The CAV Filter Exposed

Pre Filters

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Th following is a few thoughts on filtration - not Twin Turbine units with change over valves - filtration on the cheap ! We are talking about an engine that uses just 1 ltr per hour here !

Cheap does not mean 'poor quality' - it means, shop around !

After thoughts - Update !

After spending way too much time delving into filter types - I've come to this - see below for my previous stuff.

One can get swamped in all this - its not easy to sort out whats what.

For a prefilter on 1GM10 - with such a low flow - one can go with a finer filter than you would normally use for a pimary filter. Hence the Fleetguard FS19599 ( 6 micron @ 95% - Stratapore medium ) or the Mann-Hummel WDK725 ( 65% @ 3 micron ) are options to consider - despite these filters being 'high pressure rated' - and the latter having flow rates way above what the 1GM10 requires - they are ' the latest filter media' - rather than the standard treated cellulose.

If you really want to go 'fine' then these are worth a look.

The range equivalent to the Delphi HDF496a - often bundled with the cheaper spin on tops - is Mann-Hummel WK842-2 ( with a drain tap ).

The Fleetguard and Baldwin spec to these are very expensive filters - ( ie £18 as opposed to £5 ) - due to large capacities and high pressure ratings . But they are very good filters ! The Fleetguard FF5135 is a match for the Mann - cheap enough at about £5 net - M16 x 1.5 - drain etc. Its a basic treated cellulose at 20 micron 97%.

(the Mann-H WK842-2 is cited at 3 micron @ 20%. This is an odd way to rate things - and even Racor do similar. Fleetguard will quote a filter at 25 micron @ 98%. Hence Mann 3 micron @ 75% equates to a Fleetguard 6 micron rating @ 98% . Confused - I am ?

Talking to a Donladson main agent ( Filtration Ltd, Avonmouth Bristol ) - his take was Donaldson were best best by far for Air - and Mann-Hummel best for Fuel. He considered Racor as 'good stuff', but limited range, Baldwin - dodgy quality they would rather not be associated with ! - and Delphi not worth considering ! He could supply Fleetguard, but considerd them to be 'the same quality' as Mann-Hummel but more expensive !

So make what you want of that !

If using easily available M16 x 1.5 spin on heads - and want a unit with drain tap and built in collection bowl ( all the above ) - you have two chioces. Fine ( approx 6 micron ) or Primary ( 20 micron approx )


Although being 'over the top' for application - the FS19599 ( £7.20 net ) and the WDK725 (£ 5.50 net ) are still cheap enough to buy - and have drain taps and built in collection bowls.

If you don't have a huge problem with water ( ie Vetus poly tank ) then I think this fine is ok. Sailboat engines do not get many miles on them. Cav's are rated at 5 micron - but thats a low % figure. Absolute would be closer to 30 I think.

Primary - Pre-filter

The Mann-Hummel WK842-2 is probably the one for this. Filtration Ltd - over the counter (genuine Mann-Hummel )£4.25 net.( actually £3 on ebay Mann filters page ) Huge no of applications for this filter - including BMW marine engines !

Same spec as the Delphi HDF496A - which is often sold for £7 and more ! ( I have seen the Mann 842-2 at £9 ! online ! )

Also the Fleetguard FS 1276, FS1221 and the Baldwin BF1276 - these are all in the £ 16-18 range - and a little over the top, for flow rate, size and pressure rating. But - they are very good filters !

The Fleetguard FF5135 - is a match really for the Mann. Despite its drain etc - its rated as a 'filter' FF - as opposed to a filter/seperator FS. It basic treated cellulose ( as are Racors ! )

M16 x 1.5mm Head

The options above are for a spin on head, with primer bulb facility and good filter with drain bowl ( not see through ) and tap - at approx £16 all in for the complete assembly !

Thats using SSL for the head unit - and Fleetguard or Mann-Hummel filteration.

And after all this I still don't know what to go for !

Likely the spin-on head - plain 1/2 unf - ( use my banjo primer ) + Fleetguard FS19599 or FF5135 - Cheap but good !

Geoff - Feb 2014

The stuff I prepared earlier - its getting edited a bit as I find out a bit more !

Pre thoughts

Before you ditch the Cav realise there are a vast array of filter brands out there - and stay away from Marine suppliers. Places like Inline Filters - and Part and Filters have very cheap prices on genuine Delphi, Baldwin, Fleetwood, Mahle, etc.

