Hi, please can anyone help or advise me ?.
I have a Vauxhall Vectra 2.0 16v and have noticed that one of the studs that secures the exhaust manifold to the head, has sheard off.
The net result being that I can hear a very slight blow under acceleration.
The Stud in question is the lower left most stud which is opposite the power steering reservoir. I can also see that the remainder of the stud does not stand proud of the head !!.
I have heard that this is a fairly common vauxhall problem but can this be fixed simply ?.
My feeling is that it will need to be drilled and tapped but the stud is not really that accessable and I am dreading a seriously big bill to dismantle loads to get to it.
Has anyone experienced this problem and can ofer any advice
Kind regards,
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The Subject says that a bolt has sheared but the body of the posting says it is a stud. A bolt comes with a nut (otherwise it's a screw) so I am going to assume that it is a stud we are talking about.
Several ways to remove a sheared stud have been discussed here before but I don't know which would solve your situation. I will describe how and why studs are fitted in the hope that it might give you a better idea of the problem you are facing.
Studs are usually fitted into the head with a very low torque. For instance, an M8 stud will be tightened to perhaps 15 Nm whereas the nut fitted to the stud will typically be tightened to 22 Nm. This could mean that the stud will easily come undone, perhaps by tapping it round with a sharp chisel held at an angle.
On the other hand, studs may be used where the hole goes through into a water space and they are often coated with a sealing/locking compound like Loctite. In this case, they can be fairly difficult to undo unless heated to a high enough temperature to soften the Loctite, about 200 degrees C.
Another time when studs are used is in aluminium (like the Vauxhall head) where removal and replacement of a screw could cause thread wear. Again, Loctite might be used to make sure that the stud doesn't come out when the nut is removed, or the stud can have an oversize thread on the end that goes into the head.
Finally, studs may be used to help locate an item while it is being fitted, whereas using screws means holding the item in exactly the right position. However, this is more for heavy components like truck gearboxes. Studs are used only where there is a real need because the cost of making and fitting a stud & nut is much higher than for a screw.
If you can get a nut against the top of the stud, which I assume you can as it was once fitted with a nut, welding the nut onto the stud through the hole in the nut should help heat the stud so that any Loctite will be softened and will also allow a spanner to be used to undo the stud.
Not very easy, I know, unless you have access to welding gear. And you need to watch that not too much heat is applied otherwise there could be damage to the alloy of the head. It really needs just a quick dab with a stick welder or MIG welder.
I'm not sure that this is a common problem with Vauxhalls in particular; it is not unusual to find it on other makes. I think that the expansion of the manifold when it gets hot puts a side force on the studs and eventually snaps them, especially the outer ones where the movement is greatest.
On some engines, the expansion and contraction makes the nuts work loose and fall off. This used to happen on the Triumph 2000 range but I overcame this on mine by making sure that the holes in the front and rear flanges were large enough to allow movement and then using locknuts as these don't have to be tightened right up. In fact I used standard nuts but squashed the outer ends in a vice so that they would start easily but then lock. I tightened them only enough to provide a good gas seal because very tight nuts on the Triumphs could cause the exhaust manifold to crack when it expanded and contracted.
Sorry to ramble on, but hopefully there's something here to help!
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Dizzy,
Many thanks for your help on this one. You are quite right, it is a stud I am talking about.
I was tempted by the welding option but the stud has sheared off just below the surface of the cylinder head (1-2mm) and it would be very tricky to weld a nut on without damaging the head. I have thought of just gradually building up weld on top of the sheared stud so that it stands proud, then weld a nut to it. Again worried about the heat damaging the cylinder head. Also, I only have a Mig welder and think that this may damage some electrical components aswell...sound like such a whimp.
I was hoping that there was such a thing as a drill which can be used in confined spaces (drills at 90 degrees). In this case it could be tapped.
