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Fuel filter drain plug help needed


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This

 

IMG_20230505_092556.thumb.jpg.7481ab9c32d91f81a9cbf76045bf2616.jpg

 

 

 

Has failed the BS inspection. 

 

It isn't a normal CAV type as the thread on housing is male. 

 

 

Does anyone know what the thread is and if there is a metal version of this as the BS does not want plastic. 

 

 

The filter body says CY on top of it. 

 

I wonder if I need a whole new filter body. 

 

Or maybe replace bowl with one without drain plug. 

 

https://www.ebay.co.uk/itm/183175795973

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3 minutes ago, Alan de Enfield said:

Tap the stud / pipe coming out of the bottom and fit your own metal bolt,

That is an idea. I suppose just an M5 tap or something and a little stainless bolt would sort it. 

 

 

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4 minutes ago, Alan de Enfield said:

Tap the stud / pipe coming out of the bottom and fit your own metal bolt,

 

That looks like the best option to me because the base of the filter has a radius around the thread, making a cap more difficult to seal. Don't be tempted to drill the hole out too much.

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2 minutes ago, magnetman said:

That is an idea. I suppose just an M5 tap or something and a little stainless bolt would sort it. 

 

 

 

If you need to buy the tap, then buy a suitable tapping drill at the same time.

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Just now, Tony Brooks said:

 

That looks like the best option to me because the base of the filter has a radius around the thread, making a cap more difficult to seal. Don't be tempted to drill the hole out too much.

4.2mm and an m5 tap might work 

 

Bit tempted to get a new bowl with no drain and leave this one unmodified as it is a very nice drain arrangement. 

 

 

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Just now, Tony Brooks said:

That looks like the best option to me because the base of the filter has a radius around the thread, making a cap more difficult to seal.

A sealing washer around the base of the thread would sort that, or a seal inside the cap sealing on the end of the thread, as the existing plastic cap does.

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The plastic cap has a little pin in the centre which locates into that hole so if it was drilled to pass the BS then it could never be used as designed. 

 

 

It doesn't rely on a sealing washer as designed. 

 

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Find out what the thread is (try a selection of nuts) then buy a suitable cap nut or dome nut. Put a couple of copper washers or a fibre washer inside the nut. Not totally elegant but it will work.

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Dome nut is a good idea. 

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2 minutes ago, MtB said:

 

Often, the dome is a separate pressed steel component affixed to the machined nut and may not be diesel-tight. 

 

Get a solid brass dome nut 😀. A cap nut might be slicer nicer but they are not quite as easy to get.

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5 minutes ago, dmr said:

 

Get a solid brass dome nut 😀. A cap nut might be slicer nicer but they are not quite as easy to get.

 

 

I don't think any of this is viable for the OP. That thread profile looks unnaturally large and coarse in the photo, and is probably designed specifically for use with plastic components like that 'thumbscrew' style of cap. 

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I've ordered a bowl with no drain. Whack that on job done. Then put the original one back on and die in an awful inferno which also kills 27 children on a towpath walk expedition plus their teachers and the ambulance driver. 

50 minutes ago, dmr said:

I think its UNC, in fact I am so confident that I am prepared to bet you half a pint of beer on this 😀

 

It is about 8mm outside diameter but I didn't have my dial caliper to measure it. 

 

I suppose it does make sense it would be a normal thread size but there was something funny with it. 

 

The female thread type on the cav filter bodies is described as 7.8mm but they don't say what thread it actually is. 

 

 

5/16 unc I guess. 

 

Stainless single piece dome nut ordered to cover all the angles. 

The problem is that 5/16 unc is not 7.8mm it is 7.9mm. 

 

This could be a silly thread I think. 

 

Someone must have established what is going on with these things. 

 

 

I know this is the opposite type but if this was a UNC thread why would they not mention it ? Seems a strange way to describe a thread. To me it looked more coarse than a UNC. 

 

IMG_20230505_142246.jpg.20e142648d62050928521ecc42a1a867.jpg

Edited by magnetman
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12 minutes ago, magnetman said:

I've ordered a bowl with no drain. Whack that on job done. Then put the original one back on and die in an awful inferno which also kills 27 children on a towpath walk expedition plus their teachers and the ambulance driver. 

 

 

Yes this happens all the time with plastic drain plugs and caps. 

 

Which is why the regulation exists, as any fule kno. 

 

 

 

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IMG_20230505_142246.jpg.c5e4378c637bb10e37bcb56421b7e311.jpg

2 minutes ago, MtB said:

 

 

Yes this happens all the time with plastic drain plugs and caps. 

 

Which is why the regulation exists, as any fule kno. 

 

 

 

 

The last time this happened it played havoc with my premiums. 

 

They had to pay out £3m per victim which was not really what they were expecting. It almost bankrupted the unsurance company and the man in charge had to wait an extra 13 months before he could get a new BMW. 

 

All for the sake of a small non specific threaded nut. 

 

 

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The CAV plastic drain plug is 5/16" UNC.  I know because I have fitted dozens of them over the years. Get a 5/16" UNC set screw, put a flat on most of the thread so it woll drain without removing it, and a rubber washer and you are set to go.

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25 minutes ago, Tracy D'arth said:

The CAV plastic drain plug is 5/16" UNC.  I know because I have fitted dozens of them over the years. Get a 5/16" UNC set screw, put a flat on most of the thread so it woll drain without removing it, and a rubber washer and you are set to go.

 

Except....

 

In the OP's photo it is a male thread on the filter.

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I think this requirement should be in the same file as the flame arrestor  gauze in diesel tank vents. I wonder how big and hot a fire would be required to melt the plastic plug to let all that diesel out to feed the fire. When I was at school I remember boiling water in a paper cup over a bunsen burner flame

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3 minutes ago, ditchcrawler said:

I wonder how big and hot a fire would be required to melt the plastic plug to let all that diesel out to feed the fire.

 

 

I feel driven to agree.

 

If the fire is hot enough to melt a plastic plug, the boat is probably well beyond lost. A further 1/4 of a litre of diesel really isn't going to make any difference. 

 

One more example of pointless catastrophising by them BSS chair polishers. 

 

 

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