tandem fuelpump calling materials specialists

have been trying to cure the tandem pump outer cover leak, after various attempts -gaskets and varoius "goo's" including Indian head shelac, the best (so far) has been the use of rubber sheet 1.5mm thick which did not even weep but then gave up in a big way after six weeks, I used nitrile rubber which the seller did say he couldn't guarrantee--can some one give me any help with regard to a suitable type of rubber or similar( fuelproof) to withstand diesel with bio content we have here

Cheshire Cat said:

have been trying to cure the tandem pump outer cover leak, after various attempts -gaskets and varoius "goo's" including Indian head shelac, the best (so far) has been the use of rubber sheet 1.5mm thick which did not even weep but then gave up in a big way after six weeks, I used nitrile rubber which the seller did say he couldn't guarrantee--can some one give me any help with regard to a suitable type of rubber or similar( fuelproof) to withstand diesel with bio content we have here

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Try Viton, much better than Nitrile although more expensive. You may also want to find some Viton sheeting that is dimensionally stabilized with embedded threads so that it resists extruding outward from the internal pressure.

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Mine is leaking and I was hoping for an easy task, but I better listen to the proper material to use before I touch it.

I second the reccomendation for using Viton. Viton is good for relatively high temperatures & is chemically resistant to most everything including fuels, acids & caustics. You will find that it is a bit expensive however.

josh8loop said:

You may also want to find some Viton sheeting that is dimensionally stabilized with embedded threads so that it resists extruding outward from the internal pressure.

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ah-ha just what I was thinking but there again I have seen the streching on the nitrile that came out!!! I decided to make a solid sheet as opposed to a gasket with a hole in the middle-working on the principle that it would halve the "escape area" unlike other more conventional methods it didn't even sweat or weep until it let go and then it looked horendous with all the stretching almost being in reverse as if the pressure was on the other (cover plate side) won't bore you with any more, but thanks for the info VITON it is, must be cheaper than a pump @ $450?

You could use a graphite sheet. It's solid but flexible and makes excellent gaskets for high heat and is one of the chemically most resistant materials.

I had thought graphite sheet would be brittle but will take a look at availability--- I have some viton coming but not the reinforced type---yet approx £9 for a piece which would make 3 hope I don't need them-- thanks for the help chaps --will post results if successful but it will take time

I've found a thin sheet of Viton the maintenance people stock at work, maybe 1mm.

@Cheshire: have you sourced and installed yours?

This gasket is just containing fuel in the pump, right? Mine is weeping ever so slowly but I am concerned about the small coolant hose that runs below it. Although the hose is sheathed, I am worried it could still burst

Why not use Yamabond 4 or something like that? It's used to seal two cycle engine crankcases together since they don't use a gasket. If it can hold the pressure from my 500cc dirt bike engine, I would be surprised if it wouldn't work for the tandem pump cover. It's also impervious to gasoline and oil.

pedroYUL said:

I've found a thin sheet of Viton the maintenance people stock at work, maybe 1mm.

@Cheshire: have you sourced and installed yours?

This gasket is just containing fuel in the pump, right? Mine is weeping ever so slowly but I am concerned about the small coolant hose that runs below it. Although the hose is sheathed, I am worried it could still burst

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sorry only just seen these posts--thanks for the offer but I sourced some 1mm viton close by @£9 enough to make 3 gaskets-- the fuel is at about 1=bar and gets quite hot which I am thinking is what does the damage so far I am on the second "solid" gasket, Nitrile, which was fitted after no1 let go, it has just matched no1 on time but has only been on short runs so I will stick with it 'till it goes then try the viton- the supplier told me that nitrile ain't what it used to be as most is chinese sourced and there is less nitrile in the mix to keep costs down- I am loath to try liquid sealants to keep them out of the very clean fuel area will keep posting as we go cheers Nic