Many thanks for your help
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90 degree drills are fairly common. Not cheap but cheaper than a new head. This is the sort of job that pays for a specialist tool the first time you use it. Or hire one, or get a garage/ engineering shop to drill it? Or what about one of those cheap flexible drill attachments from the cheap tool shops? Only needs to work once to pay for itself.
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Shep,
Not sure if this thread (excuse pun) is any good to you or not? It refers to a sheared thread ona motorbike, but *might* give you some ideas how to approach removing yours.
www.honestjohn.co.uk/forum/post/index.htm?t=5788
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This is all good stuff.....thanks for all your help guys.
If there is such a thing as a means of drilling in a confined space, then surely there must be some means of getting the stud out. Im sure I have heard of something like a stud extractor which works by drilling a smaller bore hole down the length of the stud and tapping this with a reverse thread and using a reverse threaded extractor which effectively unscrews the stud as you screw in the extractor.
Is this me just watching too much telly or is this actually some sort of standard garage practice ??
Cheers,
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Shep, I won't make any more pedantic comments about bolts versus studs!
The stud extractors you mentioned are commonly called Easi-outs. I haven't used these for years and, when I did, I wasn't very impressed. However yesterday a diesel engineer friend retrieved two broken bolts from a very difficult position on a Paxman railway locomotive engine using Easi-outs. You don't have to drill very far down the stud with these because, if you think about it, a tapered item inserted into a parallel hole will only go in until it bites, and this will be at the top of the hole rather than deep down.
This forum introduced me to another kind of stud extractor made by Snap-on (and therefore bound to be expensive). It is hexagonal rather than threaded and the corners of the hexagon bite very hard when it is tapped into a hole drilled in the stud. My railway diesel-engineer friend has used these and he says they are very effective, so much so that it is very difficult to retrieve the extractor from the removed stud. As you say though, the problem is getting access to drill a hole.
Someone here once suggested using Araldite to lock something on to a broken stud so as to undo it. If the stud isn't too tight, that just might work. Again, I would try a nut because filling the hole with Araldite will give a good bond and a spanner can then be used to gently ease the stud undone. If it is possible to first get a small chisel onto the end of the stud so as to roughen up the surface, that would help the bond. Smearing a thin film of vaseline around the exposed part of the thread in the head before starting should stop the Araldite bonding to it.
Can't think of anything else, except to wish you the best of luck!
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Shep, I just read your last post again. You seem to have got the impression that you have to tap a hole in the stud when using Easi-outs. As you may have gathered from what I said, only a hole is needed, not a thread. The thread is cut by the Easi-out as it is wound in.
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Just incase this hasn't been suggested before. This has worked for me on a number of occasions..
take a length of 3/4" x 1/4" flat steel bar
Drill a hole in the end a couple of mm less that the diameter of the stud.
Countersink hole
mig weld through hole onto end of stud.
You do need reasonable access to 'sight' the broken stud. The idea is that the bar shields the aluminium from the worst of the heat. Let it cool down after welding so that the expansion/contraction loosens the stud before trying to turn it.
Best of luck
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If you still need to drill a hole with limited access a right angle attachment to an electric drill is probably what you need.
I have the following: see www.maplin.co.uk
Product RM52G angle driver £4.99 and RD80B quarter chuck £2.99
Both are the little hex drive that all the screwdriver bits fit.
The chuck is not highly engineered but together with the angle driver it will give you a better chance of access. Gently does it with sharp drills. Just attach to an electric drill or screwdriver. For a one off job and retaining the tools it might be an option. I find them quite useful.
I have had a right angle unit for my drill for decades. You might be able to hire one.
Take it easy as a right angle attachment out of control is not funny.!!!!
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Dieselhead, I agree about expansion/contraction loosening tight threads. I am currently stripping and restoring a 1949 steam locomotive that hasn't been touched for 20 years and this method has worked wonders with rusted nuts and bolts. I don't always wait for the nuts to cool though, in fact they often turn more easily whilst still hot.
