This Does Not Sound Good ....

[Purple AK]

Originally Posted by conrod

Wilf,

Been there - done that! I removed the fanbelt and the noise was still there. I've just whipped the carb off and fitted a new base gasket, and also gave the inlet manifold bolts a tweak. Again the noise is still there It seems to be coming from the rear of the engine - but it is very difficult to tell. The noise stops as I blip the throttle, and it only rises in pitch slightly with increasing revs - not proportionally. So all this does indeed seem to point to a vacuum leak - but who'd have thought it could make such a bl00dy racket!


I'll go in search of an inlet manifold gasket tomorrow. Then I guess the process is:

1) Drain the cooling system.

2) Disconnect all hoses.

3) Mark and remove the dizzy (at base and rotor position).

4) Disconnect throttle and choke cables and remove the carb.

5) Remove the twelve bolts.

I guess I should also check the manifold with a straight edge to see if it's warped. If it is, I assume it's just a case of taking it to a machine shop to have it machined flat?

Thanks for your help guys - any other ideas/suggestions welcome.

And in answer to your last point Wilf - yes you do indeed! I remember being in a BMW showroom looking at paint colours for the Cob I'd just ordered from DB, seeing a Z4 and thinking - I could buy one of those for similar money. But one look under the bonnet was enough for me - how the hell could you tinker with that lot? And that is, after all, half the fun - eh Dave?

Alan. Before you "invest" any money try the WD40 (or even soapy water) sprayed around the Inlet Manifold/Carb Base and Hoses and listen for a change in noise/pitch.

[conrod]

Originally Posted by Purple AK

Alan. Before you "invest" any money try the WD40 (or even soapy water) sprayed around the Inlet Manifold/Carb Base and Hoses and listen for a change in noise/pitch.

Thanks Chris. All the symptoms and feedback point to a vacuum leak, so I'm doing no more tonight - I can have a good night's sleep now it looks unlikely to be a major mechanical problem!

I'm going to give all the vacuum pipes a thorough check tomorrow morning, and also try the WD40/soapy water trick.

I'm just amazed that a noise so deafeningly loud can come from a leak that's so hard to pinpoint!

Thanks again for all your input guys - I'll keep you posted on progress.

Cheers

[Purple AK]

Originally Posted by conrod

Thanks Chris. All the symptoms and feedback point to a vacuum leak, so I'm doing no more tonight - I can have a good night's sleep now it looks unlikely to be a major mechanical problem!

I'm going to give all the vacuum pipes a thorough check tomorrow morning, and also try the WD40/soapy water trick.

I'm just amazed that a noise so deafeningly loud can come from a leak that's so hard to pinpoint!

Thanks again for all your input guys - I'll keep you posted on progress.

Cheers

Good Luck

[wilf]

Tip to help track down the exact point where the noise is coming from:

Take a metre or so of 1/4" dia plastic pipe or similar. Put one end in your ear, move the other end around the engine bay close to and all over the engine. Will intensify the location of the noise - you will have to be pretty much directly over it before the noise will travel up the pipe (might be worth an ear plug in the other ear as well).

[conrod]

Originally Posted by wilf

Tip to help track down the exact point where the noise is coming from:

Take a metre or so of 1/4" dia plastic pipe or similar. Put one end in your ear, move the other end around the engine bay close to and all over the engine. Will intensify the location of the noise - you will have to be pretty much directly over it before the noise will travel up the pipe (might be worth an ear plug in the other ear as well).

Eh? Pardon? Sorry Wilf - I've still got this ringing in my ears!

Great idea - I'll give that a whirl tomorrow.

[Steve]

could try disconnecting the various pipes before taking the manifold off, see if that changes anything.

luck

[conrod]

Originally Posted by Steve

could try disconnecting the various pipes before taking the manifold off, see if that changes anything.

luck

Thanks Steve.

Vac advance and vac gauge pipes already checked. Will check the PCV and brake servo pipes tomorrow morning. I'm also going take the carb right off and inspect it thoroughly for any cracks/leaks.

[slogger]

A mate of mine had the crankcase breather block up enough to draw air into the crankcase via a poorly fitted rear intake manifold gasket. This made a similar noise.

Just another thought.

Good luck.

[conrod]

Originally Posted by slogger

A mate of mine had the crankcase breather block up enough to draw air into the crankcase via a poorly fitted rear intake manifold gasket. This made a similar noise.

Just another thought.

Good luck.

Thanks Ian.

Following Wilf's earlier suggestion, I've modified my mechanic's stethoscope tonight. A large tube going into two smaller tubes connected to each earpiece. My missus thinks I'm completely mad now she's seen me wandering around wearing this contraption!

What with all the time I've spent over the past six weeks or so either under the car or with my head under the bonnet, I fear she's going to be calling for the men in white coats soon .....

[slogger]

Originally Posted by conrod

Thanks Ian.

Following Wilf's earlier suggestion, I've modified my mechanic's stethoscope tonight. A large tube going into two smaller tubes connected to each earpiece. My missus thinks I'm completely mad now she's seen me wandering around wearing this contraption!

What with all the time I've spent over the past six weeks or so either under the car or with my head under the bonnet, I fear she's going to be calling for the men in white coats soon .....

Sounds perfectly normal to me.............