The engine is lovely, smooth and quiet as it should be having only covered 38K, apart from after it has been left ticking over for more than ten seconds, when the top end starts to get noisy.
It's as if there isn't enough oil getting to the tappets at idle speed and after what is there drains away it just starts to rattle. once you give it a few revs again the noise disappears and all is well.
Any thoughts will be gratefully recieved.

Vernon.

 

[Most Easterly Pandas]

I think you've answered your own question. Sounds like oil feed to the rocker cover to me. Sounds like a slight blockage.

Oil light doesn't come on at tickover does it?

 

[VmanC]

Thanks for the reply.
No, oil light stays out. I replaced the head gasket earlier this year so I know the spray bar is clean, as is the feed to it, and no I didn't put the gasket on the wrong way round, though that's not beyond me!

I've not had this problem on any of my other Pandas so I'm guessing it's not a common problem on the fire engine.

 

[Chas Uno]

Are you sure it's the top end rattling? Other culprits at tickover could be:

• Cambelt tensioner
• Water Pump
• Alternator
• Clutch release bearing

You may even have something loose - sometimes these only show up at tickover due to the low frequency of the engine vibrations at those rpms.

Also check that the cambelt cover is on properly. I thought I had a failing alternator or water pump but it turned out the cover was just rubbing on the camshaft sprocket

 

[VmanC]

Thanks for that, I know the tensioner is ok coz I fitted a new one along with a new belt when I did the head gasket, but will check out the rest.

 

[Pandarus]

Vernon, your 750 is amazing.

Well done!

 

[VmanC]

Are you sure it's the top end rattling? Other culprits at tickover could be:

• Cambelt tensioner
• Water Pump
• Alternator
• Clutch release bearing

You may even have something loose - sometimes these only show up at tickover due to the low frequency of the engine vibrations at those rpms.

Also check that the cambelt cover is on properly. I thought I had a failing alternator or water pump but it turned out the cover was just rubbing on the camshaft sprocket

Well, thank you for this comprehensive list. I've finally had a bit of time this weekend to check on some of your suggestions.

I took off the alternator drive belt, which did not make a difference, so that's the alternator ticked off. Everything under and around the timing belt cover also passed inspection, so that ticks off the water pump, belt tensioner, timing belt cover etc.

So, still stumped, I thought I'd try and listen really hard to try and narrow down the area the rattle is coming from. The trouble is, everywhere I stuck my ear I thought the noise was coming from that area! :bang: how does it do that?

I have ruled out my initial theory that it's a top end rattle, so the title of this thread no longer applies. It's now starting to look like the gearbox is the culprit. I don't think it's the clutch thrust bearing as the rattle doesn't change when I depress the clutch, nor do I think there's anything particularly wrong with the gearbox, It's just that it has a habit of chattering when the engine is at idle. I've increased the tickover speed and this has helped, but to stop the noise altogether would require an idle speed of 1200 rpm, so I think I've set it at about 1000rpm and left it at that. Unless anyone has any other ideas of course.

Thank you all for your suggestions so far.

 

[lewey]

If the noise stops when you dis-engage the box, it won't be the box making the noise, will it?

 

[VmanC]

If the noise stops when you dis-engage the box, it won't be the box making the noise, will it?

Sorry Lewey you've lost me, did you mean it the other way around or am I being thick?

This is looking more like I may have fall back on my tried and trusted plan of 'wait till something falls off '.

 

[lewey]

Sorry Lewey you've lost me, did you mean it the other way around or am I being thick?

Quite right, I meant to say "If the noise doesn't stop.."

 

[VmanC]

Ah , yes, you are quite right too. I had thought that maybe it was the first motion shaft chattering, but as you say, depressing the clutch should stop the noise if that was the case, and it doesn't. At least you've helped me rule out half the engine bay.