exhaust nuts backing off???

[sethyboy85]

thought my pyrometer was leaking, saw some smoke come from around turbo area the other night when it was dark out thought nothing off it... today in daylight after oil change i start it up and notice that when revved smoke comes from both sides of the exhaust manifold... that would explain the extra clacky sound the motor has been making when on the gas, thought it was just the pryo leaking.

tightend the one side up (drivers) side started back up no smoke out of that side only the other but it was too hot to bother to try and tighten so tomorrow morning I will go back out and tighten that side..

question why would it do this?

[fspGTD]

I can think of a few things which could cause this...

1.  When these nuts were last torqued, was a torque wrench used and them all brought up to the full 18 ft-lbs specification?

2.  Were any of these nuts old and re-used, so their locking mechanisms were worn out?  The safest recommendation is to replace with new, sourcing them from the dealer.  The genuine VW TD exhaust manifold nuts are specialty parts, IE not your average locking nut.  They have a 12mm wrenching surface size and have a "cutout" near their outer end leaving a separated ring of material that does the locking.  When new the ring is peened tight with the main nut body.  I have found when used, the ring is no longer tight with the nut body, so doesn't lock very well.  But you can peen it back with a hammer to restore its locking qualities.  Safest option is of course brand new nuts specifically for VW TD application purchased from VW dealer.

3.  Do you have washers behind the nuts?  When original, the VW TDs had special, extra-thick washers behind the nuts.  Some sort of washers behind the nuts are important because the manifold expands and contracts with heat cycles independently form the head.  The washers allow the manifold to slip and slide without it "catching" (and possibly rotating) on a nut.

[jackbombay]

They have a 12mm wrenching surface size and have a "cutout" near their outer end leaving a separated ring of material that does the locking.

  The dealer in Portland sold me ones that were the typical locking nut where it is dented inward on 3 sides, not the ones with the cut you speak of. My 2.0 TD came with a few of them, but they had little locking action left. I wonder if the cut style nuts are no longer used or if the dealer I bought them from provided me with the wrong nuts, I'd bet on the latter.

[fspGTD]

I got a whole bag of the nuts you speak of with the 13mm wrenching surfaces, very wide shoulders, locking "dents" in the end, and mine also have a copper coating, looking very similar to this:


If you might use them for TD exhaust manifold hardware, I would recommend making sure that the clamping surface on the manifold is wide enough to allow the wider shoulder to fit properly, and also I would try and still run some kind of smooth stainless or hardened steel washers underneath them.  I would also not re-use the "crimp" lock nuts after they have been heat cycled.  You can test the locking devices by trying to thread the used nuts by hand onto a bolt.  Then compare how much torque is required to run them over the threads with new ones.

FYI, I found on a visual inspection of an '01 Golf TDI that it has the exact same exhaust manifold nuts and washers as VW put on their first A1 1.6lTDs.  ETKA confirmed that the part numbers matched.  The part numbers for the TD-specific exhaust manifold hardware are N 900 955 01 for the thick TD-specific washers, and N 902 002 01 for the TD-specific "shouldered self-locking" hex nuts.  Given how recently they were used by VW I would guess they are still available, but I am not sure.

[sethyboy85]

hmm, thanks for the responses. I am enjoying all 4 cyclinders exhaust gasses spooling the turbo now... lol

[veeman]

Thanks for the info Jake... I've seen/used those split exhaust manifold nuts on a few engines.  It seems like they don't like to back off very well (as designed) and end up pulling the stud out as well when you go to remove them.

Good info about the washers on the EM.  Some of the Audi turbo 5 cyl engines had the same washers for the same reasons.  Do you know if the NA diesel engines used those washers as well?  When I put together the 1.5, I thought about putting them on, but didn't.

[sethyboy85]

3 of my studs broke off today... so I just ordered some off of the net and hopefully they come mon/tuesday so I don't have to drive the gas guzzler too much... going 300 miles for a few $ is alot better than 250 miles and $25....
sheesh