Cheshire Cat said:

sorry only just seen these posts--thanks for the offer but I sourced some 1mm viton close by @£9 enough to make 3 gaskets-- the fuel is at about 1=bar and gets quite hot which I am thinking is what does the damage so far I am on the second "solid" gasket, Nitrile, which was fitted after no1 let go, it has just matched no1 on time but has only been on short runs so I will stick with it 'till it goes then try the viton- the supplier told me that nitrile ain't what it used to be as most is chinese sourced and there is less nitrile in the mix to keep costs down- I am loath to try liquid sealants to keep them out of the very clean fuel area will keep posting as we go cheers Nic

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Nic,

Great job on the progress and thanks for keeping us up to date on the process of finding the solution to the issue! The Viton sheet you have will most likely be of a higher durometer than the Nitrile and should resist extrusion better than the Nitrile too. Hopefully your 1mm Viton gasket material matched the original gasket thickness so it doesn't change any internal pump dimensions. Would love to see some photos of this beast!

Interesting:

http://www.google.com/imgres?imgurl=http://i568.photobucket.com/albums/ss128/Stevenlee02a4/tandem.jpg&imgrefurl=http://uk-audis.net/topic/3118-tandem-pump/&usg=__RPsf1IFFmsOzJ2TzVWIJOlCqk90=&h=433&w=468&sz=40&hl=en&start=8&zoom=1&tbnid=_GRSragIjU2KjM:&tbnh=118&tbnw=128&ei=ADTIUJqBCJHo9gSggIHADg&prev=/search%3Fq%3DVW%2Bdiesel%2Btandem%2Bpump%26um%3D1%26hl%3Den%26safe%3Dactive%26sa%3DN%26gbv%3D2%26tbm%3Disch&um=1&itbs=1


Potential replacement parts??...

http://www.google.com/imgres?imgurl...n&safe=active&sa=N&gbv=2&tbm=isch&um=1&itbs=1




..

@josh8loop: The question is which kind of tandem pump?
The LuK one (mine) is a vane pump as far as I know because I haven't opened it yet.
The Bosch one is a gear pump. Both were factory installed, some of the LuK recalled (for leaking) and I am sure they have different outer lids.

I looked once at a French website with a similar gasket kit and I wrote to them about a kit for LuK pumps but got no response. For sure they have a way of fixing this in Europe, we just have to find the right connection with people.

just had these two posts thro' I was just thinking a couple of days ago it was time for an update despite tempting fate--------the replacement Nitrile gasket is still in place 4 months + it was fitted roadside in a rush but I think perhaps not tightened up as mutch as the first one whilst not doing huge milage the car is used almost every day, the viton replacement is still in the boot with it's fitting kit(allen key& 10mm spanner) p.s you prob'ly know by now the outer cover /gasket does not impinge on the working parts of the pump----doing it again/next time I would "break" the sharp inner edge of the machined pump gasket face before fitting

And I forgot there also a Pierburg pump

I just replaced my LUK tandem pump, which was leaking, with a Pierburg one. No more leaks.

When I replaced my LUK tandem pump, a Bosch came from the dealer (I bought on-line). I had a leak, but I think it was the mounting gasket, so technically I did not have to replace it, but I am glad I did. I disassembled the LUK, and yes, it is a vane-type pump.

--Nate

update--- nitrile number 2 has just let go --luckily just on start up at home- now for the viton

update the Viton has just started to leak not huge milage but lots of start and stops=heat cycles so that wasn't too bad will take a look for reinforced viton

cheers for that I'll take a look at Loctite I'd tried other types of similar and "Indian Head" shellac but with no joy-----keep warm up there cheers Nic p..s. how long since was that?

Cheshire Cat said:

update the Viton has just started to leak not huge milage but lots of start and stops=heat cycles so that wasn't too bad will take a look for reinforced viton

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NEXT INSTALLMENT well the next one has just started to weep--at least it didn't let go in a rush but it was getting some beanz at the time (unusually approx 4k revs for approx 1 mile) so it's lasted approx 2 years--I will nip it up to see if it stops before fitting another never did find any reinforced stuff may have another look

UPDATE at the risk of tempting fate I did nip it up approx 1/2 turn back to 10Nm and so far so good