If the hexagon is badly corroded, I heat the nut very close to melting, quickly hammer on the next-size-down socket then turn it while it is still glowing. It works (almost) every time, especially if the rust is first burnt off the exposed threads of the bolt so that the nut doesn't bind up as it is undone. I've had to cut off a couple of bolts with oxy-acetylene but have saved 100 or more, and avoided possible collateral damage where the flame of the torch damages surrounding components.
Well, that's my fix of steam for today. Back to motor cars ...
Welding a flat bar onto a broken stud sounds a good idea but I doubt if it will work in Shep's case because there won't be room to turn it without removing the manifold, and maybe not even then. A nut won't give as much protection against the heat but I think it ought to be enough if the welding is done very carefully, especially if MIG welding as this limits the spread of heat quite well in any case.
If the exposed bit of thread in the head gets damaged when welding a nut (or bar) onto the end of the stud, I don't think this would be disastrous. Winding out the broken stud will 'remake' any distorted thread and even if the exposed bit of thread gets destroyed altogether, what remains should be sufficient if the new stud is given a drop of Loctite and is then wound in gently. It is amazing how much a thread can be damaged yet still do its job.
Good point, Shep, about being careful not to harm the car's electronics. It's not at all 'wimpish' to want to avoid causing hundreds of pounds worth of damage! I'm quite ignorant on these modern fandangles so don't know the level of risk. Perhaps non-welding methods of stud removal are better after all!
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Dizzy, Good tips but for clarification a bolt has a thread up the entire length of the shank, a ?set screw? has part of the shank threaded. Now on with the ideas, firstly get some ?Plus Gas? on that thread, I have on several occasions used a stick welder and tacked the rod to a stub face then used the rod to unscrew the stud. These have mostly been larger bolts but a couple of M8 have come out this way. If this fails you are down to drilling and either an ?easy out? other type stud extractors. The hole you drill should be as near central as possible due to the fact that if the easy out fails you may have to drill out to the core size and clean the threads out so the more central you are the less damage you will do. This is not easy even with reasonable access and particularly hard with the manifold still on. My first option would with out doubt be a stick welder with a 30 degree cone shape on the end to ensure the arc strikes in the centre. Wrap the rod in suitable number of layers of masking tape to centralise it in the manifold hole. Then gently offer it up to stick and get a make to kill the supply on your command. Good Luck, let us know the out come. No pun intended. Regards Peter
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If all else fails you might be down to simply drilling out the entire stub and tapping a new thread. Any thread would do as long as you have a new "bit of circular rod with sufficient thread" (technical term) exposed to clear the manifold flange. You could screw in a long set-screw and then cut the head off.
Every time I have tried using an Easyout it has snapped before the stub has moved. It is then even more difficult to drill because the Easyout is very hard, and the drill tends to veer off course and break into the threads.
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Dizzy, Good tips but for clarification a bolt has a tread up the entire length of the shank, a "setscrew" has part of the shank threaded. <<
Peter, sorry to disagree ...
National and international standards (British Standards, etc.) define a standard *bolt* as having a thread length of twice the diameter of the shank. (Longer or shorter thread is 'non-standard' but still a *bolt* if the thread doesn't go to the head).
Where the thread extends the full length of the shank (except for a short run-out under the head) it is correctly known as a *screw*.
The word *setscrew* has come into common use for these parts but is, correctly, a threaded screw used to 'set' a moveable part in position, not to clamp two parts together. It is usually headless and threaded for the full length, like the small parallel screws that are used to set and lock a Picador pulley in position on a shaft.
Here endeth today's pedantic lesson!
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Cool !! Wrong way round. May be my grey matter is fading. Regards Peter
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Cool !! Wrong way round. May be my grey matter is fading. Regards Peter
Makes a change -- it's usually *me* that gets things about face (to put it politely and avoid the swear filter!).
