Dave_Bratley

Hi

I am new to the forum and also new to owning a 928 - buying my 1985 S2 Automatic back in June of this year.

The exhaust has a leak and makes a blowing noise on start up and under load. It reduces slightly after warming up fully - but I think it is generally getting worse (louder).

The blow is from the nearside / passenger side (please note right hand drive - UK car).

I had a look underneath and felt along the manifold to see if I could find any holes or corrosion - I found that the rear bolt on the manifold literally came off in my hand.

So here is my plan: I have purchased a right angled attachment for my drill and two left handed drill bits. I thought I'd start with a small pilot hole and then try to expand the hole. I am hoping that the drilling action may loosen the bolt and let me get it out and if not then I'll try a stud extractor.

Todays steps were to get the car up and onto axle stands and I've soaked the manifold bolts in WD40.

My next step is to soak the bolts again tomorrow! and also double check the blow is actually coming from the suspect area...

Then I was going to start with the bolts attaching to the exhaust pipe flange before trying to remove the ones from the cylinder head end.

Now the problem and what I need advice on...

1. Is this approach remotely likely to succeed?
2. If you have or know someone who has removed the manifold are there any lessons I can take on board before starting?

Whilst spraying WD40 all over the exhaust manifold and my face all afternoon - my biggest concern is the space...

I think that I'm lucky it's the last stud that has gone - as that looks like the only one I could possibly get the right angled drill bit onto.
Some of the other studs look pretty inaccessible and I'm not sure if I can get to them with the engine in the car...

I'm not working at the moment - so that's one reason I am not taking it to my friendly neighbourhood Porsche specialist and why I'm having a go myself... he's a great guy and a real enthusiast but I am on a low budget having recently been made redundant. However, that does mean I've got plenty of time!!

I'm restricted on space so want to avoid pulling the engine out if I can.

P.S. just in case this helps orientate anyone who has a left hand drive vehicle - from the underneath I am talking about the side with the oil filter.

Anyway - so far I've not caused any damage and just preparing and taking a look and letting the WD40 soak in... so perfect time to reflect on any lessons from anyone experienced in this.

Many thanks in advance,

Dave

tv

Do you believe that 1 loose bolt is allowing a leak from the space between the block and manifold from the rear-most exhaust valve? I would think it would still be snug from all the others.

Screwing with these bolts is something I passed on when I did have my engine out. The heat induced galling that I was sure existed was something I did not want to deal with. I left well enough alone. I can not imagine a more frustrating job than trying to deal with them while in place.

I have an S2 also and all I can say to help is your plan sounds good for extracting the bolt if it is so corroded - similar situation mention in a brake caliper thread in the last day or so. Expect the threads to come out also. Try to stay calm and wear a full face mask to protect eyes.

Hilton

Hi Dave, welcome to Rennlist.

Before you start this heinous job - check that the blow isn't from one of the exhaust test tubes (not sure if S2's had them? my ex-UK 87's both did despite being non-cat cars).

The exhaust test tubes rust out and leave a hole in the manifold just about where you're describing - they're attached with an M14 compression fitting, and a thin-walled steel tube coming out of it that goes up to somewhere around the airbox.

The M14 fitting is hidden just at the wrong angle to be able to see it - on the top side, just in front of the flange where the exhaust pipes bolt onto the manifold.

If S2's don't have the test pipes, then plan to pull the engine to do this job - and while its out replace the engine mounts, pan gasket, and intake/cam seals (all relatively cheap - and will probably fix a bunch of oil and vacuum leaks).

Mrmerlin

I agree that trying to repair the broken stud in place will be hard.
BUT if you can remove all of the other bolts holding the manifold in place and remove it from the engine,
then it will be quite possible to weld a nut onto the broken stud and simply unscrew it.
I would leave drilling the broken stud as a last resort with the engine out of the car, if your not straight with the drill then you can possibly damage the head and then have to pull the engine out anyway.
Also use a chemical called PB blaster not WD40 the WD isnt as good for loosening the bolts as the PB is.
Also look at the EX manifold,
as Hilton said ,
there may be a leak in another part of it or the manifold may be cracked and the broken bolt could be left alone

danglerb

Also try some Wurth Rostoff.