By CAV - I mean the one with the stupid bolt right through the middle of the unit ! Usually glass bowl - 296 filter.

Check out your local area for a 'Filtration specialist' main dealer etc. I found one in Avonmouth and over the counter price was exactly the same, or cheaper than the cheapest source online ! No postage either !

One thing that is not so clear is there are two differing types of CAV filter - I'm not really sure how they differ ?

All CAV's exit up the middle tube. I have read that the type with the solid tube right through are stronger and less likely to collapse under any fuel pressure ?

One type has 'solid' coils of filter material right up to a tube right through the middle - and 'holes' on the top plate.

The other - has an unperforated top plate, but gaps around the edge - has a ring to fit the spigot, but the actual centre tube is hollow - and you can see the backside of the filter material.

Both exit up the middle hole.

Its a shame with the Cav.

The filter units are OK, cheap and simple - yet no one has bothered to re-engineer the head units - which are severely lacking to my mind.

I have read comments that the filter material itself is wildly outdated - but most good suppliers make units for 286, Baldwin, Fleetwood, Mann Hummel etc - I would think their filter materials would be up to spec. Fleetwood certainly specify the filter material on 'some' of their filters if you care to pour through the huge pdfs of details. ( Baldwin's pdf of 'applications' was 1300 pages ! - I should get out more )

Inline filters ( see above ) will give you the direct technical phone no for Fleetguard filters - and a name ! - Nigel - and it was Nigel ! - and he was helpful ! Just wish I didn't have to phone him - the info could have been online easily ( he was just looking at a screen after all )

We don't want flashy pictures - we want a list of no's and specs - easy, no bandwidth invloved - download of an Excell file - all there ! I dream !

Take a look at SSL diesel parts - they have a vast array of filter heads, parts, bowls etc - and non filter water separators - all very affordable and flexible.

I have never had a cav leak on me - so I don't know why everyone says they are leaky !

What I don't like is the fact there are 'so' many seals - ie, rubber to tap, rubber to bottom glass, rubber to glass top, rubber to filter top, rubber to centre bolt, bleed screw and two unused blanked off outlets !

- and I'm never really happy that these things are bled out properly. So many 'dead' high spots to trap air - and when the boats getting tossed around some is not when you want trapped air getting loose in the line !

It helps to fit an alloy bowl - as they have the centre spigot captive in the alloy - the drain bung is a separate tapped hole to one side. Also the alloy base has a flange lip which fits the base of the filter unit more pricisely. You still have that stupid small o ring top bolt head though.

Why they ever designed this with a bolt boing through the outlet port is beyond me.

An M10 dowty fits ok for the bleed bolt - its actually 3/8.

For a £10 you can change to a spin on head (SSLdieselparts)

Depending on the filter type - you then just have the one rubber seal ! You still have to break the fuel line integrity to replace one - but that applies to just about everything other than the top end Racor Turbine - and similar Dahl, Fleetguard, Separ top opening units.

One advantage of the spin on head is at 16 x 1.5mm centre spigot one has a much larger array of filter types to choose from than you have with the 296. These can be straight filters - or dedicated filter/water separators with drain bowls and drains - and various micron ratings and filter material types.

Also - its the only size thats available at a basic price ( I'm wokring on a source for a 1 x 14 un head ( Racor, Fleetfuard clear bowl type units )

Basic options for the 16 x 1.5mm head.

Fine filters

Baldwin 5587D - filter 5 micron - with built in bowl and drain bung. Equiv - to Fleetguard FS19599 or to the Mann-Hummel WDK725. All good filters - with drain taps - but a little fine for Primary filtration.

Primary separator/filters.

These genarally are about 20 micron range and mostly over spec for the 1GM10. The Baldwin 1276 - Fleetguard FS1276 and the FS 1221 - are in the £ 16-18 range - large capacity, high pressure - but state of the art filter materials ( you get what you pay for here )

The Fleetguard FF5135 is close to the 842-2 - basic filter with drain.

The Mann-Humel WK842-2 is the best option here. Quality product at 20% @3 micron spec ( this sort of equates to 20 micron absolute - I think ! ) and is also the spec to the very common Delphi HDF496A.

The WK842-2 - at an industrial filter outlet is £4.25 plus vat - cheaper than online and no postage ! Look around !

Strainer filters - 60 micron.

The Baldwin 1365 - rated as 9 micron nominal/40 micron absolute.The Fleetguard FS19821 is 60 micron @ 97% - the Mann-Hummel WK842/6 - 60 micron.

