XJ6 & XJ12 Series I, II & III 1968-1992

thermostat removal cautions

 
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Old 09-07-2014, 02:12 PM
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Default thermostat removal cautions

I’m about to undertake what should be a fairly straightforward procedure- the replacement of the thermostats in a Series II fuel-injected V12 engine- but I wanted to check first with those who have been down this road so as to minimize my own chances for error.

I purchased the recommended 180 degree thermostats with jiggle pins as well as the two gaskets. The left bank thermostat housing is triangular at its base and is attached with three ˝” headed bolts. The right bank housing is square at its base and is attached with four 7/16” headed bolts.

As far as I know, the thermostats have never been changed. The engine is more than thirty years old. I have the following question: With steel bolts seated in aluminum threads for this length of time, how difficult will it be to remove those bolts and the two housings to gain access to the thermostats? What is the risk of wringing one or more of the bolts off because they’re “frozen” and how may I avoid that tragic outcome?

I was thinking of something like WD-40 to help ease them out combined with a gradual loosening and tightening of the bolts as they are removed. Perhaps heat would help. Maybe there are other, better ways to get the job done. I would appreciate your help.
 
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Old 09-07-2014, 06:00 PM
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the caution should be focused on trying to not break the thermostat cover studs when you try to remove the nuts, one or more stubs will usually snap in two, then you need to extract the broken stud, a serious situation.

soak the nuts with Rust-Buster, over a few days before putting a wrench to them.

And on the first attempt at each nut, try to slightly TIGHTEN the nut FIRST, before trying to loosen it.
 
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Old 09-08-2014, 09:09 AM
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Thanks for your post, Jose. I'll be very careful as you advise. This is clearly an exercise in finesse and not one of muscularity. Slow and easy will be the order of the day. I'm not familiar with Rust-Buster but I've used PB Blaster on similar nut and bolt problems in the past . Is Rust-Buster a similar product? Again, thanks for your help.
 
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Old 09-08-2014, 09:20 AM
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If possible to use a 3/8" air rachet, use one. As you have a the possibility of pushing to hard with a hand wrench. Must move back and forth slowly with least possible exertion until loose. As above lots of penetrating lube.
 
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Old 09-08-2014, 10:23 AM
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yes, RustBuster is the same thing as PB Blaster, just get some "industrial-strength" penetrant, and also follow Larry K's tips above, although I am a bit scared of using an air tool due to the heavy torque they produce.

what I have done in the past is to attach the ratchet and socket to the nut, then slightly tap the ratchet arm forward and back with a small hammer or tool until I see some movement of the nut. Later on re-assembly, I applied anti-seize paste to the stud and nut.
 
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Old 09-09-2014, 10:01 AM
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Thanks for your help, Larry and Jose. That's exactly why I posted on the Forum. I knew there would be help on the way from those who know. Jaguar Forums comes through once again.
 
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Old 09-09-2014, 11:08 AM
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That's why I suggested air rachet not a 3/8" torque impact. Impact ca be 200lbs whereas the air rachet is about 30lbs. Tighten, loosen, tighten loosen. Being a miniature per se impact it does hammer and will apply less torque than the human hand on a 3/8" socket wrench. Learned the use on outboards, and aluminum engines.
 
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