Fuel filter conspiracy theorist

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Fuel filter conspiracy theorist

Postby piglet » Mon Jul 17, 2017 2:24 pm

I may (am) be getting grumpy & cynical BUT:
I read a lot of guff from motor technicians insisting that diesel fuel filters should be replaced whenever there is an R in the month.

My little understanding of filter technology is that filters get clogged with crap and will finally reach the point where demand exceeds supply and the filter just can't pass enough fluid to perform the task at hand.
This is a real life scenario when running plant on dirty fuel from rusty barrels.
However in the case of a domestic cars that are filled from garage forcourts this would be several years and tens of thousands of miles.

Or do filters really become less able to remove small particles with age?
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Re: Fuel filter conspiracy theorist

Postby Doggy » Mon Jul 17, 2017 5:42 pm

I have run 3 hdi's for about 100k each and have never noticed any benefit from changing a fuel filter.
The first one got changed twice after about 20k each time, then some tw*t tightened it up so much I could never undo it.
My two 2.2's were changed roughly every 2 years / 40k miles, never had an issue.
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Re: Fuel filter conspiracy theorist

Postby jasper5 » Mon Jul 17, 2017 10:17 pm

It's fine if you don't want to replace your fuel filter, as long as you accept the blame for any problems that may occur.

I've been in the car repair business a long time and seen the consequences of not changing filters...or oil for that matter.
Being so stingy as to spend just a few quid on a fuel filter or tin of oil is crazy!
I've rebuilt and replaced engines that have cost hundreds of pounds when the cost could have been saved by spending Just a measly few quid on a filter or tin of oil...what is half an hour's work and about less than a tenner to give you peace of mind and better performance from the engine?

Just one thing though...fuel filters these days, especially the sealed unit ones, don't need to be replaced for upwards of 75,000 miles, depending on the car in question, but these are designed to last that long.
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Re: Fuel filter conspiracy theorist

Postby Welly » Tue Jul 18, 2017 7:19 am

The fuel filter on my S40 Volvo (petrol) is a 'lifetime' filter somehow? they are not a service item and very few people know where the filter is? I believe it's near the tank but every time I asked about it I always got the "don't need it" response :?
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Re: Fuel filter conspiracy theorist

Postby PeterN » Tue Jul 18, 2017 9:52 am

I had to change the filter at 20k on my CX diesels otherwise they would literally stop, but that was a few years ago when not nearly so much diesel was being used, I think the fuel now must be cleaner and possibly the filters better.

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Re: Fuel filter conspiracy theorist

Postby piglet » Tue Jul 18, 2017 10:31 am

jasper5 wrote:It's fine if you don't want to replace your fuel filter, as long as you accept the blame for any problems that may occur.
seen the consequences of not changing filters...or oil for that matter.
Being so stingy as to spend just a few quid on a fuel filter or tin of oil is crazy!
.


Oil is going to degrade, and the oil filter contains a fair bit of old oil anyway AND they are a about a fiver.
So regular oil & filter is a no-brainer.

But in your experience, what happens to a modern common rail if you leave the fuel filter 'too' long?
What damage to the pump/injectors is caused by a partially clogged fuel filter?

MANN filter for 1.8Tdci is almost 20 quid, and they are prone to air locking when changed.
Plus, everytime you break open the system you expose your pump & injectors to all the crap in the engine bay.
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Re: Fuel filter conspiracy theorist

Postby jasper5 » Tue Jul 18, 2017 1:42 pm

I've never left a fuel filter change too long, but the simple answer is that due to the close tolerances that the injectors and pumps work off, any contamination can possibly cause damage or failure of pumps and/or injectors.

When you replace the filter on the 1.8 TDCi always have the car facing downhill when bleeding, but better still use a vacuum pump or an old mechanical petrol pump operated by hand to pump out the air.

When you have the top off the filter housing clean it out with brake cleaner and an air line if you have one available.
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Re: Fuel filter conspiracy theorist

Postby piglet » Tue Jul 18, 2017 3:26 pm

jasper5 wrote: close tolerances that the injectors and pumps work off, any contamination can possibly cause damage or failure of pumps and/or injectors.
When you replace the filter on the 1.8 TDCi always have the car facing downhill when bleeding


Good tip about parking downhill thanks. I learned the hard way to pre-fill the new filter, nightmare! Why can't Fords fit primer bulbs.

Now the thing about tolerances and extreme high pressures is all valid but my original question still stands.
ie. Does an old fuel filter allow more damaging particles through? Or do they just slowly clog?

