Cavalier exhaust downpipe bolts.

Soak them in penetrating oil for a few hours.

Yup.

At worst, removing the head so the stubs can be taken out and replaced. Garages do not accept any liability for snapped manifold bolts/studs.

Anything recommended? I have used Plus-Gas, but haven't seen it about for a while. Paraffin and a drop or two of oil? Thinners and oil? Something else?

That's what I'm worried about - no particular skin off their nose if the bolts break. I can get the section of pipe for about £24 (inc. VAT) - National want £61 to fit. I'm tempted to have a go. However, I've never done an exhaust like this

- does it need a gasket? Was thinking of applying heat from a plumbing gas torch, and perhaps giving the bolts a bit of a tap. Maybe a drop of hydrochloric acid.... and penetrating oil.

Has anyone here replaced this item, or similar, and can pass on info?

The threads are not visible on this one at all, it uses bolts through a flange into the manifold.

I would usually try to get the exhaust hot after a good run and immediately try to undo them with an impact wrench. This usually works.

There is something to be said for cutting the bolt heads off and removing the manifold then you can get penetrating oil on the actual thread bits and use heat, mole grips etc on the remains of the stud without the exhaust in the way, with it all the right way up, in a vice in the warm. The manifold to head bolts are not usually a problem, even if they look very rusty.

Get a gasket for the joins, top and bottom and manifold to head if needed.

mrcheerful

You seem to have experience of this! The car's a J-reg 1600 petrol. I have a 1/2" sq. drive "impact driver" - is this likely to fit, with a suitable socket? Are any of the bolts particularly hard to get at? Thanks for the information, I'm getting my courage up to have a go!

I work as a mechanic, so yes, I have done some of these. You will need a short extension and a proper impact socket, since you will be working below take great care that the extension and socket do not fly off, as I recall all the bolts are just about getatable, if possible use a 'universal' (Snap-On type) socket (the one with a ball joint built in and made for impact use and use the shortest extension you can.

mrcheerful

Oh, bum. I don't like the sound of that. Might I be able to buy something suitable at a reasonably good local motor factor? I'm not even sure what an "impact socket" is!

Sounds like the sort of fears that I had when I wrote to this thread about a year ago, asking a similar question about an H reg Astra 1.7 diesel downpipe, however I decided to give it a whirl. By using a long socket extension from underneath the vehicle, the bolts came out pretty easily and went back in without problems. A lot less hassle than I had at first anticipated.

Did you do anything special at all? The bolt ends that I can see flush with the end of the manifold casting flange have now been annointed with a few drops of rather strong hydrochloric acid, when that's used up I'll put on some more, then give it a blast with paraffin and a drop of oil (all I have to hand), and have a go at it tomorrow.

I sprayed the whole area with some 3-in-1 penetrating oil the day before I attempted the job.

I can't remember whether I warmed up the engine, but have a strong feeling that I did.

Whether the Astra arrangement is similar to the Cavalier I don't know, but as with your description it did look pretty messy and rusted up, although like I said I was amazed at how easy the whole job worked out.

I also found that a useful tool to have at hand was a small (cheap) angle grinder, which made short work of a couple of rusted up brackets around the tailpipe box area

It's a big chunky six sided one. If you get a blank look ask for an airhammer socket. (or print this off and give it to the counter guy - they'll know what you want)

An impact socket is invariably black and usually has only 6 internal sides.

mrcheerful

Or if its silver, it still has 6 internal sides but they'll be hard to distinguish from each other..

If they are mild steel chances are they're rusted solid, although mild steel into cast iron isn't as bad as mild steel nuts on studs. Otherwise heat. Penetrating oil won't touch them. Trouble is if National break them I'm willing to bet they'll say take it to a garage. Does the manifold look easy to remove if they do? Having had just that problem with the SD1 I removed both the manifolds fitted new studs where needed and found brass nuts to replace the originals. Stainless steel nuts and bolts are also available - although I'm not sure these would be as good, corrosion wise.

From experience with stainless steel fasteners in high(ish) temperature applications in industry, I'm sure that brass nuts would be the best bet.

HTH

Chris

Impact sockets are black rather than chromed, partly because chrome can peel and leave the socket slightly loose. May also be slightly thicker walled to stop socket splitting under agressive use.They are also 6 sided rather than `star` or `bi-hex` as sometimes called, because a six sided socket will apply force to walls of nut rather than corners.

Replaced all my cheap, bi-hex, sockets with Facom six siders after an altercation with a particularly tight nut, anti roll bar, got nowhere with cheapo socket and 3 foot power bar, nut was beginning to round off. Trip down lane to borrow SnapOn 6 sided socket and 1 foot power bar and said nut came off like it was hand tight. Good tools will more than pay for themselves in saved time, frustration and skinned knuckles.

Adam

Is copperslip ever worth applying pre-emptivly to exhaust fastenings? I've got a mate Rover with a cracked manifold to sort in a week or so so I expect I'll be having fun getting the olds ones off and fitting new.

Big snag with six siders is the walls are thicker and may not give enough clearance in tight spots. A choice is best.

IMO yes, but I'm sure others will disagree!

In the plastics industry many extruder parts need to be treated with Coppaslip if there is to be any chance of getting them undone in the future. The only difference I can see is that manifold fasteners are probably at a bit higher temperature..

FWIW, I always use it on exhaust fasteners generally.

Chris

I find a 2' wobble drive extension & a deep socket works lovely. Buy new studs before you start, get the engine really hot before you start & if they really don't want to shift then oxy mapp torches are really handy for those of us who can't justify the acetylene cylinder rental.