Regular Bleeding Of Fuel Filter?

[Victory Red]

With all the talk lately of air in the fuel systems of our Dmax's I have a question I couldn't find an answer to in the searches.

Although most of the people stating air in fuel systems have gone to a secondary setup, what about us guys that are running stock?

Should we on occasion open up our bleeder valves on our filters to purge the air out? I personally havent had any fuel issues yet, my lifetime mileage so far is a hair above 17mpg(low 14.3, high 18.6).

Or should I just stay with "if it isn't broke" and stay as is until I do my first filter change?

[Grizz272]

I just broke 10000 miles with my DMAX and no air problem. I broke 20mpg at aboout 8000 miles. and running good.

Grizz :D

[Buck]

Apparently, there is no place in the stock fuel system for air to build up. Rather, the air passes through the system. I've never gotten any air out of the factory bleeder after its primed. Kennedy's design "traps" the air and keeps it from the engine.

[Jelisfc]

Here's a wild thought. Is there any connection between air entrapment and the fact the fuel is heated as it passes through the injector controller? It seems to be a good use of the fuel to cool the controller but potentially at the cost of high fuel temps. In a gasser you want to keep the gasoline cool. I'm don't know about diesel fuel. With the addition of a second, rather large filter maybe the second filter, post oem, allows the fuel to cool and there by releasing air bubbles.

Air seems very elusive. Just a random thought.

[chuntag95]

In theory, it works the other way. If you cool down the fuel, it would be less likely to release air. If you heat it (add energy) then the air or vapor can break free. However, as pressure is reduced, it takes less energy for the air to escape. You might think the additional restriction would be causing the problem, but I have not put my mega on yet and I am seeing bubbles coming out of the OEM filter. Check my Air in fuel testing tread.
Chris

[pinehill]

Jelisfc,

Fuel will hold *more* air when it cools, less when it's hot.

How are things in Stillwater? I kept a boat at Wolf Marine for nearly 20 years.

[chuntag95]

Pinehill, thanks for converting to english. :D

[56Nomad]

Victory Red,

I do not recall reading on TDP about problems with
air in the fuel until JK and others using the Mega Filter
found air being trapped and then needed to bleed it off.

It is my humble opinion that the large Baldwin filter that
is used, somehow is trapping all the air normally found
in our diesel fuel. The OEM Racor fuel filter allows this
normally occurring air and vapors to pass thru the
system. Therefore there is NO need to have to bleed
the factory air bleed..... because you will not find air
there unless you have a air leak in your fuel system.

What I really find strange is that.... not all who have
installed the Mega filter are experiencing this problem.

Also, those who have installed CAT, Stanadyne or Racor
secondary fuel filtration have not reported finding air
being trapped. This is to the best of my recollection.

[Victory Red]

Thanks for all the replies.

Being only a 5 month old truck with just under 7000 miles, I'm still in the 'new truck' phase. I just want to make sure that I don't ignore any service points, or skip over some routine maintenance that goes with diesels(first one I've owned).

[chuntag95]

I would say all of the fluid changes and stuff are higher on the list than the air in the fuel line. This air problem is one the may or may not be a problem long term. The stock system seems to handle it without any problem. The debris in the fuel is another issue all together. The question is what's that doing to those $600 ea injectors. :confused: There is data out there that says you can go a long time without anything happening, but there is also data that says more filtration and less air are better. How you solve (or don't solve) these is like picking your oil. Lots of advice, but it's really a personal choice. When all else fails... Stand on it! :D

[Jelisfc]

Thanx for setting me straight on the air.

Pinehill, Stillwater's great. I've been here for 14 years now.

56Nomad, an interesting test would be to put a 10 micron Baldwin and or a 2 micron CAT on the Mega Filter to see if your theory is right.

[TraceF]

Hello- I have not kept up with the board for the past several weeks but I was forwarded this entire thread by one of the forum members who has stayed in touch with me after my Baldwin 2-micron pre-oem filter install.

I am at 13,300 miles or about 4500 miles on the pre-filter. My GTech is telling me that there is no measurable restriction, the truck is turning 6.3 0-60 times easily on Juice 90.

I have been checking for air every week or so and I have none at the OEM bleeder.

My theory is that the compression fittings may be the problem with the Kennedy system. What is interesting is that not all installations are experiencing air build up. I have installed hundreds and hundreds of similar fittings in lube delivery systems and a fair percentage leak and need to be tweaked.

These fittings are better suited for pressurized systems because a leak is easily detected.

Flared fittings may resolve these problems.