What really matters is that you have clearly had lots of practical experience and that is far more useful than being able to recall exact definitions from textbooks!
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Henry,
Nice one....
these hobby tools are probably small enough to do the job without too much dismantling..if any. Also cheap enough to be a shot to nothing.....many thanks
Just out of curiosity, I called in at a masterfit place to enquire about costs and they quoted me £250. Funny thing was that I started to describe the problem and they knew straight away exactly which stud it was and how far down the shaft the shear was. This is obviously more common than I thought.
Their suggested approach was to actually drill out the entire stud and re-tap the hole but advised me that this was very risky because the hole was so close to the water gallery that it is all too easy to go off centre slightly and break into the water gallery.
I am actually quite stunned that they would take such drastic action when attempting to extract the stud is a far more practical proposition.
What do they know that I don't ??
Cheers,
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What do they know that I don't ??
Nothing, so far as I can see!
I agree with you, Shep, why go to such extremes as to drill out and tap a new hole before trying to remove the stud as it is and then re-using the tapping, especially if there is a risk of damaging the head.
To go to a larger stud would also mean making the hole in the manifold flange larger, unless they are suggesting a specially made stepped stud. A larger stud also means a larger nut (and washer?) and you would need to check that there is room for this, and for the larger spanner that would be needed.
Vauxhall may not have got their calculations exactly right but they designed the manifold and head for the size of stud that is fitted, not the next size up.
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Another thought -- a larger stud and a larger hole in the manifold would perhaps mean that next time it is the manifold that breaks, not the stud.
Apologies for taking over this thread!
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I doubt it will be fixed while in situ.ie too many probs.will be better to take manifold off and fix from there.
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I wasn't suggesting going to a thicker sized stud, with its obvious problems. If there is space to drill at all, drill and retap with the same diameter. The remains of the old stud usually crumple as you carefully advance the tap.
But obviously that is a last resort if there is a chance of extracting the stump. It would all be much easier of course with the head removed and clamped under a pillar drill.
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So what do you think my chances are ??
I will definitely remove the manifold. I will have to use a 90 degree drill to get at the stud even if I dismantle the power steering reservoir assembly.
So what is the stud made of and what sort of drill bit do I need?
I was concerned about what you said about the stud crumbling as the tap/extractor goes in so what is the "optimum" diameter size of hole to drill in the first place ?.
There seem to be 3 types of extractors available, the standard "easy out" type, the "helix" type and the splined hammer in and turn type. Any recommendations ?
My reading on this subject has told me that I should only attempt an extraction with a tap wrench to minimise the risk of snapping the extractor.
I am not expecting the stud to be particularly tight in the hole but someone has suggested that thet are also glued in at the factory ?
So all told......what are my chances of getting this thing out ?
Thanks for all you help guys,
Steve.
PS Do nothing is an option as the blow is almost undetectable. Thing is, I know the problem is there and can only get worse !! and cou tHING IS i KNOWHt so sl
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This is what I would do, if it were mine.
1) Remove manifold, so that you can get a better view of the depth of the break and get better access
2) Attempt to drill a small pilot hole down the broken stub. Possibly put some kind of guide on the bit, eg a rawlplug, to keep it centralised
3) See if it will turn quite easily, eg with the square shank of a file tapped in gently
4) Drill a larger hole as required for the extractor, and very gently try the extractor. I would be very wary of applying "too much" (hard to judge I know) force, in case it snaps.
5) using the pilot hole as a guide, drill out the whole stub to a depth that would give sufficient thread depth (1/2 - 3/4 inch?). I would use the size bit that corresponds to a bit thinner than the width to the inside of the threads.
6) Tap a new thread appropriate to whatever you are going to screw in - replacement stud, bit of threaded rod, sawn off screw etc.
If it doesn't work, check the condition of the remaining studs, and reassemble with a new gasket, lots of sealer, and cautious torgueing, and see if that will hold the seal.