This Baldwin seems a good option - but some seem not to rate Baldwin ? Its a good basic sort of 30 micron filter - which is lacking in the M16 x 1.5 spin on range. A 1 x 14 head would give way more options, but not easy to obtain under a premium price !

Bear in mind - small engines cannot pull too much on a small lift pump.

I'm not sure how much of an issue this is - so I dug in a bit !

What is going through the lift pump is a piddle by most standards - but the thing still has to suck fuel up to itself. If your tank is low - then thats some head - then maybe through a primer bulb ? ( suck through a primer bulb and it takes a bit to 'break' the one way on it ? )

Yanmar 1GM10 lift pump can pull 2.6in hg ( 60mm hg in yanmar terms ) - ie that what it will 'pull' not push. That equals approx - 1.3 psi.

2.6 in hg is about 80 Mbar

100 mb = 1.45 psi

1in hg = 0.49 psi

The Racor 200 series (with a primer) are quoted as a clean pressure drop of 0.12 psi

The Racor 500 turbine @ 0.25 psi.

Since I found my old Mityvac in a locker - I tested my dry line, through the cav and filter and my primer bulb ( asap type banjo unit ) As far as i could read on a 0-30 psi scale it was about 0.4in hg.

So the Yanmar lift pump can pull 1.8 psi - fine ?

These figures of course are for the filter unit clean - but also at its rated max flow - often 35 ltr an hr even on the smallest of units. Whats going through a 1GM10 - with fuel return, maybe 2 ltrs an hr ?

This is why I say primary filters can be finer than normally recommended on these engines.

But how it goes up with older filters is unknown. We know we should change them - but do we, other than once a season ?

One of my reasonings here - is the more the filter costs the less likely you are to change it ! Cavs are so cheap you could stick a new one in every month ! There again - the Fleetguard I above is only £6.30 net or so - and the Mann-Hummel (genuine) WK842-2 is only £4.25 net . They are very good quality and not breaking the bank.


Dahl - make a nice small unit ( Baldwin/Dhal )

As far as Racor filters go -

the head sizes vary. I am not sure if the 200- 400 - 600 series fit the general range of 1 x 14 un filters. They are 1 x 14 spigots - but depends maybe on the filter rings width ? I suspect they do.

The 300 series seem to be 11/16 - 16 centre spigot size - ( to suit Quickslver/Mercury )

The 100 - 120 series are M18 x 1.5mm

The 400 - 600 series though are 1" - 14.

You can get 1" - 14 heads, Fleetguard/cummins

but they are a fair price generally - there is a generic one for around £30 ( still looking on this one )

Cummins/Fleetguard spin-on series

Fleetguard is quality stuff - and not expensive really. Difficult to source though.

They make three very nice spin on units - similar to Racor 120 series. Head - 1 x 14 un - 14mm ports - separate clear bowl £6 ! - filters about £14. Heads separate are £56 net. Filters are Stratopre medium - and 25micron @ 98% - 98% water separation. Cannot yet find a price or supplier on a complete assembly.

The separate head may be overpriced ? They may fit the racor 200, 400, 6000 series - which are 1 x 14 un ?

The market is all sewn up - similar in price to the Racor 120 or 230 ! - these people do their homework !

I cannot find an aftermarket M18 spin on head.

You can get US import alloy Mercruiser/ quicksilver units - 11/16 - 16 - from various sources at about £28 inc Quicksilver filter. Racor make some filters for this size - 300 series, mostly petrol/gas.

Cheap Crap

Ebay a Chinese Racor 500 series copy - Hanwei £49 inc post - buy now !

Gael Force Marine are putting out a 500 series copy at 80 quid or so - and fit it with 500 Racor filters - which are cheap enough. That of course presumes these units are directing flow the right way for the filter material - are not going to fall apart - and that spares are available when they do break ( and they will ) These things often look good - but generally are made of absolute crap materials. I would stay away - but that Hanwei is cheap if you just wanted a polishing circuit loop.

Racor also make a 'Snappit' complete assembly
for about £38 inc. It looks like the Racor 120 series - has clear bowl, drain etc - but is a throwaway unit. The retaining bracket is stainless - and stays.

