I hate my exhaust manifold! Rusting/seizing prevention??

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Water247

Water247

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Bit of a hobo but often around the Surrey/Berkshir
Are they always so **** on Series 3 2.25 motors? When bought, the manifold had an inch gap between it and the downpipe. I tried to tighten it up and realised someone had previously attempted a weld as one of the lugs had broken off so it was pretty unfixable. :doh: SO, I got a manifold out a non-runner with seemingly sound lugs and studs and fitted that. It was rusty as **** but appeared to instantly improve things (thought I didn't tighten it right up as didn't have a gasket at the time). I now have gasket material - so began to undo it to get a gasket cut and fitted - and the bloody stud (the one which is cast as part of the manifold) has decided to snap off :mad:

This brings me on to a question I have been meaning to ask for a while: What is the best way to stop bolts rusting/seizing? ...I was bought up being told to lightly grease bolt threads to aid removal in future but as an adult have read many dull and boring explanations of why this is bad and how it affects torque when tightening. To be honest, I never do up with a torque wrench anyway just trusting how it feels by hand so do I really need to worry if I grease the thread a little? Or am I living dangerously and should I really be tightening clean, dry threads to the correct torque each time (or maybe just on wheels, but not necesarrily something as non-critical as an exhaust manifold)? I have also read suggestions to use a sealant around the bolt head to stop water penetrating to the threads. Does this work? What sealant would I use for that? Presumably you would also need to apply it at the nut if applicable. Would this option also affect potential torque readings?

I would like to try everything possible when fitting the new exhaust manifold to make sure I don't have such a ballache with it again in the future :)

Thanks,

Andy.
 
Last edited:
wouldn't worry overly about torque settings.....its not like your not gonna know if it starts rattlin loose! Always found heat very useful from a small torch.
 
must be the manifold season,I took mine off today to fix a blow and replace a broken stud,only problem is that when I removed all the bolts the manifold fell in half,its obviously been briken for a long time as the fracture is covered in carbon,the annoying thing is everything undid fairly easly but the inlet manifold refuses to come of the studs joining it to the exhaust manifold so thats a job for tomorrow and then wait till january for my local dealer to reopen so I can order a new manifold
 
I figured the torque malarky can drop off my radar, thanks. Not as if I'm racing in it!

They do seem to be a real bastard. Anyone have a suggestion for getting a nice cheap manifold replacement? Seems to be the one thing on ebay no-one sells!

So is the jury still out on greasing threads? I guess if I am just hand tightening and not worried about them being done up as critical top-end performance components then a little grease to stop them rusting really won't do much harm right?
 
I noticed my manifold is loose today, probably from the Xmas drive home!

I use a torque wrench, easy to use, refer to the workshop manual for settings where relevant. Saves guesswork, sheared bolts and things too loose. Also serves as a guage for how much something may have become loosened. Then I put a blob of grease over the assembled fastener to protect it from the weather.

I have got into the habit of almost anything I change, just buying the fasteners I need and replacing or cutting off the old ones.
 
i had to get the manifolds off my tdi....

ended up replaceing two engine studs...slipped them when refitted and just did em up till they nipped up.that seemed fine.just do em up tight....

i used valvoline penetrating oil to good succuss.
 
Water247 said:
Are they always so **** on Series 3 2.25 motors? When bought, the manifold had an inch gap between it and the downpipe. I tried to tighten it up and realised someone had previously attempted a weld as one of the lugs had broken off so it was pretty unfixable. :doh: SO, I got a manifold out a non-runner with seemingly sound lugs and studs and fitted that. It was rusty as **** but appeared to instantly improve things (thought I didn't tighten it right up as didn't have a gasket at the time). I now have gasket material - so began to undo it to get a gasket cut and fitted - and the bloody stud (the one which is cast as part of the manifold) has decided to snap off :mad:

This brings me on to a question I have been meaning to ask for a while: What is the best way to stop bolts rusting/seizing? ...I was bought up being told to lightly grease bolt threads to aid removal in future but as an adult have read many dull and boring explanations of why this is bad and how it affects torque when tightening. To be honest, I never do up with a torque wrench anyway just trusting how it feels by hand so do I really need to worry if I grease the thread a little? Or am I living dangerously and should I really be tightening clean, dry threads to the correct torque each time (or maybe just on wheels, but not necesarrily something as non-critical as an exhaust manifold)? I have also read suggestions to use a sealant around the bolt head to stop water penetrating to the threads. Does this work? What sealant would I use for that? Presumably you would also need to apply it at the nut if applicable. Would this option also affect potential torque readings?

