Leaking pre filter

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Lodds

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Guys,
I have a diesel pre filter that after having the filter changed just keeps leaking. I have lost count the amount of times I have had this unit off and disassembled only to find the leak is still there. It appears to be coming from the top of the filter.

All seals are in place and clean.

I'm confused how something so simple can be so difficult?

What alternatives are there if any to this type of set-up?

Does anyone have any experience of the "Racor" style filter system.

The thought of doing this each year is enough to bring me out in a cold sweat.

As always thank-you for your comments.

Tony
 

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Lodds said:
Does anyone have any experience of the "Racor" style filter system.

The thought of doing this each year is enough to bring me out in a cold sweat.
Click to expand...

To the first: yes. Good, but the filters are expensive.
CAV filter housings of the type you have are usually reliable (half the diesels on the planet use them), but can be finicky, especially if access is poor. You might want to consider a spin-on CAV conversion, much cheaper than the Racor alternative. Google will find you several sources.
 
Lodds said:
Guys,
I have a diesel pre filter that after having the filter changed just keeps leaking. I have lost count the amount of times I have had this unit off and disassembled only to find the leak is still there. It appears to be coming from the top of the filter.

All seals are in place and clean.

I'm confused how something so simple can be so difficult?

What alternatives are there if any to this type of set-up?

Does anyone have any experience of the "Racor" style filter system.

The thought of doing this each year is enough to bring me out in a cold sweat.

As always thank-you for your comments.

Tony
Click to expand...

Assuming it has sealed satisfactorily in the past, indicating there is not a manufacturing defect, then it should seal perfectly as these filters are very common indeed and i have not had a problrm with mine for the last 16years. However, they are not the easiest to get right, particularly in a confined space. If the leak is between the filter top and the aluminium housing then the only culprit is the rectangular section sealing ring. Get a new seal, take out the old one, now check there is not another old seal still in the groove! Yes, i have seen this where someone in the past has forgotten to remove the seal and just added a new one on top and the next time one seal was removed and one new one fitted. Over time the very old seal deteriorated, or maybe the second seal twisted as it did not have a deep enough recess to locate in, and they leaked. Just a thought.

Racor 500FG filters are very easy to change the element and reseal but are a lot more fiddly to remove the bowl to clean it out.

Www.solocoastalsailing.co.uk
 
Plum said:
Assuming it has sealed satisfactorily in the past, indicating there is not a manufacturing defect, then it should seal perfectly as these filters are very common indeed and i have not had a problrm with mine for the last 16years. However, they are not the easiest to get right, particularly in a confined space. If the leak is between the filter top and the aluminium housing then the only culprit is the rectangular section sealing ring. Get a new seal, take out the old one, now check there is not another old seal still in the groove! Yes, i have seen this where someone in the past has forgotten to remove the seal and just added a new one on top and the next time one seal was removed and one new one fitted. Over time the very old seal deteriorated, or maybe the second seal twisted as it did not have a deep enough recess to locate in, and they leaked. Just a thought.

Good advice above.
I leave the old top seal in place if it does not leak. The only problem I have had recently is the new seal falling out of the groove on the top housing. Vaseline or thick grease can help with this but it is awkward in tight places.
As a previous thread pointed out the sediment in your glass bowl is on the clean side of the filter and is intended to capture and show the water that is agglomerated as it passes through the filter media. For this reason I would take with a pinch of salt any advice to simply purge out the sediment with the filter drain valve.

Racor 500FG filters are very easy to change the element and reseal but are a lot more fiddly to remove the bowl to clean it out.

Www.solocoastalsailing.co.uk
Click to expand...
 
My bit in the above was

Good advice above.
I leave the old top seal in place if it does not leak. The only problem I have had recently is the new seal falling out of the groove on the top housing. Vaseline or thick grease can help with this but it is awkward in tight places.
As a previous thread pointed out the sediment in your glass bowl is on the clean side of the filter and is intended to capture and show the water that is agglomerated as it passes through the filter media. For this reason I would take with a pinch of salt any advice to simply purge out the sediment with the filter drain valve.
Read more at http://www.ybw.com/forums/showthread.php?472708-Leaking-pre-filter#hyjDV92673OaszzE.99
 
There is a tiny (6mm OD ?) O ring in the seal at the top of the Aluminium housing - around the bleed screw. Just about nobody provides this when selling a new filter, yet it's an essential item to replace at the same time. I had such a CAV filter which leaked air in past this O ring (it was, as is usual I suspect on the vacuum side). So have you found and renewed this O ring?
 
jdc said:
There is a tiny (6mm OD ?) O ring in the seal at the top of the Aluminium housing - around the bleed screw. Just about nobody provides this when selling a new filter, yet it's an essential item to replace at the same time. I had such a CAV filter which leaked air in past this O ring (it was, as is usual I suspect on the vacuum side). So have you found and renewed this O ring?
Click to expand...

