New inlet manifold gasket is leaking

[Tractor Dave]

There shouldn't be any gaps.

[k.alle]

Yes I know.
That is what I have been trying to verify that the both flanges are in fact parallel against each other.
Thanks to your info I found out that the inserts were interfering and not making them parallel.

But since the cyl 4 & 5 is till leaking I will try to check the IM flange again with a steel ruler, if I find nothing wrong I will try to inc that flange and bolt it naked to head to see the contact pattern.
This way I might hopefully be able to spot any rises or lows on the head flange surface which could explain these issues.

[Tractor Dave]

Good luck. I personally would be careful using the blue sealant. It might end up in your injectors.

[k.alle]

Thanks.
I hope I can find something off so I know what to correct.
Hopefully the head flange is straight so I don't have to pull the head.


I'm not sure I will use any sealant, I shouldn't need to.
That is mainly for last hail mary if all else fails.

[steve briance]

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.

I definitely don't understand boost leak checks then! I thought they involved putting pressure into the inlet manifold and seeing/listening where the leaks may be, I could see how this would work if an inlet valve was open hence the leak down test idea.

I'm happy my engine sucks rather than blows. Hehe.

[k.alle]

OK, bit of an update.

Got hold of a small 150 mm steel ruler from a good manufacturer instead of the 1500 & 2000 mm steel rulers I got.
Turns out the mani flange was a bit un-true after all in a weird way, even though it was machined / sanded.
So the workshop took it again and this time milled it.
milling.jpg

Now it is verified 100% true.


Bolted the IM back up and it leaks from Cyl 1 - 5, yikes.
I inspected the gasket and noticed it had almost no imprint, this gasket was a thinner paper core version.
What could cause this?

I removed the IM and screwed down all the bolts in all the holes.
Turns out the drilling and threading depth on my 7A head is not uniform at all.
Cyl 5 and a couple of other odd holes are much shallower than the rest making them bottoming out before clamping the gasket.
I took this hint and changed from M8x30 to M8x25 bolts, a bit risky since the protruding thread from the flange was less then "Diameter of thread x 1.5" which is needed to give it full strength.
Unfortunately the lower of cyl 5 threaded hole gave in when torqueing it up so that needs to be heli-coiled next time but fortunately the bolt still gave decent clamping force.

This time the result is much better.
Instead of a big leak and a source of pressure drop it is reduced to more of a creep if that makes sense?
The leak is not audible and can only be spotted with soapy water and let it sit and after some time it will eventually "froth" a little.
No "large" bubbles anymore.

I timed the pressure drop this time and it takes 30+ sec from 1 bar to 0.

Next time IM comes off I think a smidge of sealant + heli coil will cure the last creeping issue, fingers crossed.
I think I can use the car now as it is and adress that small issue at a later date.

Any thoughts?

[Tractor Dave]

Well done! You got there in the end.
My preference would be to measure the depth of each thread hole and cut the individual bolts to size. This way you will not risk pulling the threads as has happened with one hole. make the bolts slightly shorter than the depth and therefore avoid the risk of bottom out.

[k.alle]

Thanks.
A bit disheartening to see it still "creep" a bit but quite an improvement from the starting point nonetheless.

Yes, that is for sure the proper way. Either that or add washers to a longer bolt until a correct protruding lenght is reached.
I should add that all bolt holes with the 30 mm bolts were giving around +-0 clamping force.
Best case would be maybe a few tenths of a mm of clamping force, that's how close ALL 30mm bolts was to bottoming out (with 2 washers!).

Since the Victor Reinz gasket is thicker those did display an imprint given that they are bit thicker than the paper core gaskets but still did not fully compress.
It would seem that it all was a numbers game in the end (+ the dodgy flange).