Mutilated Thermostat Housing Screws

[DOF]

Guys,

Went to have a crack at changing the two Thermostats in my V12, and was faced with 6 obviously VERY tight screws, that someone previously had tried to remove, and had instead pretty much stripped them....

Tried to post a pic, but can't seem to do it...

Does anyone have any ideas? If I drill them out, I'm paranoind I won't be able to get the ends out of the block...

Thanks for any wise words you may have!

Simon

[davidr]

Use an impact driver. The action of hammering it into the screw head locates it and will stand the best chance of loosening it.

[DOF]

Hi David,

Thanks for replying to my plea.
I've already tried my impact driver. It did remove one screw, but even having applied heat, it sheared the next one, on the same side, and I am loathe to shear the last one on that side...
God knows how long they've been in there...and given the state they were in, I think someone has tried (and failed) to get them out before me...the one I got out was very crusty....
Have you done this job yourself?

Thanks

Simon

[davidr]

Hi Simon - yes I have done this before on my V12 XJ-S but I can't recall it being as challenging as your experience! Sounds like you've some galvanic corrosion going on. I don't know what to suggest short of drilling them out

[DOF]

Hi David,

Took your advice, threw caution to the wind, and drilled the little buggers out!
All done now, very second hand looking thermostats replaced with new, new gaskets, and 6 bright shiny new screws...
Just need to finish flushing it out, and replacde the coolant, and I'm hoping it's there...

Thanks for your help, just needed someone to shore up my confidence!

Simon

[davidr]

Simon - well done! It's amazing what you can do if you take a brave pill first!
I hope the thermostats you used had the jiggle pins to let the air out and you positioned them at 12 o'clock. Here's a picture. I don't know if you saw my article in the June magazine that explains more.

I'd also recommend running a tap down the threads in the thermostat housing to clean them up and then some copper grease on the new screws to prevent a repeat of the corrosion.

[DOF]

Yep, have Thermostats with jiggle pins...they came from a Jag specialist spares place, so I would hope they are up to spec!
All done in line with your advice, and the article which I referred back to...
She's running cooler now, but need to take her out for a proper run to be sure my issue is sorted.
Going slightly off topic, have been considering adjusting the tappets....is this something you've done on your car? does this have the potential for issues, or are they left well alone?

Thanks again for all your help and advice.

Simon