Talbot
Well-Known Member
I have been having trouble sealing my CAV diesel fuel filter/separator to prevent air leaks. What type do forum members use, and how do you prevent the entry of air?
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Diesel filter/water separator
- Thread starter Talbot
- Start date
paulrossall
Well-Known Member
I have a CAV filter. When you get a new filter element you also get a number of rubber washers. There should be one that fits top and bottom of the filter from memory. There might also be a small seal which fits the bleed valve. Make sure old washers/seals have been removed completely and new ones are sitting properly. There is little to go wrong with these filters, it must be something you are doing wrong fitting it. Make sure there are no fractures in the filter body. If necessary take filter body off fixing so you can inspect it easily. Good Luck. Paul
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johnsomerhausen
Well-Known Member
I also have a CAV filter/water separator and I fully agree with Paul's recommendations. I have recenttly changed the two bolts holding the unit so that , after closing the fuel supply, I can take it completely off to change the filter because it is not easily accessible (in the after part of the engine compartment) and it's quite acrobatic to install the O-rings perfectly in that position. Much easier to do it on the saloon table...
john
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john
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dickh
Well-Known Member
I also have the CAV filter/seperator and I must be honest, I've never replaced the sealing ring in the housing, and to date have never had any leaking problem(in 6 years). I'm about to winterise the engine this weekend, so perhaps I should remove the housing completely and do a proper job.
<hr width=100% size=1>dickh
I'd rather be sailing...
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<hr width=100% size=1>dickh
I'd rather be sailing...
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Talbot
Well-Known Member
I replaced all the washers the first time, with a new diesel filter - still leaking. I then bought a completely new filter separator (in case the problem was the glass or the metal) and yet another new filter, and assembled it in the cabin before fitting to ensure that I got a good fit, and to make sure I got it right! I used ptfe tape on all the fittings, and made a good job of tightening them. On starting I had no leaks, but as soon as I opened throttle, the air started to poor in. I over tightened the bolt secuuring the glass/filter/body together and it did improve somewhat, but still air was getting in. I use a piece of transparent hose temporarily either side of the filter to again prove to myself that the problem was in the filter. I am now at the end of my capability and seeking solution - cause this is really p*ssing me off.
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longjohnsilver
Well-Known Member
Maybe the problem lies in what you say you're doing. Overtightening can distort the O rings to such an extent that they will then let air in, you should really just pinch them tight. It's always tempting to keep on tightening but from bitter experience this can and does cause problems.
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chriscallender
Well-Known Member
Two possibilites I can think of (from experience!!!)
- its possible to swap the top sealing ring that goes between the filter and the top of the unit, with the one at the bottom that seals the filter to the bowl. They are similar sizes but different by a few mm. And if you replace the filter and rings but copy the old setup to the new then you'll make the same mistake when you put it all back together again. My boat ran like this for 6 months, so it is possible!
- The fuel hoses are usually connected to the CAV filter unit by a couple of threaded ports. (?UNF?UNC? thread on old ones, M14 on new ones). It could be that air gets in via these connectors. I can't recall how these connectors are supposed to be sealed but it could be worth putting some sealant/PTFE on the threads if its designed to be sealed by the threads . Perhaps there is some washer or seal in this port that needs replaced, I can't remember how it works.
I'm replacing the fuel hose and CAV filter on my boat over the weekend - I'm swapping the CAV for one with a priming pump in it, as in my case the CAV is above the height of the diesel in the tank and its really difficult to bleed. The current hose is crappy drinking water hose or something similar and the whole lot leaks air in like you wouldn't believe. So I've got all my ISO 7840 hose, connectors etc and I'm hoping I will get rid of all the air leaks.
My experience so far is that air will always get in through the tiniest and most improbable places! So far this has only stopped the engine running once, but thats once too often for me ... it happened when I tried to go astern, approaching a pontoon at about 5kts! Just as well the hull is an inch thick!
Chris
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- its possible to swap the top sealing ring that goes between the filter and the top of the unit, with the one at the bottom that seals the filter to the bowl. They are similar sizes but different by a few mm. And if you replace the filter and rings but copy the old setup to the new then you'll make the same mistake when you put it all back together again. My boat ran like this for 6 months, so it is possible!
