You need a ratchet long extensions and I think a 10mm socket. On the drivers side follow the radiator hose to the junction where you see two bolts, remove and that is where the thermostat is. It's a pain but take your time and you will be fine. Don't forget to "burp" the system when putting in coolant, fill till full, remove the bolt on the front of the intake manifold and fill till full. Squeeze the hose lightly a couple of times and the coolant should go down, keep filling until it stays full, replace bolt and drive and watch the temp. gauge, if it heats up you need to repeat the filling up by removing the bolt and repeating until it runs normal. Sometimes it can take a few times before it's right. Sorry about the novel.
This link has detailed instructions and photos http:/www.lincolnvscadillac.com/tech/lincoln-mark-viii/Thermostat-Replacement/index.htm
Bad thermostat?
It is under the power steering reservoir and can be removed by removing two bolts. It has three hoses going to it
You have to replace it.
Go to http://www.lincolnvscadillac.com/tech/lincoln-mark-viii/Coil-Spring-Conversion/index.htm
hi man i am awsome
No
of course
go to markviii.org. they have a answer for almost anything with the lincoln mark viii
Drivers side under the hood look to the right and down from the radiator and you will see a journal, where the hoses meet, in that journal is the thermostat
This is easier than I thought it would be. Took about 20-30 mins. The housing itself is not attached to the block or any stationary object under the hood. It is actually held up and in place by the 4 hoses that attach to it. Remove the hose clamps and the hoses and the thermostat housing will just come out. Scott Fuller 1993 Lincoln Mark VIII owner
Save yourself some grief and take it to a repair shop