And all this cleaning, air-lining, bleeding, pre-filling etc. etc. is giving opertunity for ingress that couldn't happen if the damned thing was left sealed.
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Re: Fuel filter conspiracy theorist

Postby Welly » Wed Jul 19, 2017 7:46 am

It sounds like you want to leave the filter alone, which is fine, but the warnings are there. Changing an eventually clogged filter will lead to even more care needed removing the thing and cleaning everything up like jasper says. I've seen an air filter 'let go' once on a diesel and it literally had a huge hole in it where the air just burst through the path of least resistance. I don't think fuel filters do this, they just block up and lead to fuel starvation/faults.

Lots of members on here have changed their own filters (usually including a new housing is best) without any issues. Key thing is keep everything clean and don't let any contamination into the filter bowl and piping.
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Re: Fuel filter conspiracy theorist

Postby stevewalsh » Wed Jul 19, 2017 8:00 am

I have been in the engine trade for 42 years, from Motorcycles, Marine, trucks, cars, agricultural and industrial, and out of all of them modern cars and bikes very rarely have dirty fuel filters, Probably down to better fuels and dispensing equipment, not many old garages around with ancient fuel tanks and pumps. If you do your own servicing, you get to know what the state of the filters are when you change them, I have 2 HDI 406's and dont bother looking in the fuel filter anymore, 1 is just coming up to 248000 miles, I changed the lift pump recently and checked the inside of the tank whilst it was out, it was immaculate inside

If it was a marine or HGV or industrial engine I would not hesitate to fit a new one, due to the conditions they are refuelled in

Just my opimion
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Re: Fuel filter conspiracy theorist

Postby Welly » Wed Jul 19, 2017 4:05 pm

That's a good shout steve, especially when folk go on about having 'crap' in the bottom of your fuel tank - that's just old bollocks.

I thought diesel filters were more prone to blocking than petrol's but again that may be outdated opinion creeping in. That's interesting sharing your experience of what you've found, thanks.
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Re: Fuel filter conspiracy theorist

Postby jasper5 » Wed Jul 19, 2017 7:29 pm

I've been in the car repair business for 47 years :)

I can't help thinking of something someone said to me when my mother died at 56 of a smoking related disease....my dad smoked 40 Capstan Full Strength a day until he was 85 and didn't have any problem....which one was the exception?
Would you ignore the warning or play it safe?
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Re: Fuel filter conspiracy theorist

Postby piglet » Wed Jul 19, 2017 10:29 pm

I know what you mean, millions has been spent on medical research to establish the well proven health risks of tobacco, and people still ignore it.

However no-one is that bothered about what our high pressure pumps will do after 150,000 miles, so there is no research and there is no data.
Car manufacturers have to specify a maintenance routine that will protect their products reputation for reliability and it has to work across all continents where those products are sold.
So
Our fuel filter replacement period is set taking into account all the Pugs running around the Sahara filling up from oil drums in sand storms.
But if you have an anally retentive owner who won't even put supermarket Diesel in his Hdi or Tdci then is he doing more harm than good by regularly opening up a hermetically sealed system housed in a filthy environment to change a filter that is not even slightly clogged..
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Re: Fuel filter conspiracy theorist

Postby dirtydirtydiesel » Sun Jul 30, 2017 7:27 am

Just my two penith worth :wink: ,
Another reason for changing the fuel filter at every service.
To check for the in-tank lift pump dieing & filling the fuel system with tiny metal particals :roll:
At least on 406's anyhow as these had a reputation for the lift pump dieing & if left unchecked
would lead to high pressure fuel pump damage & injector damage.
If you've seen the price of these parts, I'll stick to changing the fuel filter every 12k or so thank you very much

I can't speak about the Ford's tdci as I've never owned one but I believe that the injectors have to be coded
at great expence, so I know what I would do :)

Welly,
Lot's of car's have sealed for life gearboxes & diff's, just depends on what you expect the life to be I guess :lol:
Just ask any independent BMW / Mercedes-Benz specialist if they would recommend changing the oils at anything
over 75k.
They will ask you if you want a expensive gearbox rebuild / replacement :roll:
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Re: Fuel filter conspiracy theorist

Postby Bailes1992 » Sun Jul 30, 2017 7:39 am

My Focus is supposed to have a sealed for life gearbox. I spent £30 on some oil and changed it at 50k and it made a huge difference to the gear change, I think these things creep up so slowly you never notice how bad things get.

Trying to convince my Father to spend £500 and get his 8 speed ZF box serviced on his BMW now it's 5 years old and on 115k but he's not budging because BMW say it's 'sealed for life' and why would they lie? Lets totally ignore that ZF themselves say the box should be serviced every 100,000kms.
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