- The fuel hoses are usually connected to the CAV filter unit by a couple of threaded ports. (?UNF?UNC? thread on old ones, M14 on new ones). It could be that air gets in via these connectors. I can't recall how these connectors are supposed to be sealed but it could be worth putting some sealant/PTFE on the threads if its designed to be sealed by the threads . Perhaps there is some washer or seal in this port that needs replaced, I can't remember how it works.
I'm replacing the fuel hose and CAV filter on my boat over the weekend - I'm swapping the CAV for one with a priming pump in it, as in my case the CAV is above the height of the diesel in the tank and its really difficult to bleed. The current hose is crappy drinking water hose or something similar and the whole lot leaks air in like you wouldn't believe. So I've got all my ISO 7840 hose, connectors etc and I'm hoping I will get rid of all the air leaks.
My experience so far is that air will always get in through the tiniest and most improbable places! So far this has only stopped the engine running once, but thats once too often for me ... it happened when I tried to go astern, approaching a pontoon at about 5kts! Just as well the hull is an inch thick!
Chris
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burgundyben
Well-Known Member
praps you have a blockage some where between filter and tank, maybe pick up pipe and the resistance is making it suck air in?
Its the problem I had.
<hr width=100% size=1>Sod the Healey - I think I'll buy an E-Type.
Its the problem I had.
<hr width=100% size=1>Sod the Healey - I think I'll buy an E-Type.
Talbot
Well-Known Member
tank is only 6 months old. fuel was all put through a smarttech funnel (=filter) before going into tank. distance tank to filter is 1.5m and from filter to fuel pump abt 1.5m. Fuel was conditioned with fuel set not long before I started having problems. Will try to back flush the pipe with an air blast. failing that some C4 may solve the problem.
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Talbot
Well-Known Member
Does your new filter also have a water separator on it, and if so what make is it and price as this would enable me to get rid of one potential week link.
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pvb
Well-Known Member
The tiny little seal...
The tiny little seal which you get with a new filter element isn't for the bleed screw, it's to seal the central bolt which holds the thing together. The tiny O-ring seal goes on the bolt, below the washer, and seats into a conical depression in the top housing. If this isn't replaced, air could easily enter.
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The tiny little seal which you get with a new filter element isn't for the bleed screw, it's to seal the central bolt which holds the thing together. The tiny O-ring seal goes on the bolt, below the washer, and seats into a conical depression in the top housing. If this isn't replaced, air could easily enter.
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paulrossall
Well-Known Member
Re: The tiny little seal...
pvb
I stand corrected. I now remember I did not like the look of the seal on the bleed valve and I did replace it but the small washer which comes with the new filter is as you say for the cenral spindle.
I remain convinced the problem is with the re-assembly and it is very unlikely to be a fault with the filter. I would not expect overtightning to cause a problem in this case, more likely problem is a seal missing. IMHO. Paul
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pvb
I stand corrected. I now remember I did not like the look of the seal on the bleed valve and I did replace it but the small washer which comes with the new filter is as you say for the cenral spindle.
I remain convinced the problem is with the re-assembly and it is very unlikely to be a fault with the filter. I would not expect overtightning to cause a problem in this case, more likely problem is a seal missing. IMHO. Paul
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saturn
Active Member
maybe this will help,i have posted this before but,do not use ptfe tape on diesel.most fittings on fuel filters are parallel thread with a copper washer, or compression.
on parallel type renew copper washer and do not use any sealant on threads if it leaks then renew it.
compression fittings,if they leak they will have to be replaced.
taper fittings are best sealed with a hydraulic type sealer, i use the loctite brand obtained from any engineering supplies shop.
the rubber seals should be supplied with a new filter and be changed,lubricate with clean engine oil before fitting.when tightening, do up hand tight(by holding bolt head with spanner and turning by hand the bottom part of filter) and then use spanner on fixing bolt,don't overtighten at first you can nip up after bleeding if you think it is needed.
on difficult to access filters i have sometimes found it easier to fit new filter cartridge and seals by removing the filter from the engine to do the job.
if your engine is gravity fed then its obvious where the leak is but if your fuel is lifted from below then some temporary made up clear plastic piped fittings will help you track down air leaks.
