They are actually on the back of the block and get covered up by the flywheel. They very rarely go bad but when one does it can be a bear to find without dropping the tranny and bellhousing. I've only known it to happen twice and that was from owners using well water in their cooling systems up here where the mineral content is carries 5 times the minimum daily requirements of One a day vitamin
Which brings up my favorite pet peeve, probably yours as well; Folks, when mixing coolant, please go to the grocery store and spend the $0.69 a gallon for
DISTILLED WATER a.k.a. Demineralized or De-Ionized Water. The minerals in tap water, and some parts of the country its a huge mineral content, reacts with the anti-corrosion additives in the anti-freeze and forms all sorts of goop, it creates SCALE that will coat and clog the system, and since it turned the anti-corrosion additives to goop, rust and corrosion will start in the system sooner.
Softened water is even worse, they soften water by adding even more minerals to it, to neutralize the minerals already in it.
As well, completely drain your cooling system before adding new coolant. Remove the water jacket drain plug, hard the 1st time easier after, and drain the half gallon trapped in it. Disconnect a heater hose and shoot a little compressed air in there and it will force out the half gallon of coolant trapped in there.
I'll back flush with tap water from the hose, since my Jeep has so much scale in it I have to do it repeatedly every time. BUT, the last flush, I fill up with all distilled water, that way any left over water in the system is almost all distilled, NOT tap water with minerals in it.
I'm still trying to flush out all the goop in the cooling system caused by the previous owner of my jeep. I just flushed out the coolant a 2nd time in a year and it was full of brown and rusty deposit that is still flaking off the coolant system because the PO never changed the coolant and kept driving with a leaking radiator.
BTW, many stores are selling
All Makes and Models Anti-Freeze, that mixes with All Colors of Anti-Freeze don't buy it, its a Dex-Cool derivative. Do NOT use Dex-Cool, especially in a vehicle that did NOT come OEM with Dex-Cool. Check the ingredients in the fine print, if it says it has 2-EHA or 2-Ethylhexyl Acrylate its Dex-Cool or a derivative. If it says it has Silicates and Phosphates or a chemical compound with those, then its the
Original Green Anti-Freeze your suppose to use, some manufacturers have started to put
Original Green on the label to let the buyer know. If your NOT going to change your Anti-Freeze every 2 years, then retro-fit to Zerex G-05, the long life anti-freeze that Chrysler and Ford has adopted as their factory fill. From my research that is the best long life anti-freeze and the best to retro-fit to older cars. Make sure you completely flush all old coolant out. Although G-05 mixes just fine with other anti-freezes (except dex-cool, dex-cool does NOT mix with any other anti-freeze and it reacts to form goop), other anti-freezes will dilute it and it won't last the full 5 year life span.