[chuntag95]

TraceF,
I have plenty of air in my lines, but no mega filter installed. As a matter of fact, the only change to my system from original is the two clear hoses. No CAT, Stanadyne, Racor (except OEM) filters or pump have been added. I added the clear lines to the stock system to separate the issue from the mega or any other unit. I have air both before and after my OEM filter and have not been able to get it into the filter to get it out at the bleeder.

This air issue is a design flaw in my opinion. If you look at your OEM filter, it is below the EDU. There is always air in the top of the EDU on my system. There is no way to bleed the dirty side of the system. The bleeder is on the clean side and even then, the outlet is higher than the bleeder. All of the other systems I have seen pictures of, the fittings are on the top so they won't trap air. We all are pushing air through everytime we change the fuel filter. I drained my filter in an attempt to get the air out of the EDU without success.

I have not even starting on those push fittings with a single oring seal. Vibration from just idle will put the seal on the back side under stress and cause a leak. JK reported the return in the tank is next to the inlet and that there is a cup that you can drain starving the system and pulling in air. There has also been information posted on the fuels ability hold air. The number of sources are staggering.

To repair all of the flaws takes a huge amount of work. It is arguable that you need a lift pump to put the system under positive pressure to stop the air from coming in. Due to JKs design with the long nipple, he accidently found a bandaid. We had all assumed the system was air tight, but folks started to get air. First assumption was a self induced leak, but that wasn't the case. Too many people were seeing the same issue. JK, Tommy and others have been working to eliminate each air source with a variety of methods.

I have looked at a different solution. I got the idea from John's system. I have designed an air trap that I want to make the highest point in the system. I also want it to be the last thing the fuel goes through before the engine inlet. It will have a clear sight glass with a vent on top. Every time I fuel, I can bleed any air it has trapped. Same with the mega filter I am installing tomorrow. I would have installed it at the same time, but couldn't get all of the required parts. I even considered installing 2, one before all of the filters and the one just before the engine. That does 2 things, first, it increases the volume of air that can be trapped and second it shows where the air is coming from, but it filters, lines, ect. There are systems that will let the air out and not the fuel, but they are all for positive pressure systems. I would need to use the priming pump to bleed my contraption as well. :rolleyes:

I know that the air is compressed when it goes through the pump. Some is injected and some is returned to the tank. The question is, what damage is that doing to the pump, if any? Time will tell, but it will take the general a while to figure it out and they aren't going to fix all of our trucks out of the kindness of their hearts if it is found to be an issue. If I can spend under 300 bucks to keep the air and the junk from the pump an injectors, I think it is a wise investment. Plus, to be honest, I enjoy the challange of designing a solution and working with others to continuously improve that solution. I even learn new stuff.

I believe A64 found a solution from Racor, but they was a measly $700 plus for it.

Modify on! :D

[a64pilot]

Chris,
Just a thought. These pin sized air bubbles that you see in your clear hose are pin sized under a slight vacuum. How big are they at 30,000 PSI or what ever our system operates at. Isn't it plausable that at such high pressures they are forced back into solution and there may in fact be no air on the high pressure side of our fuel systems? That would explain why most of us seem to experience no symptoms of air in the lines. I'm theorizing that as long as there is a steady stream of tiny bubbles there in fact be no problem. However a problem may be induced by allowing these tiny bubbles to accumulate into a large bubble and then the large bubble being passed on at one time due to attitude changes in the truck, high fuel delivery rates etc.
Just a theory, but here may be something to it.

[FirstDiesel]

The bottom line seems to be that without someplace for the air to settle it passes on through the system. You will not see it at the bleed point for the stock filter. Is it making it through the pump and injectors?? I don't know but I'm not happy it's there and will be waiting to see what solutions become available.

[ 04-28-2003: Message edited by: FirstDiesel ]</p>

[a bear]

a64pilot,
The EDU is also a place where I noticed the tiny bubbles accumulate into larger bubbles. If they stayed pin sized throughout the flow it may be OK.

[chuntag95]

a64,
You might be 100% correct, but I cannot think of a way to check your theory, other than working out the math. I am not going there. Design a simple air trap and bleeder, you bet, but my calculus is way rusty. I saw a BIG slug of air go into my engine, but there was no way around it. Whenever you change your filter, you get a slug of air. She choked it down, but definitly didn't like it. I hope to stop that. Also, if my mega fills up, I should trap in my contraption, instead of letting it go through or have a no start condition. I check oil and fluids at every tank fill, so if I can go that long, I will be in good shape.

[NWDmax]

Chris I'll post in the A.M. and let you know if I have to bleed again.
Keep me in mind with your sight glass project!
Thanks and keep up the good work!
Blake