vacuum leak

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Re: vacuum leak

Postby andyd » Sun Jun 14, 2020 9:26 am

drtony wrote:
The whistle frequency drops momentarily when I rev up but then quickly returns to as it was before


I think that would suggest that it's vacuum related...

Good luck,

Andy
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Re: vacuum leak

Postby Admin-bloke » Sun Jun 14, 2020 4:54 pm

Have you investigated the vac pipes on the charcoal canister? There's a vac pipe from under the throttle plate area and this goes to the charcoal canister. There's a small vac plug that goes on the stub labelled "carb" (short for carburettor) that is not used on the D. This can split and cause a leak.

The above is assuming that it is by a vac leak of course. A smoke test is ye best tool to use for visibly seeing air leaks.
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Re: vacuum leak

Postby cis6409 » Mon Jun 15, 2020 2:50 pm

A video of the sound would be useful to if you can try to upload it.
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Re: vacuum leak

Postby drtony » Mon Jun 29, 2020 12:39 am

Thank you all for yor kind advices about the vacuum leak and whistle. It got worse, such that it then became easier to find. Lo and behold it was, as suggested, the inlet manifold, where the W pipe (or, in my case, the inlet box from the turbo) goes into the inlet manifold. Simples (I hope)! I have taken the box off and cleaned the surfaces of several generations of gunk, and obtained two gaskets at an outrageous cost of £1.20. I am awaiting delivery of online ordered black sealant (Sealpro Pro Sealant black), and will reassemble. Slightly concerned about the amount of torque to exert on the four steel bolts going into the cast aluminium. I guess you don't know if you've overtightened til it's too late.

I'll have a go at the interior light as well. Happy days.
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Re: vacuum leak

Postby Rissy » Mon Jun 29, 2020 8:51 am

drtony wrote:Thank you all for yor kind advices about the vacuum leak and whistle. It got worse, such that it then became easier to find. Lo and behold it was, as suggested, the inlet manifold, where the W pipe (or, in my case, the inlet box from the turbo) goes into the inlet manifold. Simples (I hope)! I have taken the box off and cleaned the surfaces of several generations of gunk, and obtained two gaskets at an outrageous cost of £1.20. I am awaiting delivery of online ordered black sealant (Sealpro Pro Sealant black), and will reassemble. Slightly concerned about the amount of torque to exert on the four steel bolts going into the cast aluminium. I guess you don't know if you've overtightened til it's too late.

I'll have a go at the interior light as well. Happy days.


Although they're virtually impossible to torque; the four air intake bolts which clamp the air intake down on to the block only take about 11-15Nm to be tight. You do not want to over torque them whatever you do. As long as you're using new rubber o rings around the cylinder air intake holes on the block underneath, they WILL squidge down, even just with the air intake resting one them without bolting down. You can use spring washers on those four bolts too. This help help to stop any vibrating loose in case you don't tighten them enough. Better to be too loose to begin with, than to over torque and go into a world of pain.

I also coat the 6 o rings with silicone grease before hiding them under the air intake assembly. Just a personal choice.
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Re: vacuum leak

Postby andyd » Mon Jun 29, 2020 11:25 am

I think there;s a good chance you'll probably end up helicoiling those holes in the ally... May actually be better, if they are actually carrying weight, and perhaps thats part of the issue causing the original leak.

I have had quite good success in this position with M7 V-Coil kits. Good to have on the shelf!

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Re: vacuum leak

Postby Rissy » Mon Jun 29, 2020 2:03 pm

Although it has been done; it's still risky helicoiling those four holes. They come within millimetres of the water jacket and the spark plug recesses (the former being the most issue prone if breached) near the bottom 1/3 of the holes. I'd avoid helicoiling those holes at all costs simply down to the risk of breaching your water jacket in doing so (not to mention the obscure angle at which they have to be drilled to make them right). As always, just my opinion.
Rissy
Chris M. Morionem qui loquitur multus sine cogitatione.

May 1981 vin#1458
"LEX" - Officially used in Britain's Greatest Machines (80's episode) with Chris Barrie.
Grey Wheels
Grooved, flapped Bonnet
Black Leather Interior
Chassis: #1073
Engine: #2839

Main Car(s):

2005 BMW M3 E46 Shape 3.246 Straight Six in Velvet Blue
1999 Honda Civic MB6 Shape 1.8VTi VTEC in Pirates Black
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Posts: 226
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Re: vacuum leak

Postby andyd » Mon Jun 29, 2020 2:48 pm

Ah, sorry, I was meaning the ones holding on the ram horns
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