You swap the whole thing ! At least no fittings to work loose. Again - no primer bulb. If you don't want a primer bulb - and are happy with the ethos of 'chuck the whole thing' ( I'm not ) then its worth a look. Interesting - not a seal to leak except in/out fittings - and in some ways a sign of the times. 'Duhh, I just rip this out and stick that in, Duh - thats easy - Duhh' - maybe I'm being cynical !

Replacement filter ( no bracket - £ 24 ! ) Another thing I don't like, and there is no option, is the built in barbs are 10mm - which messes thngs up a bit if your present set up is 8mm !

Racors in general

Don't forget the 140 series, Simple alloy head, takes standard filter and bowl ( R12T ) - but no bracket for fixing ( make a strap for it ! ) £46 all in inc vat. Cheap option - but no primer. ( the head is M18 x 1.5 unfortunately )

You can buy a 120 head for about £45 ( hyphose ) but as I say - it is 1 x 14 un - but I am not sure if the Fleetguard FS1240 filter and bowl fit ?

That filter and bowl - even the larger FS1241, is about £15 filter and £6.50 bowl net ( £ 25 ) - so for £60 you could have a Fleet-Cor ! ( if they fit ? )

Stanadyne make an interesting small unit

about £45 - Fuel Master.

You can double up

- ie have two filters in line. First as a water separator, no filter - then into a filter unit at a chosen micron size - 16 x 1.5 heads are cheap. ( see top page comment ) and also available in 1/2 unf. So - if you have a remote primer - it is a way to use it alongside a Racor or fleetguard non primer unit.

But its all extra stuff to leak or work loose ?

So - whats cheap - whats good - what have I decided ?

Ha - decided, what's that !

M16 x 1.5mm spin on head

is a good option for price ( £11 primer - £8.50 plain )

Two versions geerally around - no primer bulb, available in 1/2 unf or 14mm on the 'normal' 2 in 2 out side ports.

Bosch type - 3 in side 1 out top - only 14mm ports.

With primer - nice Bosch style 5 port. ( this is available without primer from Biodieselsupplies - at a premium price !)

14mm 1.5mm hose spigots are cheap.

Both cheap at about £11 inc from SSL

Since my primer bulb is now many years old - I am very tempted by the primer version of this unit.

Or I may try it without - now the tank is higher and I have positive pressure to the filter and lift pump. Primers do make bleeding up to the injector pump very quick and easy - and I still have a top feed tank. I do have a tap - lower than the tank base - but still could lose syphon. ( ie rough water low on fuel - sloshing etc.

I have existed with my primer bulb for so long I wouldn't want to be without it I think !


If M16 x 1.5m head

Very likely the Fleetguard FS19599 - or maybe go with the cheaper, 20 micron FF5135 or the WK842-2. All these have drains and built in bowls - but I like the FS19599 for it dedicated water separation - and Stratopore medium.

Splashing out !

Parts & Filters have the Fleetwood FS1240 range + heads, bowls etc - and I do like this range. 25 micron absolute @ 98% - clear bowl and drain - Stratopore medium. Filters £14 - bowl £6.50.

There is an option on the larger filter FS1242 of a 10 micron @ 98% stratopore.

Problem is the head as cited is separate - and £56 net. I am enquiring as to a unit price, or if there are any cheaper options on the head. If it were M16 x 1.5 I could just stick it on a £10 head unit - life is not so simple !

But I still would not have my primer. The head is 14 mm - so essentially I could add a 14mm primer - but that adds another £9.

I can get a Racor 230R10 for £92 inc vat and delivery - that has a primer built in ( hyphose - main website not ebay )

What I am really doing !

Ha - nothing really, just yet. I'm going to re-route my main fuel supply to shift the filter to the left bulkhead - front engine - for ease of access. It also means a tidier run of the 8mm marine grade hose - then a much shorter run from the filter to the lift pump. I have some braided 7.5mm nitrile for this as the yanmar lift pump spigot is 7mm ( thanks Yanmar ) - its not as tough as the marine Lloyds stuff.

I also am undecided on a primer or no primer ( I thought I had decided that ! ) ?

Otherwise - as above. Probably Mann-Hummel, maybe Fleetguard - probably primer built in ( maybe not - ha !! )

Decisions are not my best area !

Geoff - going Goggle eyed !

Feb 2014

Racor spigot sizes -

S3213 0 ( 300 series - 11/16 - 16 ) odd to fit Qicksilver/Mercury

R 13T - R 12T - M18 - 1.5mm

R20T - R 45 T - all 400 & 600 series - 1" - 14.

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