Dave_Bratley

Bad news I am afraid... despite hoping it wasn't this broken stud causing the blow - I've double checked it this morning and can feel hot gas escaping around the joint. Putting a rag over it muffled the noise so I am pretty certain.

Mrmerlin - I have the broken end to the stud with the nut on it - it literally came off in my hand on my first inspection a few weeks ago - and from the look of it the break is flush with the head and end of the thread - so too early to be sure, but I suspect there won't be enough of the stud to weld onto. In fact it might be partially below the level of the head from the look of the stud.

I'm begiining to think the only way to do this is with the engine out - which is beyond my resources.

Thanks for the suggestions and advice so far.

Dave

John Speake

Where are you in UK, Dave ?

Dave_Bratley

John - I live close to Stansted Airport and near M11 junction.

Regards,

Dave

Mrmerlin

Dave the stud can be welded .
how you do it is to take a paire of vice grips and a nut ,
Hold the nut over the stud, then you weld the nut to the stud from the inside using a mig welder,
build up the weld till the nut is filled,
this operation works about 90% of the time drain the block first so it will stay hot when the welding is done

John Speake

OK, quite close to me.

The problem is that you don't want to spend money in a garage to keep costs down. But this seemingly simple issue is going to cost some cash, either for you to buy tools or for you to employ someone.

Suggest you join 928uk.org mail list, some good advice there and maybe willing hands to help BTDT...

Dave_Bratley

Thanks John - I have a small garage it's just not practical for me to pull the engine and yes I am going to have to invest so I need to spend wisely. Clearly getting a professional to do it increases the chances of it getting done right first time.

I'll get some PB Blaster and whilst that is soaking in I'll have a think about options - I have your address details now and might be in contact shortly.


Thanks for your suggestion Mrmerlin I've got access to a Mig welder - the beauty of your suggestion is that even if the weld breaks then I'm no worse off. But the lack of space up there is troubling me I'm just not sure I can get the manifold off... unless I can train my nine year son to do it - my hands are just to big!

I'm glad I asked anyway - as the suggestions and comments have helped me prepare and think about the options.

Mrmerlin

soak your nuts in PB for a few days they should come off

SteveG

I've heard that 50/50 acetone + ATF is an excellent penetrating solution.

Dave_Bratley

Just a quick update - feel free to offer any advice... keen to learn.

So I managed to get the rest of the manifold bolts and the manifold itself off without breaking anything!
It was slow work and I took my time...

The broken stud was a few millimetres below the level of the casing so I decided not to opt for trying to weld a nut on.

Instead I have gone for the drilling approach - I got a couple of left hand drill bits, a small cordless drill and a right angle attachment - it just about fits.

I drilled a small pilot hole first of all and used child's plastercine to take a mould/impression and check that I was drilling straight.

I tried using a centre punch to loosen the stud and get it turning - but it didn't move - there is so little room I just couldn't get the right angle or enough force in the hammer I think.

I've now gone to a slightly larger drill bit and again repeating the use of the plastercine to make sure I'm drilling straight - I think it's pretty close to the limit but still within the stud at the moment.

I tried a stud extractor tool but it didn't want to budge and I didn't want to try too hard.

So I am going to keep going with drilling a little deeper and soaking in penetrating oil and then try the extractor again.

I couldn't find PB Blaster here in the UK or Kroil so have just tried various penetrating fluids I could get locally.

So my plan is drill a millimetre os so, soak in penetrating oil, try the stud extractor - repeat...

John Speake

Sounds like you're making good dsteady progress Dave. You are right to be careful with the extractor as if that breaks it is pretty much impossible to drill it out.

I assume you are using LH drill bits still ?