CAV filter not sealing

[Kelpie]

Changed my engine's CAV filter the other day and I'm really struggling to get the new one to seal. I've tried a different filter just in case, but no luck there either. There were two different O-rings supplied so I've tried swapping them over and even tried doing without them. I've also cranked up the bolt as tight as I dare, but still the diesel weeps out. It's a problem because as idle the engine is drawing in air and this causes it to stall after about ten minutes of idling- made for a very interesting approach to a pontoon the other day!
The weep is coming from the joint between the bottom of the filter and the (metal) bowl. I can't see any deformities, damage, or debris in there.
The filters are Delphi 296. Maybe I should try a different brand?

 

[pvb]

The large O-rings are 2 different sizes; you must fit them in the correct positions.

There's no point trying a different brand of filter.

 

[lpdsn]

Is the seal seated correctly before you go to assemble it?

I usually don't change the seals. They last a lot longer than the frequency of changing the filter.

And as pvb says, can't see that the brand would make any difference. I use all sorts of equivalents because they're cheaper than Delphi and it's never made a difference.

 

[Minchsailor]

I've found that overtightening can displace the seals and make them leak. Ideally spin on the lower bowl handtight.

 

[pvb]

Ideally spin on the lower bowl handtight.

This might confuse! The bowl is generally held static and the top bolt is tightened up.

 

[Stemar]

I've been caught out by PRV's suggestion.

Then a bumpy trip with low fuel stirred up the crap in my tank, so my engine stopped a few yards outside No 4 buoy, coming into Portsmouth. Changing a CAV filter when you're effectively single handed on a lee shore isn't something I was prepared to risk. Sailing in with the wind coming over Fort Blockhouse is, err, interesting. Then a ferry came out .

Shortly after, I went to a car dump and got a couple of spin-on type fuel filters. Some taps and a bit of pipe from ASAP and I now have twin filters. I run on one, and if it blocks, I can switch to the the other in seconds.

 

[Graham376]

I went to a car dump and got a couple of spin-on type fuel filters. Some taps and a bit of pipe from ASAP and I now have twin filters. I run on one, and if it blocks, I can switch to the the other in seconds.

I won't have another CAV filter, they may be OK on land based engines but can be a nightmare afloat. Best to have separate sediment bowl and then a spin on.

 

[lpdsn]

Then a bumpy trip with low fuel stirred up the crap in my tank, so my engine stopped a few yards outside No 4 buoy, coming into Portsmouth. Changing a CAV filter when you're effectively single handed on a lee shore isn't something I was prepared to risk. Sailing in with the wind coming over Fort Blockhouse is, err, interesting. Then a ferry came out .

I went for fitting a vacuum gauge to avoid that scenario. I can now change the filters pre-emptively.

 

[rogerthebodger]

Ideally spin on the lower bowl handtight.

I found that trick when I used to work part time in a garage changing oil and filters on old A and B series BMC engines. I would nip up the center bolt then spin the filter bowl to seat the seal then just tighten a little more to ensure leek free filter.

I do the same with my CAV filters but only ever change then when in dock as I have duel filters that can be changed over with a turn of 2 valves.

 

[pvb]

I wouldn't ever turn the bowl on a CAV filter to tighten it - unlike spin-on filters, the O-ring seal on the bowl is loose and is only supported on the outside edge and could easily be displaced by turning the bowl.

 

[rogerthebodger]

The bowl seal is supported on the inside by the filter its self so if nipped up then twisted the square seal will not go anywhere.

In fact twisting the bowl would help to centralise and seat the seal correctly.

 

[Kelpie]

Ah what a great piece of design it is! The two o-rings are virtually identical to each other. Can anyone remember which one goes at the top and which one at the bottom? And should I be having to wrestle them into place?? I'm assuming that both rings go onto the new filter, rather than trying to fit them to the housing and bowl?

They do have one redeeming feature- I can buy ten CAV filters for the cost of a single Racor.

 

[pvb]

Ah what a great piece of design it is! The two o-rings are virtually identical to each other. Can anyone remember which one goes at the top and which one at the bottom? And should I be having to wrestle them into place?? I'm assuming that both rings go onto the new filter, rather than trying to fit them to the housing and bowl?

They do have one redeeming feature- I can buy ten CAV filters for the cost of a single Racor.

The rings fit into the housing and the bowl, you can't fit them on the filter element. The housing has a recessed groove into which the larger ring fits - be sure to remove the old one first! The metal bowl has a depression into which the smaller O-ring fits. Fit the top ring, press the new filter element on to the spigot (there's another O-ring here which holds it on). Put the second big O-ring in the metal bowl, offer the bowl up to the filter element, centralise it, hold it in place and screw the bolt in.

 

[PaulRainbow]

Ah what a great piece of design it is! The two o-rings are virtually identical to each other. Can anyone remember which one goes at the top and which one at the bottom? And should I be having to wrestle them into place?? I'm assuming that both rings go onto the new filter, rather than trying to fit them to the housing and bowl?

They do have one redeeming feature- I can buy ten CAV filters for the cost of a single Racor.

Did you remove the old seals from the housing top and the bowl ? There is also a seal on the spigot that goes into the filter and another (small) one that fits the bolt.

You fit the two new seals to the housing top and the bowl, not to the filter. Do not over tighten, just over hand tight is correct.

 

[lpdsn]

And should I be having to wrestle them into place?? I'm assuming that both rings go onto the new filter, rather than trying to fit them to the housing and bowl?

They do have one redeeming feature- I can buy ten CAV filters for the cost of a single Racor.

You should have to wrestle them into place but you definitely need to make sure they're properly seated. There is a knack to that comes with time. For example the o-ring that sits on the glass bowl should be fitted within the rim at the very top of the bowl. It won't do that on its own so you have to manipulate it into place. It should also be wetted with diesel for a better seal but I guess that'll have happened by now.

The other one should be fitted within the rim of the top housing. Again, it just doesn't fall into place on its own, but you can manipulate it in with your fingers. As PaulRainbow said, the old one often stays in place. If you haven't removed it you may as well leave it and just push the filter up into it. Again if using new one better if it is wetted with diesel.

 

[pvb]

For example the o-ring that sits on the glass bowl should be fitted within the rim at the very top of the bowl.

I fear this is further confusing the OP - he doesn't have a glass bowl.

 

[lpdsn]

I fear this is further confusing the OP - he doesn't have a glass bowl.

OK. Just re-read the thread. You're correct. I'm sure the OP can substitute glass in my post for metal without too much mental anguish.

 

[ctva]

Ah what a great piece of design it is! The two o-rings are virtually identical to each other. Can anyone remember which one goes at the top and which one at the bottom? And should I be having to wrestle them into place?? I'm assuming that both rings go onto the new filter, rather than trying to fit them to the housing and bowl?

They do have one redeeming feature- I can buy ten CAV filters for the cost of a single Racor.

From memory, three weeks ago, the large one is on top and sits in the underside recess of the housing, the smaller on should fit the indent on the filter it’s self. Remember to put a bit of diesel on the o rings to lubricate them.

 

[pvb]

Remember to put a bit of diesel on the o rings to lubricate them.

I'm confused by this advice. This isn't a spin-on filter, so there's no need to lubricate the seals.

 

[RichardS]

I'm confused by this advice. This isn't a spin-on filter, so there's no need to lubricate the seals.

I always lubricate all "rubber" seals and o-rings with silicon grease, or similar, whatever their application just to help them bed-in evenly and help ensure a good seal. I'm not sure if this is standard practice but it has always worked for me.

Richard