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on parallel type renew copper washer and do not use any sealant on threads if it leaks then renew it.
compression fittings,if they leak they will have to be replaced.
taper fittings are best sealed with a hydraulic type sealer, i use the loctite brand obtained from any engineering supplies shop.
the rubber seals should be supplied with a new filter and be changed,lubricate with clean engine oil before fitting.when tightening, do up hand tight(by holding bolt head with spanner and turning by hand the bottom part of filter) and then use spanner on fixing bolt,don't overtighten at first you can nip up after bleeding if you think it is needed.
on difficult to access filters i have sometimes found it easier to fit new filter cartridge and seals by removing the filter from the engine to do the job.
if your engine is gravity fed then its obvious where the leak is but if your fuel is lifted from below then some temporary made up clear plastic piped fittings will help you track down air leaks.
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HaraldS
Well-Known Member
Have two of those and change filters once a year. Had a leak once and it was due to mixing up the two large rubber rings, like somebody already pointed out.
When I fitted an Algea-X in addition I had to take a fitting off the CAV unit and found that I could only get it tight gain by using fresh copper rings. I didn't use any PFTE tape on any of the fitting, just the regular copper rings, and I think that is also the case for the bleed screw.
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When I fitted an Algea-X in addition I had to take a fitting off the CAV unit and found that I could only get it tight gain by using fresh copper rings. I didn't use any PFTE tape on any of the fitting, just the regular copper rings, and I think that is also the case for the bleed screw.
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Talbot
Well-Known Member
Thanks - I have done all this. I have proved to my satisfaction that the leak is from the separator by using transparent tubing. I have not only re-newed the seals, but actually the whole of the water separator filter, and have tightened it up in the saloon before installing to ensure that it was seated correctly, yet still the bl**dy thing is leaking. I think I can see some ingress through the seal between the glass and the new filter, and thus renewed rubber and filter without solving the problem. The filter I am using is the standard CAV with water seperator. I suppose I could upgrade to one of these expensive purealotor ones, but this is really bugging me. I have sealed these up perfectly before and it has run without problem since the start of the season.
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david_bagshaw
Well-Known Member
Did you change / adjust /disturb the pipe fittings on the lid ?
unfortunately it is V easy to crack the lid by overtightening the pipe fittings, & hence the air ingress.
been there & done it & had to pay for the replacement out of my pocket money, when I was 14.
<hr width=100% size=1>David
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unfortunately it is V easy to crack the lid by overtightening the pipe fittings, & hence the air ingress.
been there & done it & had to pay for the replacement out of my pocket money, when I was 14.
<hr width=100% size=1>David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>
G
Guest
Guest
Having considered all the posts I believe the problem is with the bellnose connections on the end of your copper pipes. The sealing of the threads does nothing as it is the fit of the bellnose end held against the end of the fitting that creates the seal. It's the equivalent of an olive in plumbing. These ends are probably now too distorted. I don't think this type of connection is good for constant dismantle/remantle. You will have to get two new lengths of copper with new bell ends made up. The trick will then be to never undo these fittings just remove the fuel hose off the copper pipes.
Incidently, the Vetus water separator (WS180) comes with connection nipples for 8mm hose. I thing these connection nipples are the way to go. The doen side is that the Vetus replacement cartridges are about £22.
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Incidently, the Vetus water separator (WS180) comes with connection nipples for 8mm hose. I thing these connection nipples are the way to go. The doen side is that the Vetus replacement cartridges are about £22.
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Heckler
Well-Known Member
have worked on these all my life and they are almost bullet proof, not trying to wind you up and i bet you are totally pissed off but are you sure all the old rings are out of the grooves before you put new in? sometinmes previous owners put 2 in and when you take one out you still have 2 in, other wise have you tightened too much and distorted housing or filter?
stu
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stu
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Talbot
Well-Known Member
Thanks, - these seemed ok but the leak would appear to be between the glass and the filter - have tried more new gaskets and have locktite sealed all fittings and still it leaks. My engineer has taken the seperator to his garage for further tests/replacement so hopefully by next weekend all will be well
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