I have a few posts on the topics over the last 2 years.
So i had done my t-stat housing about a year ago. it was a pain in the pain for my 2000 SOHC. I trace it back to the issue was really from the original owner requesting the t-stat be replaced and an over torque, and or coolant getting into one of the bolt wells. Mine was not cracked per se, but suffered damage during routine maintenance, in my opinion. My version was like $500-700 at ford, and hard to match up too. I found a decent one at junkyard for 5 bucks. In fact I was at one today and seen a good one, i.e no scarring of leaks. I may pull that one if they charge me 5 bucks again. Being yours is a 98, i think your sensors in the housing are different than mine so hopefully your parts would be much cheaper. I think my sensors are more really molded into the housing so my part includes all that stuff new, hence a high costs vs others where the sensors are clipped in and removable. These housing seem to fail at the "glued" joints. I think many have maybe 3 layers that are glued together and failures typically appear there. On mine, one of the three bolt sleeves failed, hence not securing the upper housing and allowing a leak.
in doing the job, i think i damaged my upper neck on my radiator during removal of upper house... had to replace that soon after. Probably Should have simply bite the bullet and cut that hose and replaced it rather than trying to save it since it had never been off before. I replaced a few small connecting hoses to the housing as space was too tight to try and remove so I just cut them off.
As usual when I see cooling systems start to have issues, it ends up snowballing, one thing after another for some time as fixes get pressures back up to 16lb, i think, then the next weak link goes.
right now i have a very slight leak maybe from the water pump gasket... i cant see it and have tried 2 now to find it (pressure tester). when I loosen the cap to half pressure it barely leaks. Its leaking on my right front somewhere. I feel that the only good way i have to verify exactly what it is would be to first pull out my alternator and idler pulley mount assembly. And btw, if your set up is like mine, thats the best approach to doing the t-stat housing for some access and removing an alternator harness that crosses over the housing. Also, if like my 2000, a few items on the right side will need unbolted to get out of the way for a clean removal and replacement. A fuel line and the heater lines, just my quick remembrance.
If you do the housing, yes, absolutely do the left bank cam tensioner, i did as i was in there and the access was optimal. those tensioners are to have a service interval of 60k as i understand it. I did mine at 140k+. I did the other right bank one as well.
Good Luck.
