New inlet manifold gasket is leaking

[Tractor Dave]

I would remove them otherwise you might damage the manifold. Are they metal or the ceramic type? If you don't want to remove the underside, you could mark each one with marker pen where it's proud, remove and file where marked in a vice. Don't crush them mind!

[k.alle]

OK, I understand. That sounds reasonable.

They are OEM (from Audi Tradition) so I assumed plastic but maybe they are ceramic?
If so I understand why a knife wouldnt suffice.

I have a few in my stash so I could experiment on those first.

[Tractor Dave]

A knife will work if they are plastic but it will be difficult to get a nice clean finish. If they are plastic you could sand them using sand paper or emery. Clean them really well before you put them back. Only take off what you need otherwise the injectors might not seat properly.

[k.alle]

Excellent, I really hope this works.
This has been driving me insane.
Thank you Tractor Dave.

[Tractor Dave]

Excellent, I really hope this works.
This has been driving me insane.
Thank you Tractor Dave.

Good luck then. Hope it works

[k.alle]

It helped for sure but it is still not air tight.
Cyl 4 & 5 (closest to throttle body) is still creeping a bit, didn't check leakage at "bottom" of the flange.
When pressure testing it goes from 1 bar to 0,5 bar in 10-20 sec (guesstimation) compared to 4-5 sec before.

Starting to lose hope and Im out of ideas (and gaskets).
Should I just use it as is or gather some strength and pull the IM yet another time?

One thing that I noticed was that Cyl 5 & maybe 4 top bolts were a bit harder to wind in.
Maybe this is affecting somehow or not relevant at all.
Dont know if it was dirty threads, gasket cathing on the bolt or some other lovely phenomenon.


Bubbles:
bubbles.jpg

Trimmed down insert:
trimmed.jpg

Trimmed down under gasket:

trimmed gasket.jpg

[Tractor Dave]

Did you put a straight edge across to check its true? Another possible cause could be a hairline crack. You can get a special dye to check.

[k.alle]

I don't have a special tool for checking the straightness so I used the back of a Mitutoyo caliper measuring tool.
Looked over the flange with main focus in the areas of inserts but it seemed true to me.

[Tractor Dave]

I don't have a special tool for checking the straightness so I used the back of a Mitutoyo caliper measuring tool.
Looked over the flange with main focus in the areas of inserts but it seemed true to me.

Do you have a steel ruler? You need to check across its entire length ideally.

[k.alle]

I do but not sure of the straightness tolerance on it, I can try using it though.

I would be surprised and disappointed if the IM flange is not true after being machined so recently.

[steve briance]

This is a bit of a head scratcher!

It seems like the inserts being trimmed has helped out as you have seen an improvement, and your pictures look like your trimming is spot on.

Are you able to reach the torque figures for the head bolts? It really should clamp up and work from what you are saying so, if you are able to torque properly, maybe there is another problem...

Dave suggests a crack test, you don't hear much about manifolds cracking or heads apart from around the spark plugs but it might be worth considering.

Excuse my lack of knowledge but does testing for boost leaks also test the seal between inlet and exhaust valves in their seats on piston tdc? Perhaps you are losing pressure here? My car is normally aspirated so have never done boost leak checking.

A leak down test done by feeding compressed air through the sparkplug hole can show up leaks in the head. Listen for air leaking into either the inlet or exhaust and leaks past the rings show up as noise of air leaking into the crank case.

It was surprisingly clear where the noise comes from when I did it on my car, it showed up bore wear.

[steve briance]

Just re read your thread and saw you've reached the torque so ignore that bit of my reply.

At least a leak down test doesn't need the manifold to come off again if you decide to have a go!

[Tractor Dave]

I don't think a leak down test will help here as it only tests cylinder pressure. A boost leak test will show up IM leaks. You say the IM flange has been machined but what is the actual IM face like.
On a standard set up you might get away with a very minor leak here but on your set up you will be running higher boost? 2 bar? Remember that IM normally runs at vacuum.

[Tractor Dave]

The only sealant I would use together with the gasket would be Loctite 515. Paint on thin on both surfaces and assemble. Leave overnight to set. It will only work If your mating surfaces are true and crack free mind.

[k.alle]

Thanks for the response guys!

Steve:
Yes the issue did improve when I trimmed them so I'm staring to feel that I should not give up just yet.
Appreciate the leak down test suggestion, although in this case I do have a visible leak in between the IM and head.
I'll keep it in mind for future problems though.

I haven't measured each and every bolt hole in the head flange so maybe I should try M8x25 next time to rule out any issues with any odd bolt bottoming out before proper compression is reached.


Dave:
The IM flange face is very smooth after machining, I can see that a sand paper belt of some kind was used but I can not feel it.
They took off ~0.15mm across that face to get it flat across. This ofcourse made the inserts protrude ~0.15 mm more adding to that issue.
I measured 1 of them before trimming and that one was sticking out 0.8 mm.

I'm running 1.9 bar boost.
Even though under vacuum the idle valve has to fight this leak since it is not in complete control of air supply to the engine so ideally I'd like to get it tight.

I'll keep that crack test in mind as a last resort.

I have Hylomar Blue incoming since I in desperation googled about sealers.
That one seems to be well liked and resistant to gasoline and hopefully E85, but it isn't a gap filler.