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Thread: Seized Inlet manifold stud

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  1. #1 Seized Inlet manifold stud 
    frequent forum contributor Club Member stewartdjones's Avatar
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    In the process of removing the engine to carry out various repairs and mods, got as far as removing the inlet manifold and cannot remove it due to the stud at the front is seized (see pics)
    Have soaked in penetrating fluid but still no joy, any suggestions please?
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  2. #2 Re: Seized Inlet manifold stud 
    forum contributor philmcgrath's Avatar
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    Hi Stewart, I had to replace the cylinder head on my Cabrio earlier this year. Mine is the 8V Ford DOHC engine also and there was a crack between the inlet and exhaust valves on No 2 cylinder. I bought it in January and the bills I got with it showed a history of overheating which I believed had been rectified. This was unfortunately not the case. I was fortunate to find a fully reconditioned head for it but it was an expensive and tricky job.
    The front stud on mine was troublesome also. It is 100 mm long and a lot of corrosion occurs between the steel stud and the aluminium manifold where the thermostat is located. Eventually I removed the plastic front timing chain cover to protect it. It is fragile and not easy to find another one if it gets damaged, same as the plastic rocker cover. I used a flat tipped crowbar between the head and the thermostat housing to ease the manifold free. I took a while but I got it off in the end.
    You need to be careful with the fuel injectors. The plastic inserts in the head can crack and are a pig to replace.
    Once I got the head off I took out the two studs and binned them, along with the useless Torx bolts which just chew up. Replaced the lot with zinc plated passivated HT hex headed M8 flanged bolts. From memory you need 11 x 30 mm long and 1 x 100 mm long. I got mine from Kayfast on eBay. Use plenty of copper grease in the threaded holes in the head, and on the bolt shafts, to protect from the dreaded corrosion reaction. Run an 8 mm drill through the long hole in the manifold to get rid of the corroded residue.
    Hope you manage to get it off. The engine will come out with the manifold still attached but it is worth getting it off first if you can.
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  3. #3 Re: Seized Inlet manifold stud 
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    Cycle repair shops have a similar problem on occasion removing seat posts from frame. Seems one of the 'tricks' is to build up a reservoir around the joint with plasticine then fill said reservoir with acetic acid.
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  4. #4 Re: Seized Inlet manifold stud 
    frequent forum contributor Club Member Tony Stott's Avatar
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    ^ +1
    You could also use citric acid/lemon juice or oxalic acid - the latter is poisonous, absorbed through the skin so use of latex or vinyl gloves is a must! oxalic acid will also remove iron stains from wood.
    Last edited by Tony Stott; 17-11-2019 at 07:01 AM.
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  5. #5 Re: Seized Inlet manifold stud 
    frequent forum contributor Club Member stewartdjones's Avatar
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    Am I assuming that acid eats away at the corrosion only around the manifold and the stud?
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  6. #6 Re: Seized Inlet manifold stud 
    frequent forum contributor Club Member stevejgreen's Avatar
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    Quote Originally Posted by stewartdjones View Post
    Am I assuming that acid eats away at the corrosion only around the manifold and the stud?
    This might allay your worries. https://www.corrosionpedia.com/defin...68/oxalic-acid
    MOC member since 05/97
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    The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

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  7. #7 Re: Seized Inlet manifold stud 
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    I’m not familiar with this engine so I’ll ask the dumb question: can the inlet manifold be removed with that stud in place? Once removed the errant stud would be more accessible.

    Sometimes heating up the stud and allowing it to cool can help.
    Paul
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  8. #8 Re: Seized Inlet manifold stud 
    frequent forum contributor Club Member stevejgreen's Avatar
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    Quote Originally Posted by milliemarlin View Post
    I’m not familiar with this engine so I’ll ask the dumb question: can the inlet manifold be removed with that stud in place? Once removed the errant stud would be more accessible.

    Sometimes heating up the stud and allowing it to cool can help.
    Paul
    If the stud is 100mm long as suggested, heat will take a long time to transfer that sort of length to have any significant result.
    My preference is always PlusGas.
    I learned it’s benefits whilst working on plastic injection moulds back in the very early 70’s, but like all things, don’t expect instant results, wait 24hrs at least between applications and repeated attempts, patience is a virtue.
    MOC member since 05/97
    1984 Marlin Roadster SWB.
    1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
    Three core radiator, Renault Clio vented front discs.
    The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

    Loads of Marlin Reference can be found documents here or there.
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  9. #9 Re: Seized Inlet manifold stud 
    frequent forum contributor Club Member
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    I've not worked on this engine but understand that if you damage the inlet manifold it will be difficult to replace.

    As you intend to remove the engine and apparently from above advice it's doable. Ultimately that stud should be pointing upwards not horizontal and build a Plasticine mound all the way around it and use printed circuit board etching acid and soak for 2-3 days.
    I have used this method successfully on similar situations on other engines.

    Apparently Coke a Cola works ok too , but I've not tried using that yet.

    Another thing you can try provided it's feasible is remove the nearby injector and any surrounding plastic covers eg the timing cover . Then heat the inlet manifold using a mains powered paint stripping heat gun ( Using the appropriate nozzle attachment)

    You need to move the gun around the hole and minimize heating the stud. The Aluminium will expand greater than the steel stud . If you get it too hot to touch and then spray GT85 with a straw around the hole, some may get in there and allow you to remove the inlet manifold.

    The key here is don't rush it , plenty of patience. Locating a replacement inlet manifold will take you a lot longer.
    If that doesn't work remove either the head or the engine whole , tip on its side and use the Plasticine method as above.
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