Diesel Filter (CAV) Leakage

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neil1967

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Hi

I have a CAV diesel filter connected to my Beta diesel. I recently replaced it because it was leaking, but the replacement leaks too - apparently from the seals between the glass bowl and the metal fittings. Is this a common problem and how can I remedy it? The fuel tank is about 10cm above the filter, so there is a slight positive pressure, but I still wouldn't expect the filter to leak. I turn the diesel off at a tap between the tank and the CAV when not in use (in port), but I wouldn't want to turn this off when at sea - one more thing to remember to turn on when needing to use the engine!

As always, your collective wisdom much appreciated!

Regards

Neil
 
Check you have not got TWO sealing rings in the groove! This happened to me when I changed thye filter and it was only after I removed the filter completely that I discovered there were two sealing rings! After removing both rings, carefully cleaning the grove and fitting a new ring it was perfect.
 
The two seals supplied with the filter are different sizes - one for top and one for bottom - if incorrectly fitted they will leak.
 
you need three sealing rings, to employ the glass bowl, one at the filter head, one at the filter bottom, and one at the base of the glass bowl. As stated dig out the seal at the head, remove the bolt and renew that small seal, remove the seal on the inside of the head bolt extrusion, all this is done standing on your head. then assemble filter/ seal, bowl /seal, bowl/seal/base, insert bolt, offer up the assembly and spin on until hand tight, then nip up on bolt. I find this way a seal is made, by simply tightening with the bolt one or all of the seals displace and the thing leaks or draws air in.
 
I've had the same problem numerous times and agree with the different sized sealing rings, some fit better than others. I'm going to change the whole unit for a racor type at next service as these are a right pain and messy; the diesel engineer who did the last service also had quite a job trying to seal the new element. I fitted my CAV type about 6 years ago and soon wished I hadn't. I wouldn't like to have to change a blocked filter at sea.
 
CAV filter leakage

Slowtack said:
The two seals supplied with the filter are different sizes - one for top and one for bottom - if incorrectly fitted they will leak.
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When you buy a new element you actually get 4 seals. 2 of them are very much smaller than the other 2. The problem is that if you have a glass bowl below the filter element and a metal base plate under the glass bowl you need 3 of the larger type seals but only 2 are supplied. At least this is the case with a Crosland element and I think that is probably true for other manufacturers. I phoned Crosland and they willingly sent me (free of charge) 4 sets of spare seals. You do need to make sure that the groove into which you fit the top seal has only 1 seal in it. It is very easy to overlook removal of the old seal and it can be fiddly to get the 2 lower seals to seat correctly. They are not very positively located so care is needed.

If all is correct there will be no leak.
 
I sacked my CAV after it blocked in a choppy sea, just when I really needed the engine. I realised there was no way I was going to be able to change the filter quickly in a chop, which is just when it's most likely to give up.

I went to a scrap yard and got a couple of fuel filter bodies for a Volvo V40, which just happens to take the same filter as the secondary on my engine. I fitted them in parallel with taps upstream & downstream of each (4 simple taps were a lot cheaper than two T valves). Total cost was about £80.

Now I run on one filter, but can have a new filter on line in a few seconds, and I can change the blocked one under way. I don't know if I could bleed it with the engine running, as I've never tried.

The filters are more expensive, but with this setup, I've been happy to run a filters for two or three years instead of changing them religiously every year, so they may even work out cheaper.
 
Apart from all the other good suggetsions, I slightly grease the sealing rings. This will make them stay in place better and help to achieve a good sealing.
On assembly, I thighten the bolt sligtly and turn the filter and the glass bowl independently to find the orientation where the tension is the least. Then tighten up.
 
I have had trouble with a CAV leaking despite new sealing rings and carefully cleaning everything. I came to the conclusion that the aluminium top housing had been distorted or damaged; probably by previous owners over-tightening it to try and stop the leaking!.

Anyway I chucked it out and fitted a Racor, which doesn't leak a drop. Cost more but worth every penny. It also has a handy drain cock underneath so if you need a bit of diesel to clean something you can easily get some.
 
CAV are stone age (Luddites luv 'em, which says it all). Racor much better, especially if access is a bit awkward. Or you can get a converter (from ASAP Supplies, if memory serves) which allows Racor spin-on filters to be used on a CAV base: no glass bowl and finicky seals.
 
Solved the problem - it was nothing to do with the seals, it was one of the blanking plugs - one of the copper washers was not seated properly and so there was a slight leak, which was allowing a small amount of diesel to run down the filter and then accumulate in the grove between the filter and the glass bowl - thus giving the appearance of the filter seal leaking.

Thanks for your advice.

Regards

Neil
 
Well done to find that Neil. After all the slagging off CAV have taken in this thread it is time to defend them. Do the job properly and they don't leak. I've never had a leak after changing elements. And Stemar, why change the whole lot to make up a parallel system when you could have done the same using CAV?
 
PCUK said:
Well done to find that Neil. After all the slagging off CAV have taken in this thread it is time to defend them. Do the job properly and they don't leak. I've never had a leak after changing elements. And Stemar, why change the whole lot to make up a parallel system when you could have done the same using CAV?
Click to expand...
Two reasons.

1. If the crud in my tank has been stirred up enough to cause a filter to block, my second filter may only have a life of a few minutes too, so I'd like to be able to change the blocked one with Jissel still leaping around. OK with a spin on filter, but I can't see me leaving a by now panicked SWMBO on the helm while I sort out a CAV one while everything's going up and down several feet. My set up allows me to change a filter and bleed it while the engine's running.

2. Cost. I got the filter holders from a car breakers and paid £30 for the pair.

Of course, the real answer to No 1 is to clean the tank, but it's glassed in with no access apart from the filler, which is an inch and a half diameter at most. A new tank is on the to do list, but it's a big job that I'd rather do out of the water and I'm staying in this winter.
 
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