Bolts on top of CAV pre-filter

[Upnorth]

I have a CAV type pre filter and am about to change the filter cartridge for the first time. As there is little info apart from draining the sediment bowl I am after a bit of help.

I assume that of the two bolts on the top, the 'centre' one screws into the bowl and clamps the filter in place. What is the other one for, is it a bleed?

 

[pappaecho]

You have got it exactly right! Dont forget to switch of the flow from the tank to the filter specially if the filter is below tank level

 

[savageseadog]

Don't forget to change the O ring on the spigot that protrudes down from the top. It's quite hard to get hold of, don't use anything that will damage the alloy material.

 

[Talbot]

When you purchase a replacement filter, you will only get one large O ring. If your CAV also has the see through bowl on the bottom, you will also need that O ring. Personally hate them as they can be brutes to get fully air tight, whereas the Racor variants are much easier. Mine also has a priming pump.

 

[Poignard]

Agree. I had a CAV which I could never get not to leak a little. I think it had been over tightened and distorted.

Like you I changed it for a Racor; much easier to change, especially in a restricted space.

 

[duke]

re o ring in centre spigot : just changed mine today. Had to cut through mine ( very carefully) to get it off.

 

[david_bagshaw]

with genuine filters usually you get the element plus 2 large rubber rings, smaller one lower bowl larger , upper, o ring inside spigot, tiny o ring , retainig bolt. change all = no trouble.


personally I use electrical screw driver to flip o ringout and the upper lid ring, other 2 are easily removed.

we have 2x on each main engine and another on the larger generator, since 1990 of the main filter design, prefilter is similar

 

[boatmike]

Yes but as Talbot said there is also one one between the aluminium bottom plate and the glass bowl. This does not usually come with a new filter and is a major cause of leaks. That then causes owners to try to do up the centre screw even tighter which distorts the top plate and causes more leaks...

 

[boatmike]

Actually most filters come with two seals for top and bottom of filter +o ring for screw but never include the one between the glass bowl and bottom plate, which is probably what you had in mind.

 

[PCUK]

Glass bowls are not recommended for boats. Replace the glass with an all-in-one alloy bowl type and there is no problem as the extra seal is no longer needed.

 

[smeaks]

If you take your time and are carfull about catching the oil released from the filter it can be an easy job.... If the filter is above the tank and yo prime through the engine (Volvo or similar manual prime pump you know if the seal is incorrect because the filter will not fill. First time i changed it i pumped for ages not knowing how long it took. I then checked the filter and found i had trapped an o ring, refitted and found it primed in a couple of mins.

Another occasion on another boat i was over zealous in tightening the assembly and smashed the bowl. I was stuck in Eyemouth whilst I tracked one down in a local tractor parts supplier. Since then I carry a spare and am very carefull about tightening, "just enough" is my Saftey zone!

 

[michael_w]

Unless you are a Zen master, don't take the O-ring out of the glass bowl unless absolutely necessary. It is a sod to fit. You have been warned!

 

[davidbains]

They are awkward especially if an out of the way place.
It is possible to convert a CAV Fuelfilter head to a Racor spinon filter,
which makes life much easier.
ASAP sell the parts.

 

[RestlessL]

[ QUOTE ]
Unless you are a Zen master, don't take the O-ring out of the glass bowl unless absolutely necessary. It is a sod to fit. You have been warned!

[/ QUOTE ]

Everything to do with that glass bowl is a sod. I have broken 2 by overtightening.

The CAV may be the cleaper option, but the Racon is an attractive altenative.

 

[boatmike]

Not recommended by whom? You and who else?

 

[Upnorth]

Thanks for all the wisdom that followed from my simple (or so I thought) question.

I have an alloy bowl so the issues with glass breaking hopefully won't be a problem for me. The new filter cartridge has come with a five piece gasket set, two O rings - tiny and small, and three rubber rectangular section gaskets two of one size and one slightly bigger.

Two minor questions - Will I need alll of these if I have an alloy rather than glass bowl? and is there a website where I can download a parts drawing of the whole assembly. It makes things easier if you know how things are put together before you start dismantling.

Thanks again everyone.

Mike

 

[Talbot]

[ QUOTE ]
Actually most filters come with two seals for top and bottom of filter +o ring for screw but never include the one between the glass bowl and bottom plate, which is probably what you had in mind.

[/ QUOTE ]

Yes /forums/images/graemlins/smirk.gif

 

[david_bagshaw]

see my post above, as I dont have the glass version either

to quote
The new filter cartridge has come with a five piece gasket set, two O rings - tiny and small, and three rubber rectangular section gaskets <span style="color:red">two of one size will only need one of these </span> and one slightly bigger.

 

[damo]

(With reference to boatmike's diplomatic question /forums/images/graemlins/wink.gif)

From the Boat Safety Scheme regs:

"You must only use appropriate fire resistant and impact resistant fuel filters designed for marine
use. Clear bowl, glass or plastic filters meeting these criteria are acceptable, as
long as they are designed for use with the fuel-type. "

 

[pvb]

But isn't the Boat Safety Scheme only relevant for certain inland waterways?