Honda prelude 88 4ws si

1. blown head gasket.
2. tw sensor not bathed in coolant. see #1 above.

look in the coolant expansion bottle when the engine is [warm] running. you'll see bubbles.

from there, you have a couple of options: changing the whole motor or repairing the current one. if you're doing the work yourself, it affects the math, but check out jdm import engines and balance that against the considerable labor charges of paying someone else to do this work [and not necessarily doing a very good job].

if repairing, it's essential that whoever changes the gasket does not use abrasives, and that includes scotchbrite, when cleaning the head and block surfaces. if they are used, tiny particles will remain in the cylinder and cause rapid wear and thus high oil consumption and low compression. use a knife blade [carefully so you don't gouge], or better yet, spray-on gasket remover. i prefer the latter. use lots of it repeatedly until the surfaces are clean. be prepared to spend some time doing it properly.

i would also advise you to avoid having the head skimmed if you can avoid it. unless completely cooked, honda heads rarely warp so it's unlikely to be necessary for that reason, and skimming affects the compression and valve timing. it's also the lazy mechanics way of cleaning the head. google this group for more info. go to home depot and get a large builder's straight edge then use your feeler gauges to inspect.

last thing, i strongly recommend getting the honda workshop manual from helminc.com. it is by far the best way to keep a great car like this on the road.

Yup. You have a blown head gasket. Possibly a warped head. The sealant will not fix it.

and worse, the sealant can block the oil cooler...