It's actually on the long bolt which holds the thing together, not the bleed screw, and every filter I've bought has had one of these O-rings included.
 
pvb said:
It's actually on the long bolt which holds the thing together, not the bleed screw, and every filter I've bought has had one of these O-rings included.
Click to expand...

yes, you're quite right it is around the bolt. But I assure you that it's never been included in any new filter I bought, nor was it changed by the boat yard during the winter services. Anyway, it's a thought: do you agree that it's worth the OP checking it?
 
jdc said:
yes, you're quite right it is around the bolt. But I assure you that it's never been included in any new filter I bought, nor was it changed by the boat yard during the winter services. Anyway, it's a thought: do you agree that it's worth the OP checking it?
Click to expand...
Yes all O-rings have been renewed. This was a new assembly. All seals and O-rings were already in place.

Writing this I'm now thinking. I had to replace the tails. The shape of the fitting on these tails I considered to be sufficient and that I didn't need to add PTFE tape or any other sealer. Do you think this maybe the issue?
I would have thought though that I would see it dripping from the fitting if that was the cause.

I'll check it out next week when I'm next down there.

Tony
 
You should not need PTFE tape on the tails; if fact, just don't go there. Always use a pukka Delphi 296HDF filter as they are far superior to the pattern options (just compare the amount of filter paper). This may sort your leak too.
 
>Does anyone have any experience of the "Racor" style filter system.

Our boat had two Racors and never leaked also they have the added advantage that they have a pump on top if you need to bleed the system. They are worth the money.
 
Lodds said:
Yes all O-rings have been renewed. This was a new assembly. All seals and O-rings were already in place.

Writing this I'm now thinking. I had to replace the tails. The shape of the fitting on these tails I considered to be sufficient and that I didn't need to add PTFE tape or any other sealer. Do you think this maybe the issue?
I would have thought though that I would see it dripping from the fitting if that was the cause.

I'll check it out next week when I'm next down there.

Tony
Click to expand...

It depends which part of the tails you're referring to, of course. My Racors have a thread tapped into the each side of the housing and a spigot/tail fitting has to be screwed into this thread and the flexible fuel pipe is then pushed over the tail and hose clamped.

When I replaced/rebuilt the filters I used PTFE tape on the screwed fitting into the housing. I reckon that they would definitely leak without some kind of thread sealant.

Richard
 
You need to find exactly where it's leaking from. Clean it all up and use some coloured paper towelling, blue or green is good to find where the leak is. The seals need to be lined up correctly it's also easy to get them out of line if you overtighten it. I've had trouble in the past with them but seem to have mastered it now.
 
I have had a problem with a weep from the bleed screw in the filter housing not sealing properly. It should have a copper washer (as should, I think, the clamping bolt for the filter itself). Worth changing both.

On another filter the housing itself was damaged where the bleed screw is. A new housing was only a few £s. Problem sorted.
 
If the unit is in an awkward place consider fitting studs where it is mounted so that you can then bolt the filter to the studs with butterfly nuts or more nuts. Then by having longer hoses you may be able to just undo the nuts & move the filter unit into an easier position to work on. I can get mine over a bucket just alongside the engine bay.

Next point to check is that you do have a CAV ( now made by Delphi) unit & not a clone. I had trouble for years & it drove me mad with leaks until I sussed the problem. I changed it for genuine Delphi & can do the job first time. Futher more it is not necessary to overtighten the bolt. Otherwise it tends to eject the seals.

One other point is that whilst there are loads of different makes of filter- Perkins, New Holland, Davidson etc etc I took a micrometer to the supplier to check & found they varied in diameter by about 2mm. With the clone this made a difference to the sealing & how it seated.
 
There were 2 ways of sealing the centre fixing bolts, the early type ( pre about 1970) was a flat Ali washer. The later type had a chamfer in the filter head hole and was sealed by a rubber 0 ring, then a flat washer. the wrong seal on the wrong head makes life very difficult ! I read this post yesterday evening, got up for a pee about 3 am, got a sudden flash of memory, looked up the manuals, went back to bed satisfied in both ways !
 
An easy and relatively cheap solution is to change the filter head for a 'screw on' type filter. Fitted one to my boat a couple of years ago and it makes filter changing so much easier, and NO leaks! Easy Peasy. Go to SSL diesel parts :--https://www.ssldieselparts.co.uk/filter-assembly-sfa11-p-718.html Filters obtainable from motor factors. Make sure your filter has ½" UNF threads for the in and out pipes and it is a direct replacement. (they also do an equivalent for the later M14 screw threads). Their CAV filters for this head are also reasonable. I'm just about to order this again for a friend who spent hours trying to change the filter, managing to break the stupid nylon drain screw. Only disadvantage is there is no glass bowl so you can't see the fuel/sediment but have never found this a problem - there is a drain screw which does work!
Go for it - you won't regret it, and then scrap or sell the old filter assembly on ebay!
 
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