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Shep,
The bulk of the replies to you whilst optimistic, lack experience of the actual problem. The stud diameter for the manifold is typically 8mm on other Vauxhall models that I have experienced this problem with. Apart from limited space and the issue of head waterways, the almost impossible problem you have is drilling a parallel pilot hole into a tensile bolt whist operating in an extremely confined space. It can be done with a jig and a high quality drill bit, but the average garage will remove the head and send it to a machine shop for drilling out and helicoiling.
My recommendation to you is to find a quality specialist who has a well tried procedure for removing the stud in situ. Spark erosion for example may be a practical solution. The resolution to my stud failure was for the cylinder head to be removed and the unit sent to a machine shop for the fitting of a helicoil. Its expensive of course, but it depends how much time you have to spare to explore other lower cost options without at the same time giving yourself a bigger headache.
Regards,
Julian Lindley
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Shep,
My advice is to mark the position of the hole with a centre punch. Start drilling with a 3mm bit and keep checking that it's going central. If not you can drill in from either side to correct it then drill on to a depth of about 20mm or so. It's quite easy to tell when your into the alloy by feel but wrap some insulating tape around the bit as a marker.
I would be cautious before taking the hole out to the full 6.5mm tapping size (if it's an 8mm stud) drilling a hard stud out of soft alloy. Your likely to butcher the threads if you do as it's not possible to get the hole accurate enough in a situation like this.
Better to drill well undersize to weaken the stud enough to allow you to extract the remains with a small sharp chisel/scriber then clean up the threads later with a tap. You will need a good selection of drill bits and the correst tap for the very coarse threads in the alloy.
Would be much easier with the manifold out the way and possibly the radiator/slam panel removed.
hope this helps
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but try the stud extractor methods first. My favourite is the tapered square type that you drive in....but go steady they are glass hard and break very easily.
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Having tried many times in a (different trade) and suceeded a few times I would agree with Julian and take it to a small local engineering outfit. Drilling and using an extractor works with a soft material stud but if its hardened little chance of success.
And drilling by hand exactly in the centre is well nigh impossible. Even getting a punch mark which you think is central turns out not to be so when you begin drilling.
We found extractors were worth trying on large whitworth and similar such as on boilers but smaller hardened ones never worked. Find someone who can do it before you take it off.
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I'd just like to say that dieselhead's advice seems the best.
If the hole is drilled at 3mm, it won't matter if it's a bit off-centre and it can be followed up with a larger drill until the threads in the aluminium are getting close (I think that's what dieselhead meant).
Regarding the strength of the stud affecting the ability to drill it, I feel fairly sure that it will be in what is known as 8,8 steel. This is fairly hard but not so hard that it cannot be drilled with an ordinary HSS drill bit. Also, a stud extractor should be able to bite into it fairly easily. I think this is worth a go before paying out for a machine shop to do the job.
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So, you've had lots of advice. Why not get a quote for getting the stud taken out and line this up against a quote for a new cylinder head, if you screw up the drilling. That should clear the air considerably.
Best of luck either way.
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John24, You mentioned getting a quote for a new cylinder head. Did you really mean this ... or did you mean a quote for helicoiling? Shep would have to *very* badly mess up for a new head to be required!
Messing up the drilling and needing to have the head helicoiled (about £50 if the head is delivered to the machinist?, a bit more if a house call is required to do the job in situ) should still give a very good saving over having a specialist remove the head and extract the stud.
But, in talking of helicoiling etc., I think we are delving into a bit of scaremongering anyway. I still say that it is worth a Sunday morning trying to extract the stud in the way that dieselhead recommended. Only if that fails is it time to start thinking of calling in specialist help. Doing it yourself saves money and gives a sense of satisfaction.
Shep, you now know what you are faced with and I feel sure you won't do great damage if you remember dieselhead's advice and drill carefully and in easy steps. If Loctite on the stud won't let it undo with an extractor, you could try applying heat as I mentioned in my first posting.
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