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Massive Air Leak

Hanaldo

By Hanaldo,
in Engines & Forced Induction

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Mitcho_7 Mentor

Mitcho_7

Posted
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Yeh I paid. I don't think I had any choice. What I think happened and what I can prove happened are two very different things. I wouldn't have had a foot to stand on if I refused to pay.

Yeh, they kinda had you up against a wall. I feel for you man, you have had such bad luck with your car.

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Hanaldo Grand Master

Hanaldo

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man that casting is rough on that manifold... but never the less some heavy handed spanner work obviously caused it.

i find it strange that its fine when warm but once hot it reads 0 psi compression... usually takes a hole or a valve stuck open to actually get NO compression.

That's exactly what my tuner thinks is happening... That the valve is sticking open. But why would it be temperature related? Surely there's either fragments in there or there isn't?

Hanaldo Grand Master

Hanaldo

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The work and the tune where done at 2 different workshops werent they?

How did they stop the leak then? Metal putty?

I did the original work of installing the plenum, fuel rail, injectors, etc. after doing the injectors I obviously wasn't able to start the car, so I towed it to the workshop a bit over a month ago expecting that all it would need was a tune. Then the problems developed and the workshop did all work from there until I picked it up today.

They pulled the whole manifold off and replaced it.

GTScotT Grand Master

GTScotT

Posted
Posted

my original theory when i heard about this is that a valve is burnt and still seats ok in its place.

dont forget that while the motor is running the valves can rotate, just like the rings can.

so my theory goes; the valve seats OK in one spot, but rotates a little and jams open. could definitely be related to a LITTLE bit of debris being ingested AND revving to redline the moment its started would quite easily do some damage.

Hanaldo Grand Master

Hanaldo

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my original theory when i heard about this is that a valve is burnt and still seats ok in its place.

dont forget that while the motor is running the valves can rotate, just like the rings can.

so my theory goes; the valve seats OK in one spot, but rotates a little and jams open. could definitely be related to a LITTLE bit of debris being ingested AND revving to redline the moment its started would quite easily do some damage.

Possible. But if that were the case, why would it only come good after the motor has been switched off and allowed to cool down?

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

It could be something totally different. I have found when listening to someones diagnosis alot of time can be spent chasing what they think is the issue.

I think it would be good to try and get the issue to happen on the road ( if it happens) and then check urself if it is a compression issue or a simple ignition issue etc

Hanaldo Grand Master

Hanaldo

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It could be something totally different. I have found when listening to someones diagnosis alot of time can be spent chasing what they think is the issue.

I think it would be good to try and get the issue to happen on the road ( if it happens) and then check urself if it is a compression issue or a simple ignition issue etc

I do agree, and I would actually really like to see for myself what is going on. Except I can't, because he hasn't tuned the thing above 5000rpm. He set a 5000rpm limiter, which I could remove if I wanted to, but with no tune in the thing I really don't want to be smashing around under full load trying to get it to drop a cylinder.

Hanaldo Grand Master

Hanaldo

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How can he not have tuned it above 5000? So the issue is happening during low load steady state tuning?

If he has tuned up to 5000 then the rest will be there.

No, the issue is happening under full load. He didn't manage to do the full load tune because of the issue, so he has tuned it where it is ok and set the rev limiter to where he has tuned to. If that makes sense?

75coupe Grand Master

75coupe

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I cant see how they justify the cost when the full tune really hasnt been done.

Do they expect you to come back to complere the task?

Or are they saying once the 'leak' has been fixed its ready to drive?

Hanaldo Grand Master

Hanaldo

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I cant see how they justify the cost when the full tune really hasnt been done.

Do they expect you to come back to complere the task?

Or are they saying once the 'leak' has been fixed its ready to drive?

I don't know. The majority of the cost was for "diagnosing running problems and replacing intake manifold". There was a fair bit of GST as well. There is no leak anymore, it's driving fine. The issue now is that it loses compression on one cylinder under load. It won't be ready to drive once I've fixed that, because it isn't tuned under full load.

Hanaldo Grand Master

Hanaldo

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Did you drill the lower manifold for the studs to push through origionally? Or did you somehow manage to screw the studs through both manifolds with an air gap between the 2?

Didn't drill them. Screwed them in from the top, then put the plenum on and threaded them back up. There was definitely no gap, I did the other studs first.

If I was to do it again, I would drill out the holes.

Hanaldo Grand Master

Hanaldo

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Well there's your air leak. Tightening the the nuts with the stud threaded into both sides would not of clamped the manifolds together.

I uh... I think you should read the last couple of pages of the thread :mellow:

GTScotT Grand Master

GTScotT

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Well there's your air leak. Tightening the the nuts with the stud threaded into both sides would not of clamped the manifolds together.

I uh... I think you should read the last couple of pages of the thread :mellow:

TL:DR strikes again

ARTZ Grand Master

ARTZ

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Martin, when you tightened the bolts on the plenum how did you do it.

Did you start in the middle and work your way around tightening them like you would headbolts.

Or did you just tighten one end right up tight then do the other end.

This could of quite easily slightly twisted the manifold to some extent, then starting it up and applying some heat and vibration has cracked it pretty much instantly.. I would say the shop has just taken it off to see if it is leaking and thats when they spotted it..

Hanaldo Grand Master

Hanaldo

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Martin, when you tightened the bolts on the plenum how did you do it.

Did you start in the middle and work your way around tightening them like you would headbolts.

Or did you just tighten one end right up tight then do the other end.

This could of quite easily slightly twisted the manifold to some extent, then starting it up and applying some heat and vibration has cracked it pretty much instantly.. I would say the shop has just taken it off to see if it is leaking and thats when they spotted it..

I did them up as you said, starting from the middle and going around. Didn't tighten them up straight away either, I would wind each stud in a few threads, then do the next one and so on until I had them all done up. Took me a good hour to hour and a half to do.

75coupe Grand Master

75coupe

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did you use a torque wrench of sorts when you did up the bolts?

Im thinking if the sealant used was uneven it could of created pressure on that part.

if there was more sealant near cylinder 2,3,4 then that would create a lump or see-saw that cylinder 1 bolt (the flange part that broke) had more pressure on it.

could of been like bolting it up to a warped flange.

I dont think its clear who or what has broken that part.

Still damn annoying that they charged for the tune considering it couldnt be complete, I guess its still time spent working on it though.

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