how many engine hours before CAV filter change?

KellysEye said:
>Not necessarily, the crud isn't visible, as it's inside the filter.

From experience if the filter is getting crud in it then there will be some in the bowl because the diesel surrounds the filter and some crud will drop in the bowl before being taken out by the filter.
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I'm fairly sure that a properly-plumbed CAV filter has the glass bowl after the filter element. So you won't see any crud in the bowl unless the filter is in such a bad state that it's passing through. Daft, but true.

Pete
 
>I'm fairly sure that a properly-plumbed CAV filter has the glass bowl after the filter element. So you won't see any crud in the bowl unless the filter is in such a bad state that it's passing through. Daft, but true.

I just looked at pictures of CAV filters and they have clear bowls under the filter so you would see dirty fuel, Racors have the same. As you said to have a glass bowl after the filter would be daft or worse.
 
KellysEye said:
I just looked at pictures of CAV filters and they have clear bowls under the filter so you would see dirty fuel
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I know they have clear bowls under the filter. But if I'm right (I'm not 100% certain, but I'm pretty sure) then you won't see dirty fuel because you're looking at it after it's been through the filter.

Pete
 
I have a CAV filter on my desk and Pete is right the fuel pass down through the element then into the glass bowl then up the sealed center of the filter and to the outlet port of the ports.

That is following the arrows on the connection ports on the top of the filter.

It also looks like it could be piped in reverse so the full passed down the center into the glass bowl then up through the filter element and out
 
KellysEye said:
From experience if the filter is getting crud in it then there will be some in the bowl because the diesel surrounds the filter and some crud will drop in the bowl before being taken out by the filter.
Click to expand...

As prv has pointed out, a properly-plumbed CAV filter passes the fuel through the filter first, it then goes into the glass bowl, and exits up the pipe through the centre of the filter. All the crud is retained in the filter. The purpose of plumbing it this way is to help with agglomeration of tiny water particles - when passing through the filter medium, they are encouraged to form droplets which will settle out in the glass bowl.
 
davidej said:
I am absolutely not an expert but 1/2 atm seems an awful lot to me - 7 1/2 psi

i would have thought 2-3 psi would indicate a well blocked filter
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No, a 1 atm gauge is fine. I have a Racor vacuum gauge, and its full deflection is 100kPa (1 atm, about 15psi). The "warning" red sector starts at around 35kPa, say 5psi.

instruments.jpg
 
pvb said:
No, a 1 atm gauge is fine. I have a Racor vacuum gauge, and its full deflection is 100kPa (1 atm, about 15psi). The "warning" red sector starts at around 35kPa, say 5psi.

instruments.jpg
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Presumably the gauge reads more suction the higher you rev the motor?
I would think that a sudden change in suction would tell you that you have taken on dirty fuel.
Personally, I changed the CAV filter fairly often as they were cheap, and the yanmar less often.
If the yanmar filter only sees clean fuel it should last a long time, and every time you open it there is a slight risk of dirt getting in.
As other have said, knowing that the tank is clean saves a lot of grief.
Filters are cheap, failures are expensive.
But if a filter does not last say 200 hrs motoring without clogging, there must be a risk it will clog if you get rough weather shaking up your tanks.
 
PVB, Nice picture from the HR.

The important reading on the gauge is that it is rising and above 1/4 to 1/3. Absolute figure is not importsnt.
You change the filter when it is convenient, not at an absolute value.
I changed my filters from 296 CAV to the spin-on 496?
these are twice the height and each has a drain on it. Yes they are twice the price in quantity but for twice the height/size and the ease of changing a spin-on compared with a CV they are a bargain.
I fitted the new filter heads when I installed a dual filter changeOver system.
 
>I know they have clear bowls under the filter. But if I'm right (I'm not 100% certain, but I'm pretty sure) then you won't see dirty fuel because you're looking at it after it's been through the filter.

In the Caribbean all the fuel is dirty and many pumps also have water in the diesel. It reached the point that we only filled containers and stopped filling the tank when we saw the dirt, we had a filter that took out the water. What happened was you could clearly see the dirty diesel in three filter bowls two on the engine and one on the generater. Obviously we had the tank cleaned but you could never get all the dirt out.
 
KellysEye said:
>I know they have clear bowls under the filter. But if I'm right (I'm not 100% certain, but I'm pretty sure) then you won't see dirty fuel because you're looking at it after it's been through the filter.

In the Caribbean all the fuel is dirty and many pumps also have water in the diesel. It reached the point that we only filled containers and stopped filling the tank when we saw the dirt, we had a filter that took out the water. What happened was you could clearly see the dirty diesel in three filter bowls two on the engine and one on the generater. Obviously we had the tank cleaned but you could never get all the dirt out.
Click to expand...

Were they CAV filters? Racor ones have the bowl on the dirty side of the filter as you'd expect.

I have seen dirt in a CAV filter bowl, but that was when the filter was so dirty that the engine cut out and presumably some was leaking through the overloaded filter.

Pete
 
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