I would like to try everything possible when fitting the new exhaust manifold to make sure I don't have such a ballache with it again in the future :)

Thanks,

Andy.
Click to expand...

the easiest way is to use the correct brass nuts on exhaust componants.....

Water247 said:
I figured the torque malarky can drop off my radar, thanks. Not as if I'm racing in it!

They do seem to be a real bastard. Anyone have a suggestion for getting a nice cheap manifold replacement? Seems to be the one thing on ebay no-one sells!

So is the jury still out on greasing threads? I guess if I am just hand tightening and not worried about them being done up as critical top-end performance components then a little grease to stop them rusting really won't do much harm right?
Click to expand...

i never torque up bolts and nuts unless they are torque sensitive applications like headbolts.....

i am breaking a series 3 btw.....
 
The good news is that all three studs can be replaced - one is in a blind hole but it isn't part of the casting. If you can't get them out yourself then an engineering workshop should be able to remove them for a small fee.
You don't need a gasket between the exhaust and the manifold - the belled end of the exhaust should form a good enough seal in the concave socket in the manifold.
Most things you apply to the manifold threads will burn off anyway so I'm not sure it's worth it.
 
I guess I still haven't learnt that prior to trying to undo anything on my S3 I should spray it with penetrating fluid for a week first!

So that Copper Slip is a grease that goes on the threads. I got the impression from somewhere that there is also a way of using a kind of rubbery sealant just around the bolt head to stop water running down to the threads (hence protecting them from rust without actually greasing them). Thinking about it I think my wheel bolts had this, when I removed each one recently they had a kind of black rubberized ring around just under each bolthead and they showed no signs of rust so seems like it may work well. However, I think I am coming to the conclusion that for a simple old S3 like mine I can get away with greasing each of the bolts a bit just like the old man taught me 20 years ago :) In fact, I still have his jar of grease from his days working on the buses for London Transport. Ahhh, happy days, I am getting all sentimental and I am not even 'that' old :eek:

Thanks for the posts so far :)
 
use copper grease on every bolt before you replace it, you'll be a lot happier next time you've got to undo them.
 
oxides said:
The good news is that all three studs can be replaced - one is in a blind hole but it isn't part of the casting. If you can't get them out yourself then an engineering workshop should be able to remove them for a small fee.
You don't need a gasket between the exhaust and the manifold - the belled end of the exhaust should form a good enough seal in the concave socket in the manifold.
Most things you apply to the manifold threads will burn off anyway so I'm not sure it's worth it.
Click to expand...

Should it just screw out? With the stud snapped flush I guess I would need to use a left handed drill bit to remove the remnants? Ooooh fun, I've not done that yet :D

I didn't realise about the gasket, thanks.
 
Water247 said:
I understand I should/could paint to avoid the manifold rusting. Why on earth don't they do this from the factory if they are so prone to rusting?

AND, what if the manifold is already rusty? Would painting over the top not just result in it flaking off? - it is a second hand manifold I fitted so not pristine :(
Click to expand...

frost do paints for car restoration.
Centre punch stud and drill hole, use
Stud Extractor Set 8 Pc - Screwfix.com, Where the Trade Buys

you may need cutting compound and cobalt drill bit if very hard
 
There are high temperature paints for things like manifolds. I've never tried it but I wonder if you could wire brush it smooth and use a black lead paste like Zeebrite? It works on grates and ranges.
If anyone fancies a try let us know if it works.
 
oxides said:
There are high temperature paints for things like manifolds. I've never tried it but I wonder if you could wire brush it smooth and use a black lead paste like Zeebrite? It works on grates and ranges.
If anyone fancies a try let us know if it works.
Click to expand...

I have a tin of heat resistant paint from Specialized (for a Victorian fireplace I renovated). When I get it off to sort the stud I'll give it a hard wirebrush and slap the paint on. Will post the photos.
 
never mind the high temp paints i just get black lead polish for stoves from any fireplace shop its only £4 for a 500ml tube and can take temps up to 2500 degrees and lasts a lot longer and dont stink like the dikkens when yer get it hot for the first time
 
johnny curt 1 said:
never mind the high temp paints i just get black lead polish for stoves from any fireplace shop its only £4 for a 500ml tube and can take temps up to 2500 degrees and lasts a lot longer and dont stink like the dikkens when yer get it hot for the first time
Click to expand...

That's the stuff I meant - must give it a try.
 
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