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Old April 19th, 2010, 11:48   #1
That Guy
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Default Extreme Cold - To tee or not to tee

Hi guys....

I looked around here for a definitive answer to this question but I can't find one...so here it is:

For those of us who live in climates where the temperature can get very cold...say -30ish...is it worth keeping the Thermostatic Tee on the fuel filter or not?
(It also gets very hot here in the summer so it's kind of a catch 22.)


Pro removal Comments:
- Cold fuel is easier for the IP to pump as warm fuel is thinner
- The Tee is a known weak link. They can crack or the seals go bad...which lets air into the line and also possibly leaks fuel
- Properly treated fuel does away with the need for the Tee
- If the fuel is going to freeze it will do so in the lines as well as anywhere else. If no fuel is flowing the Tee won't help anyway

Con removal Comments:
- It was put there for a reason by engineers who know better than us
- Other diesel engines also use them (CAT for example)... so again it must be there for a good reason.
- It warms the fuel in the filter in cold weather, thereby eliminating gelling or gelled fuel from the filter which would reduce fuel flow



So if you live in a cold climate is it worth getting rid of the Tee?

And do the new TDI's still have the Tee? Or are they doing something different?

Thanks guys
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Old April 19th, 2010, 12:49   #2
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I would keep it on, but I don't know why you say this T is a weak link. If it is mishandled and cracked then yes then it does become a weak link, but not the engineers fault. I don't know if the newer TDI's have a tee.
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Old April 19th, 2010, 14:48   #3
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Quote:
Originally Posted by That Guy
Pro removal Comments:
- Cold fuel is easier for the IP to pump as warm fuel is thinner
Lets try a gedanken experiment. You have a really neat little pump capable of handling a wiiiide range of fluid viscosities. You have to pump a gallon of STP Bunker-C and a gallon of gasoline - which takes more energy, which is easier?
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Old April 19th, 2010, 16:00   #4
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http://forums.tdiclub.com/showthread.php?t=262613

Dig around on this thread. There is discussion about the need or utility of the T fitting relative to fuel gelling.
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Old April 19th, 2010, 16:22   #5
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It's not the "T" so much as the filters, IMO. I've had to try multiple filters before the "T" would seal properly before. Complaints of air bubbles and it's the first thing I check. New O-Rings or not, some filters just want to leak, others not so much. I think the machining techniques (stamping) and other factors lead to inconsistencies in the tolerances of the T "socket" on the filter. I don't imagine the mfg's treat it as rocket science. JMHO, as usual.
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Old April 20th, 2010, 07:37   #6
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The points I listed above were basically ones I found while looking into this topic.

The microglass fuel filter is something that I am strongly considering...and they make some good points on that related thread. But I'm prone to over thinking things before I jump.
Since I found a wide array of thoughts on the Tee and since there was no existing thread that specifically talked about just it, I made this one to address it.

FlyTDI Guy....interesting observation about the fuel filter. Might be another reason to switch to something like the microglass filter and do away with the Tee.
Poor fueling problems can be such a pita...and not likely good for the IP either.



So basically what I'm seeing so far (including info from other sources)...

- non-microglass fuel filter = keep the Tee (for colder climates)
- microglass fuel filter = no need for the Tee (any climate)

In either case this assumes the use of winterized fuel and/or the addition of an anti-gel fuel additive for colder weather.

I'm thinking that one of those microglass filters is going to be making it's way onto my list for upgrades. I can always switch back if there are issues.
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Old April 20th, 2010, 09:31   #7
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I would argue that if you use the microglass filter, you have a greater need for the T. Gelling fuel will hit first in the fuel filter, as it is there that the passages through which fuel flows are the smallest. Gelled fuel plugs small holes and passages with wax crystals, ergo the smaller the holes, the more easily or more quickly clouded fuel will stop flowing. Using the T would warm the fuel, and allow the filter to flow at colder temperatures.
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Old April 20th, 2010, 10:11   #8
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It wasn't stated directly, but cold fuel (higher viscosity) is HARDER to pump.
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Old April 20th, 2010, 12:58   #9
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(Powerd Hound).....that's what I was thinking....but they claim to have tested this in cold climates (Alaska & Canada) with no issues.
But what you say makes perfect sense.

Now that I think of it.....it may be possible to continue to use the Tee with one of these microglass filters. It probably doesn't have to be plugged right into the top of the filter to work. Wouldn't it be possible to just connect the bottom of the Tee to a short hose that connects to the return line on the new filter?
My delema may be solved.


(UFO)...But then why are people putting fuel coolers on their vehicles? Plus someone here said that cold fuel was easier to pump...can't remember who, but I did see that. Just asking as I don't know either way.
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Old April 20th, 2010, 15:17   #10
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Quote:
Originally Posted by That Guy
(UFO)...But then why are people putting fuel coolers on their vehicles? Plus someone here said that cold fuel was easier to pump...can't remember who, but I did see that. Just asking as I don't know either way.
Circulating fuel through the injection pump gets hot, and diesel fuel supposedly can get too hot to lubricate the pump effectively. They are also sold as performance enhancers, I don't know about that. But we are talking about keeping the fuel above the gel point (-20F) vs. fuel getting too hot to lubricate (+180F). Large spread.
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Old April 21st, 2010, 07:25   #11
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Makes sense and also seems like another reason to keep the Tee.

So....Getting warmed fuel to the filter early improves fuel flow by preventing blockage at the filter from gelling and improving the pump's ability to pump the fuel. Thereby allowing the engine to run normally and warm up faster than the alternative. And putting less wear on the IP.

I still like the idea of the microglass filter due to the filtration and now the fact that the Tee's "direct" connection to the OEM filters (which can be problematic for various reasons) can be removed.

Using this filter and a hose to attach the Tee to it would seem to be the best solution. A hose is flexible and can make a better connection to the Tee (assuming I can get a good connection with a clamp) than the solid metal hole that it usually fits into in the normal filters. Thereby eliminating the current possibility of a sealing problem between the filter and the O-rings on the Tee.

Hmmm....also use of a clear hose between the Tee and the return line on these microglass filters might be helpfull too as you might be able to see if the Tee is working as it should....assuming you can see if the fuel is flowing or not back to the filter.

Thanks guys! Whatever I do I'm keeping the Tee.
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Old April 21st, 2010, 13:08   #12
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'98 Beetles don't use a tee, I don't remember hearing a lot about them gelling more than newer cars. I bought a fuel filter (from a dealer, of course) and they gave me one for an early Beetle. I ended up running it for most of a winter, and while it doesn't get as cold here as Alberta, I had no issues. The Nicktane filter is in my future and I don't have any fears of using it.
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Old April 21st, 2010, 13:24   #13
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Seems to me that if a person were pro-actively dosing their fuel, the "T" becomes less necessary... to ensure starts anyways. As far as warm-up time, etc. the "T" probably has value, especially in colder climates.
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Old April 21st, 2010, 13:54   #14
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is there a vaccum that closes the T once it gets warm. i remember reading something like that about the '10 that I have. I would assume something like that exists on yours
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Old April 21st, 2010, 14:32   #15
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It's not vacuum. Must be a temp sensitive spring or similar.
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