Thread: TD5 Fuel Cooler O rings...

From what I've read they are not meant to be flat/square in profile - they are intended to be round but as they age they develop the flat profile...and then the leaks.

Urban Panzer's site has a great tutorial with some photos for comparison too.

This task is on my list of to-do's as I bought a couple of Viton BS225s last week. At $7 or so each I hope they seal for longer than 12 months. Were yours the brown coloured Viton ones?

Originally Posted by BIG O

Last year due to coolant dripping from both our TD5 fuel coolers during the night , cold nights that is and never while engine running, I replaced the old square cross section O rings with commonly available normal round profile O rings. Leaks stopped for about 12 months, but has now returned to one of the engines and is dripping again on cold nights. I have just put another new O ring in to replace the one dripping and I can see that the one I put in last year has gone flat on the small area of contact it has to seal, approx 1/2 to 1mm of contact area.

Maybe unrelated but the engine that runs pink OAT is the one dripping???

Anyway, my question is, has any one been able to source the original square cross section O rings that would naturally have a wider contact area and to my knowledge would last at least 8 years before they drip as opposed to 1 year.

BIG O
03 D2 TD5 AUTO
99 D2 TD5 AUTO ACE
94 D1 TDI 3 DOOR (GONE)

Anyway, my question is, has any one been able to source the original square cross section O rings that would naturally have a wider contact area and to my knowledge would last at least 8 years before they drip as opposed to 1 year.

BIG O
03 D2 TD5 AUTO
99 D2 TD5 AUTO ACE
94 D1 TDI 3 DOOR (GONE)
[/QUOTE]

Those O Rings are supposed to be round not square most definitely.

Were yours the brown coloured Viton ones?

No but thanks interesting.

I'm sure the old ones are much squarer in cross section, the Urban Panzer thing also confirms that. They had to have a larger sealing surface than ordinary O rings.

Originally Posted by BIG O

Were yours the brown coloured Viton ones?

No but thanks interesting.

I'm sure the old ones are much squarer in cross section, the Urban Panzer thing also confirms that. They had to have a larger sealing surface than ordinary O rings.

The OLD ones did not have a better sealing area - they have taken a heat induced "set" and have lost their ability to deform and return to their original profile...

Its a very common misunderstanding of how O'rings actually work.. People often think a lump of rubber is just stuffed in and 'jams' up the groove.
Some even put silicone in there too it does nothing but help the seal leak by preventing the correct sealing action.

Factors that will cause it to leak once replaced will be improper surface preparation (cleaning) prior to re-installation or a worn groove in either the 'gland' or housing seal surfaces.

Grease the o'ring and housing before re-fitting, and being its in the coolant area use something like "KY Jelly" or the like as it doesnt affect the fluid...

Be careful to not pinch or cut the o'ring when refitting and not to roll it when fitting onto the end of the gland. If its rolled (spiralled) when put in the groove it will surely leak soon

Material selection for that environment should be at minimum "FPM" or 'Viton' as its commonly known.

The brown ones are made in Taiwan / China.... The American versions are often their natural matt black colour.

For my vehicle - I'm 'snobbish' and only use the American made gear - its tolerances are better on finish and grade... But there is nothing wrong with the other product - I sold / fitted / used millions of them over the years in the industry.

There are X-rings (Quad rings) which have multiple sealing surfaces, but running in the coolers environment will be on the higher edge of NBRs optimum operating range and will take a set and leak again in about the same time frame as the originals... (Not that this is too bad at all)

Originally Posted by bell1975

This task is on my list of to-do's as I bought a couple of Viton BS225s last week. At $7 or so each I hope they seal for longer than 12 months. Were yours the brown coloured Viton ones?

WHAT......

Where did you get them from.....???