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topic 7501

Corrosion on Studs


(2001)

I have a 67 Jaguar which has a steel block with an aluminum head. The studs which hold the head on is steel. The studs seem to be stuck in the head making the head extremely hard to remove. I assume the cause of this is corrosion due to the dissimilar metals. What can I do to make it easier to remove the head and how can I prevent this from reoccurring?

Roger McLaren
- Oxnard, California, USA


(2001)

Roger,

I think that you'd have to carefully heat up the Aluminum around each stud. You are probably not the only one who has had this problem before as other cars have similar set-ups.

However, 2 suggestions. Contact any local Jag repair shop for their thoughts. Also go to info@kelsey.co.uk and ask them as they print the JAGUAR MONTHLY magazine. They'd either know or could put you in touch with people, unlike me, who really know what to do.

Cheers! Buy an XJR (Wish I could afford one)

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



(2001)

Use Kroil by Kano [linked by editor to product info at Amazon] industries. My brother went through the same thing and didn't like all the other 'destructive' methods. He was told to use Kroil and the stud came loose after a 20 minute wait with a medium blow by hand on the wrench. Cadillac engine. Steel studs going through aluminum heads, outside block (exposed to weather) then into aluminum block.

David Domm
- Rochester, New York


(2001)

Roger, Freeman's suggestions were right on and I have another. If you do manage to get the studs out, you'll probably have to replace them, not because of corrosion but because header bolts are usually tightened to their plastic limit. This means that once they are unstressed, they will no longer have the necessary mechanical properties. This "extreme" tightening is one reason why they are so difficult to remove. Good luck!

Peter Weber
- Creil, France


(2001)

Roger,

It's good to see some real useful tips by others, isn't it? Now I had completely forgotten the replacement problem that Peter had pointed out. Sounds like a damn good idea. Yes, the studs DO get stretched with time and load. But after my first reply I realized I hadn't answered at all the query about preventing this from happening again ... so two thoughts came to mind.

l. Use a graphite material on the lower part of the stud. Preferably a 'pure' graphite or Moly with very little lubricant, sic. oil.

2. What about, I pondered, using an ordinary Teflon tape ... again on the lower part of the studs and NOT where the bolt it. Teflon should be OK to 350 degr. F ... the pundits will say I'm wrong and that the figure is 450 F but that's the McCoy SINTERED tfe not the extrudable and lower temperature FEP teflon that I think is what is used for teflon tape. Food fer thort, as they say in eddikated zirkels.

Freeman Newton
Freeman Newton
White Rock, British Columbia, Canada

(2001)

Kroil by Kano [linked by editor to product info at Amazon] oil is good, Use six point socket and impact gun. After removal, chase threads in block and blow out with air and always replace with new bolts. Torque in proper sequence and to proper tightness. Additionally, and hopefully you had the head and block checked by a machine shop or equivalent for cracks,warpage, pressure check head and block. Valve Job ? You don't want to have to repeat procedure so do it right the first time. Remember a chain is only as strong as its weakest link! Also remember, valve guide seals and new gaskets. don't forget, while you have it apart you might as well replace the timing chain or belt (that goes for any engine )and the water pump, oil pump, clean drains and all passageways. Use coolant compatible with aluminum. Flush cooling system. Change oil. Three angle valve job? Ported and polished? Bore that Bad Boy Out to the Max. Lets get crazy!

Laters,

Rog Orvern
Rogwrench Ink. - Chicago, Illinois


(2002)

At first you required rust loosener spray to open your seized and rusted stud from Aluminium block , it will penetrate and loose the rust etc. Why this problem occur, This is because two different material (alloy)change their metallurgy on high temp and oxide layer from between nut or block Thread and fastener or stud, become seizure. Temperature is not only the cause of seizing, other factors are aggressive environments like chemical zone, low temperature etc.

Vinit Jain
- Kanpur, U.P., India


(2003)

Additionally, To the post concerning seized head bolts. I would say that if vehicle owners replaced head gaskets at the interval rate suggested in almost all manufacturers tech. manuals, then the occurence of seized head bolts would be a rarity. Especially if the bolts are replaced with new ones and coated with an anti seize compound. Also chasing threads in block and cleaning out with solvent/compressed air. Torquing to specs. etc.

Roger Holmes
- Chicago, Illinois



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